Chapter 1

Basics of Windows Programming

1. 1 Paradigms of Programming Languages Although many different computer architectures are being developed, the most prevalent is still the traditional von Neumann architecture - consisting of a single sequential CPU separate from memory, with data piped between cpu and memory. This is reflected in the design of the dominant computer languages, with dynamic variables (representing memory cells with changing values); sequential iteration (reflecting the single sequential cpu); assignment statements (reflecting piping). This combination of choices gives rise to the imperative language paradigm - C, Ada, Pascal, FORTRAN, COBOL, Basic etc. But other choices are possible - variables do not have to directly reflect memory cells (logic programming); repetition need not be iterative (logic, functional, concurrent); assignment need not be important (logic, functional); data and control need not be separated (object oriented, functional). A paradigm is essentially a high level model of what computation is about - the unifying factor that makes Ada and C seem very similar, ignoring details such as what data or control structures are available, exactly how variables are passed to procedures, and so on.

Some Paradigms Procedural (COBOL, FORTRAN, Pascal, C) functional (LISP) logic (PROLOG) structured object-oriented (Smalltalk) 4GL (Dbase) Visual (Visual Basic) 1.1.1 Procedural This is focusing on grouping organizations and/or code by similar operations or by the operations that can be done on them. 1.1.2 Functional Functional programming is so called because a program consists entirely of functions. The program itself is written as a function which receives the program's input as its argument and delivers the program's output as its result. Typically the main function is defined in terms of other functions, which in turn are defined in terms of still more functions, until at the bottom level the functions are language primitives. These functions are much like ordinary mathematical functions. Functional programs contain no assignment statements, so variables, once given a value, never change. Functions can be described intentionally by a rule describing the association, or extensionally as a set of associated pairs (argument, result) which are called the graph of the function. Functional programming also provides greater abstraction for solution. One such a feature is polymorphism which allows general definition of functions which could be applied to objects of any type. To achieve such a behavior we use type variables which stand for any type. Further higher order functions provide facility to treat functions as a data objects and use them like other data objects. It means that function (higher order function) can manipulate and create other functions. Another important feature of the functional programming is that evaluation of arguments could be delayed but done at most once. This technique is called lazy evaluation. Postponing sometimes can lead to such a situation that postponed value could be found as not necessary to evaluate, even when argument is undefined. If such a function can return a defined result we call it non-strict, else if returns undefined is called strict. 1.1.3 Logic The basic constructs of logic programming, terms and statements are inherited from logic. There are three basic statements: facts, rules and queries. There is a single data structure: the logical term. In a logic programming language the logical relationship between various entities are declared. The programmer writes a database of facts and rules. The user supplies a queries (goals) which the system tries to prove. This involves matching the current goal against each fact or the left hand side of each rule using unification. If the goal matches a fact, the goal succeeds; if it matches a rule then the process recurses, taking each sub-goal on the right hand side of the rule as the current goal. If all sub-goals succeed then the rule succeeds. Logic programming languages tend to be declarative programming languages, as opposed to the more traditional imperative programming languages. In a declarative language, you concentrate on the relationships between the parts of the problem, rather than on the exact sequence of steps required to solve the problem. An example of a well-known declarative languages are SQL, Prolog.

1.1.4 Structural

Two mathematicians, Corrado Bohm and Guiseppe Jacopini proved that any computer program can be written with the three structures : sequences, decisions and loops. This discovery led to the method of modern programming known as structured programming. Structured programming can be seen as a subset or sub discipline of Procedural programming one of the major paradigms (and probably the most popular one) for Programming computers. It is possible to do structured programming in almost any procedural programming languages. Edsger Dijkstra a professor of computer science at the Technological University at Eindhoven proposes that GOTO statements be abolished from all high-level languages such as BASIC. Modern programming languages such as Visual Basic do away with the need for GOTO statements. A computer program is said to be structured if it has a modular design and uses only the three types of logical structures, sequences, decisions and loops. Sequences: Statements are executed one after another. Decisions: One of two blocks of program code is executed based on a test for some condition. Loops (Iteration): One or more statements are executed repeatedly as long as a specified condition is true. One major shortcoming of earlier programming languages was their reliance on the GoTo statement. This statement was used to branch (that is jump) from one line of the program to another. It was common for a program to be composed on a convoluted tangle of branching that produced confusing code sometimes referred to as spaghetti code. The logic of a structured program can be pictured using a flowchart that flows smoothly fro the top to the bottom without unstructured branching (GoTos). Here is an example of a flowchart showing the structure with and without the GoTo statement: Advantages of Structured Programming The goal of structured programming is to create correct programs that are easy to write, understand and change. Easy to writeModular design increases the programmer's productivity by allowing them to look at the big picture first and focus on details later. Several Programmers can work on a single, large program, each working on a different module. Studies show structured programs take less time to write than standard programs. Procedures written for one program can be reused in other programs requiring the same task. A procedure that can be used in many programs is said to be reusable Easy to debugSince each procedure is specialized to perform just one task, a procedure can be checked individually. Older unstructured programs consist of a sequence of instructions that are not grouped for specific tasks. The logic of such programs is cluttered with details and therefore difficult to follow. Easy to UnderstandThe relationship between the procedures shows the modular design of the program.Meaningful procedure names and clear documentation identify the task performed by each module. Meaningful variable names help the programmer identify the purpose of each variable. Easy to ChangeSince a correctly written structured program is self-documenting, it can be easily understood by another programmer.

Earlier Analysis and Design As programs got more complex, programmers realized that there might be a better way to write programs than getting a problem statement and sitting down and writing code. In other words, a little abstract planning might help. Along these lines, some abstract modeling techniques were developed. Earlier methods included flowcharts and functional specifications, functional decomposition. Later techniques involved: data flow diagrams (functionality) data dictionaries (functionality) Decision trees process specifications (structured English) entity relationship diagrams (data -- Information modeling) The later techniques arose from the structured programming languages, and became used in structured analysis and design. The intention of the models was to create extra levels of abstraction between the real-world problem/system and the computer implementation of the system. They served as a bridge between the real world situation, and the computer code. The problem was mapped into a verbal problem statement, and then into a requirements analysis model, which was far removed from the machine implementation. The analysis model was then mapped into a design model, which was one step closer to the machine implementation (the code). Finally, code was written from the design model. However, these earlier abstract models all ran on one premise -- there is data, and there are functions that process the data. The first models attempted only to model the functionality of the real-world systems. Later, entity relationship diagrams were added -- these modeled the data, or the static nature of the system. However, the functionality models and the data models were distinct and separate entities. 1.1.4 Object-oriented In object-oriented programming programmers define not only the data type of a data structure, but also the types of operations (functions) that can be applied to the data structure. In this way, the data structure becomes an object that includes both data and functions. In addition, programmers can create relationships between one object and another. For example, objects can inherit characteristics from other objects. Objects and object interactions are the basic elements of design. One of the principal advantages of object-oriented programming techniques over imperative programming techniques is that they enable programmers to create modules that do not need to be changed when a new type of object is added. A programmer can simply create a new object that inherits many of its features from existing objects. This makes object-oriented programs easier to modify. The advantages of object-oriented programming do not evidence themselves when you are writing a single function for a particular purpose. Instead, the advantages arise when you are designing a large system that will do similar , but not identical, things to a variety of data objects. By specifying classes of data objects for which identical effects will occur, you can define a single generic function that embraces the similarities across object types, but permits individual implementations or methods for each defined class. As an example of languages that implements object paradigm are Smalltalk, Delphi and Java.

OO The Object Oriented Paradigm Is it possible to make a computer think the way people naturally think, rather than in terms of data and instructions that process data? The base machine will probably always think in terms of data and instructions that process data. However, are there high-level languages that can add another layer of abstraction on top of the machine, so that the high level languages can be written in code that mirrors the way people think? Yes, of course -- these are the OO languages! Some OO languages are better at hiding the basic premise of the machine. Smalltalk is probably the best, while C++ is probably the worst .

History of OO languages First OO language was Simula -- 1967. Used widely in Europe, it never caught on in the U.S. Then came Smalltalk -- 1972. In 1986, Bjarne Stroustrup invented C++, and Brad Cox created Objective-C. OO languages began taking off at this time. But as of 1994, OO languages have been around for 24 years. Earlier versions, such as Smalltalk, may have been unpopular because machines weren't powerful enough to handle them.

What Makes a Language Object-Oriented? According to Bertrand Meyer, an OO programming language should contain the following 7 qualities [7]: The support of modules. The modules must support data abstraction, which entails: a.) Information hiding and b.) Encapsulation. Automatic memory management (not necessarily garbage collection). All data are defined by abstract data type (ADT) based modules. (e.g. classes). Ability to extend existing classes (i.e. inheritance). Support of polymorphism and dynamic binding. Multiple inheritance (the need for this feature in an OO language is disputed by many in the OO field.)

Objects Basic building block of OO languages is the object. Like objects of human thought, OO objects combine both data (nouns and adjectives) and actions (verbs) into one package. Data is implemented as data, while actions are implemented as functions. The machine still sees a data-functionality split. But the outside world sees data and functionality merged into one whole.

Classes OO Languages promote classification at two levels. First, there is the class construct. Classes are like "cookie cutters" from which objects are moulded. We have a "cat" class from which we create cat objects, each with different attributes. The class specifies the attributes (and the functionality) while the objects fill in the attribute values. For example, we have a cat class that has weight, color, and name attributes specified. From the cat class, we create cat objects, through which the program is actually run.

Inheritance A looser classification scheme is obtained through inheritance. We can tie in our cat class into a whole inheritance hierarchy which includes the entire cat family, the mammals, all animals, and then all living things.

Polymorphism Polymorphism is the method by which OO languages mirror the human thought processes' tendency to group certain actions together. We can call similar functionality by the same name -- e.g. cats eat and cows eat, but the way they eat is different. However, we still call their actions "eating". OO languages allow for similar functions (actions) to be given similar names. This allows for conceptual clarity in writing code. Note that C and other traditional languages use polymorphism to some extent. For example, the arithmetic operators act on both floating point numbers and integers with the same operators (+, - , /, *, etc) even though the underlying implementation is radically different.

Abstraction Software objects mirror the human mind's tendency to abstract out details. Software objects hide the internal details of an object behind the walls of an interface. The "user" or "client" of an object does not have to worry about the inner details of the object, only the abstract principles of the object, as defined by the interface. 1.2. The Windows Environment Windows is a Graphical User Interface (GUI). It uses graphics to organize the user’s workspace. User’s choose items and execute programs by pointing and clicking with a mouse. The program that run from within Windows also have a Graphical User Interface (GUI); for example, MS-Excel and MS-Word. Moreover these programs can run only within Windows. This is because Windows provides these programs with a number of built in functions and data which are not available in other environments. The functions that are provided by windows include functions with the functionality to draw text in different sizes and styles using font data. Windows provides a broad range of graphical functions for drawing lines and geometric shapes and changing color. Windows program make use of these built in functions and do not have to be coded to perform these tasks. These system defined functions that an application can call are provided by an interface known as the Application Program Interface (API) Every Windows environment has its unique API. For example, the API that Windows 95 supports (also called the Win32 interface) is a 32-bit API. All the functions supported by the API can work with 32 bits of information at any given time. Writing programs for the Windows environment using the API functions is referred to as SDK programming where SDK stands for Software Development Kit. 1.3 A History of Windows Windows promised an easy-to-use graphical interface, device-independent graphics and multitasking support. The development was delayed several times, however, and the Windows 1.0 hit the store shelves in November 1985. The selection of applications was sparse, however, and Windows sales were modest. Windows 1.0 package, included MS-DOS Executive, Calendar, Cardfile, Notepad, Terminal, Calculator, Clock, Reversi, Control Panel, PIF (Program Information File) Editor, Print Spooler, Clipboard, RAMDrive, Windows Write, Windows Paint. On November 10, 1983, Microsoft announced Microsoft Windows, an extension of the MS-DOS operating system that would provide a graphical operating environment for PC users. Microsoft called Windows 1.0 a new software environment for developing and running applications that use bitmap displays and mouse pointing devices. With Windows, the graphical user interface (GUI) era at Microsoft had begun. The release of Windows XP in 2001 marked a major milestone in the Windows desktop operating system family, by bringing together the two previously separate lines of Windows desktop operating systems. With the upcoming release of Windows .NET Server, Microsoft will complete a cycle of server operating system upgrades it began nearly a decade ago in 1993, with the release of the first version of Microsoft Windows NT Server. To understand the progression of Windows server operating systems you have to look back earlier than 1993, however, to the even longer line of Windows desktop operating systems stretching back to the early 1980s. To explain the many advances since Windows 1.0, the following pages summarize milestones in the development of Windows desktop operating systems at Microsoft. Many longtime PC users trace Windows to the 1990 release of Windows 3.0, the first widely popular version of Windows and the first version of Windows many PC users ever tried. But Microsoft actually released the first version of Windows six years earlier, in 1985. To understand the roots of today's Windows operating systems, we must journey back nearly 20 years. The Windows 1.0 product box showed the new tiled windows and graphical user interface in the operating system

1985: Windows 1.0 The first version of Windows was a milestone product because it allowed PC users to switch from the MS-DOS® method of typing commands at the C prompt (C:\) to using a mouse to point and click their way through functions, such as starting applications, in the operating system. Windows 1.0 also allowed users to switch between several programs—without requiring them to quit and restart individual applications. The product included a set of desktop applications, including the MS-DOS file management program, a calendar, card file, notepad, calculator, clock, and telecommunications programs, which helped users manage day-to-day activities. Even before the Windows 1.0 graphical user interface, there was this pre-Windows 1.0 Interface Manager

1987: Windows 2.0 With the second version of Windows, Microsoft took advantage of the improved processing speed of the Intel 286 processor, expanded memory, and inter-application communication capabilities using Dynamic Data Exchange (DDE). Windows 2.0 featured support for the VGA graphics standard, and also allowed users to overlap windows, control screen layout, and use keyboard combinations to move rapidly through Windows operations. Many developers started writing their first Window-based applications for Windows 2.x. Following the release of Windows 2.0 was Windows/386 2.03, which took advantage of the protected mode and extended memory capabilities of the Intel 386 processor. Subsequent Windows releases continued to improve the speed, reliability, and usability of the PC, and improved the interface design and capabilities. 1990: Windows 3.0 Microsoft's first mainstream computing platform offered 32-bit performance, advanced graphics, and full support of the more powerful Intel 386 processor. A new wave of 386 PCs helped drive the popularity of Windows 3.0, which offered a wide range of new features and capabilities, including: Program Manager, File Manager, and Print Manager A completely rewritten application development environment with modular virtual device drivers (VxDs), native support for applications running in extended memory, and fully pre-emptive MS-DOS multitasking An improved set of Windows icons The popularity of Windows 3.0 blossomed with the release of a completely new Windows software development kit (SDK), which helped software developers focus more on writing applications and less on writing device drivers. Widespread acceptance among third-party hardware and software developers helped fuel the success of Windows 3.0. Windows 3.0 featured a new File Manager

1993: Windows for Workgroups 3.11 A superset of Windows 3.1, Windows for Workgroups 3.11 added peer-to-peer workgroup and domain networking support. For the first time, Windows PCs were natively network-aware and became an integral part of the emerging client/server computing evolution. Windows for Workgroups was used in local area networks (LANs) and on stand-alone PCs and laptop computers. It added features of special interest to corporate users, such as centralized configuration and security, significantly improved support for Novell NetWare networks, and remote access service (RAS). Windows for Workgroups also offered the performance benefits of Microsoft's new 32-bit file system. 1993: Windows NT 3.1 The release to manufacturing of Microsoft Windows NT® on July 27, 1993, marked an important milestone for Microsoft. It completed a project Microsoft began in the late 1980s to build an advanced new operating system from scratch. "Windows NT represents nothing less than a fundamental change in the way that companies can address their business computing requirements. Windows NT was the first Windows operating system to combine support for high-end client/server business applications with the industry's leading personal productivity applications. The operating system broke new ground in security, operating system power, performance, desktop scalability, and reliability with a range of key new features. These included a pre-emptive multitasking scheduler for Windows-based applications, integrated networking, domain server security, OS/2 and POSIX subsystems, support for multiple processor architectures, and the NTFS file system. Windows NT 3.1 contained overlapping windows and other features similar to Windows 3.1

