四、程序中的命中测试—在CHECKER中加入键盘接口
程序7-3所示的CHECKER2程序，除了包括键盘接口外，和CHECKER1是一样的，您可以使用左、右、上和下方向键在25个矩形之间移动光标。Home键把光标移动到矩形的左上角， End键把光标移动到矩形的右下角。Spacebar和Enter键都能切换X标记。
程序7-3 CHECKER2
CHECKER2.C
/*----------------------------------------------------------------------------
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 (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("Checker2") ;
HWND hwnd ;
MSG msg ;
WNDCLASS wndclass ;
wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
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 0 ;
}
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, iCmdShow) ;
UpdateWindow (hwnd) ;
while (GetMessage (&msg, NULL, 0, 0))
{
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 0 ;
case WM_SETFOCUS :
ShowCursor (TRUE) ;
return 0 ;
case WM_KILLFOCUS :
ShowCursor (FALSE) ;
return 0 ;
case WM_KEYDOWN :
GetCursorPos (&point) ;
ScreenToClient (hwnd, &point) ;
x = max (0, min (DIVISIONS - 1, point.x / cxBlock)) ;
y = max (0, min (DIVISIONS - 1, 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 = 0 ;
break ;
case VK_END :
x = y = DIVISIONS - 1 ;
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 / 2 ;
point.y = y * cyBlock + cyBlock / 2 ;
ClientToScreen (hwnd, &point) ;
SetCursorPos (point.x, point.y) ;
return 0 ;
case WM_LBUTTONDOWN :
x = LOWORD (lParam) / cxBlock ;
y = HIWORD (lParam) / cyBlock ;
if (x < DIVISIONS && y < DIVISIONS)
{
fState[x][y] ^= 1 ;
rect.left = x * cxBlock ;
rect.top = y * cyBlock ;
rect.right = (x + 1) * cxBlock ;
rect.bottom = (y + 1) * cyBlock ;
InvalidateRect (hwnd, &rect, FALSE) ;
}
else
MessageBeep (0) ;
return 0 ;
case WM_PAINT :
hdc = BeginPaint (hwnd, &ps) ;
for (x = 0 ; x < DIVISIONS ; x++)
for (y = 0 ; y < DIVISIONS ; y++)
{
Rectangle (hdc, x * cxBlock, y * cyBlock,
(x + 1) * cxBlock, (y + 1) * cyBlock) ;
if (fState [x][y])
{
MoveToEx (hdc, x *cxBlock, y *cyBlock, NULL) ;
LineTo (hdc, (x+1)*cxBlock, (y+1)*cyBlock) ;
MoveToEx (hdc, x *cxBlock, (y+1)*cyBlock, NULL) ;
LineTo (hdc, (x+1)*cxBlock, y *cyBlock) ;
}
}
EndPaint (hwnd, &ps) ;
return 0 ;
case WM_DESTROY :
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}
CHECKER2中的WM_KEYDOWN的处理方式决定光标的位置（用GetCursorPos），把屏幕坐标转换为显示区域坐标（用ScreenToClient），并用矩形方块的宽度和高度来除这个坐标。这会产生指示矩形位置的x和y值（5×5数组）。当按下一个键时，鼠标光标可能在或不在显示区域中，所以x和y必须经过min和max宏处理以保证它们的范围是0到4之间。
对方向键，CHECKER2近似地增加或减少x和y。如果是Enter键或Spacebar键，那么CHECKER2使用SendMessage把WM_LBUTTONDOWN消息发送给它自身。这种技术类似于在第六章SYSMETS程序中把键盘接口加到窗口滚动条时所使用的方法。WM_KEYDOWN的处理方式是通过计算指向矩形中心的显示区域坐标，再用ClientToScreen转换成屏幕坐标，然后用SetCursorPos设定光标位置来实作的。
