求助：关于在兼容DC上使用TextOut丢失问题

Question

【1】我的想法是先在hdcm上绘图(单击鼠标左键一次就绘制一遍)，但不立即更新客户区(未立即InvalidateRect)。
【2】在绘制后，先最小化窗口、再恢复窗口(windows应自动更新客户显示区)后，没有看到文字(矩形正常显示)！这是为什么呢？
【3】特别的，若连续使用多条TextOut，则只有最后一条TextOut不显示，其余均正常显示！若在最后一条TextOut后面再加一些函数，如：Rectangle/LineTo/GetPixel/InvilidateRect等等，就全都正常显示了！

如下是代码：

#include <windows.h>
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
DWORD WINAPI yzx(LPVOID asd);//在兼容DC上绘图的(专用)线程

char szClassName[ ]="WTF";
HBITMAP hbitmap;
HDC hdcm;
HANDLE hev;//控制(绘图)线程的开关


int WINAPI WinMain (HINSTANCE hThisInstance,
                    HINSTANCE hPrevInstance,
                    LPSTR lpszArgument,
                    int nFunsterStil)

{
    HWND hwnd;     
    MSG messages;       
    WNDCLASSEX wincl;    

    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = szClassName;
    wincl.lpfnWndProc = WindowProcedure;      
    wincl.style = CS_DBLCLKS;              
    wincl.cbSize = sizeof (WNDCLASSEX);
    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;   
    wincl.cbClsExtra = 0; 
    wincl.cbWndExtra = 0; 
    wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

    /* Register the window class, and if it fails quit the program */
    if (!RegisterClassEx (&wincl))
        return 0;

    /* The class is registered, let's create the program*/
    hwnd = CreateWindowEx (
           0,                   /* Extended possibilites for variation */
           szClassName,         /* Classname */
           "hjdl",       /* Title Text */
           WS_OVERLAPPEDWINDOW, /* default window */
           0,       /* Windows decides the position */
           0,       /* where the window ends up on the screen */
           1000,                 /* The programs width */
           800,                 /* and height in pixels */
           HWND_DESKTOP,        /* The window is a child-window to desktop */
           NULL,                /* No menu */
           hThisInstance,       /* Program Instance handler */
           NULL                 /* No Window Creation data */
           );

    /* Make the window visible on the screen */
    ShowWindow (hwnd, nFunsterStil);

    /* Run the message loop. It will run until GetMessage() returns 0 */
    while (GetMessage (&messages, NULL, 0, 0))
    {
        /* Translate virtual-key messages into character messages */
        TranslateMessage(&messages);
        /* Send message to WindowProcedure */
        DispatchMessage(&messages);
    }

    /* The program return-value is 0 - The value that PostQuitMessage() gave */
    return messages.wParam;
}


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

    switch (message)                  /* handle the messages */
    {   
        case WM_CREATE:
                       hdc=GetDC(hwnd);
                       hdcm=CreateCompatibleDC(hdc);
                       hbitmap=CreateCompatibleBitmap(hdc,500,500);
                       SelectObject(hdcm,hbitmap);
                       ReleaseDC(hwnd,hdc);

                       hev=CreateEvent(NULL,0,0,NULL);
                       CreateThread(NULL,0,yzx,hwnd,0,NULL);
                       break;
        case WM_PAINT:
                      hdc=BeginPaint(hwnd,&ps);

                      BitBlt(hdc,0,0,500,500,hdcm,0,0,SRCCOPY);

                      EndPaint(hwnd,&ps);
                      break;

        case WM_LBUTTONUP:

                          SetEvent(hev);

                          break;

        case WM_DESTROY:
                        CloseHandle(hev);
                        DeleteObject(hdcm);
                        DeleteObject(hbitmap);
                        PostQuitMessage (0);       /* send a WM_QUIT to the message queue */
                        break;
        default:        /* for messages that we don't deal with */
                return DefWindowProc(hwnd, message, wParam, lParam);
    }

    return 0;
}


DWORD WINAPI yzx(LPVOID asd)
{
char temp[111];      
int k=0;

while(1)
{
WaitForSingleObject(hev,INFINITE);

Rectangle(hdcm,0,0,500,500);
sprintf(temp,"%d",++k);
TextOut(hdcm,10,10,temp,strlen(temp));    
}

return 0;      
}

Answer 1

建议在主线程中进行界面更新操作