The new operating system began with version 3.1 in order to maintain consistency with Windows 3.1, which at the time was a well-established operating system for both home and business users. Windows NT was geared toward business users and was initially available in both a desktop (workstation) version and a server version called Windows NT Advanced Server. The desktop version was well received by developers because of its security, stability, and rich Microsoft Win32® application programming interface (API)—a combination that made it easier to support powerful programs. Windows NT was a strategic platform that could integrate client/server applications with existing Windows-based desktop applications, or function as a technical workstation to run high-end engineering or scientific applications. 1993: Windows NT Workstation 3.5 Windows NT Workstation 3.5 supported the OpenGL graphics standard, which helped power high-end applications for software development, engineering, financial analysis, scientific, and business-critical tasks. The Windows NT Workstation 3.5 release provided the highest degree of protection yet for critical business applications and data. The product also offered 32-bit performance improvements, better application support, including support for NetWare file and print servers, and improved productivity features, such as the capability to give files 255-character names. 1995: Windows 95 Windows 95 was the successor to Microsoft's three existing general-purpose desktop operating systems—Windows 3.1, Windows for Workgroups, and MS-DOS. Windows 95 included an integrated 32-bit TCP/IP stack for built-in Internet support, dial-up networking, and new Plug and Play capabilities that made it easy for users to install hardware and software. The 32-bit operating system also offered enhanced multimedia capabilities, more powerful features for mobile computing, and integrated networking. In order to keep memory requirements to a minimum, it did not include support for such features as system-level security or Unicode, which came later. 1996: Windows NT Workstation 4.0 This upgrade to Microsoft's business desktop operating system brought increased ease of use and simplified management, higher network throughput, and a complete set of tools for developing and managing intranets. Windows NT Workstation 4.0 included the popular Windows 95 user interface and improved networking support, providing secure, easy access to the Internet and corporate intranets. In October 1998, Microsoft announced that Windows NT would no longer carry the initials NT," and that the next major version of the operating system would be called Windows 2000. 1998: Windows 98 Windows 98 was the upgrade to Windows 95. Described as an operating system that "Works Better, Plays Better," Windows 98 was the first version of Windows designed specifically for consumers. Windows 98 enabled users to find PC- or Internet-based information easily, it opened and closed applications more quickly, and it included support for reading DVD discs and connecting to universal serial bus (USB) devices. 1999: Windows 98 Second Edition Microsoft Windows 98 SE, as it was often abbreviated, was an incremental update to Windows 98. It offered consumers a variety of new and enhanced hardware compatibility and Internet-related features. Windows 98 SE delivered an improved online experience with Internet Explorer 5 browser software and Microsoft Windows NetMeeting® version 3.0 conferencing software. It also included Microsoft DirectX® API 6.1, which delivered a variety of Windows multimedia improvements, and offered home networking capabilities through Internet connection sharing (ICS). Windows 98 SE was also Microsoft's first consumer operating system capable of using device drivers that also worked with the Windows NT business operating system. 2000: Windows Millennium Edition (Windows Me) Windows Me offered consumers numerous music, video, and home networking enhancements and reliability improvements. System Restore let users roll back their PC software configuration to a date or time before a problem occurred. Windows Movie Maker provided users with the tools to digitally edit, save, and share home videos. Microsoft Windows Media™ Player 7 technologies allowed users to easily find, organize, and play digital media. Windows Me was the last Microsoft operating system to be based on the Windows 95 kernel. Microsoft announced that all future operating system products would be based on the Windows NT and Windows 2000 kernel. 2000: Windows 2000 Professional

Windows 2000 Professional was the upgrade to Windows NT Workstation 4.0, but it was more than just that. Windows 2000 Professional was designed to replace Windows 95, Windows 98, and Windows NT Workstation 4.0 on all business desktops and laptops. Built on top of the proven Windows NT Workstation 4.0 code base, Windows 2000 added major improvements in reliability, ease of use, Internet compatibility, and support for mobile computing. Windows 2000 Professional also made hardware installation much easier than it was with Windows NT Workstation 4.0 by adding support for a wide variety of new Plug and Play hardware, including advanced networking and wireless products, USB devices, IEEE 1394 devices, and infrared devices. 2001: Windows XP Windows XP is a unifying leap forward for desktop operating systems. With the release of Windows XP Home Edition and Windows XP Professional in October 2001, Microsoft succeeded in merging its two Windows operating system lines for consumers and businesses, uniting them around the Windows NT and Windows 2000 code base. With Windows XP, consumers and home users now have performance, stability, and security that business users benefited from in Windows 2000. Windows XP also includes the broad base of application and hardware compatibility of Windows 98 and Windows Me, while adding new tech-support technology, a fresh user interface, and many other improvements that make it easier to use for a broad range of tasks. Windows XP is available in two main versions, Windows XP Professional and Windows XP Home Edition, as well as a 64-bit edition, Windows XP 64-Bit Edition, for power users with workstations that use the Intel Itanium 64-bit processor. 2001: Windows XP Professional Windows XP Professional benefits from the long track record of Microsoft Windows NT technology: superior operating system performance, including preemptive multitasking, fault tolerance, and system memory protection. Windows XP Professional also offers a redesigned interface and includes features for business and advanced home computing, including Remote Desktop, encrypting file system, system restore and advanced networking features. It also offers numerous key enhancements such as wireless 802.1x networking support, Windows Messenger, Remote Assistance, and the System Restore feature. 2001:WindowsXPHomeEdition Windows XP Home Edition offers a clean, simplified visual design that makes frequently accessed features more accessible. The product offers many enhancements aimed at home users such as the Network Setup Wizard, Microsoft Windows Media™ Player, Windows Movie Maker, and enhanced digital photo capabilities. 1.4 Windows Programming Model Programs written for traditional operating environments use a procedural programming model in which programs execute from top to bottom in an orderly fashion. The path taken from start to finish may vary with each invocation of the program depending on the input it receives or the conditions under which it is run, but the path remains fairly predictable. In a C program, execution begins with the first line in the function named main and ends when main returns. In between, main might call other functions and these functions might call even more functions, but ultimately it is the program—not the operating system—that determines what gets called and when. Windows programs operate differently. They use the event-driven programming model illustrated in Figure 1.4, in which applications respond to events by processing messages sent by the operating system. An event could be a keystroke, a mouse click, or a command for a window to repaint itself, among other things. The entry point for a Windows program is a function named WinMain, but most of the action takes place in a function known as the window procedure. Figure 1.4 Windows Programming Model The window procedure processes messages sent to the window. WinMain creates that window and then enters a message loop, alternately retrieving messages and dispatching them to the window procedure. Messages wait in a message queue until they are retrieved. A typical Windows application performs the bulk of its processing in response to the messages it receives, and in between messages, it does little except wait for the next message to arrive. The message loop ends when a WM_QUIT message is retrieved from the message queue, signaling that it's time for the application to end. This message usually appears because the user selected Exit from the File menu, clicked the close button (the small button with an X in the window's upper right corner), or selected Close from the window's system menu. When the message loop ends, WinMain returns and the application terminates. 1.5 Dynamic Link Library (DLL) Dynamic Link Library (DLL) is a collection of software routines programmed in a language such as C or Pascal, which has been packaged especially for use from another program. For example, a C programmer might write a routine that accesses a laser disc player. By compiling this as a DLL, it might be usable by an author of a Windows Help hyper book, without them having to know anything about the programming. In windows programming DLL plays an important part. Windows provides function calls to implement its user interface and display text and graphics on the video display. These functions are implemented in DLL. These are files with extension .DLL or .EXE. The original idea for the DLL system was that there would be a central repository of code. Here are the advantages: Applications would link to this code library, thus saving greatly on duplication of effort and storage space. Applications that used the DLL system would behave exactly the same as all other applications that used it. If a problem arose, or a new feature was desired, it could be written once and all would benefit. In this sense, the DLL system is a weak version of the object-programming paradigm. Naturally enough, along with these advantages came some responsibilities. An application should only place a DLL in the central repository if: The DLL was newer and/or better than the ones already there. The DLL was uniquely named, i.e. did not conflict with a DLL for another purpose with the same name. If the DLL replaced another with the same name, then the code in the DLL would be exhaustively tested, so that on replacement, other applications could use it in the same way as its predecessor. In time, all these rules have been broken, even by Microsoft itself, the originator of the idea. On several occasions Microsoft has created and distributed DLL files that instantaneously broke every Windows application in the world. Regularly, end users will install an application that has a DLL with the same name as a "system" DLL, thus mysteriously bringing down the system until an expert can sort it out. Over time, the "synchronization" problem becomes more severe. In this scenario, a DLL is replaced that brings it into conflict with other DLLs it must work with. The service pack problem is becoming severe. In this scenario, Microsoft releases a service pack that updates all key system DLLs. All the elements of the service pack must simultaneously be present in their most recent form or the system will crash. Then the user installs an application that blithely replaces one or more of the DLLs from the service pack. Result – system failure, even on Windows NT 4.0, which, notwithstanding its reputation for stability and resilience, will fail utterly and completely. This is an example of a collision between an idea and reality, a key element in the human drama. The idea was sound, but it failed to take into account the imperfections in the human character, in particular those imperfections that influence the creation and operation of computer programs. The reality is that Microsoft and any number of software vendors regularly risk the stability and security of the end user's machine by writing DLL code as though it were normal programming. It isn't. To write a DLL, you must imagine the effect of your changes and additions on every computer program that uses it. This is obviously impossible. The solution to these problems is to go back to the system that preceded the DLL system. Every application should place as many DLL files as possible in its own directory (some DLL files are part of Windows itself, these must be accessed in common). No application should assume that it can copy DLLs into the system directory or that its newer version of a system DLL is safe to copy solely because it is newer. Many applications (including Microsoft's own) have rendered systems unstable or unusable through this reasoning.

