双缓冲ListBox

Question

我有一个CheckedListBox(WinForms)控件(它继承自ListBox; googling显示问题在于ListBox),它固定在其表单的所有四个边上.调整窗体大小时,ListBox有一个丑陋的闪烁.我想继承CheckedListBox和设置DoubleBuffered,以true在构造函数(此技术也适用于其他控件,包括ListView和DataGridView中),但它没有任何效果.

我尝试添加WS_EX_COMPOSITED样式CreateParams,这有帮助,但使表单调整大小更慢.

有没有其他方法可以防止这种闪烁？

Answer 1

我有类似的问题,虽然有一个所有者绘制的列表框.我的解决方案是使用BufferedGraphics对象.如果您的清单不是所有者绘制的,那么您的里程可能因此解决方案而异,但也许它会给您一些灵感.

我发现TextRenderer很难渲染到正确的位置,除非我提供了TextFormatFlags.PreserveGraphicsTranslateTransform.替代方法是使用P/Invoke调用BitBlt直接在图形上下文之间复制像素.我选择这个作为两个邪恶的较小者.

/// <summary>
/// This class is a double-buffered ListBox for owner drawing.
/// The double-buffering is accomplished by creating a custom,
/// off-screen buffer during painting.
/// </summary>
public sealed class DoubleBufferedListBox : ListBox
{
    #region Method Overrides
    /// <summary>
    /// Override OnTemplateListDrawItem to supply an off-screen buffer to event
    /// handlers.
    /// </summary>
    protected override void OnDrawItem(DrawItemEventArgs e)
    {
        BufferedGraphicsContext currentContext = BufferedGraphicsManager.Current;

        Rectangle newBounds = new Rectangle(0, 0, e.Bounds.Width, e.Bounds.Height);
        using (BufferedGraphics bufferedGraphics = currentContext.Allocate(e.Graphics, newBounds))
        {
            DrawItemEventArgs newArgs = new DrawItemEventArgs(
                bufferedGraphics.Graphics, e.Font, newBounds, e.Index, e.State, e.ForeColor, e.BackColor);

            // Supply the real OnTemplateListDrawItem with the off-screen graphics context
            base.OnDrawItem(newArgs);

            // Wrapper around BitBlt
            GDI.CopyGraphics(e.Graphics, e.Bounds, bufferedGraphics.Graphics, new Point(0, 0));
        }
    }
    #endregion
}

该GDI课程(由frenchtoast建议).

public static class GDI
{
    private const UInt32 SRCCOPY = 0x00CC0020;

    [DllImport("gdi32.dll", CallingConvention = CallingConvention.StdCall)]
    private static extern bool BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, UInt32 dwRop);

    public static void CopyGraphics(Graphics g, Rectangle bounds, Graphics bufferedGraphics, Point p)
    {
        IntPtr hdc1 = g.GetHdc();
        IntPtr hdc2 = bufferedGraphics.GetHdc();

        BitBlt(hdc1, bounds.X, bounds.Y, 
            bounds.Width, bounds.Height, hdc2, p.X, p.Y, SRCCOPY);

        g.ReleaseHdc(hdc1);
        bufferedGraphics.ReleaseHdc(hdc2);
    }
}