CMPT 212 Object-Oriented Applications Design in C++ Fall 1997

Read chapters 1 to 3 from Schildt's Windows 95 Programming in C and C++, by Herbert Schildt.

Callbacks

• With callbacks, the application "registers" some of its subroutines with the GUI system. Then when an event occurs, the GUI system call the appropriate application subroutine to handle the event.
  • Note the important difference compared to "normal" programming style: the OS is calling your function.

• Some GUI systems allow the application to register several subroutines (each of which could handle one event), and others allow the application to register only one subroutine.

Microsoft Windows Programming

• An application programming interface (API) is a specification of the way an application programmer can use an OS or GUI library.

• An API generally consists of
  • constants,
  • variables,
  • types,
  • functions.

• In MS-Windows, you will typically include the header file <windows.h>, which contains the declarations of the constants, variables, types, and functions in the MS-Windows API.

• The MS-Windows API is not object-oriented.
  • The API must be usable with different programming languages.

• There are object-oriented C++ class libraries that make MS-Windows programming easier. These include:
  • Microsoft Foundation Classes (MFC),
  • Borland Object Windows Library (OWL),
  • Visual Age C++ from IBM.

• We will be using the raw C API in order to learn the basics. Learning these class libraries is fairly easy once we have learned the API basics.

• MS-Windows has several APIs:
  • Win16 is used for 16-bit programs that will run with Windows 3.x. Windows 3.x is 16-bit.

  • Win32 is a 32-bit API for programs that will run with Windows NT. Windows NT is 32-bit.

  • Win32s is a subset of Win32. Programs that use this API can be recompiled with no change to the source code to run on Windows NT or Windows 3.x (provided a special run-time library is loaded for Windows 3.x).

  • Win95 is an API for Windows 95. It contains most of Win32 and additionally has some things that Win32 does not have.

A Simple MS-Windows Program

• See the example program on pages 20-21 of Schildt's Windows 95 Programming in C and C++, by Herbert Schildt.

• You must include <windows.h>.

• A MS-Windows program does not have a main function. Instead it must have a WinMain function.

• The variable wcl is a structure which describes the windows class used by the program.
  • A "class" in this sense is not related to a C++ class.

  • This simple program has only one window class.

  • The name of a window class (szWinName is this case) must not be stored on the stack. It must be declared outside of any function or be declared with static.

  • The window class must be registered before it can be used.

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