c - WM_TIMER 在特定条件下丢失

Question

#include <windows.h>
#include <stdio.h>

class tWnd {
private:
    static LRESULT CALLBACK Disp_test_WndProc(
        HWND hwnd,        // handle to window
        UINT uMsg,        // message identifier
        WPARAM wParam,    // first message parameter
        LPARAM lParam)    // second message parameter
    {
        switch (uMsg) 
        {
            case WM_TIMER:{
                printf("timer\n");

                return 0;
            }

            case WM_PAINT: 
                // Paint the window's client area. 
                return 0; 

            case WM_DESTROY: 
                return 0; 

            case WM_HOTKEY:{

            } return 0;
            // 
            // Process other messages. 
            // 
            default: 
                return DefWindowProc(hwnd, uMsg, wParam, lParam); 
        } 
        return 0; 
    }

public:     
    tWnd() {

            WNDCLASSA wc;
            wc.style = CS_HREDRAW | CS_VREDRAW; 
            wc.lpfnWndProc = (WNDPROC) Disp_test_WndProc; 
            wc.cbClsExtra = 0; 
            wc.cbWndExtra = 0; 
            wc.hInstance = GetModuleHandle(NULL); 
            wc.hIcon = LoadIcon(NULL, IDI_APPLICATION); 
            wc.hCursor = LoadCursor(NULL, IDC_ARROW); 
            wc.hbrBackground = (HBRUSH) NULL; 
            wc.lpszMenuName =  ""; 
            wc.lpszClassName = "Test"; 

            if (!RegisterClass(&wc)) 
               return; //cannot register window class



        HWND testingWindow = CreateWindowEx(WS_EX_TOPMOST,"Test","topmost",WS_VISIBLE,0,0,200,200,0,0,0,0);

        SetTimer(testingWindow,101,500,(TIMERPROC)NULL);

        MSG recent;
        BOOL result;
        while((result=GetMessage(&recent,testingWindow,0,0))&&result!=-1) { //bool can be -1 in MS world
            if(recent.message==WM_USER+1) break;
            TranslateMessage(&recent);
            DispatchMessage(&recent);
        }
    }
};

int main(int argc, char **argv)
{
    tWnd();
    return 0;
}

此代码永远不会收到 WM_TIMER 消息。

#include <windows.h>
#include <stdio.h>

class tWnd {
private:
    static LRESULT CALLBACK Disp_test_WndProc(
        HWND hwnd,        // handle to window
        UINT uMsg,        // message identifier
        WPARAM wParam,    // first message parameter
        LPARAM lParam)    // second message parameter
    {
        switch (uMsg) 
        {
            case WM_TIMER:{
                printf("timer\n");

                return 0;
            }

            case WM_DESTROY: 
                return 0; 

            case WM_HOTKEY:{

            } return 0;
            // 
            // Process other messages. 
            // 
            default: 
                return DefWindowProc(hwnd, uMsg, wParam, lParam); 
        } 
        return 0; 
    }

public:     
    tWnd() {

            WNDCLASSA wc;
            wc.style = CS_HREDRAW | CS_VREDRAW; 
            wc.lpfnWndProc = (WNDPROC) Disp_test_WndProc; 
            wc.cbClsExtra = 0; 
            wc.cbWndExtra = 0; 
            wc.hInstance = GetModuleHandle(NULL); 
            wc.hIcon = LoadIcon(NULL, IDI_APPLICATION); 
            wc.hCursor = LoadCursor(NULL, IDC_ARROW); 
            wc.hbrBackground = (HBRUSH) NULL; 
            wc.lpszMenuName =  ""; 
            wc.lpszClassName = "Test"; 

            if (!RegisterClass(&wc)) 
               return; //cannot register window class



        HWND testingWindow = CreateWindowEx(WS_EX_TOPMOST,"Test","topmost",WS_VISIBLE,0,0,200,200,0,0,0,0);

        SetTimer(testingWindow,101,500,(TIMERPROC)NULL);

        MSG recent;
        BOOL result;
        while((result=GetMessage(&recent,testingWindow,0,0))&&result!=-1) { //bool can be -1 in MS world
            if(recent.message==WM_USER+1) break;
            TranslateMessage(&recent);
            DispatchMessage(&recent);
        }
    }
};

int main(int argc, char **argv)
{
    tWnd();
    return 0;
}

此代码可以很好地获取 WM_TIMER 消息。

两者之间的唯一区别是 WM_PAINT 消息在第二种变体中是默认处理的。为什么处理 WM_PAINT 会阻止程序接收 WM_TIMER 消息？我该如何解决这个问题？

如果重要的话，我正在使用 MingW w64 (GCC 5.3.0)。

Answer 1

当窗口的无效区域非空时，它会收到 WM_PAINT 消息。 ValidateRect() 的文档中对此进行了说明。 :

The system continues to generate WM_PAINT messages until the current update region is validated.

标准 WM_PAINT 处理程序会验证无效区域(例如通过调用 BeginPaint() )，默认实现会这样做。简单地返回 0 不会验证窗口，并且它会继续接收 WM_PAINT 消息。

WM_TIMER 消息的优先级低于 WM_PAINT 消息。您的窗口消息处理程序永远不会看到计时器消息，因为它一直忙于忽略绘制消息。 WM_TIMER 的文档中对此进行了说明。 :

The WM_TIMER message is a low-priority message. The GetMessage and PeekMessage functions post this message only when no other higher-priority messages are in the thread's message queue.