Win32s DLL Libraries The Win32s DLL Libraries are an add-on set of programs that expand the MS Windows 3.1 and MS Windows for Workgroups 3.11 systems so that they can run programs that follow the Win32s standard from MicroSoft. By allowing them to run Win32s compliant programs, programers can write programs to follow that standard and have it run, hopefully, on MS Windows 3.1, MS Windows for Workgroups 3.11, MS Windows 95 and MS Windows NT. MS DOS and MS Windows 3.1/MS Windows for Workgroups 3.11 run 16-bit coded programs. The limit to 16-bit allows them to run on older computers with no significant changes. MS Windows 95 and MS Windows NT run 32-bit coded programs and do not need DOS at all. The 32-bit code needs at least a 386 IBM Compatible computer to run because the code is 32-bits instead of 16-bits it can: Use the full BUS width of the CPU to tranfer more information per computer clock cycle Have a more robust command structure with a possible 2^32 ( 4294967296 ) commands. Of course, at this stage of computer development there is no need for THAT MANY commands. But it is useful for splitting up common functions into seperate commands that were previously combined or grouping some common groups of commands into single commands. In the course of writing and distributing Windows applications, the majority of customer problems were related to DLLs. If you create a program that assumed that standard Windows system DLLs would be present, those DLLs would not be present or would not be current, and the application would fail. If I took it upon myself to follow the DLL guidelines and copy DLLs into the system directory after ascertaining that my DLL was newer than the current one, other applications would fail. To avoid this problem it is better to include in the application all required DLLs in the program directory. 1.6 API (Application Programming Interface) A set of routines, protocols, and tools for building software applications. A good API makes it easier to develop a program by providing all the building blocks. A programmer puts the blocks together. API (Application Programming Interface) is a set of commands, which interfaces the programs with the processors. The most commonly used set of external procedures are those that make up Microsoft Windows itself. The Windows API contains thousands of functions, structures, and constants that you can declare and use in your projects. Those functions are written in the C language, however, so they must be declared before you can use them. The declarations for DLL procedures can become fairly complex. Specifically to C# it is more complex than VB. You can use API viewer tool to get API function declaration but you have to keep in mind the type of parameter which is different in C#. Most of the advanced languages support API programming. The Microsoft Foundation Class Library (MFC) framework encapsulates a large portion of the Win32 (API). ODBC API Functions are useful for performing fast operations on database. With API your application can request lower-level services to perform on computer's operating system. As API supports thousands of functionality from simple Message Box to Encryption or Remote computing, developers should know how to implement API in their program. API\’s has many types depending on OS, processor and functionality. OS specific API: Each operating system has common set of API's and some special e.g. Windows NT supports MS-DOS, Win16, Win32, POSIX (Portable Operating System Interface), OS/2 console API and Windows 95 supports MS-DOS, Win16 and Win32 APIs. Win16 & Win32 API: Win16 is an API created for 16-bit processor and relies on 16 bit values. It has platform independent nature. e.g. you can tie Win16 programs to MS-DOS feature like TSR programs. Win32 is an API created for 32-bit processor and relies on 32 bit values. It is portable to any operating system, wide range of processors and platform independent nature. Win32 API’s has ‘32’ prefix after the library name e.g. KERNEL32, USER32 etc… All APIs are implemented using 3 Libraries. Kernel User GDI KERNEL It is the library named KERNEL32.DLL, which supports capabilities that are associated with OS such as Process loading. Context switching. File I/O. Memory management. e.g. The GlobalMemoryStatus function obtains information about the system's current usage of both physical and virtual memory USER This is the library named "USER32.DLL" in Win32. This allows managing the entire user interfaces such as : Windows Menus Dialog Boxes Icons etc. e.g. The DrawIcon function draws an icon or cursor into the specified device context. GDI (Graphical Device Interface) This is the library named "GDI32.dll" in Win32. It is Graphic output library. Using GDI Windows draws windows, menus and dialog boxes. It can create Graphical Output. It can also use for storing graphical images. e.g. The CreateBitmap function creates a bitmap with the specified width, height, and color format (color planes and bits-per-pixel). 1.7 The Programming Environment The Microsoft Visual C++ package includes more than the C compiler and other files and tools necessary to compile and link windows programs. It also includes the Visual C++ Developer Studio an environment in which you can edit your source code, create resources such as icons and dialog boxes and edit, compile, run and debug your programs. The msdn portion of the Microsoft URL stands for Microsoft Developer Network which is a program that provides developers with the frequently updated CD-ROMs containing much of what they need to be on the cutting edge of windows development. 1.7.1 Graphical User Interface Concepts Since the invention of Graphical User Interface (GUI) is in 1972 from that we have seen a good number of attempts to define and build the perfect GUI. GUI consists of number of elements such as: The Explorer – Program that manages the GUI. The Taskbar – Gray bar across the bottom of the screen. It contains icons representing all active programs, the clock and various utilities. The Start Menu – A one button approach to accessing programs, help, and system settings. GUIs offer a standard look and feel to application thus reducing development and learning time. A GUI is an environment that can work with graphic objects and it allows event-based interaction with program for e.g., clicking on mouse buttons, entering data through a text field (like for the calculator tool). Each event triggers the execution of event handler function to take appropriate action. Microsoft Windows a typical example has the following components. Menus (Including placement and names of options and styles such as pull down or popup). Icons (for identifying application and resources). Tiled Windows (for views of multiple programs or data or for multiple views of a single program or a data block). Dialog Boxes (for selecting files, options and settings when an option is selected, the one previously selected is turned off). Check Lists (from which the user can make multiple selections as in specifying print or file attributes). Support for a pointing device, typically a mouse (especially to select and drag screen elements). Scroll bars (along the edges to show the relative position of the contents such as the end or beginning of the text or to move to a different position such as another part of a spread sheet). A GUI enforces consistency by restricting developers they must support features for the program to run under the GUI. In addition one benefit of GUI is that the user can learn a second application faster because he or she is familiar with the environment. Note that the benefit comes with succeeding applications. Consistency and familiarity help produce shorter learning curves. Users generally prefer the interface style they know, whether it be Macintosh or Microsoft Windows. The consistency offered by a GUI trades on the users familiarity with the environment. Drawing and CAD programs are the best suited to GUI. Since, by their nature they manipulate objects lines and curves, fill closed areas with color. For database programs, such manipulation is not as useful. However they can use GUIs effectively to: Specify data fields when setting up reports. Select sort keys. Transfer data to or from other applications (such as a spread sheet). The last point is particularly important. Database applications often must transfer data to and from spreadsheets, word processors, desktop publishing programs, business or presentation graphics programs, statistics programs or project management software. GUIs generally have data exchange features, such as Microsoft windows dynamic data exchange (DDE) to handle such transfers. A final benefit of GUI is that it lets you see the final product before you print it. What You See Is What You Get (WYSIWYG) is a feature essential to desktop publishing and drawing applications and useful in database applications (so you can inspect reports to see that all data fits on the page). However there are drawbacks associated with using GUI. The cost includes the expense of graphics cards, pointing device (such as mouse) and extra memory. Because GUIs run in graphics mode, screen refresh is usually slower as well. If speed is important, a GUIs consistency may not be sufficient compensation. 1.8 Event Driven Programming While your program was looking for a particular kind of input, be it a mouse click or a key press, it wasn’t doing any other work. If at a particular place in your program you were looking for a mouse click and a key was pressed, generally the key press was ignored (at least at that instant). While this approach to programming is functional in many situations, it does not work very well when there are multiple possible sources of input whose arrival time you cannot predict and where it is unacceptable to ignore any of the inputs. As an example consider the case of a VCR. On a typical VCR there are a number of buttons, sensor inputs for tape in and the end of the tape as well as commands that can be received from the remote control. The program for the embedded computer controlling the VCR must be able to respond to any of those inputs at any time and in any sequence. For example, while running fast forward, you can stop, play, change channels, and program the VCR to record or any number of other actions. The program cannot move to only looking for the channel select buttons while you are programming, or it would miss the end of tape sensor for the rewinding tape. Clearly, what we need is a program structure that will allow us to respond to a multitude of possible inputs, any of which may arrive at unpredictable times and in an unpredictable sequence. While this problem is very common in embedded systems, like the VCR, it is also very common in modern desktop computers. Think about using a word processor. While you are typing, the program is accepting your keys and entering the characters into your document. You can also click with the mouse at any place on the screen. If the mouse pointer is at another place in your document, the point of insertion moves. If it is in the menu bar, a menu will drop down. If it is over a formatting button, it may change the format of the next character entered. Your word processor, or most other programs running under Windows, MacOS, X-Windows or any other modern Graphical User Interface(GUI), must also be capable of dealing with the same kind of variable input that the VCR must handle. All of these operating systems, and many embedded applications, have adopted a common program structure to deal with the need to respond to many asynchronous (not time sequence) inputs. This program structure is generally called event driven programming. Under the event driven programming model, the program structure is divided into two rough groups, Events and Services. An event represents the occurrence of something interesting. A service is what you do in response to the event. While events most often originate from the outside your program, such a mouse click, events can also generated by other parts of the program. The program executes by constantly checking for possible events and, when an event is detected, executing the associated service. In order for this approach to work, the events must checked continuously and often. This implies that the services must execute quickly, so that the program can get back to checking for events. In order to meet this requirement, the service can not to go into a state where it is waiting for some long or indeterminate time. The most common example of this would be a while loop where the condition for termination was not under program control, for example; a switch closure. This kind of program structure, an indefinite loop is referred to as ‘Blocking ‘ code. In order for the even t driven programming model to work, you must only write ‘Non-Blocking’ code. So how to deal with the need to wait for the switch close? You make the switch closure an event. Then, rather than waiting in a loop for the switch to close, you program a service that does the right thing when the switch closes and let all of the event checkers run while you are waiting for the switch to close. In this way, you could also react to another event while you were waiting for the switch to close. Event Checkers An event, by its nature, represents a discrete point in time. At one instant, the event has not occurred , at the next it has. In the case of a switch, the opening or closing of the switch represents an event. The switch being open or closed does not represent an event. The event is marked by the transition from open to closed. 1.9 Header Files Windows programs begin with a processor directive at the top such as : #include <windows.h> WINDOWS.H is a master file that includes other Windows header files, some of which also include other header files. The most important and most basic of these header files are: WINDEF.H Basic type definitions. WINNT.H Type definitions for Unicode support. WINBASE.H Kernel functions. WINUSER.H User interface functions. WINGDI.H Graphics device interface functions. These header files define all the Windows data types, function calls, data structures and constant identifiers. They are important part of Windows documentation. 1.10 Program Entry Point In windows program the entry point is WinMain similar to the main function in C program. The WinMain function appears like this: int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR szCmdLine, int nCmdShow) It is declared in WINBASE.H like so (line breaks and all) : int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd ); This declaration uses a system called “Hungarian notation” through which the variable name is indicated with a short prefix that indicates the variables data type. This notation will be discussed later. The first parameter to WinMain is an “instance handle”. In windows programming a handle is simply a number that an application uses to identify something. In this case the handle uniquely identifies the program. It is required as an argument to some other windows function calls. In early versions of windows when you run the same program concurrently more than once, multiple instances of that program will be created. A program can determine if other instances of itself are running by checking the hPrevInstance parameter. In 32 bit versions this concept has been abandoned. The second parameter to WinMain is always NULL (defined 0). The third parameter to WinMain is command line used to run the program. The fourth parameter to WinMain indicates how the program should be initially displayed either normally or maximized to fill the window or minimized to be displayed in the task list bar. 1.11 Compile, Link and Run Windows program When you are ready to compile your program named samplewinprg, you can select Build samplewinprg.exe from the Build menu or press F7, or select the Build icon from the Build toolbar. The appearance of this icon is shown in the Build menu. If the Build toolbar is not currently displayed you can choose Customize from the tools menu and select the Toolbars tab. Pick Build or Build MiniBar. Alternatively you can execute samplewinprg.exe from the Build menu by pressing Ctrl+F5 or click the Execute program icon. From the Build toolbar. A message will be displayed asking if you want to build the program. During compilation the compiler generates an .OBJ(object) file from the C source code file. During the ling stage the linker combines the .OBJ file with .LIB(library) files to create the .EXE(executable) file. You can see a list of these library files by selecting settings from the Project tab and clicking the Link tab. In particular you’ll notice KERNEL32.LIB, USER32.LIB, and GDI32.LIB. These are “import libraries” for the three major Windows subsystems. They contain the dynamic-ling library names and reference information that is bound in to the .EXE file. Windows uses this information to resolve calls from the program to function in the KERNEL32.DLL, USER32.DLL and GDI32.DLL dynamic link libraries. In Visual C++ Developer Studio, you can compile and link the program in different configurations. By default these are called Debug and Release. 1.12 MessageBox Function The MessageBox function is designed to display short messages. The window that a MessageBox displays is considered to be a dialog box. The first argument to MessageBox is normally a window handle. The second argument is the text string that appears in the body of the message box and the third argument is the text string that appears in the caption bar of the message box. The fourth parameter can be any of the combination of constants beginning with the prefix MB_ that are defined in the WINUSER.H. The list of buttons that can appear in dialog box are: MB_OK MB_OKCANCEL MB_ABORTRETRYIGNORE MB_YESNO MB_YESNOCANCEL MB_RETRYCANCEL The appearance of the icon in the message box can be any one of the following: MB_ICANHAND MB_ICONEXCLAMATION MB_ICONASTERISK 1.13 Data Types Windows programming has a reputation for its variety of data types, it uses all C data types and also introduces a few data types of its own. The sample windows application illustrated in this chapter uses a few of the Windows data types. The following code displays a message as displayed in figure 2.10(a) # include <windows.h> int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,PSTR szCmdLine, int nCmdShow) {int i; MessageBox(0,"Application executing","Application",MB_OK); return(0); } Figure 2.10(a) Sample Output In this program, the MessageBox function returns the value 1, but it is more proper to say that it returns IDOK, which is defined in WINUSER.h as equaling 1.Each running copy of a program is called an instance. To refer to a particular instance of a program, a handle is required. A handle is an unsigned integer that Windows uses internally to keep track of objects in memory. For example, every window on the screen has a unique window handle. Handles are also used to keep a track of running applications, allocated memory blocks and a host of other objects. A handle is simply a number assigned by the system to a particular entity. It serves to identify the entity, whether it is an instance, a window, a control or a block of memory. All objects in windows are referred to by handles. Handles are a replacement of pointers. There are a number of related data types for describing different kinds of handles. All these data types begin with the letter H. Thus, HWND is the data type for a window handle, and HPEN is the handle to PEN. In the program shown above, hInstance is the handle that identifies the current instance of the application and hPrevInstance contains the hInstance value for the last copy of application. Internally the Kernel of windows maintains tables that allow windows to convert handles to physical memory addresses. A handle is a pointer to a memory location. The reason for this complexity is that windows moves objects (memory blocks, programs and so on) in memory to make room for others. If windows moves and object in memory, the handle table is updated. The handle used by the program does not need to change since it always gets correctly translated to the right physical memory addresses by the windows kernel, no matter where the object is moved in memory. Figure 2.10(b) displays a representation of handles in the memory. Program Windows Kernel Memory HandleHandle TablePhysical Address Figure 2.10(b) Handles in the Memory If a pointer was used to refer to an object in memory, the pointer will be invalid when the object is moved by windows as a part of its memory management. Thus pointers can be dereferenced whereas handles will continue to be valid since the handle to pointer table will be updated automatically by windows whenever it moves an object in memory. In the above program, LPSTR is another new windows data type that is used; it is used to store a Long Pointer to a String same as the char data type of C. The MessageBox function of the Win32 API displays a message on the screen, with the specified title and message text, the message displayed will show an OK button also, which will dismiss the MessageBox as specified by the MB_OK parameter. 1.14 Hungarian Naming Convention The names of the variables used in a window program follow a naming convention called Hungarian notation, in honor of its inventor Charles Simonyi. The idea is to precede variable names with key letters that describe the type of data the variable represents and follow a verb-noun combination. The Table 1.14 represents the Hungarian notations. Table 1.14 Variable Name Codes in Hungarian Notation Variable Name PrefixCode Data Type b BOOL(Boolean). The variable here can take either True or False values. by BYTE(unsigned character) c Char(character) dw DWORD(double word) fn Function h Handle i int(integer) l Long n Short(int) or near pointer p Pointer s Character string sz Character string terminated by zero w Word(two bytes)

1.15 Windows String Functions

The collection of string functions included in windows to calculate string length, copy string, concatenate strings and compare strings are listed below:

lstrcmpi - Compares two strings, ignoring case.

lstrcmp – Compares two strings.

lstrcpyn - Copies one string to another, with a maximum length.

lstrcpy - Copies one string to another.

lstrlen - Gets the length of a string in characters.

lstrcmpi Compares two character strings. The comparison is not case sensitive. Syntax int lstrcmpi(LPSTR lpszString1,LPSTR lpszString2); The first parameter lpszString1 is the pointer to the first null-terminated string to be compared. The second parameter lpszString2 is the pointer to the second null-terminated string to be compared. This function returns a negative value if the function succeeds and the string that lpszString1 points to is less than the string that lpszString2 points to. Returns a positive value if the string that lpszString1 points to is greater than the string that lpszString2 points to. Returns zero if the strings are equal. The lstrcmpi function compares two wide strings by checking the first characters against each other, the second characters against each other, and so on until it finds an inequality or reaches the ends of the strings. Similarly two wide strings can be compared using the function lstrcmpiW and also the wide character string can be represented using LPCWSTR (long pointer to wide character string).

lstrcmp Compares two strings. The comparison is case sensitive. Syntax int lstrcmp(LPSTR lpszString1,LPSTR lpszString2); The first parameter lpszString1 is the Pointer to the first null-terminated wide string to be compared. The second parameter lpszString2 is the Pointer to the second null-terminated wide string to be compared. Returns a negative value if the function succeeds and the string that lpszString1 points to is less than the string that lpszString2 points to. Returns a positive value if the string that lpszString1 points to is greater than the string that lpszString2 points to. This function returns zero if the strings are equal. The lstrcmp function compares two strings by checking the first characters against each other, the second characters against each other, and so on until it finds an inequality or reaches the ends of the strings. Similarly two wide strings can be compared ignoring case using the function lstrcmpW.

lstrcpy Copies a string to a buffer. Syntax LPSTR lstrcpy(LPSTR lpszString1,LPSTR lpszString2); The first parameter lpszString1 is the Pointer to a buffer to receive the contents of the string pointed to by the lpszString2 parameter. The buffer must be large enough to contain the string, including the terminating wide null character. The second parameter lpszString2 is the pointer to the null-terminated wide string to be copied. This function returns a pointer to the buffer. Similarly two wide strings can be copied using the function lstrcpyW.

