第七章 鼠标（CHECKER2）

CHECKER2程序包含一个键盘接口，内容与CHECKER1完全相同。利用←、→、↑、↓四个方向键可以在25个矩形之间移动鼠标指针。Home键把鼠标指针移动到左上角的矩形；End键使鼠标指针落到右下角的矩形。空格键和回车键都可以切换X形标记。

 /*---------------------------------------------
 CHECKER2.C -- Mouse Hit-Test Demo Program No.2
               (c) Charles Petzold, 1998
 ---------------------------------------------*/
 
 #include <Windows.h>
 
 #define DIVISIONS 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("Checker2");
     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("Checker2 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[DIVISIONS][DIVISIONS];
     static int cxBlock, cyBlock;
     HDC hdc;
     int x, y;
     PAINTSTRUCT ps;
     POINT point;
     RECT rect;
 
     switch (message)
     {
     case WM_SIZE:
         cxBlock = LOWORD(lParam) / DIVISIONS;
         cyBlock = HIWORD(lParam) / DIVISIONS;
         return ;
 
     case WM_SETFOCUS:
         ShowCursor(TRUE);
         return ;
 
     case WM_KILLFOCUS:
         ShowCursor(FALSE);
         return ;
 
     case WM_KEYDOWN:
         GetCursorPos(&point);
         ScreenToClient(hwnd, &point);
 
         x = max(, min(DIVISIONS - , point.x / cxBlock));
         y = max(, min(DIVISIONS - , point.y / cyBlock));
 
         switch (wParam)
         {
         case VK_UP:
             --y;
             break;
 
         case VK_DOWN:
             ++y;
             break;
 
         case VK_LEFT:
             --x;
             break;
 
         case VK_RIGHT:
             ++x;
             break;
 
         case VK_HOME:
             x = y = ;
             break;
 
         case VK_END:
             x = y = DIVISIONS - ;
             break;
 
         case VK_RETURN:
         case VK_SPACE:
             SendMessage(hwnd, WM_LBUTTONDOWN, MK_LBUTTON, MAKELONG(x * cxBlock, y * cyBlock));
             break;
         }
 
         x = (x + DIVISIONS) % DIVISIONS;
         y = (y + DIVISIONS) % DIVISIONS;
 
         point.x = x * cxBlock + cxBlock / ;
         point.y = y * cyBlock + cyBlock / ;
 
         ClientToScreen(hwnd, &point);
         SetCursorPos(point.x, point.y);
         return ;
 
     case WM_LBUTTONDOWN:
         x = LOWORD(lParam) / cxBlock;
         y = HIWORD(lParam) / cyBlock;
 
         if (x < DIVISIONS && y < DIVISIONS)
         {
             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 < DIVISIONS; ++x)
             for (y = ; y < DIVISIONS; ++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);
 }

CHECKER2.C

在CHECKER2程序中，处理WM_KEYDOWN时利用GetCursorPos判断指针的位置，并利用ScreenToClient将屏幕坐标转换成客户区坐标，然后将坐标值除以矩形块的宽和高，得到x和y。这些x和y的值表示了矩形在5*5数组中的位置。当按下某个键时，鼠标指针可能在客户区也可能不在客户区内，因此x和y必须包含在min和max的宏处理中，保证它们的范围处于0和4之间。

对于方向键，CHECKER2程序相应的增加或减少x和y的值。若按下回车键或空格键，CHECKER2程序调用SendMessage给自己发送一个WM_LBUTTONDOWN消息。最后，WM_KEYDOWN处理逻辑计算得到指向矩形中心的客户区坐标，并调用ClientToScreen将其转换成屏幕坐标，最后调用SetCursorPos设置指针的位置。