当样式为 WS_CHILD 时，通过 ps.rcPaint 查找脏区不起作用

Question

我用C++写过用WinApi画的程序。 我的回调函数：

/*  This function is called by the Windows function DispatchMessage()  */
LRESULT CALLBACK WindowProcedure(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)                  /* handle the messages */
    {
        case WM_DESTROY:
            PostQuitMessage(0);       /* send a WM_QUIT to the message queue */
            break;
        case WM_ERASEBKGND:
            {
                elWidget *widget = (elWidget *)GetWindowLong(hwnd, GWL_USERDATA);
                if (widget)
                {
                    PAINTSTRUCT ps;
                    HDC hdc = BeginPaint(hwnd, &ps);
                    HBRUSH hBrush = CreateSolidBrush(widget->color.ColorRef());
                    FillRect((HDC)wParam, &ps.rcPaint, hBrush);
                    DeleteObject(hBrush);
                    EndPaint(hwnd, &ps);
                }
            }
            break;
        default:                      /* for messages that we don't deal with */
            return DefWindowProc(hwnd, message, wParam, lParam);
    }
    return 0;
}

它适用于独立窗口（样式为WS_OVERLAPPED），但当样式为WS_CHILD 或WS_CHILD | WS_VISIBLE 时，ps.rcPaint 始终为 (0,0,0,0)。不知道怎么解决。

elButton::elButton(elWidget *owner)
        : elWidget(owner)
{
    WNDCLASSEX winclChild;        /* Data structure for the windowclass */
    /* The Window structure */
    winclChild.hInstance = gThisInstance; //global variable instance
    winclChild.lpszClassName = L"Child";
    winclChild.lpfnWndProc = WindowProcedure;      /* This function is called by windows */
    winclChild.style = CS_DBLCLKS;                 /* Catch double-clicks */
    winclChild.cbSize = sizeof (WNDCLASSEX);

    /* Use default icon and mouse-pointer */
    winclChild.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    winclChild.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    winclChild.hCursor = LoadCursor (NULL, IDC_ARROW);
    winclChild.lpszMenuName = NULL;                 /* No menu */
    winclChild.cbClsExtra = 0;                      /* No extra bytes after the window class */
    winclChild.cbWndExtra = 0;                      /* structure or the window instance */
    /* Use Windows's default colour as the background of the window */
    winclChild.hbrBackground = 0;// CreateSolidBrush(RGB(255, 200, 200));//(HBRUSH)COLOR_WINDOW;//COLOR_BACKGROUND;

    /* Register the window class, and if it fails quit the program */
    if (!RegisterClassEx(&winclChild))
        return;
    hwnd = CreateWindowEx(
        0,                   /* Extended possibilites for variation */
        L"Child",         /* Classname */
        L"Title",       /* Title Text */
        WS_CHILD | WS_VISIBLE,
        100,
        100,
        40,
        40,
        owner->getHwnd(),        /* The window is a child-window to desktop */
        NULL,                /* No menu */
        gThisInstance,       /* Program Instance handler */
        this                 /* to lParam */
       );
    SetWindowLong(hwnd, GWL_USERDATA, (long)this);
}

我可以在 Google Disk 上添加指向整个项目的链接，但我不能保证它会永久保存多年。

Answer 1

BeginPaint 只能在 WM_PAINT 上调用，

要获取 WM_ERASEBKGND 上的剪切框，请改为调用 GetClipBox((HDC)wParam,&rect);

Answer 2

仅将BeginPaint/EndPaint 用于WM_PAINT。

来自WM_PAINT: 的 Windows 文档

应用程序不应调用 BeginPaint，除非响应 WM_PAINT 消息。对BeginPaint 的每次调用都必须有一个 对应调用EndPaint函数。

虽然您的代码看起来可以工作，但它可能会在其他地方引起问题，例如WM_PAINT

要从WM_PAINT 外部获取更新区域，请使用GetUpdateRect。但是，GetUpdateRect 不能用于WM_ERASEBKGND。另见GetUpdateRect