lstrcpyn Copies a string to a buffer, up to a specified number of characters. Syntax LPSTR lstrcpyn(LPSTR lpszString1,LPSTR lpszString2,int iMaxLength); The first parameter lpszString1 is the pointer to a buffer to receive the contents of the string that the lpszString2 parameter points to. The buffer must be large enough to contain the string, including the terminating wide null character. The second parameter lpszString2 is the pointer to the null-terminated string to be copied. The third parameter iMaxLength gives the maximum number of characters to copy, including a terminating null character. This function returns a pointer to the buffer. If iMaxLength is nonzero, lstrcpyn always inserts a terminating null character in the destination string, which could result in the source string being truncated. Similarly lstrcpynW copies a wide string to a buffer, up to a specified number of wide characters. lstrlen Retrieves the length of the specified string. Syntax int lstrlen(LPSTR lpszString); The first parameter lpszString is the pointer to a null-terminated wide string. If the function succeeds, the return value specifies the length of the string. Similarly lstrlenW retrieves the length of the specified wide string. 1.16 The Sample SDK Program Creating a window first requires registering a window class and that requires a window procedure to process messages to the window. This involves a bit of overhead that appears in almost every windows program. The program shown below is a simple program that handles only three windows messages(two mouse click messages and a quit message). Figure 1.16(a) shows the applications only window. Figure 1.16 (a) A Minimal Windows Program written using SDK // Sample SDK program to display window #include <windows.h> WNDCLASS wc; MSG msg; HWND hwnd; LRESULT CALLBACK wndproc(HWND,UINT,WPARAM,LPARAM); int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nCmdShow) { wc.style=CS_HREDRAW|CS_VREDRAW; wc.lpfnWndProc=wndproc; wc.hInstance=hInstance; wc.hCursor=LoadCursor(hInstance,IDC_ARROW); wc.hIcon=LoadIcon(hInstance,NULL); wc.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH); wc.lpszClassName ="Sample"; wc.lpszMenuName =NULL; if (!RegisterClass(&wc)) return false; hwnd=CreateWindow(“Sample”,”AsampleSDK Window”, WS_OVERLAPPEDWINDOW,//window style CW_USEDEFAULT, //initial x position CW_USEDEFAULT, //initial y position CW_USEDEFAULT, //initial x size CW_USEDEFAULT, //initial y size NULL,//parent window handle NULL,//window menu handle HINSTANCE,//program instance handle NULL);//creation parameters ShowWindow(hwnd,nCmdShow); UpdateWindow(hwnd); while(GetMessage(&msg,NULL,0,0)) { TranslateMessage(&msg); DispatchMessage(&msg); } return true; } LRESULT CALLBACK wndproc(HWND hwnd,UINT wm,WPARAM wp,LPARAM lp) { char left[]="You have pressed left mouse button"; char right[]="You have pressed right mouse button"; switch(wm) { case WM_LBUTTONDOWN: { MessageBox(GetFocus(),left,"About",MB_OK|MB_ICONINFORMATION); break; } case WM_RBUTTONDOWN: { MessageBox(GetFocus(),right,"About",MB_OK|MB_ICONINFORMATION); break; } case WM_DESTROY: { PostQuitMessage(0); return 0; } default: break; } return(DefWindowProc(hwnd,wm,wp,lp)); } Figure 1.16 (b) The sample SDK program responding to a left mouse click message 1.16.1Dissecting the Program The code for this program deserves a closer examination. The program starts with #include<windows.h>. This statement includes the main windows header file(WINDOWS.H) that in turn includes all the windows header file that contain structures, macros, API prototypes and everything else that the SDK program needs. Then the two SDK functions declared are: the program entry point WinMain() and the application’s window procedure in this case wndproc. However there is a reference to wndproc in WinMain, which is why the function is declared near the top of the program. Windows function calls The sample SDK windows program makes calls to fewer windows functions. These functions with a brief description are: Load IconLoads an icon for use by a program. Load CursorLoads a mouse cursor for use by a program. GetStockObjectObtains a graphic object in this case a brush used for painting the windows background. RegisterClassRegisters a window class for the program’s window MessageBoxDisplays a message box. CreateWindowCreates a window based on a window class. ShowWindowShows the window on the screen. UpdateWindowDirects the window to paint itself. GetMessageObtains a message from message queue. TranslateMessage Translates some keyboard messages. DispatchMessage Sends a message to a window procedure. PostQuitMessage To insert a “quit” message in to the message queue. DefWindowProc Performe default processing of messages. Window Class Structure(WNDCLASS) The WNDCLASS structure is used to define all windows that you can view on your monitor. The structure of a window class looks like this: typedef struct_WNDCLASS {UINT style; //window class style WNDPROC lpfnWndProc; //window procedure int cbLlsExtra; //extra class bytes int cbWndExtra; //extra window bytes HANDLE hInstance; // instance handle HICON hIcon; // icon handle HCURSOR hCursor; // cursor handle HBRUSH hbrBackground; // background brush color LPCTSTR lpszMenuName; // menu resource LPCTSTR lpszClassName; // window class name }WNDCLASS ; Message Structure Because almost everything in windows happens in response to messages, the windows message structure MSG is extremely important. This structure is defined as follows: typedef Struct tagMsg {HWND hwnd; // handle of the windows to retrieve messages UINT message; // message value for each windows identified by macros in WINDOWS.H WPARAM wp; // additional information about the message DWORD time; //time at which the message was posted to the queue POINT pt; // screen coordinates of the cursor when the message was posted }MSG; Uppercase Identifiers These identifiers are defined in the windows header files. The identifiers contain a two-letter or three-letter prefix followed by an underscore: CS_HREDRAWDT_VCENTERSND_FILENAME CS_VREDRAWIDC_ARROWWM_CREATE CW_USEDEFAULTIDI_APPLICATIONWM_DESRTOY DT_CENTERMB_ICONERRORWM_PAINT DT_SINGLENAMESND_ASYNCWS_OVERLAPPEDWINDOW These are simply numeric constants. The prefix indicates a general category to which the constant belongs. CS Class style option CW Create window option DT Draw text option IDI ID number for an icon IDC ID number for a cursor MB Message box options SND Sound option WM Window message WS Window style Initializing and Registering the Window Class Windows allows multiple instances of a single application to run concurrently each application window has a window class. A window class must be initialized and registered when the first instance begins execution. If there are no previous instances of the application running the WNDCLASS structure variable wc is initialized with values and registered with windows by calling the RegisterClass() API function with a pointer to wc as the only parameter. Here is the way to handle the RegisterClass function call: if(!RegisterClass(&wc) return false; In some sample windows programs you may see the following code in WinMain: If(!hPrevInstance) {wc.style=CS_HREDRAW | CS_VREDRAW; [ other wndclass initialization] RegisterClass(&wc); } This declaration is necessary only for 16 bit version of windows, if you started up a new instance of a program that was already running then the hPrevInstance parameter should be the instance handle of the previous instance. The window class can be registered only if hPrevInstance was NULL, indicating no other instances of the program were running. But in 32 bit versions of windows hPrevInstance is always NULL, it is not necessary to check hPrevInstance. Creating the Window The application window is created by calling the API function CreateWindow(). The CreateWindow() function takes 11 parameters. Here’s the CreateWindow call with comments identifying the parameters. hwnd=CreateWindow( SZAPPNAME, // window class name SZAPPTITLE, // window caption WS_OVERLAPPEDWINDOW, // window style CW_USEDEFAULT, // initial x position CW_USEDEFAULT, // initial y position CW_USEDEFAULT, // initial x size CW_USEDEFAULT, // initial y size NULL, // parent window handle NULL, // window menu handle HINSTANCE, // program instance handle NULL); //creation parameters The window created by this program is a normal overlapped window. It will have a title bar, system menu button to the left of the title bar, a thick window sizing border and minimize, maximize and close buttons to the right of the title bar. This is the standard style for windows. By using the identifier CW_USEDEFAULT to indicate (initial x , y position and initial x , y size) we are indicating that we want windows to use the default position for an overlapped window. The argument marked “parent window handle” is to set to NULL when creating a “top level” window such as an application window. Normally, when a parent-child relationship exists between two windows the child window always appears on the surface of its parent. The “window menu handle” is also set to NULL because the window has no menu. The “program instance handle” is set to the instance handle passed to the program as a parameter of WinMain. Finally a “creation parameter” is set to NULL. The CreateWindow function call returns a handle to created window which is stored in the variable hwnd. It is defined to be of type HWND (handle to a window). Displaying the Window After the CreateWindow call returns the window has been created internally in windows. However the windows do not yet appear on the video display, two more calls are needed. They are: ShowWindow(hwnd,nCmdShow); UpdateWindow(hwnd); The ShowWindow call determines how to display the window on the screen., whether it is normal, minimized or maximized. The first argument is the handle to the window just created by CreateWindow. The second argument nCmdShow is the value passed as a parameter to WinMain which determines how the window is to be internally displayed on the screen whether it is normal, minimized or maximized. This can be done by defining the second parameter to have one of the fields given below: SW_SHOWMAXIMIZED - To display maximized window. SW_SHOWMINIMIZED – To display minimized window. SW_SHOWNORMAL – To display normal window. SW_SHOWMINOACTIVE – To display the window in task bar. If the second argument to ShowWindow is SW_SHOWNORMAL the client area of the window is erased with background brush specified in the window class. The function call UpdateWindow causes the client area to be painted. Window Procedure The window procedure determines what the window displays in its client area and how the window responds to user input. A windows program can contain more than one window procedure. The window procedure can be defined like this: LRESULT CALLBACK wndproc(HWND hwnd, UINT message, WPARAM wp, LPARAM lp) These parameters are identical to the first four fields of the MSG structure. The first parameter hwnd is the handle to window receiving the message. If a program creates multiple windows based on the same window class and hence the same window procedure, hwnd identifies the particular window receiving the message. The second parameter is a number that identifies the message. The last two parameters are 32 bit message parameters that provide more information about the message. Handling Messages in Window Procedure After the UpdateWindow call the window is fully visible in the screen. The program must now make itself ready to read input from the user through mouse and keyboard. Message queue is maintained for each windows program currently running under windows. When an input event occurs windows translates the event in to a message that it places in the message queue. The messages can be retrieved from the message queue by executing the message loop: While(GetMessage(&msg,NULL,0,0)) { TranslateMessage(&msg); DispatchMessage(&msg); } The GetMessage call retrieves a message from a message queue and passes to window a pointer to a MSG structure named msg. The TranslateMessage call passes the msg structure back to windows for some keyboard translation. The DispatchMessage call passes the msg structure back to windows and the windows then sends the message to the appropriate window procedure for processing. Every message that window procedure receives is identified by a number. This is defined with the identifiers beginning with the prefix WM(Window Message) for each type of message. This can be done through switch and case statement. To process a message, the window procedure should return 0. All the messages not to be processed must be passed to a windows function named DefWindowProc. The value returned from DefWindowProc must be returned from the window procedure. In the sample windows program, wndproc chooses to process four messages: WM_CREATE, WM_LBUTTONDOWN, WM_RBUTTONDOWN and WM_DESTROY. The messages can be defined like this: switch(msg) { case WM_CREATE: [process WM_CREATE message] return 0; case WM_LBUTTONDOWN : [process WM_LBUTTONDOWN message] return 0; case WM_RBUTTONDOWN : [process WM_RBUTTONDOWN message] return 0; case WM_DESTROY : [process WM_DESTROY message] return 0; } return DefWindowProc(hwnd,msg,wp,lp); Windows Messages Windows messages are sent by Windows to your application. These messages begin with the WM_ prefix. The WM_* messages are sent by windows and are usually handled by windows and views, some of the commonly processed windows messages are: WM_COMMAND, WM_CHAR, WM_DESTROY and WM_QUIT message. WM_COMMAND Message This message notifies the program that the user has selected a menu item, a child window control or has used an accelerator key. An accelerator key is a key combination which is used to invoke the options of a menu and other controls. WM_CHAR Message This message is used to retrieve ASCII keyboard inputs such as letters, numbers and printable symbols. This message is generated when the user presses a character with an ASCII value on keyboard. WM_DESTROY Message This message notifies the program that a window is being destroyed after it is removed from the screen. The message is sent after the window image is removed from the screen. For example WM_DESTROY is sent to the parent window before a child window is destroyed. WM_QUIT Message This message indicates a request to terminate an application and is done when the application calls the PostQuitMessage function. It causes the GetMessage function to return a zero and drop out from message loop. The return statement exits from WinMain and terminates the program. Exercises 1 Differentiate Structured Programming and Object Oriented Programming. Define Object and Class. Explain the Windows Programming Model. What is DLL? What is API? Explain the GUI concepts. Write short notes on Event Driven Programming. What is Hungarian Notation? Write short notes on Windows String Functions. Explain the Message function calls used in Windows Programming. Write the Window Class structure, Message structure and explain them. Explain how to register the Window class. List out the options available to display the Window. Write short notes on Window Procedure. Write about the Windows Messages. Chapter – 2 Basics of GDI and DC

2.1Graphics Device Interface (GDI) The graphics device interface (GDI) provides functions and related structures that an application can use to generate graphical output for displays, printers, and other devices. Using GDI functions, you can draw lines, curves, closed figures, paths, text, and bitmap images. The color and style of the items you draw depends on the drawing objects — that is, pens, brushes, and fonts — that you create. You can use pens to draw lines and curves, brushes to fill the interiors of closed figures, and fonts to write text. Applications direct output to a specified device by creating a device context (DC) for the device. The device context is a GDI-managed structure containing information about the device, such as its operating modes and current selections. An application creates a DC by using device context functions. GDI returns a device context handle, which is used in subsequent calls to identify the device. For example, using the handle, an application can retrieve information about the capabilities of the device, such as its technology type (display, printer, or other device) and the dimensions and resolution of the display surface. Applications can direct output to a physical device, such as a display or printer, or to a "logical" device, such as a memory device or metafile. Logical devices give applications the means to store output in a form that is easy to send subsequently to a physical device. After an application records output in a metafile, it can play that metafile any number of times, sending the output to any number of physical devices. Applications use attribute functions to set the operating modes and current selections for the device. The operating modes include the text and background colors, the mixing mode (also called the binary raster operation) that specifies how colors in a pen or brush combine with colors already on the display surface, and the mapping mode that specifies how GDI maps the coordinates used by the application to the coordinate system of the device. The current selections identify which drawing objects are used when drawing output. Figure 2.1 shows the diagrammatic representation of GDI. Application obtains aGDI uses DC to locate DC “handle” from the correct window or Windows GDI anddevice driver and perform Passes it to all GDIrequested function. Functions Figure 2.1 Graphics Device Interface

2.2 Device Context Returns an integer that identifies the device-context of window if it has one, or nil otherwise. A device-context is a construct used in the Windows API to specify a set of parameters that are used when drawing on a window. A common graphics application does not normally need to deal with a window's device-context directly, but if you need to pass the window to a WINAPI function that calls for the window's device-context (or hDC), then you should pass the integer returned by this function for that argument. Every non-control window in common graphics (and every lisp-widget window) is automatically assigned a device-context, which it keeps until it is closed. Controls supplied by the OS (all controls except lisp-widgets), on the other hand, are not automatically given device-contexts in lisp since it is normally only the OS rather than lisp that draws on the control. If you do want to draw directly on a non-lisp control, then you must give the window of the control a device-context while drawing on it.

2.3 The WM_PAINT message The WM_PAINT message is a request to repaint the window. Every application is responsible for redrawing its window(s). This means that the application will have to keep track of the current state, so that it knows that to draw. In most cases, the WM_PAINT message will be triggerd from the outside. However, it is also possible to trigger WM_PAINT from inside the application. With the Invalidate() function, you can tell that the contents of a window are no longer valid so that it will need to be redrawn. With the InvalidateRect() function, you can specify that only part of the window content is invalid, so that only that part will be redrawn. In this way, you can prevent the flickering of the screen when redrawing. Because paint message have very low priority, you might want to send an immediate redraw request. You can do this with the UpdateWindow() function. 2.4 Getting a Device Context Handle There are two methods in getting a Device Context handle. The first method is by processing WM_PAINT messages. Two functions involved in this process are BeginPaint and EndPaint. These functions require the handle to window, which is passed to the window procedure as an argument and the address of a structure variable of type PAINTSTRUCT which has to be defined within the window procedure like so: PAINTSTRUCT ps; // where ps is the paint structure variable While processing a WM_PAINT message the window procedure first calls the function BeginPaint which causes the background of the invalid region to be erased and prepare the window for painting. This function fills the fields of the paint structure. The value returned by BeginPaint is a device context handle. This value can be stored in a variable commonly named as hdc, which has to be defined in window procedure like so: HDC hdc; // handle to DC HDC is a data type defined as a 32 bit integer. After the definition of HDC the program can use functions like TextOut. The call to EndPaint releases the device context handle. The processing of WM_PAINT message looks like this: case WM_PAINT: hdc = BeginPaint(hwnd,&ps); [ GDI functions] EndPaint (hwnd,&ps); return 0;

2.5 The Paint Structure(PAINTSTRUCT) The PAINTSTRUCT structure contains information for an application. This information can be used to paint the client area of a window owned by that application. typedef struct tagPAINTSTRUCT { // ps HDC hdc; BOOL fErase; RECT rcPaint; BOOL fRestore; BOOL fIncUpdate; BYTE rgbReserved[32]; } PAINTSTRUCT; hdc Handle to the display DC to be used for painting. fErase Specifies whether the background must be erased. This value is nonzero if the application should erase the background. The application is responsible for erasing the background if a window class is created without a background brush. For more information, see the description of the hbrBackground member of the WNDCLASS structure. rcPaint Specifies a RECT structure that specifies the upper left and lower right corners of the rectangle in which the painting is requested. fRestore Reserved; used internally by the system. fIncUpdate Reserved used internally by the system. rgbReserved Reserved used internally by the system. Windows erases the background using the brush specified in the hbrBackground field of the WNDCLASS structure that is used when registering the window class during WinMain initialization. Many windows programs specify a white brush for the windows background. This is indicated in the program with the statement like this: wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ; The second method to get a handle to DC of the client area of the windows js by calling GetDC to obtain the handle and ReleaseDC to release the handle. This can be done with the statement like this: hdc = GetDC (hwnd) ; [ GDI functions] ReleaseDC (hwnd,hdc); The functions GetDC and ReleaseDC should be called in pairs like BeginPaint and EndPaint. GetDC is used while processing message and ReleaseDC is used to exit the window procedure. Do not call GetDC in one message and ReleaseDC in another message. A function similar to GetDC is GetWindowDC. While GetDC returns a device context handle for writing on the client area of the window, GetWindowDC returns a device context handle for writing on the entire window.To use the function GetWindowDC your program has to process WM_NCPAINT (non client paint) message.

