Win32 程序双缓冲不起作用

Question

我认为这是一个基本的双缓冲 win32 程序。在启动开始时，它运行良好，但大约 1 分钟后（在我的电脑上），它卡住了。当您将SetTimer(hwnd, 1, 2, NULL) 的第三个参数设置为更大的值时，卡住所需的时间会增加。

我已经用谷歌搜索并检查了将近两个小时的答案，但我找不到错误所在。

代码如下：

#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("HelloWin");
    HWND         hwnd;
    MSG          msg;
    WNDCLASS     wndclass;

    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("Something Wrong!"),
            szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName,      // window class name
        TEXT("DoubleBuffer"), // window caption
        WS_OVERLAPPEDWINDOW,        // window style
        GetSystemMetrics(SM_CXSCREEN) / 2,
        GetSystemMetrics(SM_CXSCREEN) / 4,
        GetSystemMetrics(SM_CXSCREEN) / 3,
        GetSystemMetrics(SM_CXSCREEN) / 3,
        NULL,                       // parent window handle
        NULL,                       // window menu handle
        hInstance,                  // program instance handle
        NULL);                     // creation parameters

    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);

    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static HBITMAP hBitmap, moldbmp;
    static HDC     hdcMem;
    static int     cxClient, cyClient;
    HDC            hdc;
    HMENU          hMenu;
    int            x, y;
    PAINTSTRUCT    ps;
    SIZE           size;

    static int  i = 50, j = 70;
    static BOOL bFlipUD = TRUE, bFlipLR = TRUE;
    static BOOL bTimerRunning = TRUE;

    switch (message)
    {
    case WM_CREATE:
        hdc = GetDC(hwnd);
        hdcMem = CreateCompatibleDC(hdc);

        hBitmap = CreateCompatibleBitmap(hdc, 750, 824);

        ReleaseDC(hwnd, hdc);

        moldbmp = SelectObject(hdcMem, hBitmap);
        SetTimer(hwnd, 1, 2, NULL);

        return 0;

    case WM_TIMER:

        if (bFlipUD)
        {
            i += 20;
            if (i >= 200)
            {
                bFlipUD ^= TRUE;
            }
        }
        else
        {
            i -= 20;
            if (i <= 0)
            {
                bFlipUD ^= TRUE;
            }
        }
        //
        if (bFlipLR)
        {
            j += 20;
            if (j >= 200)
            {
                bFlipLR ^= TRUE;
            }
        }
        else
        {
            j -= 20;
            if (j <= 0)
            {
                bFlipLR ^= TRUE;
            }
        }

        //background
        RECT rtClient;
        GetClientRect(hwnd, &rtClient);
        SetBkMode(hdcMem, TRANSPARENT);
        HBRUSH hBrush = CreateSolidBrush(RGB(155, 155, 155));
        FillRect(hdcMem, &rtClient, hBrush);
        DeleteObject(hBrush);
        //background

        //  1
        HPEN hPen = CreatePen(PS_SOLID, 7, RGB(255, 0, 0));
        HPEN hOldPen = (HPEN)SelectObject(hdcMem, hPen);

        MoveToEx(hdcMem, 0, i, NULL);
        LineTo(hdcMem, cxClient, i);
        TextOut(hdcMem, 30, i + 20, TEXT("88"), 2);
        //  2
        hPen = CreatePen(PS_SOLID, 7, RGB(55, 250, 0));
        hOldPen = (HPEN)SelectObject(hdcMem, hPen);

        MoveToEx(hdcMem, 0, i + 20, NULL);
        LineTo(hdcMem, cxClient, i + 20);
        TextOut(hdcMem, 70, i + 40, TEXT("1439"), 4);
        //  3
        hPen = CreatePen(PS_SOLID, 7, RGB(225, 150, 5));
        hOldPen = (HPEN)SelectObject(hdcMem, hPen);

        MoveToEx(hdcMem, j, 0, NULL);
        LineTo(hdcMem, j, cyClient);
        TextOut(hdcMem, 70, i + 40, TEXT("1439"), 4);

        //InvalidateRect(hwnd, NULL, FALSE);
        InvalidateRgn(hwnd, NULL, FALSE);

        return 0;

    case WM_SIZE:
        cxClient = LOWORD(lParam);
        cyClient = HIWORD(lParam);
        return 0;

    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        BitBlt(hdc, 10, 10, 750, 824,
            hdcMem, 0, 0, SRCCOPY);

        EndPaint(hwnd, &ps);
        return 0;

    case WM_DESTROY:
        KillTimer(hwnd, 1);

        SelectObject(hdcMem, moldbmp);
        DeleteObject(hBitmap);
        DeleteDC(hdcMem);

        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

Answer 1

经典的资源泄漏。每次运行通过您的 WM_TIMER 处理程序都会创建 3 个 Pens，它永远不会释放。正如CreatePen 的文档中所指出的：

当你不再需要笔时，调用DeleteObject函数将其删除。

您没有这样做，最终会耗尽可用的 GDI 资源。您可以使用任务管理器来验证 GDI 对象计数随时间的增加，方法是转到 详细信息 选项卡，右键单击标题，选择 选择列 选项并启用GDI 对象。