PostMessage似乎不起作用？

Question

我正在尝试学习如何使用和接收原始输入消息,因此我设计了以下程序来测试我迄今为止的理解...

当我收到输入消息时,我尝试更改显示的字符串并WM_PAINT在队列中放置新消息.但这个消息似乎没有被调用.只有当我调整窗口大小时,文本才会显示不同.

为什么WM_PAINT消息根本没有得到处理,直到我调整窗口大小为例？

#define _WIN32_WINNT 0x501
#include <Windows.h>
#include <assert.h>
#include <cstring>
#include <cstdio>

LRESULT CALLBACK WinProcedure(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam);

int WinMain(HINSTANCE hInst,HINSTANCE,LPSTR,int nCmdShow)
{
    WNDCLASS wc;
    HWND hwnd;

    wc.hInstance = hInst;
    wc.lpfnWndProc = WinProcedure;
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hIcon = LoadIcon(NULL, IDI_WINLOGO);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)COLOR_WINDOWFRAME;
    wc.lpszMenuName = NULL;
    wc.lpszClassName = "Untitled";

    if (!RegisterClass(&wc)) {
        // Error registering class
        return -1;
    }

    if (!(hwnd = CreateWindow(wc.lpszClassName, wc.lpszClassName, WS_OVERLAPPEDWINDOW, 
                    CW_USEDEFAULT,CW_USEDEFAULT,500,300,NULL,NULL,hInst,NULL))) {
        // Error creating window
        return -1;
    }

    ShowWindow(hwnd,nCmdShow); 
    UpdateWindow(hwnd);

    RAWINPUTDEVICE Rid[1];

    Rid[0].usUsagePage = 0x01; 
    Rid[0].usUsage = 0x06; 
    Rid[0].dwFlags = 0;   // adds HID keyboard and also ignores legacy keyboard messages
    Rid[0].hwndTarget = 0;

    if (RegisterRawInputDevices(Rid, 1, sizeof(Rid[0])) == FALSE) {
        return -5;
    }

    MSG msg;
    while (GetMessage(&msg,NULL,0,0) > 0) 
    { 
        TranslateMessage(&msg); 
        DispatchMessage(&msg); 
    }
    return 0;
}

LRESULT CALLBACK WinProcedure(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
    static char buffer[5000] = "hi";

    if (msg == WM_PAINT) {
        PAINTSTRUCT ps; 
        HDC dc; 
        RECT r; 
        GetClientRect(hwnd,&r); 
        dc=BeginPaint(hwnd,&ps); 
        DrawText(dc,buffer,-1,&r,DT_SINGLELINE|DT_CENTER|DT_VCENTER); 
        EndPaint(hwnd,&ps);
        return 0;
    }

    if (msg == WM_INPUT) {
        strcpy(buffer, "Recieved input.");
        //assert(false);
        PostMessage(hwnd, WM_PAINT, wparam, lparam);
        return 0;
    }

    if (msg == WM_DESTROY) {
        PostQuitMessage(0);
        return 0;
    }

    return DefWindowProc(hwnd, msg, wparam, lparam);
}

Answer 1

如果您查看邮件的文档WM_PAINT,它会非常清楚地说:

的WM_PAINT由系统生成的消息,并且不应由应用程序进行发送.

如果某些内容无法按预期方式运行,请先查阅文档.这就是他们存在的原因.使用它们对您有利.

之所以发布WM_PAINT不起作用,是因为绘画的方式多于发送WM_PAINT消息.例如,系统设置适当的结构以允许应用程序在窗口上绘画.发送WM_PAINT到窗口只是整个绘画过程的一小部分.

您可能需要的是该InvalidateRect()函数,它告诉操作系统您要重新绘制窗口的某个区域.操作系统然后执行适当的绘画程序.