2.6 TextOut The TextOut function writes a character string at the specified location, using the currently selected font, background color, and text color. BOOL TextOut( HDC hdc, // handle to device context int x, // x-coordinate of starting position int y, // y-coordinate of starting position LPCTSTR lpString, // pointer to string int cbString // number of characters in string ); The first argument is the handle to the device context either the hdc value returned from GetDC or from BeginPaint during the processing of a WM_PAINT message. The second and third arguments x and y defines the starting point of the character string within the client area. The fourth argument lpsring is a pointer to character string and the last argument cbString indicates the number of characters in the string. Eg: TextOut (hdc,x,y,”LeftButtonPressed”,17); 2.7 System Font and Text Metrics The device context defines the font that windows uses to display the text when TextOut function is called. The default font is a system font which is used by windows for text strings in title bars, menus and dialog boxes. In earlier versions of windows the system font was a fixed pitch font in which all the characters had the same width. But now the system font is a “raster font” which means that the characters are defined as blocks of pixels. The size of a character is based on the size of the video display. To display multiple lines of text by using the TextOut function the dimensions of characters in the font should be known The successive lines of the text can be spaced based on the height of the characters and the columns of the text can be spaced on the average width of the characters. Just as a program can determine information about the sizes or metrics of user interface items by calling the GetSystemMetrics function, a program can determine font sizes by calling GetTextMetrics. GetTextMetrics requires a handle to a device context because it returns information about the font currently selected in the device context. The TEXTMETRIC structure has 20 fields but only the first seven fields are essential. typedef struct tagTEXTMETRIC { LONG tmHeight; LONG tmAscent; LONG tmDescent; LONG tmInternalLeading; LONG tmExternalLeading; LONG tmAveCharWidth; LONG tmMaxCharWidth; [ other structure fields] } To use the GetTextMetrics function a structure variable tm should be defined. TEXTMETRIC tm; To determine the text metrics you get a handle to a device context and call GetTextMetrics hdc = GetDC (hwnd) ; GetTextMetrics (hdc , &tm); ReleaseDC (hwnd, hdc); The most important value in TEXTMETRIC is the tmHeight which is the sum of tmAscent and tmDescent. These two values represent the maximum vertical extents of characters in the font above and below base line. The term leading refers to the space that the printer inserts between the lines of text. In the TEXTMETRIC structure internal leading is the space in which accent marks appear and the external leading is not included in the tmHeight value. It is an amount of space that the designer of the font suggests be added between successive rows of displayed text. The TEXTMETRIC structure contains two fields that describes the character width one is tmAveCharWidth field which is a weighted average of lowercase characters and another is tmMaxCharWidth which is the width of the widest character in the font.

2.8 System Metrics Display elements are the parts of a window and the display that appear on the system display screen. System metrics are the dimensions of various display elements. Typical system metrics include the window border width, icon height, and so on. System metrics also describe other aspects of the system, such as whether a mouse is installed, double-byte characters are supported, or a debugging version of the operating system is installed. The header file SYSMETS.H responds to GetSystemMetrics function call. The GetSystemMetrics function retrieves the specified system metric. If the function succeeds, the return value is the requested system metric or configuration setting. If the function fails, the return value is zero. System metrics may vary from display to display. Applications can also retrieve and set the color of window elements such as menus, scroll bars, and buttons by using the GetSysColor and SetSysColor functions, respectively. GetSystemMetrics The GetSystemMetrics function retrieves various system metrics (widths and heights of display elements) and system configuration settings. All dimensions retrieved by GetSystemMetrics are in pixels. int GetSystemMetrics ( int nIndex) The nIndex parameter can be one of the following values. Note that all SM_CX* values are widths and all SM_CY* values are heights. Table 2.8 (a) nIndex parameter values Value Meaning SM_ARRANGE Flags specifying how the system arranged minimized windows. For more information about minimized windows, see the following Remarks section. SM_CLEANBOOT Value that specifies how the system was started: 0 Normal boot1 Fail-safe boot2 Fail-safe with network bootFail-safe boot (also called SafeBoot, Safe Mode, or Clean Boot) bypasses the user's startup files. SM_CMONITORS Windows 98/Me, Windows 2000/XP: Number of display monitors on the desktop. SM_CMOUSEBUTTONS Number of buttons on mouse, or zero if no mouse is installed. SM_CXBORDER, SM_CYBORDER Width and height of a window border, in pixels. This is equivalent to the SM_CXEDGE value for windows with the 3-D look. SM_CXCURSOR, SM_CYCURSOR Width and height of a cursor, in pixels. The system cannot create cursors of other sizes. SM_CXDLGFRAME, SM_CYDLGFRAME Same as SM_CXFIXEDFRAME and SM_CYFIXEDFRAME. SM_CXDOUBLECLK, SM_CYDOUBLECLK Width and height of the rectangle around the location of a first click in a double-click sequence, in pixels. The second click must occur within this rectangle for the system to consider the two clicks a double-click. (The two clicks must also occur within a specified time.) To set the width and height of the double-click rectangle, call SystemParametersInfo with the SPI_SETDOUBLECLKHEIGHT and SPI_SETDOUBLECLKWIDTH flags. SM_CXDRAG, SM_CYDRAG Width and height of a rectangle centered on a drag point to allow for limited movement of the mouse pointer before a drag operation begins. These values are in pixels. It allows the user to click and release the mouse button easily without unintentionally starting a drag operation. SM_CXEDGE, SM_CYEDGE Dimensions of a 3-D border, in pixels. These are the 3-D counterparts of SM_CXBORDER and SM_CYBORDER. SM_CXFIXEDFRAME, SM_CYFIXEDFRAME Thickness of the frame around the perimeter of a window that has a caption but is not sizable, in pixels. SM_CXFIXEDFRAME is the height of the horizontal border and SM_CYFIXEDFRAME is the width of the vertical border. Same as SM_CXDLGFRAME and SM_CYDLGFRAME. SM_CXFOCUSBORDER, SM_CYFOCUSBORDER Windows XP: Width of the left and right edges and the height of the top and bottom edges of the focus rectangle drawn by DrawFocusRec. These values are in pixels. SM_CXFRAME, SM_CYFRAME Same as SM_CXSIZEFRAME and SM_CYSIZEFRAME. SM_CXFULLSCREEN, SM_CYFULLSCREEN Width and height of the client area for a full-screen window on the primary display monitor, in pixels. To get the coordinates of the portion of the screen not obscured by the system taskbar or by application desktop toolbars, call the SystemParametersInfo function with the SPI_GETWORKAREA value. SM_CXHSCROLL, SM_CYHSCROLL Width of the arrow bitmap on a horizontal scroll bar, in pixels; and height of a horizontal scroll bar, in pixels. SM_CXHTHUMB Width of the thumb box in a horizontal scroll bar, in pixels. SM_CXICON, SM_CYICON Default width and height of an icon, in pixels. The LoadIcon function can load only icons of these dimensions. SM_CXICONSPACING, SM_CYICONSPACING Dimensions of a grid cell for items in large icon view, in pixels. Each item fits into a rectangle of this size when arranged. These values are always greater than or equal to SM_CXICON and SM_CYICON. SM_CXMAXIMIZED, SM_CYMAXIMIZED Default dimensions, in pixels, of a maximized top-level window on the primary display monitor. SM_CXMAXTRACK, SM_CYMAXTRACK Default maximum dimensions of a window that has a caption and sizing borders, in pixels. This metric refers to the entire desktop. The user cannot drag the window frame to a size larger than these dimensions. A window can override these values by processing the WM_GETMINMAXINFO message. SM_CXMENUCHECK, SM_CYMENUCHECK Dimensions of the default menu check-mark bitmap, in pixels. SM_CXMENUSIZE, SM_CYMENUSIZE Dimensions of menu bar buttons, such as the child window close button used in the multiple document interface, in pixels. SM_CXMIN, SM_CYMIN Minimum width and height of a window, in pixels. SM_CXMINIMIZED, SM_CYMINIMIZED Dimensions of a minimized window, in pixels. SM_CXMINSPACING SM_CYMINSPACING Dimensions of a grid cell for a minimized window, in pixels. Each minimized window fits into a rectangle this size when arranged. These values are always greater than or equal to SM_CXMINIMIZED and SM_CYMINIMIZED. SM_CXMINTRACK, SM_CYMINTRACK Minimum tracking width and height of a window, in pixels. The user cannot drag the window frame to a size smaller than these dimensions. A window can override these values by processing the WM_GETMINMAXINFO message. SM_CXSCREEN, SM_CYSCREEN Width and height of the screen of the primary display monitor, in pixels. These are the same values obtained by calling GetDeviceCaps (hdcPrimaryMonitor, HORZRES/VERTRES). SM_CXSIZE, SM_CYSIZE Width and height of a button in a window's caption or title bar, in pixels. SM_CXSIZEFRAME, SM_CYSIZEFRAME Thickness of the sizing border around the perimeter of a window that can be resized, in pixels. SM_CXSIZEFRAME is the width of the horizontal border, and SM_CYSIZEFRAME is the height of the vertical border. Same as SM_CXFRAME and SM_CYFRAME. SM_CXSMICON, SM_CYSMICON Recommended dimensions of a small icon, in pixels. Small icons typically appear in window captions and in small icon view. SM_CXSMSIZE SM_CYSMSIZE Dimensions of small caption buttons, in pixels. SM_CXVIRTUALSCREEN, SM_CYVIRTUALSCREEN Windows 98/Me, Windows 2000/XP: Width and height of the virtual screen, in pixels. The virtual screen is the bounding rectangle of all display monitors. The SM_XVIRTUALSCREEN, SM_YVIRTUALSCREEN metrics are the coordinates of the top-left corner of the virtual screen. SM_CXVSCROLL, SM_CYVSCROLL Width of a vertical scroll bar, in pixels; and height of the arrow bitmap on a vertical scroll bar, in pixels. SM_CYCAPTION Height of a caption area, in pixels. SM_CYMENU Height of a single-line menu bar, in pixels. SM_CYSMCAPTION Height of a small caption, in pixels. SM_CYVTHUMB Height of the thumb box in a vertical scroll bar, in pixels. SM_DBCSENABLED TRUE or nonzero if the double-byte character-set (DBCS) version of User.exe is installed; FALSE or zero otherwise. SM_DEBUG TRUE or nonzero if the debug version of User.exe is installed; FALSE or zero otherwise. SM_IMMENABLED Windows 2000/XP: TRUE or nonzero if Input Method Manager/Input Method Editor features are enabled; FALSE or zero otherwise. SM_IMMENABLED indicates whether the system is ready to use a Unicode-based IME on a Unicode application. To ensure that a language-dependent IME works, check SM_DBCSENABLED and the system ANSI code page. Otherwise the ANSI-to-Unicode conversion may not be performed correctly, or some components like fonts or registry setting may not be present. SM_MENUDROPALIGNMENT TRUE or nonzero if drop-down menus are right-aligned with the corresponding menu-bar item; FALSE or zero if the menus are left-aligned. SM_MIDEASTENABLED TRUE if the system is enabled for Hebrew and Arabic languages. SM_MOUSEPRESENT TRUE or nonzero if a mouse is installed; FALSE or zero otherwise. SM_MOUSEWHEELPRESENT Windows NT 4.0 and later, Windows 98/Me: TRUE or nonzero if a mouse with a wheel is installed; FALSE or zero otherwise. SM_NETWORK Least significant bit is set if a network is present; otherwise, it is cleared. The other bits are reserved for future use. SM_PENWINDOWS TRUE or nonzero if the Microsoft Windows for Pen computing extensions are installed; FALSE or zero otherwise. SM_REMOTECONTROL Windows XP: This system metric is used in a Terminal Services environment. Its value is TRUE if the current session is remotely controlled; FALSE otherwise. SM_REMOTESESSION Windows NT 4.0: This system metric is used in a Terminal Services environment. If the calling process is associated with a Terminal Services client session, the return value is TRUE or nonzero. If the calling process is associated with the Terminal Server console session, the return value is zero. SM_SECURE TRUE if security is present; FALSE otherwise. SM_SAMEDISPLAYFORMAT Windows 98/Me, Windows 2000/XP: TRUE if all the display monitors have the same color format, FALSE otherwise. Note that two displays can have the same bit depth, but different color formats. For example, the red, green, and blue pixels can be encoded with different numbers of bits, or those bits can be located in different places in a pixel's color value. SM_SHOWSOUNDS TRUE or nonzero if the user requires an application to present information visually in situations where it would otherwise present the information only in audible form; FALSE, or zero, otherwise. SM_SHUTTINGDOWN Windows XP: TRUE if the current session is shutting down; FALSE otherwise. SM_SLOWMACHINE TRUE if the computer has a low-end (slow) processor; FALSE otherwise. SM_SWAPBUTTON TRUE or nonzero if the meanings of the left and right mouse buttons are swapped; FALSE or zero otherwise. SM_XVIRTUALSCREEN, SM_YVIRTUALSCREEN Windows 98/Me, Windows 2000/XP: Coordinates for the left side and the top of the virtual screen. The virtual screen is the bounding rectangle of all display monitors. The SM_CXVIRTUALSCREEN, SM_CYVIRTUALSCREEN metrics are the width and height of the virtual screen.

GetSystemMetrics(SM_CMONITORS) counts only display monitors. The SM_ARRANGE setting specifies how the system arranges minimized windows, and consists of a starting position and a direction. The starting position can be one of the following values. Table 2.8 (b) Starting position values and direction of screen Value Meaning ARW_BOTTOMLEFT Start at the lower-left corner of the screen (default position). ARW_BOTTOMRIGHT Start at the lower-right corner of the screen. Equivalent to ARW_STARTRIGHT. ARW_HIDE Hide minimized windows by moving them off the visible area of the screen. ARW_TOPLEFT Start at the upper-left corner of the screen. Equivalent to ARV_STARTTOP. ARW_TOPRIGHT Start at the upper-right corner of the screen. Equivalent to ARW_STARTTOP | SRW_STARTRIGHT.

Table 2.8 (c) Lists the values of the direction in which to arrange the window. Value Meaning ARW_DOWN Arrange vertically, top to bottom. ARW_LEFT Arrange horizontally, left to right. ARW_RIGHT Arrange horizontally, right to left. ARW_UP Arrange vertically, bottom to top.