一个简单的解决方案是强制WM_ERASEBKGND 什么都不做，然后在WM_PAINT 中处理所有事情

switch(msg)
{
case WM_ERASEBKGND:
    return TRUE;
case WM_PAINT:
    ...
}

Answer 3

这段代码非常适合我。答案是我们必须分别为父窗口和子窗口定义单独的窗口类。我看到SetWindowLong 在所有情况下都能正常工作。但是如果你想立即用新数据重绘新窗口，你必须删除WS_VISIBLE作为你的创建样式，并在ShowWindow之前删除SetWindowLong。 ShowWindow 函数使您的窗口可见并使用新参数重新绘制它。

#include <windows.h>

LRESULT CALLBACK WndProc(HWND hWnd,
                         UINT message,
                         WPARAM wParam,
                         LPARAM lParam);

int RegClass(HINSTANCE hInstance,LPCTSTR lpszClassName)
{
    WNDCLASS wc;
    wc.style = CS_HREDRAW | CS_VREDRAW | CS_DBLCLKS | CS_OWNDC;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.lpfnWndProc = WndProc;
    wc.lpszClassName = (LPCTSTR)lpszClassName;
    wc.lpszMenuName = (LPCTSTR)NULL;
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW);
    wc.hCursor = (HCURSOR)LoadCursor(NULL,IDC_CROSS);
    wc.hIcon = (HICON)LoadIcon(NULL,IDI_APPLICATION);
    return RegisterClass(&wc);
}

HWND hWnd0, hWnd1;

int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine,
                   int nShowCmd)
{
    MSG message;

    static LPCTSTR lpszClName = L"Wnd Class";
    static LPCTSTR lpszCl0Name = L"Child Class";
    if(!RegClass(hInstance,lpszClName))
        exit(0);
    if(!RegClass(hInstance,lpszCl0Name))
        exit(0);

    hWnd0 = CreateWindow(
        lpszClName,
        L"Привіт!",
        WS_OVERLAPPEDWINDOW | WS_VISIBLE | WS_CLIPCHILDREN | WS_CLIPSIBLINGS,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        800,
        600,
        0,
        0,
        hInstance,
        NULL
        );

    hWnd1 = CreateWindow(
        lpszCl0Name,
        L"Привіт!",
        WS_CHILD | WS_CLIPCHILDREN | WS_CLIPSIBLINGS,
        40,
        40,
        400,
        300,
        hWnd0,
        0,
        hInstance,
        NULL
        );

    ShowWindow(hWnd0,SW_SHOWNORMAL);
    UpdateWindow(hWnd0);

    RECT WndRect;

    // For parent redraw
    GetWindowRect(hWnd0, &WndRect);
    MoveWindow(hWnd0, WndRect.left, WndRect.top, 801, 601, TRUE);

    SetWindowLong(hWnd0, GWL_USERDATA, RGB(0, 255, 0));

    ShowWindow(hWnd1,SW_SHOWNORMAL);
    UpdateWindow(hWnd1);

    while (GetMessage(&message,0,0,0))
    {
        TranslateMessage(&message);
        DispatchMessage(&message);
    }

    return message.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd,
                         UINT message,
                         WPARAM wParam,
                         LPARAM lParam)
{
    switch (message)                  /* handle the messages */
    {
        case WM_CREATE:
            InvalidateRect(hWnd, NULL, TRUE);
            break;

        case WM_DESTROY:
            PostQuitMessage(0);       /* send a WM_QUIT to the message queue */
            break;
        case WM_ERASEBKGND:
            {
                if (true)
                {
                    PAINTSTRUCT ps;
                    HDC hdc = BeginPaint(hWnd, &ps);

                    COLORREF color = (hWnd == hWnd0) ? RGB(255, 0, 0) : GetWindowLong(hWnd0, GWL_USERDATA);

                    HBRUSH hBrush = CreateSolidBrush(color);
                    FillRect((HDC)wParam, &ps.rcPaint, hBrush);
                    DeleteObject(hBrush);
                    EndPaint(hWnd, &ps);

                    ValidateRect(hWnd, NULL);
                }
            }
            break;
        default:                      /* for messages that we don't deal with */
            return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

结果会是。