禁用 OnPaintBackground 而不对面板进行子类化？

发布于 2024-09-24 12:12:56 字数 880 浏览 5 评论 0原文

有没有办法在不子类化Panel 和重写OnPaintBackground 的情况下禁用面板的擦除？

我试图在不子类化面板的情况下实现双缓冲效果。我知道尝试这样做可能是一件奇怪的事情，但我至少想知道我是否可以。以下代码示例说明了这一点：

public partial class Form1 : Form
{
    private Bitmap m_image;

    public Form1()
    {
        InitializeComponent();

        panel1.Paint += new PaintEventHandler(panel1_Paint);
        panel1.MouseMove += new MouseEventHandler(panel1_MouseMove);

        m_image = new Bitmap(panel1.Width, panel1.Height);
    }

    void panel1_MouseMove(object sender, MouseEventArgs e)
    {
        using (Graphics g = Graphics.FromImage(m_image))
        {
            g.FillEllipse(Brushes.Black, new Rectangle(e.X, e.Y, 10, 10));
        }
        panel1.Invalidate();
    }

    void panel1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.DrawImage(m_image, 0, 0);
    }
}

这会导致闪烁，可能是因为它在每个绘制周期都会擦除面板。

原文

Is there any way to disable the erasing of a panel without subclassing Panel and overriding OnPaintBackground?

I am trying to achieve a double buffering effect without subclassing Panel. I understand that this may be a weird thing to try to do, but I'd at least like to know if I can or not. The following code sample illustrates this:

public partial class Form1 : Form
{
    private Bitmap m_image;

    public Form1()
    {
        InitializeComponent();

        panel1.Paint += new PaintEventHandler(panel1_Paint);
        panel1.MouseMove += new MouseEventHandler(panel1_MouseMove);

        m_image = new Bitmap(panel1.Width, panel1.Height);
    }

    void panel1_MouseMove(object sender, MouseEventArgs e)
    {
        using (Graphics g = Graphics.FromImage(m_image))
        {
            g.FillEllipse(Brushes.Black, new Rectangle(e.X, e.Y, 10, 10));
        }
        panel1.Invalidate();
    }

    void panel1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.DrawImage(m_image, 0, 0);
    }
}

This causes a flickering, presumably because it is erasing the panel at each paint cycle.

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从来不烧饼 2024-10-01 12:12:56

您可以破解 OnPaintBackground() 或破解 WndProc()。两者都需要派生您自己的类。这很微不足道，我只是不明白你为什么要避免它。长距离镜头是带有 WH_CALLWNDPROC 钩子的 SetWindowsHookEx()，真的太傻了。

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赤濁 2024-10-01 12:12:56

只需添加：

panel1.BackgroundImage = m_image;
//on panel1_Paint() function.

简单不是吗？

Just add:

panel1.BackgroundImage = m_image;
//on panel1_Paint() function.

Simple isn't it?

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怪我鬧 2024-10-01 12:12:56

使用反射来设置受保护的 DoubleBuffered 属性：

System.Reflection.PropertyInfo aProp =
         typeof(System.Windows.Forms.Control).GetProperty(
               "DoubleBuffered",
               System.Reflection.BindingFlags.NonPublic |
               System.Reflection.BindingFlags.Instance);

aProp.SetValue(panel1, true, null);

您还可以通过仅使更改的区域无效来提高效率（即使没有双缓冲，这也几乎不会闪烁）：

void panel1_MouseMove(object sender, MouseEventArgs e)
{
    Rectangle r = new Rectangle(e.X, e.Y, 10, 10);
    using (Graphics g = Graphics.FromImage(m_image))
    {
        g.FillEllipse(Brushes.Black, r);
    }
    panel1.Invalidate(r);
}

Use reflection to the set the protected DoubleBuffered property:

System.Reflection.PropertyInfo aProp =
         typeof(System.Windows.Forms.Control).GetProperty(
               "DoubleBuffered",
               System.Reflection.BindingFlags.NonPublic |
               System.Reflection.BindingFlags.Instance);

aProp.SetValue(panel1, true, null);

You can also make it more efficient by only invalidating the changed area (this is almost flicker-free even without the double-buffering):

void panel1_MouseMove(object sender, MouseEventArgs e)
{
    Rectangle r = new Rectangle(e.X, e.Y, 10, 10);
    using (Graphics g = Graphics.FromImage(m_image))
    {
        g.FillEllipse(Brushes.Black, r);
    }
    panel1.Invalidate(r);
}

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~没有更多了~