GetSysColor The GetSysColor function retrieves the current color of the specified display element. Display elements are the parts of a window and the display that appear on the system display screen. The function returns the red, green, blue (RGB) color value of the given element. The parameter nIndex is used to retrieve the color and can have one of the values listed in the Table 2.8(d). If the nIndex parameter is out of range, the return value is zero. Because zero is also a valid RGB value, you cannot use GetSysColor to determine whether a system color is supported by the current platform. Instead, use the GetSysColorBrush function, which returns NULL if the color is not supported. DWORD GetSysColor ( int nIndex); Table 2.8 (d) Color values for GetSysColor function call Value Meaning COLOR_3DDKSHADOW Dark shadow for three-dimensional display elements. COLOR_3DFACE, COLOR_BTNFACE Face color for three-dimensional display elements and for dialog box backgrounds. COLOR_3DHILIGHT, COLOR_3DHIGHLIGHT, COLOR_BTNHILIGHT, COLOR_BTNHIGHLIGHT Highlight color for three-dimensional display elements (for edges facing the light source.) COLOR_3DLIGHT Light color for three-dimensional display elements (for edges facing the light source.) COLOR_3DSHADOW, COLOR_BTNSHADOW Shadow color for three-dimensional display elements (for edges facing away from the light source). COLOR_ACTIVEBORDER Active window border. COLOR_ACTIVECAPTION Active window title bar. Windows 98/Me, Windows 2000/XP: Specifies the left side color in the color gradient of an active window's title bar if the gradient effect is enabled. COLOR_APPWORKSPACE Background color of multiple document interface (MDI) applications. COLOR_BACKGROUND, COLOR_DESKTOP Desktop. COLOR_BTNTEXT Text on push buttons. COLOR_CAPTIONTEXT Text in caption, size box, and scroll bar arrow box. COLOR_GRADIENTACTIVECAPTION Windows 98/Me, Windows 2000/XP: Right side color in the color gradient of an active window's title bar. COLOR_ACTIVECAPTION specifies the left side color. Use SPI_GETGRADIENTCAPTIONS with the SystemParametersInfo function to determine whether the gradient effect is enabled. COLOR_GRADIENTINACTIVECAPTION Windows 98/Me, Windows 2000/XP: Right side color in the color gradient of an inactive window's title bar. COLOR_INACTIVECAPTION specifies the left side color. COLOR_GRAYTEXT Grayed (disabled) text. This color is set to 0 if the current display driver does not support a solid gray color. COLOR_HIGHLIGHT Item(s) selected in a control. COLOR_HIGHLIGHTTEXT Text of item(s) selected in a control. COLOR_HOTLIGHT Windows 98/Me, Windows 2000/XP: Color for a hot-tracked item. Single clicking a hot-tracked item executes the item. COLOR_INACTIVEBORDER Inactive window border. COLOR_INACTIVECAPTION Inactive window caption. Windows 98/Me, Windows 2000/XP: Specifies the left side color in the color gradient of an inactive window's title bar if the gradient effect is enabled. COLOR_INACTIVECAPTIONTEXT Color of text in an inactive caption. COLOR_INFOBK Background color for tooltip controls. COLOR_INFOTEXT Text color for tooltip controls. COLOR_MENU Menu background. COLOR_MENUHILIGHT Windows XP: The color used to highlight menu items when the menu appears as a flat menu. The highlighted menu item is outlined with COLOR_HIGHLIGHT. COLOR_MENUBAR Windows XP: The background color for the menu bar when menus appear as flat menus. However, COLOR_MENU continues to specify the background color of the menu popup. COLOR_MENUTEXT Text in menus. COLOR_SCROLLBAR Scroll bar gray area. COLOR_WINDOW Window background. COLOR_WINDOWFRAME Window frame. COLOR_WINDOWTEXT Text in windows.

SetSysColors The SetSysColors function sets the colors for one or more display elements. Display elements are the various parts of a window and the display that appear on the system display screen. BOOL SetSysColors ( int cElements , const INT* lpaElements, const COLOREF* lpargbvalues); The first parameter cElements indicates the number of display elements in the lpaElements array. The second parameter is a pointer to an array of integers that specify the display elements to be changed. The third parameter is a pointer to an array of COLORREF values that contain the new red, green, blue (RGB) color values for the display elements in the array pointed to by the lpaElements parameter. If the function succeeds, the return value is a nonzero value. If the function fails, the return value is zero. The SetSysColors function sends a WM_SYSCOLORCHANGE message to all windows to inform them of the change in color. It also directs the system to repaint the affected portions of all currently visible windows. The SetSysColors function changes the current session only. The new colors are not saved when the system terminates 2.9 Client area The client area is the portion of a window where the application displays output, such as text or graphics also called a client rectangle. Knowing the size of window’s client area the user can display the text within the client area if the client area is not large enough to hold everything. The dimensions of the client area is available from the GetSystemMetrics call (SM_CXFULLSCREEN and CY_FULLSCREEN). The GetClientRect function can be used to determine the dimensions of the client area. A better method in determining the size of the client area is to process the WM_SIZE message whenever there is a change in window size. The lparam variable passed to the window procedure contains the width of the client area in the low word and the height in the high word. For this two static variable has to be defined in the window procedure as follows: static int cxClient, cyClient ; These two variables are set static because they are set while processing one message and used while processing another message. The WM_SIZE message can be defined as: case WM_SIZE : cxClient = LOWORD (lparam); cyClient = HIWORD (lparam); return 0; The number of full lines of text displayable within the client area can be calculated using the formula : cyClient / cyChar This is zero if the height of the client area is too small to display a full character. Similarly the approximate number of lowercase characters that can be displayed horizontally within the client area is equal to cxClient / cxChar 2.10 GDI Primitives The types of graphics displayed on the screen can themselves be divided in to several categories, which are called primitives. These are: Bitmaps: A bitmap is an array of bits that represent the attributes of the individual pixels in an image (1 bit per pixel in a black-and-white display, multiple bits per pixel in a color or grayscale display). This is used to display complex images on the monitor or printer. Bitmaps are also used to display small images such as icons, mouse cursors and buttons that appear in the toolbar. Text: A Win32 macro that exists so that code can be compiled either as American National Standards Institute (ANSI) text or as Unicode. For Windows, which supports only Unicode, the macro forces the compiler to convert ANSI characters to Unicode characters. For example, passing the ANSI string "Hello Windows '' through the TEXT macro converts all characters in the string to 16-bit wide characters. Lines and Curves: A line is a set of highlighted pixels on a video display (or a series of dots on a printed page) that is defined by two points: a starting point and an ending point. GDI supports straight lines, rectangles, ellipses, arcs that are partial curves on the ellipse and Bezier splines. Different type of curve can be drawn as a polyline which is a series of very short lines that define curve. Furthermore GDI draws lines using pen selected in the device context. Filled areas: To sketch or fill in areas of a drawing with the color and pattern, brush is the tool used. Paint programs that offer a variety of brush shapes can produce brushstrokes of varying width and, in some cases, shadowing or calligraphic effects. A brush can be solid color, a pattern (which can be a series of horizontal, vertical or diagonal hatch marks) or a bitmapped image that is repeated vertically or horizontally within the area. 2.11 Drawing Point, Line and Curve Windows can draw straight lines, curved lines and Bezier splines through the following functions: SetPixelDraws a single point MoveToSets the current position in preparation for drawing LineToDraws a line from the current position to the end of the line PolylineConnects a set of points with line segments PolylineToConnects a set of points with line segments beginning with the current position and moves the current position to the end of the polyline ArcDraws an arc ArcTo draws an arc and moves the current position to the end of the arc PolyBezierDraws one or more Bezier splines PolyBezierToDraws one or more Bezier splines and moves the current position to the end of the final spline PolyDrawDraws a series of line segments and Bezier splines through a set points and moves the current position to the end of the final line segment or spline The functions that draw lines but that also fill the enclosed area within the figure they draw are as follows: ChordDraws a closed figure bounded by the intersection of an ellipse and a line EllipseDraws a circle or an ellipse PieDraws a pie shaped wedge PolygonConnects a set of points to form a polygon RectangleDraws a rectangle with square corners RoundRectDraws a rectangle with rounded corners Default line color is black and fill color is white. To draw straight line you must call two functions. The first function specifies the point at which the line begins and the second function specifies the end point of the line: In Windows 3.x, the x- and y-coordinates are 16 bits each and are packed into the 32-bit (DWORD) function return value, the largest valid size. In Win32, the coordinates are 32 bits each, totaling 64 bits, and are thus too large to fit into a single return value. Each Windows 3.x function is replaced by a Win32 function with the same name, but with an Ex suffix added. The Ex functions pass the x- and y-coordinates using an additional parameter instead of a return value. Both Win32 and Windows 3.x support these new functions. Each Ex function includes an additional parameter that points to a location to receive data. After the function call, this data provides the same information as the corresponding function’s return value. If you do not need this information, you can pass NULL to this parameter. Under Windows 3.x, a call to the MoveTo function can be written as follows: MoveTo( hDC, x, y ); In the portable version supported by both versions of Windows, the call to MoveTo is rewritten as follows. Note that the information returned by MoveToEx is ignored: MoveToEx ( hDC, x, y, NULL ); As a general rule, pass NULL as the last parameter unless you need to use the x- and y-coordinates returned by the Windows 3.x version. 2.12 Using Stock Pens The pen determines the lines color, width and style which can be solid, dotted or dashed. The default pen is BLACK_PEN which draws a solid black line. Apart from BLACK_PEN windows provides other two pens such as WHITE_PEN and NULL_PEN. NULL_PEN is the pen that doesn’t draw. You can also create your own customized pens. In windows program pen can be referred using a handle. The type HPEN is a handle to pen. You can define a variable for using this type definition: HPEN hpen; The GetStockObject function call is used to obtain the handle to one of the stock pens. For example if you want to use the stock pen called BLACK_PEN you can define the handle like this: hpen = GetStockObject (BLACK_PEN) To select that pen in to Device Context use the definition: SelectObject (hdc,hpen); Now the BLACK_PEN is the current pen. After this call any line you draw will use the BLACK_PEN until you select another pen or release the device context handle. Instead of defining hpen variable explicitly you can combine the StockObject and SelectObject call in to one statement: SelectObject (hdc, GetStockObject (BLACK_PEN)); If you want to use the WHITE_PEN then you can get that handle to that stock object and select in to the device context in one statement: SelectObject (hdc , GetStockObject (WHITE_PEN)); 2.13 Creating, Selecting and Deleting Pens Apart from solid BLACK_PEN and WHITE_PEN you can create your own pens using CreatePen function call. You can select the pen in to the device context by calling the SelectObject and then draw lines using new pen. After releasing the device context you can delete the pen by calling DeleteObject. After doing so the pen is no longer valid. The syntax for CreatePen looks like this: hpen = CreatePen ( iPenStyle , iWidth, crColor); The iPenStyle argument determines whether the pen draws a solid line or line with dash and dots. The argument may be any one of the pen styles listed in figure 2.13. PS_SOLID____________________________ PS_DASH------------------------------------------ PS_DOT…………………………………… PS_DASHDOT-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-. PS_NULL PS_INSIDEFRAME____________________ Figure 2.13 Pen Styles The iWidth argument is the width of the pen. If the value of iWidth argument is zero then Windows can use one pixel for the pen width. The stock pens are one pixel wide. The crColor argument specifies the color of the pen. The PS_INSIDEFRAME is the only pen style which uses dithered color only when the width is greater than 1. For example if your program uses three pens , a black pen of width 3, a red pen of width1 and a black dotted pen. First you have to define static variables for storing the handles to these pens: Static HPEN hpen1 , hpen2 , hpen3; During processing of WM_CREATE you can create the three pens: hpen1 = CreatePen (PS_SOLID,3,0); hpen2 = CreatePen (PS_SOLID,1,RGB(255,0,0)); hpen3 = CreatePen(PS_DOT,0,0); During processing of WM_PAINT message you can select one of these pens in to the device context and draw with it: SelectObject (hdc,hpen2) [ line drawing functions ] SelectObject(hdc,hpen1); [line drawing functions] You can delete the pens by processing WM_DESTROY message: DeleteObject(hpen1); DeleteObject(hpen2); DeleteObject(hpen3); You can also combine the CreatePen and SelectObject calls in the same statement: SelectObject (hdc,CreatePen(PS_DASH,0,RGB(255,0,0)); When you draw lines you will be using red dashed pens by executing the above command. Furthermore the coloring of the gaps between the dashes and the dots needs two attributes such as the background mode and the background color. The default background mode is opaque which uses the default background color white. You can also change the background mode to be transparent which prevents the windows from filling in the gaps by using the command: SetBkMode (hdc,TRANSPARENT) ; The current background mode can be obtained by calling GetBkMode. Similarly the background color can be changed using the command: SetBkColor (hdc,crColor); The current background color can be obtained by calling the GetBkColor function. Example program using pen styles in drawing shapes Create an application named GraphicsDemo by selecting the project type Win 32 Application in the appwizard and click OK. Now an empty project without using MFC classes is created. Click File->New and then select the option C++ Source File and give a name to the .cpp implementation file (here the name is Graph.cpp). Enter the code given below in the implementation file (Graph.cpp). int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {WNDCLASSEX wc; HWND hwnd; MSG Msg; wc.cbSize = sizeof(WNDCLASSEX); wc.style = 0; wc.lpfnWndProc = WndProc; wc.cbClsExtra = 0; wc.cbWndExtra = 0; wc.hInstance = hInstance; wc.hIcon = LoadIcon(NULL,IDI_APPLICATION); wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1); wc.lpszMenuName = NULL; wc.lpszClassName = g_szClassName; wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION); if(!RegisterClassEx(&wc)) {MessageBox(NULL, "Window Registration Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK); return 0; } hwnd = CreateWindowEx( WS_EX_CLIENTEDGE, g_szClassName, "Graphics Demo Program", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 240, 120, NULL, NULL, hInstance, NULL); if(hwnd == NULL) {MessageBox(NULL, "Window Creation Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK); return 0; } ShowWindow(hwnd, nCmdShow); UpdateWindow(hwnd); while(GetMessage(&Msg, NULL, 0, 0) > 0) {TranslateMessage(&Msg); DispatchMessage(&Msg); } return Msg.wParam; } In this application Pen style is used to draw shapes. Compile, Build and Execute the program. You will get different shapes in the output window as shown in figure 2.13. Figure 2.13 Running Instance of Graphics Demo Program 2.14 Filling Enclosed Areas Windows can draw the outline of the figure (Rectangle, Ellipse, RoundRect, Chord, Polygon etc.,) with the current pen selected as well as with the current background mode and background color. The figure is filled with the current brush selected. The default brush is the WHITE_BRUSH. Apart from the default brush windows uses five more brushes such as: GRAY_BRUSH, LTGRAY_BRUSH, DKGRAY_BRUSH, BLACK_BRUSH and HOLLOW_BRUSH or NULL_BRUSH. Any one of the brush can be selected as the same way as you select the stock pen. First you have to define a variable for the brush handle: HBRUSH hbrush; Where HBRUSH is a handle to the brush. You can get any one of the brush, for example the BLACK_BRUSH by calling the GetStockObject: hbrush = GetStockObject ( BLACK_BRUSH); You can then select in to the device context by calling the SelectObject as: SelectObject(hdc,hbrush); Now when you draw a Rectangle the interior will be black. To draw the figure without border NULL_PEN can be used as: SelectObject (hdc,GetStockObject (NULL_PEN)); To draw the outline of the figure without filling the interior NULL_BRUSH can be used as: SelectObject(hdc,GetStockObject(NULL_BRUSH)); The interiors of the figures can be filled with the current brush selected in the device context. You can select the brush in to the device context with the function SelectObject. The function to create a logical brush is: hbrush = CreateSolidBrush (crColor) ; You can also create a brush with hatch marks made up of horizontal, vertical or diagonal lines. The function for creating the hatch brush is: hbrush = CreateHatchBrush (hatchstyle,crColor) The hatchstyle argument specifies one of the hatch styles shown below. HS_HORIZONTAL: Horizontal Hatch HS_VERTICAL: Vertical Hatch HS_FDIAGONAL: Upward hatch (left to right) at 45 degrees HS_BDIAGONAL: Downward hatch (left to right) at 45 degrees HS_CROSS: Horizontal and vertical crosshatch HS_DIAGCROSS: Crosshatch at 45 degrees The crColor argument specifies the color of the hatch lines. Once you have a handle to the brush you can select the brush in to the device context using SelectObject: SelectObject(hdc,hbrush); You can later delete a created brush with DeleteObject function: DeleteObject(hbrush); Example Program for filling the area of shapes Create an application named FillArea by selecting the project type Win 32 Application in the appwizard and click OK. Now an empty project without using MFC classes is created. Click File->New and then select the option C++ Source File and give a name to the .cpp implementation file (here the name is Filling.cpp). Enter the code given below in the implementation file (Filling.cpp). #include <windows.h> const char g_szClassName[] = "myWindowClass"; LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {HDC hdc; PAINTSTRUCT ps; POINT parray[10]={10,70,50,70,50,10,90,10,90,50,30,50,30,90,70,90,70,30,10,30}; switch(msg) { case WM_PAINT: hdc=BeginPaint(hwnd,&ps); SelectObject(hdc,GetStockObject(GRAY_BRUSH)); SetPolyFillMode(hdc,ALTERNATE); Polygon(hdc,parray,10);//first parameter handle to device context,second CONST POINT //*lpPoints pointer to polygon's vertices, third count of polygon's vertices EndPaint(hwnd,&ps); return 0; case WM_CLOSE: DestroyWindow(hwnd); break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefWindowProc(hwnd, msg, wParam, lParam); } return 0; } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { WNDCLASSEX wc; HWND hwnd; MSG Msg; wc.cbSize = sizeof(WNDCLASSEX); wc.style = 0; wc.lpfnWndProc = WndProc; wc.cbClsExtra = 0; wc.cbWndExtra = 0; wc.hInstance = hInstance; wc.hIcon = LoadIcon(NULL,IDI_APPLICATION); wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1); wc.lpszMenuName = NULL; wc.lpszClassName = g_szClassName; wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION); if(!RegisterClassEx(&wc)) {MessageBox(NULL, "Window Registration Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK); return 0; } hwnd = CreateWindowEx( WS_EX_CLIENTEDGE, g_szClassName, "Filled Area", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 240, 120, NULL, NULL, hInstance, NULL); if(hwnd == NULL) {MessageBox(NULL, "Window Creation Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK); return 0; } ShowWindow(hwnd, nCmdShow); UpdateWindow(hwnd); while(GetMessage(&Msg, NULL, 0, 0) > 0) {TranslateMessage(&Msg); DispatchMessage(&Msg); } return Msg.wParam; } In this application brush style is used to fill the area of polygon. Compile, Build and Execute the program you will get the output as shown in figure 2.14. Figure 2.14 Running Instance of FillArea Program 2.15 Keyboard Messages The message that an application receives from windows about the keyboard events shows the difference between keystrokes and characters. Keyboard is a collection of keys. Pressing the key and releasing the key is called as a keystroke. For keystroke combinations that result in displayable characters windows sends both keystroke and character messages. But some keys such as shift, function keys, cursor movement keys do not generate characters. For these keys windows generates only keystroke messages. There are two types of keystrokes such as System keystroke and Nonsystem keystroke. The “SYS” in WM_SYSKEYDOWN and WM_SYSKEYUP stands for “system” and refers to system keystrokes that are more important to windows than to windows applications. Nonsystem keystroke messages refer to messages such as WM_KEYDOWN and WM_KEYUP. For all the four keystroke messages (WM_KEYUP, WM_KEYDOWN, WM_SYSKEYUP, WM_SYSKEYDOWN) wparam is a virtual key code that identifies the key being pressed or released and lparam contains other data pertaining to keystroke. Virtual Key Codes The virtual key code identifies the key being pressed or released. The virtual key code is stored in the wparam parameter . The following table shows the symbolic constant names, hexadecimal values, and keyboard equivalents for the virtual-key codes used by the Windows operating system. The codes are listed in numeric order in Table 2.15. Table 2.15 Virtual Key Codes Symbolic constant Value (Hex) Mouse or keyboard equivalent VK_LBUTTON 01 Left mouse button VK_RBUTTON 02 Right mouse button VK_CANCEL 03 Control-break processing VK_MBUTTON 04 Middle mouse button (three-button mouse) — 05–07 Undefined VK_BACK 08 BACKSPACE key VK_TAB 09 TAB key — 0A–0B Undefined VK_CLEAR 0C CLEAR key VK_RETURN 0D ENTER key — 0E–0F Undefined VK_SHIFT 10 SHIFT key VK_CONTROL 11 CTRL key VK_MENU 12 ALT key VK_PAUSE 13 PAUSE key VK_CAPITAL 14 CAPS LOCK key — 15–19 Reserved for Kanji systems — 1A Undefined VK_ESCAPE 1B ESC key — 1C–1F Reserved for Kanji systems VK_SPACE 20 SPACEBAR VK_PRIOR 21 PAGE UP key VK_NEXT 22 PAGE DOWN key VK_END 23 END key VK_HOME 24 HOME key VK_LEFT 25 LEFT ARROW key VK_UP 26 UP ARROW key VK_RIGHT 27 RIGHT ARROW key VK_DOWN 28 DOWN ARROW key VK_SELECT 29 SELECT key 2A OEM specific VK_EXECUTE 2B EXECUTE key VK_SNAPSHOT 2C PRINT SCREEN key for Windows 3.0 and later VK_INSERT 2D INS key VK_DELETE 2E DEL key VK_HELP 2F HELP key VK_0 30 0 key VK_1 31 1 key VK_2 32 2 key VK_3 33 3 key VK_4 34 4 key VK_5 35 5 key VK_6 36 6 key VK_7 37 7 key VK_8 38 8 key VK_9 39 9 key 3A–40 Undefined VK_A 41 A key VK_B 42 B key VK_C 43 C key VK_D 44 D key VK_E 45 E key VK_F 46 F key VK_G 47 G key VK_H 48 H key VK_I 49 I key VK_J 4A J key VK_K 4B K key VK_L 4C L key VK_M 4D M key VK_N 4E N key VK_O 4F O key VK_P 50 P key VK_Q 51 Q key VK_R 52 R key VK_S 53 S key VK_T 54 T key VK_U 55 U key VK_V 56 V key VK_W 57 W key VK_X 58 X key VK_Y 59 Y key VK_Z 5A Z key VK_LWIN 5B Left Windows key (Microsoft Natural Keyboard) VK_RWIN 5C Right Windows key (Microsoft Natural Keyboard) VK_APPS 5D Applications key (Microsoft Natural Keyboard) 5E–5F Undefined VK_NUMPAD0 60 Numeric keypad 0 key VK_NUMPAD1 61 Numeric keypad 1 key VK_NUMPAD2 62 Numeric keypad 2 key VK_NUMPAD3 63 Numeric keypad 3 key VK_NUMPAD4 64 Numeric keypad 4 key VK_NUMPAD5 65 Numeric keypad 5 key VK_NUMPAD6 66 Numeric keypad 6 key VK_NUMPAD7 67 Numeric keypad 7 key VK_NUMPAD8 68 Numeric keypad 8 key VK_NUMPAD9 69 Numeric keypad 9 key VK_MULTIPLY 6A Multiply key VK_ADD 6B Add key VK_SEPARATOR 6C Separator key VK_SUBTRACT 6D Subtract key VK_DECIMAL 6E Decimal key VK_DIVIDE 6F Divide key VK_F1 70 F1 key VK_F2 71 F2 key VK_F3 72 F3 key VK_F4 73 F4 key VK_F5 74 F5 key VK_F6 75 F6 key VK_F7 76 F7 key VK_F8 77 F8 key VK_F9 78 F9 key VK_F10 79 F10 key VK_F11 7A F11 key VK_F12 7B F12 key VK_F13 7C F13 key VK_F14 7D F14 key VK_F15 7E F15 key VK_F16 7F F16 key VK_F17 80H F17 key VK_F18 81H F18 key VK_F19 82H F19 key VK_F20 83H F20 key VK_F21 84H F21 key VK_F22 85H F22 key VK_F23 86H F23 key VK_F24 87H F24 key 88–8F Unassigned VK_NUMLOCK 90 NUM LOCK key VK_SCROLL 91 SCROLL LOCK key

