windows程序设计读书笔记1——创建窗口

第一个win32程序，简单的创建窗口：

#include <windows.h>

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("HelloWin") ;
     HWND         hwnd ;
     MSG          msg ;
     WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    =  ;
     wndclass.cbWndExtra    =  ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("This program requires Windows NT!"),
                      szAppName, MB_ICONERROR) ;
          return  ;
     }

     hwnd = CreateWindow (szAppName,                  // window class name
                          TEXT ("The Hello Program"), // 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

     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;

     while (GetMessage (&msg, NULL, , ))
     {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
     }
     return msg.wParam ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     HDC         hdc ;
     PAINTSTRUCT ps ;
     RECT        rect ;

     switch (message)
     {
     case WM_CREATE:return  ;

     case WM_PAINT:
          hdc = BeginPaint (hwnd, &ps) ;

          GetClientRect (hwnd, &rect) ;

          DrawText (hdc, TEXT ("Hello, Windows Program!"), -, &rect,
                    DT_SINGLELINE | DT_CENTER | DT_VCENTER) ;

          EndPaint (hwnd, &ps) ;
          return  ;

     case WM_DESTROY:
          PostQuitMessage () ;
          return  ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

窗口是由窗口类创建的即WNDCLASS，窗口类确定了处理窗口消息的窗口过程。

MSDN中是这样定义的：

typedef struct {
  UINT      style;
  WNDPROC   lpfnWndProc;
  int       cbClsExtra;
  int       cbWndExtra;
  HINSTANCE hInstance;
  HICON     hIcon;
  HCURSOR   hCursor;
  HBRUSH    hbrBackground;
  LPCTSTR   lpszMenuName;
  LPCTSTR   lpszClassName;
} WNDCLASS, *PWNDCLASS;

在程序中，我们一般这样定义和初始化

  WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    =  ;
     wndclass.cbWndExtra    =  ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;

wndclass.style字段表示类的风格，具体参加MSDN：

Style	Action
CS_BYTEALIGNCLIENT	Aligns the window's client area on a byte boundary (in the x direction). This style affects the width of the window and its horizontal placement on the display.
CS_BYTEALIGNWINDOW	Aligns the window on a byte boundary (in the x direction). This style affects the width of the window and its horizontal placement on the display.
CS_CLASSDC	Allocates one device context to be shared by all windows in the class.
CS_DBLCLKS	Sends a double-click message to the window procedure when the user double-clicks the mouse while the cursor is within a window belonging to the class.
CS_DROPSHADOW	Windows XP: Enables the drop shadow effect on a window. The effect is turned on and off through SPI_SETDROPSHADOW.
CS_GLOBALCLASS	Specifies that the window class is an application global class. For more information, see Application Global Classes.
CS_HREDRAW	Redraws the entire window if a movement or size adjustment changes the width of the client area.
CS_NOCLOSE	Disables Close on the window menu.
CS_OWNDC	Allocates a unique device context for each window in the class.
CS_PARENTDC	Sets the clipping rectangle of the child window to that of the parent window so that the child can draw on the parent. A window with the CS_PARENTDC style bit receives a regular device context from the system's cache of device contexts.
CS_SAVEBITS	Saves, as a bitmap, the portion of the screen image obscured by a window of this class.
CS_VREDRAW	Redraws the entire window if a movement or size adjustment changes the height of the client area.

我们这里选择的是CS_HREDRAW | CS_VREDRAW，表示无论垂直还是水平尺寸的改变，窗口都将重绘。

wndclass.lpfnWndProc表示窗口过程设置，指向一个函数WndProc。

wndclass.cbClsExtra和cbWndExtra用于维护内部窗口结构中一些预留的空间，可以根据需要来使用这些预留的空间。

wndclass.hInstance表示应用程序的实例句柄即WinMain第一个参数。

wndclass.hIcon为该窗口类设定图标。若要使用本地的图标，第一个参数必须为hInstance实例句柄，第二个参数为图标标示，对于预定义的图标以IDI开头。

wndclass.hCursor与上面类似，载入鼠标指针。

wndclass.hbrBackground指定背景色，这里我们用白色画刷。

wndclass.lpszMenuName即窗口菜单。

wndclass.lpszClassName为窗口类指定名字。

这样窗口类的初始化完成，使用RegisterClass注册类，下面就是窗口的创建了，

使用createWindow函数，MSDN定义如下：

HWND CreateWindow(
  __in  LPCTSTR lpClassName,　　 //窗口名称
  __in  LPCTSTR lpWindowName,　　//窗口标题
  __in  DWORD dwStyle,　　　　　　//窗口风格
  __in  int x,　　　　　　　　　　 //x坐标
  __in  int y,　　　　　　　　　   //y坐标
  __in  int nWidth,　　　　　　   //长度
  __in  int nHeight,　　　　　　　//高度　
  __in  HWND hWndParent,　　　　 //父窗口句柄
  __in  HMENU hMenu,            //窗口菜单句柄
  __in  HINSTANCE hInstance,    //程序实例句柄
  __in  LPVOID lpParam          //创建参数
);

CreateWindow只是在内部创建窗口，即windows分配了一片内存，要想显示窗口还要使用ShowWindow函数。

第一个参数是CreateWindow创建的窗口句柄，第二个是WinMain接受的iCmdShow值，该参数决定窗口初始显示格式。

UpdateWindow是重绘窗口，这是通过发送一条WM_PAINT消息完成的。

最后则是消息的循环，即不断接受消息，当有消息时调用WndProc函数进行处理。