SendMessage会跳过不执行....

Question

#include <Windows.h>
#define CellSize 15
#define Width 20
#define Height 30LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE prevInstance, LPSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("Tetris");
    WNDCLASS wndclass;
    HWND hwnd;
    MSG msg;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    wndclass.hCursor = LoadCursor(hInstance, IDC_ARROW);
    wndclass.hIcon = LoadIcon(hInstance, IDI_APPLICATION);
    wndclass.hInstance = hInstance;
    wndclass.lpfnWndProc = WndProc;
    wndclass.lpszClassName = szAppName;
    wndclass.lpszMenuName = NULL;
    wndclass.style = CS_HREDRAW | CS_VREDRAW;    
    if(!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("The programe requires Windows NT!"), szAppName, MB_ICONERROR);
        return 0;
    }
    hwnd = CreateWindow(szAppName, TEXT("Tetris Game"), WS_OVERLAPPEDWINDOW,
        (GetSystemMetrics(SM_CXSCREEN) - Width * CellSize) / 2,
        (GetSystemMetrics(SM_CYSCREEN) - Height * CellSize) / 2, 
        Width * CellSize, Height * CellSize,
        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)
{    
    HDC hdc;
    PAINTSTRUCT ps;
    RECT rect;
    static int i;
    //HPEN hPen;
    switch(message)
    {
    case WM_CREATE:     
i = 0;
        return 0;
    case WM_KEYDOWN:
        switch(wParam)
        {
        case VK_RIGHT:
i++;
break;
        }
        SendMessage(hwnd, WM_PAINT, 0, 0); //SendMessage会跳过不执行
        return 0;    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        GetClientRect(hwnd, &rect);
TextOut(hdc, i, 0 , TEXT("abc"), lstrlen(TEXT("abc")));
        EndPaint(hwnd, &ps);
        return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

Answer 1

SendMessage(hwnd, WM_PAINT, 0, 0);    //SendMessage会跳过不执行
-->
InvalidateRect(hwnd, NULL, FALSE);

Answer 2

The WM_PAINT message is generated by the system and should not be sent by an application. To force a window to draw into a specific device context, use the WM_PRINT or WM_PRINTCLIENT message. Note that this requires the target window to support the WM_PRINTCLIENT message. Most common controls support the WM_PRINTCLIENT message.

Answer 3

2楼说得很清楚了，WM_PAINT消息由系统产生而非应用程序，要强制使窗口重绘可调用InvalidateRect函数使用窗口无效，系统自动重绘窗口

Answer 4

SendMessage(hwnd, WM_PAINT, 0, 0);    //SendMessage会跳过不执行
是没效果吧。
WM_PAINT要有无效区！