2.16 Mouse Messages Windows sends keyboard messages only to the window that has the input focus. But mouse messages are different, a window procedure receives mouse messages whenever the mouse passes over the window or clicked within the window. There are two types of mouse messages such as client area mouse messages and Non client area mouse messages. The client area is the portion of a window where the application displays output, such as text or graphics. Also called a client rectangle. The parts of a window that are not a part of the client area. A window’s nonclient area consists of the border, menu bar, title bar, and scroll bar. Table 2.16 (a) Client area mouse messages Button Pressed Released Pressed (second click) LeftWM_LBUTTONDOWN WM_LBUTTONUP WM_LBUTTONDBLCLK MiddleWM_MBUTTONDOWN WM_MBUTTONUP WM_MBUTTONDBLCLK RightWM_RBUTTONDOWN WM_RBUTTONUP WM_RBUTTONDBLCLK Table 2.16 (b) Non Client area mouse messages Button Pressed Released Pressed (second click) LeftWM_NCLBUTTONDOWN WM_NCLBUTTONUP WM_NCLBUTTONDBLCLK Middle WM_NCMBUTTONDOWN WM_NCMBUTTONUP WM_NCMBUTTONDBLCLK RightWM_NCRBUTTONDOWN WM_NCRBUTTONUP WM_NCRBUTTONDBLCLK Example program for mouse and keyboard messages Create an application named MouseKeyMsg by selecting the project type Win 32 Application in the appwizard and click OK. Now an empty project without using MFC classes is created. Click File->New and then select the option C++ Source File and give a name to the .cpp implementation file (here the name is Mouse.cpp). Enter the code given below in the implementation file (Mouse.cpp). #include <windows.h> const char g_szClassName[] = "myWindowClass"; LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) { switch(msg) {case WM_LBUTTONDOWN: MessageBox(GetFocus(),"You have pressed left mouse button","About",MB_OK|MB_ICONINFORMATION); break; case WM_RBUTTONDOWN: MessageBox(GetFocus(),"You have pressed right mouse button","About",MB_OK|MB_ICONINFORMATION); break; case WM_KEYDOWN: MessageBox(0,"You have pressed down arrow key","About",MB_OK|MB_ICONINFORMATION); break; case WM_CLOSE: DestroyWindow(hwnd); break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefWindowProc(hwnd, msg, wParam, lParam); } return 0; } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { WNDCLASSEX wc; HWND hwnd; MSG Msg; wc.cbSize = sizeof(WNDCLASSEX); wc.style = 0; wc.lpfnWndProc = WndProc; wc.cbClsExtra = 0; wc.cbWndExtra = 0; wc.hInstance = hInstance; wc.hIcon = LoadIcon(NULL,IDI_APPLICATION); wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1); wc.lpszMenuName = NULL; wc.lpszClassName = g_szClassName; wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION); if(!RegisterClassEx(&wc)) {MessageBox(NULL, "Window Registration Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK); return 0; } hwnd = CreateWindowEx( WS_EX_CLIENTEDGE, g_szClassName, "Mouse and Key operations", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 240, 120, NULL, NULL, hInstance, NULL); if(hwnd == NULL) {MessageBox(NULL, "Window Creation Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK); return 0; } ShowWindow(hwnd, nCmdShow); UpdateWindow(hwnd); while(GetMessage(&Msg, NULL, 0, 0) > 0) {TranslateMessage(&Msg); DispatchMessage(&Msg); } return Msg.wParam; } Compile, Build and Execute the program. The output of the program is shown in figure 2.16. Figure 2.16 Running Instance of MouseKeyMsg Program Exercises 2 What is GDI? Define DC. What is WM_PAINT Message? List the Paint Structure (PAINTSTRUCT) and explain it. Write the syntax of TextOut function. Define System Metrics. What is Client area and Non Client area. What are the GDI Primitives? List out the Pen and Brush Styles. Write a Windows Program to draw a Bezier Spline. List out the Mouse and Keyboard Messages. Write a Windows Program to draw a Sine Wave. Chapter 3 Windows Controls and Resources 3.1 Child Window Controls Windows provides several predefined window classes which we can readily use in our own programs. Most of the time we use them as components of a dialog box so they're usually called child window controls. The child window controls process their own mouse and keyboard messages and notify the parent window when their states have changed. They relieve the burden from programmers enormously so you should use them as much as possible. Controls can be placed on a normal window by using the Create command with various styles to design them. But in reality you should put them in a dialog box. Examples of predefined window classes are buttons, listbox, checkboxes, radio buttons, edit controls, etc. In order to use a child window control, you must create it with win.CreateWindow or win.CreateWindowEx. Note that you don't have to register the window class since it's registered for you by Windows. The class name parameter MUST be the predefined class name. Say, if you want to create a button, you must specify "button" as the class name in win.CreateWindowEx. The other parameters you must fill in are the parent window handle and the control ID. The control ID must be unique among the controls. The control ID is the ID of that control. You use it to differentiate between the controls. After the control was created, it will send messages notifying the parent window when its state has changed. Normally, you create the child windows during win.WM_CREATE message of the parent window. The child window sends win.WM_COMMAND messages to the parent window with its control ID in the low word of wParam, the notification code in the high word of wParam, and its window handle in lParam. Each child window control has different notification codes, refer to your Win32 API reference for more information. The parent window can send commands to the child windows too, by calling win.SendMessage function. win.SendMessage function sends the specified message with accompanying values in wParam and lParam to the window specified by the window handle. It's an extremely useful function since it can send messages to any window provided you know its window handle. So, after creating the child windows, the parent window must process win. WM_COMMAND messages to be able to receive notification codes from the child windows. The examples in this chapter uses dialog box to place various controls. 3.2 Button Class Buttons are Windows Controls that respond to user clicks. They are created with the CreateWindow or CreateWindowEx Window function. They can have a variety of styles as shown below: BS_AUTOCHECKBOX Same as a check box, except that a check mark appears in the check box when the user selects the box; the check mark disappears the next time the user selects the box. BS_AUTORADIOBUTTON Same as a radio button, except that when the user selects it, the button automatically highlights itself and removes the selection from any other radio buttons with the same style in the same group. BS_AUTO3STATE Same as a three-state check box, except that the box changes its state when the user selects it. BS_CHECKBOX Creates a small square that has text displayed to its right (unless this style is combined with the BS_LEFTTEXT style). BS_DEFPUSHBUTTON Creates a button that has a heavy black border. The user can select this button by pressing the ENTER key. This style enables the user to quickly select the most likely option (the default option). BS_GROUPBOX Creates a rectangle in which other buttons can be grouped. Any text associated with this style is displayed in the rectangle’s upper-left corner. BS_LEFTTEXT When combined with a radio-button or check-box style, the text appears on the left side of the radio button or check box. BS_PUSHBUTTON Creates a pushbutton that posts a WM_COMMAND message to the owner window when the user selects the button. BS_RADIOBUTTON Creates a small circle that has text displayed to its right (unless this style is combined with the BS_LEFTTEXT style). Radio buttons are usually used in groups of related but mutually exclusive choices. BS_3STATE Same as a check box, except that the box can be dimmed as well as checked. The dimmed state typically is used to show that a check box has been disabled. 3.2.1 Communication between Child and Parent Windows When you click a button with the mouse the child window control sends a WM_COMMAND message to its parent window. The program traps the WM_COMMAND message and displays the values of wparam (child window ID and notification code) and lparam (child window handle). The notification code indicates in more detail what the message means. The possible button notification messages are: BN_CLICK BN_DBCLICK BN_PAINT BN_KILLFOCUS BN_HILITE BN_UNHILITE BN_PUSHED BN_UNPUSHED BN_DISABLE BN_SETFOCUS BN_KILLFOCUS In addition to the notification messages mentioned above there are also button messages each begins with letter BM. These messages are used by the window procedure to send messages to the child window control. The button messages are: BM_GETCHECK BM_GETIMAGE BM_GETSTATE BM_SETCHECK BM_SETIMAGE BM_SETSTYLE BM_CLICKED 3.2.2 Push Buttons A small rectangular control that a user can turn on or off. A push button, also known as a command button, has a raised appearance in its default off state and a depressed appearance when it is turned on. Push button controls are used to trigger an immediate action without retaining any type of on/off indication. The rectangle takes up the full height and width of the dimension given in the CreateWindow. There are two types of push buttons BS_PUSHBUTTON and BS_DEFPUSHBUTTON where “DEF” stands for default. An application sends a BM_SETSTATE message to change the highlight state of a button. The highlight state indicates whether the button is highlighted as if the user had pushed it. BM_SETSTATE message syntax: wParam = (WPARAM) fstate; // highlight state lParam = 0; // not used; must be zero where fState is the value of wParam and specifies whether the button is to be highlighted. A value of TRUE or nonzero highlights the button. A value of FALSE or zero removes any highlighting. This message always returns zero. Highlighting only affects the appearance of a button. It has no effect on the check state or a radio button or check box. A button is automatically highlighted when the user positions the cursor over it and presses and holds the left mouse button. The highlighting is removed when the user releases the mouse button. This call causes the button to be depressed: SendMessage(hwndButton,BM_SETSTATE,1,0); To return to the normal state the call to be used is: SendMessage(hwndButton,BM_SETSTATE,0,0); The hwndButton window handle is the value returned from the CreateWindow call. You can also send a BM_GETSTATE message to push button. An application sends a BM_GETSTATE message to determine the state of a button or check box. The value TRUE is returned if the button is depressed and FALSE if it is not depressed. Most applications do not require this information. BM_GETSTATE message syntax: wParam = 0; // not used; must be zero lParam = 0; // not used; must be zero The BM_SETCHECK and BM_GETCHECK messages are not used by push button because they do not retain on/off information. 3.2.3 Check Boxes An interactive control found in graphical user interfaces. Check boxes are used to enable or disable one or more features or options from a set. When an option is selected, an X or a check mark appears in the box. The two most common styles of check box are BS_CHECKBOX and BS_AUTOCHECKBOX. You can set the check state of the check box with the message BM_SETCHECK. BM_SETCHECKMESSAGE has two parameters: wParam = (WPARAM)fcheck; // check state lParam = 0; // not used; must be zero where fCheck is the value of wParam.and specifies the check state. This parameter can be one of the values mentioned in Table 3.2.3. Table 3.2.3 Values for fCheck Parameter Value Meaning BST_CHECKED Sets the button state to checked. BST_INDETERMINATE Sets the button state to grayed, indicating an indeterminate state. Use this value only if the button has the BS_3STATE or BS_AUTO3STATE style. BST_UNCHECKED Sets the button state to cleared.

