c++ - 使用 RedrawWindow 或 SendMessage(WM_PAINT) 重绘后窗口出现故障

Question

我正在使用标准 Windows API 用 C++ 编写应用程序。它使用按钮进行一些简单的注册表修改。按下按钮时，它会更改显示在底部的标签。要更改它，我需要重新绘制窗口(它会根据需要自动更改标签)。但是当我重新绘制窗口时，它开始出现故障。静态标签开始闪烁，按钮完全消失，但在移动窗口后停止。这是它发生的 GIF:

这是我的 WndProc 函数:

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
    static HFONT s_hFont = NULL;
    HWND drive;
    switch (message)
    {
        case WM_COMMAND:
            {
                int wmId = LOWORD(wParam);
                // Parse the menu selections:
                switch (wmId)
                {
                    case IDM_ABOUT:
                        DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
                        break;
                    case IDM_EXIT:
                        DestroyWindow(hWnd);
                        break;
                    case APPLY_BUTTON:
                        SetRegistryValues(hWnd);
                        break;
                    case CDRIVE_BUTTON:
                        newDriveSelection = 0;
                        RedrawWindow(hWnd, NULL, NULL, RDW_INVALIDATE); // tried both this...
                        break;
                    case DDRIVE_BUTTON:
                        newDriveSelection = 1;
                        InvalidateRect(hWnd, hWndSize, NULL); // ...and this
                        break;
                    default:
                        return DefWindowProc(hWnd, message, wParam, lParam);
                }
            }
            break;
    case WM_CREATE:
        {
        const TCHAR* fontName = _T("Tahoma");
        const long nFontSize = 10;

        HDC hdc = GetDC(hWnd);

        LOGFONT logFont = {0};
        logFont.lfHeight = -MulDiv(nFontSize, GetDeviceCaps(hdc, LOGPIXELSY), 72);
        logFont.lfWeight = FW_MEDIUM;
        _tcscpy_s(logFont.lfFaceName, fontName);

        s_hFont = CreateFontIndirect(&logFont);
        ReleaseDC(hWnd, hdc);
        //s_hFont = (HFONT)GetStockObject();
    }
    break;
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hWnd, &ps);
            HWND CDrvButton = CreateWindow(
                L"BUTTON",  // Predefined class; Unicode assumed 
                L"Set to C: Drive",      // Button text 
                WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
                20,         // x position 
                20,         // y position 
                156,        // Button width
                21,        // Button height
                hWnd,     // Parent window
                (HMENU)CDRIVE_BUTTON,       // No menu.
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND DDrvButton = CreateWindow(
                L"BUTTON",  // Predefined class; Unicode assumed 
                L"Set to D: Drive",      // Button text 
                WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
                20,         // x position 
                53,         // y position 
                156,        // Button width
                21,        // Button height
                hWnd,     // Parent window
                (HMENU)DDRIVE_BUTTON,       // No menu.
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND quit = CreateWindow(
                L"BUTTON",  // Predefined class; Unicode assumed 
                L"Quit",      // Button text 
                WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
                20,         // x position 
                125,         // y position 
                54,        // Button width
                21,        // Button height
                hWnd,     // Parent window
                (HMENU)IDM_EXIT,       // No menu.
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND apply = CreateWindow(
                L"BUTTON",  // Predefined class; Unicode assumed 
                L"Apply",      // Button text 
                WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
                220,         // x position 
                125,         // y position 
                63,        // Button width
                21,        // Button height
                hWnd,     // Parent window
                (HMENU)APPLY_BUTTON,       // No menu.
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND the = CreateWindow(
                L"static", 
                L"ST_U",
                WS_CHILD | WS_VISIBLE | WS_TABSTOP,
                35, 
                82, 
                28, 
                17,
                hWnd, 
                (HMENU)(501),
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE), 
                NULL);
            drive = CreateWindow(
                L"static",
                L"ST_U",
                WS_CHILD | WS_VISIBLE | WS_TABSTOP,
                66,
                82,
                18,
                17,
                hWnd,
                (HMENU)(501),
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND selected = CreateWindow(
                L"static",
                L"ST_U",
                WS_CHILD | WS_VISIBLE | WS_TABSTOP,
                87,
                82,
                196,
                17,
                hWnd,
                (HMENU)(501),
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            HWND newdrv = CreateWindow(
                L"static",
                L"ST_U",
                WS_CHILD | WS_VISIBLE | WS_TABSTOP,
                25,
                99,
                276,
                23,
                hWnd,
                (HMENU)(501),
                (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
                NULL);
            SetWindowText(the, L"The");
            SetWindowText(drive, GetDriveLetter());
            SetWindowText(selected, L"drive is set as the current drive.");
            switch (newDriveSelection) {
                case 0:
                    SetWindowText(newdrv, L"The C: drive will be when you click Apply.");
                    break;
                case 1:
                    SetWindowText(newdrv, L"The D: drive will be when you click Apply.");
                    break;
                default:
                    SetWindowText(newdrv, L"");
                    break;
            }
            SendMessage(CDrvButton, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(DDrvButton, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(apply, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(quit, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(the, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(drive, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(selected, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            SendMessage(newdrv, WM_SETFONT, (WPARAM)s_hFont, (LPARAM)MAKELONG(TRUE, 0));
            EndPaint(hWnd, &ps);
        }
        break;
    case WM_DESTROY:
        DeleteObject(s_hFont);
            PostQuitMessage(0);
            break;
        default:
            return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

什么可能导致我的代码出现问题？我认为这是 WM_PAINT 处理程序的问题，因为有时在取消最小化程序时也会发生这种情况。

Answer 1

每次应用程序重绘时您都在创建组件 - 处理 WM_PAINT消息，这就是为什么会出现闪烁。将所有内容从:

HDC hdc = BeginPaint(hWnd, &ps);
// move everything in here to WM_CREATE message handling section
EndPaint(hWnd, &ps);

block 到 WM_CREATE部分。 paint 事件用于绘画，而不是用于创建窗口(组件)、发送消息或处理输入。声明:

switch (newDriveSelection)

更适合 WM_COMMAND消息处理部分。