第七章 鼠标（CHECKER1）

CHECKER1程序将客户区划分成25个矩形，构成一个5*5的数组。如果在其中一个矩形内单击鼠标，就用X形填充该矩形。再次单击，则X形消失。

 /*--------------------------------------------
 CHECKER1.C -- Mouse Hit-Test Demo Program No.1
               (c) Charles Petzold, 1998
 --------------------------------------------*/

 #include <Windows.h>

 #define DIVISION 5

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

 int WINAPI WinMain( __in HINSTANCE hInstance
                     , __in_opt HINSTANCE hPrevInstance
                     , __in LPSTR lpCmdLine
                     , __in int nShowCmd )
 {
     static TCHAR szAppName[] = TEXT("Checker1");
     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("Program requires Windows NT!")
             , szAppName, MB_ICONERROR);
         return ;
     }

     hwnd = CreateWindow(szAppName, TEXT("Checker1 Mouse Hit-Test Demo")
         , WS_OVERLAPPEDWINDOW
         , CW_USEDEFAULT, CW_USEDEFAULT
         , CW_USEDEFAULT, CW_USEDEFAULT
         , NULL, NULL, hInstance, NULL);

     ShowWindow(hwnd, nShowCmd);
     UpdateWindow(hwnd);

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

     return msg.wParam;
 }

 LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
     static BOOL fState[DIVISION][DIVISION];
     static int cxBlock, cyBlock;
     HDC hdc;
     int x, y;
     PAINTSTRUCT ps;
     RECT rect;

     switch (message)
     {
     case WM_SIZE:
         cxBlock = LOWORD(lParam) / DIVISION;
         cyBlock = HIWORD(lParam) / DIVISION;
         return ;

     case WM_LBUTTONDOWN:
         x = LOWORD(lParam) / cxBlock;
         y = HIWORD(lParam) / cyBlock;

         if (x < DIVISION && y < DIVISION)
         {
             fState[x][y] ^= ;

             rect.left = x * cxBlock;
             rect.top = y * cyBlock;
             rect.right = (x + ) * cxBlock;
             rect.bottom = (y + ) * cyBlock;

             InvalidateRect(hwnd, &rect, FALSE);
         }
         else
             MessageBeep();
         return ;

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

         for (x = ; x < DIVISION; ++x)
             for (y = ; y < DIVISION; ++y)
             {
                 Rectangle(hdc, x * cxBlock, y * cyBlock
                     , (x + ) * cxBlock, (y + ) * cyBlock);

                 if (fState[x][y])
                 {
                     MoveToEx(hdc, x * cxBlock, y * cyBlock, NULL);
                     LineTo(hdc, (x + ) * cxBlock, (y + ) * cyBlock);
                     MoveToEx(hdc, x * cxBlock, (y + ) * cyBlock, NULL);
                     LineTo(hdc, (x + ) * cxBlock, y * cyBlock);
                 }
             }

         EndPaint(hwnd, &ps);
         return ;

     case WM_DESTROY:
         PostQuitMessage();
         return ;
     }

     return DefWindowProc(hwnd, message, wParam, lParam);
 }

CHECKER1.C

CHECKER1程序显示结果如图所示：

所有25个矩形具有相同的宽度和高度，这些宽度和高度被保存在cxBlock、cyBlock中。无论何时改变客户区的大小，程序都将重新计算cxBlock、cyBlock。WM_LBUTTONDOWN处理逻辑利用鼠标的坐标来判断哪个矩形被单击，然后在fState数组中使用位运算符（按位异或^）计算那个矩形的新状态，最后强制使该矩形失效，从而产生WM_PAINT消息。

如果客户区的宽度和高度不能被5整除，客户区的左边或底部就会出现一个小长条区域，不被举行覆盖。在这片区域进行鼠标单击时，CHECKER1程序会调用MessageBeep函数进行响应。

当CHECKER1程序收到WM_PAINT消息时，它会重新绘制整个客户区，利用GDI中的Rectangle函数画出所有的矩形。若fState值为真，则CHECKER1程序调用函数MoveToEx和函数LineTo函数画出两条直线。