You can initialize a check box with a check mark by sending BM_SETCHECK message: SendMessage(hwndButton,BM_SETCHECK,1,0); For BS_AUTOCHECKBOX style the button control itself toggles the check mark on and off. When the current state of the button is needed send the control a BM_GETCHECK message: iCheck = (int) SendMessage(hwndButton,BM_SETCHECK,0,0); The value of iCheck is TRUE or nonzero if the button is checked and FALSE or 0 if not checked. 3.2.4 Radio Buttons A small round button with a label next to it. The label may be text, an icon, or a bitmap. Radio buttons, also known as option buttons, are usually grouped together in a group box, representing a set of related, but mutually exclusive options. When a user selects an option button or radio button, all other option buttons in the same group is automatically unselected. The two most common styles of radio buttons are BS_RADIOBUTTON and BS_AUTORADIOBUTTON. When you receive a WM_COMMAND message from a radio button you should display its check by sending it a BM_SETCHECK with wparam equal to 1: SendMessage(hwndButton,BM_SETCHECK,1,0); For all other radio buttons in the same group you can turn off the checks by sending them BM_SETCHECK messages with wparam equal to 0: SendMessage(hwndButton,BM_SETCHECK,0,0); 3.2.5 Group Boxes The group box which has the BS_GROUPBOX style is a rectangular area within a dialog box in which you can group together other controls that are semantically related. The controls are grouped by drawing a rectangular border around them. Any text associated with the group box is displayed in its upper-left corner. It neither processes mouse or keyboard input nor sends WM_COMMAND message to its parent. In the program given below dialog box is used to place various controls. The details regarding the dialog box creation and usage is given in section 3.3.4. 3.2.6 Changing the Button Text and Input Focus The text in the button can be changed by calling SetWindowText. However, SetWindowText cannot change the text of a control in another application. SetWindowText( HWND hwnd, // handle to window or control LPCTSTR lpstring // address of string );

The parameters hwnd is a handle to the window or control whose text is to be changed and lpstring is a pointer to a null-terminated string to be used as the new title or control text.

You can also obtain the current text of a window by the command: GetWindowText( HWND hwnd, // handle to window or control with text LPTSTR lpstring, // pointer to buffer for text int nMaxCount // maximum number of characters to copy );

The parameters hwnd is a handle to the window or control containing the text, lpstring is a pointer to the buffer that will receive the text and nMaxCount specifies the maximum number of characters to copy to the buffer, including the NULL character. If the text exceeds this limit, it is truncated.

The push buttons, check boxes and radio buttons receive the input focus when they are clicked with the mouse. When the child window control gets the input focus, the parent window loses it. However the child window control responds only to the spacebar which now functions like the mouse. When the window switches the input focus from one window (parent) to another (child), it first sends WM_KILLFOCUS message to the window losing the input focus.

case WM_KILLFOCUS:

if (hwnd==GetParent ((HWND) wparam))

SetFocus (hwnd);

return 0;

This method prevents the button from responding to the space bar because the button never gets input focus. A better approach is to get input focus to the button and also include the facility to move from button to button using Tab key.

3.2.7 System Colors The parts of display can be painted using various system colors. GetSysColor and SetSysColor functions are used to set these colors. The GetSysColor retrieves the current color of the specified display element. Display elements are the parts of a window and the display that appear on the system display screen. Identifiers defined in the windows header files specify the system color. GetSysColor( int nIndex // display element ); The parameter nIndex specifies the display element whose color is to be retrieved. This parameter must be one of the values mentioned in Table 3.2.7 Table 3.2.7 Values for nInex Parameter Value Meaning COLOR_3DDKSHADOW Dark shadow for three-dimensional display elements. COLOR_3DFACE, COLOR_BTNFACE Face color for three-dimensional display elements and for dialog box backgrounds. COLOR_3DHILIGHT, COLOR_3DHIGHLIGHT, COLOR_BTNHILIGHT, COLOR_BTNHIGHLIGHT Highlight color for three-dimensional display elements (for edges facing the light source.) COLOR_3DLIGHT Light color for three-dimensional display elements (for edges facing the light source.) COLOR_3DSHADOW, COLOR_BTNSHADOW Shadow color for three-dimensional display elements (for edges facing away from the light source). COLOR_ACTIVEBORDER Active window border. COLOR_ACTIVECAPTION Active window title bar. COLOR_APPWORKSPACE Background color of multiple document interface (MDI) applications. COLOR_BACKGROUND, COLOR_DESKTOP Desktop. COLOR_BTNTEXT Text on push buttons. COLOR_CAPTIONTEXT Text in caption, size box, and scroll bar arrow box. COLOR_GRAYTEXT Grayed (disabled) text. This color is set to 0 if the current display driver does not support a solid gray color. COLOR_HIGHLIGHT Item(s) selected in a control. COLOR_HIGHLIGHTTEXT Text of item(s) selected in a control. COLOR_INACTIVEBORDER Inactive window border. COLOR_INACTIVECAPTION Inactive window caption. COLOR_INACTIVECAPTIONTEXT Color of text in an inactive caption. COLOR_INFOBK Background color for tooltip controls. COLOR_INFOTEXT Text color for tooltip controls. COLOR_MENU Menu background. COLOR_MENUTEXT Text in menus. COLOR_SCROLLBAR Scroll bar gray area. COLOR_WINDOW Window background. COLOR_WINDOWFRAME Window frame. COLOR_WINDOWTEXT Text in windows.

The SetSysColors function sets the colors for one or more display elements. Display elements are the various parts of a window and the display that appear on the system display screen. WINAPI SetSysColors( int cElements, // number of elements to change CONST int *lpaElements, // address of array of elements CONST COLORREF *lpargbValues // address of array of RGB values ); 3.2.8 List Box Class The list box is a window that displays a list of character strings. The user selects a string from the list by tapping it with the stylus. When a string is selected, it appears highlighted. You can use a vertical or horizontal scroll bar with a list box to scroll lists that are too long for the control window. The list box automatically hides or shows the scroll bar, as needed.

Messages As you may remember from our earlier discussion of the message loop, windows communicate using messages, you send them to get a control to do something, and when an event occurs on the control it will send you a notification message back. For the standard controls this notification will be a WM_COMMAND message as we've already seen with buttons and menus. For the Common Controls which I may get to later, it will be WM_NOTIFY. The messages you send are widely varied between each control, and each control has it's own set of messages. Once in a while the same message will be used for more than one kind of control, but in general they will only work on the control they are intended for. This is especially annoying with the listbox and combobox messages (LB_* and CB_*) which although they perform nearly identical tasks, are NOT interchangeable.On the other hand, generic messages like WM_SETTEXT are supported by almost all controls. A control is just a window after all. You can send messages using the SendMessage() API, and use GetDlgItem() to retreive the handle to the control, or you can use SendDlgItemMessage() which does both steps for you, the results of both methods are identical.

Adding Items to list box The first thing you'll want to do with a listbox is add items to it. int index = SendDlgItemMessage(hwnd, IDC_LIST, LB_ADDSTRING, 0, (LPARAM)"Hi there!"); As you can see, this is a pretty simple task. If the listbox has the LBS_SORT style, the new item will be added in alphabetical order; otherwise it will just be added to the end of the list. This message returns the index of the new item either way, and we can use this to perform other tasks on the item, such as associating some data with it. Usually this will be things like a pointer to a struct containing more information, or maybe an ID that you will use to identify the item, it's up to you. SendDlgItemMessage(hwnd, IDC_LIST, LB_SETITEMDATA, (WPARAM)index, (LPARAM)nTimes);

Notifications The whole purpose of listboxes is to allow the user to select things from a list. Now sometimes we don't care when exactly they do this, for example with our Remove button, we don't need to know when the selection changes right away, we just check when the user activates the button. However, sometimes you want to be able to do something right away, perhaps display different or updated information based on what items are selected. In order to do this we need to handle the notification messages that the listbox passes to us. In this case, we are interested in LBN_SELCHANGE, which tells us that the selection has been modified by the user. LBN_SELCHANGE is sent via WM_COMMAND but unlike handling the WM_COMMAND from buttons or menu's, which are usually only in response to a click, a list box sends WM_COMMAND for various reasons, and we need a second check to find out what it's telling us. The Notification Code is passed as the HIWORD of wParam, the other half of the parameter that gave us the control ID in the first place. case WM_COMMAND: switch(LOWORD(wParam)) { case IDC_LIST: // It's our listbox, check the notification code switch(HIWORD(wParam)) { case LBN_SELCHANGE: // Selection changed, do stuff here. break; } break; // ... other controls } break;

Getting Data from the ListBox Now that we know the selection has changed, or at the request of the user, we need to get the selection from the listbox and do something useful with it. In this example I've used a multiselection list box, so getting the list of selected items is a little trickier. If it were a single selection listbox, than you could simply send LB_GETCURSEL to retrieve the item index. First we need to get the number of selected items, so that we can allocate a buffer to save the indexes in. HWND hList = GetDlgItem(hwnd, IDC_LIST); int count = SendMessage(hList, LB_GETSELCOUNT, 0, 0); Then we allocate a buffer based on the number of items, and send LB_GETSELITEMS to fill in the array. int *buf = GlobalAlloc(GPTR, sizeof(int) * count); SendMessage(hList, LB_GETSELITEMS, (WPARAM)count, (LPARAM)buf); // ... Do stuff with indexes GlobalFree(buf); In this example, buf[0] is the first index, and so on up to buf[count - 1]. One of the things you would likely want to do with this list of indexes, is retreive the data associated with each item, and do some processing with it. This is just as simple as setting the data was originally, we just send another message. int data = SendMessage(hList, LB_GETITEMDATA, (WPARAM)index, 0); If the data was some other type of value (anything that is 32-bits) you could simply cast to the appropriate type. For example if you stored HBITMAPs instead of ints... HBITMAP hData = (HBITMAP)SendMessage(hList, LB_GETITEMDATA, (WPARAM)index, 0); Example Program illustrating the use of Controls Create an application named ControlDemo by selecting the project type Win 32 Application in the appwizard and click OK. Now an empty project without using MFC classes is created. Click Insert->Resource from the menu and then select the Dialog option. Design the dialog as shown in figure 3.2.8(a). Figure 3.2.8(a) Dialog design for ControlDemo program Change the ID for the controls as shown below: Control TypeID Edit ControlID_CNAME List BoxID_ITEM Option button (Cash)ID_CASH Option button(Cheque)ID_CHEQUE Select Insert-> resource from the menu and then select the option Menu from it. The menu contains two options named (Item and Exit). If the Item option is clicked Dialog box containing the controls will be displayed. If the Exit option is selected from the menu the output window will be closed. Now close your dialog window and save your design by giving a name to the Script. This will be stored in .rc extension. Include this file and the resource header file (resource.h) to your project by clicking Project->Add to Project->Files. Now select the .rc and resource.h file for your project and click OK. Now the resource is included in your project workspace. Click File->New and then select the option C++ Source File and give a name to the .cpp implementation file (here the name is Control.cpp). Enter the code given below in the implementation file (Control.cpp). # include <windows.h> #include "resource.h" HINSTANCE hInstance; WNDCLASS wc; MSG msg; HWND hwnd; LRESULT CALLBACK wndproc(HWND hwnd,UINT wm,WPARAM wp,LPARAM lp); LRESULT CALLBACK item(HWND hDlg,UINT wm,WPARAM wp,LPARAM lp); int APIENTRY WinMain(HINSTANCE hInst,HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nCmdShow) { //TODO :place code here if(hPrevInstance==NULL) { memset(&wc,0,sizeof(wc)); wc.style=CS_HREDRAW; wc.lpfnWndProc=wndproc; wc.hInstance=hInstance; wc.hCursor=LoadCursor(hInstance,IDC_CROSS); wc.hIcon=LoadIcon(hInstance,NULL); wc.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH); wc.lpszClassName="Sample"; wc.lpszMenuName=MAKEINTRESOURCE(IDR_MENU1); if(!RegisterClass(&wc)) return false; } hwnd=CreateWindow("Sample","Control Demo",WS_OVERLAPPEDWINDOW,10,10,500,500,NULL,NULL,hInst,NULL); ShowWindow(hwnd,nCmdShow); UpdateWindow(hwnd); while(GetMessage(&msg,NULL,0,0)) DispatchMessage(&msg); //return 0; return true; } LRESULT CALLBACK wndproc(HWND hwnd,UINT wm,WPARAM wp,LPARAM lp) {DLGPROC dlgproc; switch(wm) { case WM_COMMAND: switch(wp) { case ID_ITEM: dlgproc=(DLGPROC)item; DialogBox(hInstance,MAKEINTRESOURCE(IDD_DIALOG1),hwnd,dlgproc); return 0; break; case ID_EXIT: DestroyWindow(hwnd); break; } break; case WM_DESTROY : PostQuitMessage(0); break; } return(DefWindowProc(hwnd,wm,wp,lp)); } char itm[5][10]={ "Hard Disk", "Printer", "Monitor", "Scanner", "Keyboard"}; LRESULT CALLBACK item(HWND hDlg,UINT wm,WPARAM wp,LPARAM lp) {static HWND hlist; char cname[30],optionsel[10],str[100],payment[10]; int i,sel,cash,cheque; switch(wm) { case WM_INITDIALOG: for(i=0;i<5;i++) SendDlgItemMessage(hDlg,ID_ITEM,LB_ADDSTRING,0,(LPARAM)(LPCTSTR)itm[i]);