为什么当两个自定义控件添加了计时器时设计器会变慢？

Question

我有一个用于长时间处理的自定义控件。此控件围绕一个点旋转圆圈。为此，我使用了在设计时间和运行时间工作的计时器。当一个控件添加到表单时没有问题。但是加了两个成型，设计师就慢了那么多。为什么会出现此问题，我该如何解决？

我在这个项目中的代码：

 public class SpinningCircles : Control
{
    bool fullTransparency = true;
    int increment = 1;
    int radius = 4;
    int n = 8;
    int next = 0;
    int k = 0;
    Timer timer;
    public SpinningCircles()
    {
        timer = new Timer();
        timer.Tick += timer_Tick;
        timer.Enabled = true;
        SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer | ControlStyles.ResizeRedraw | ControlStyles.UserPaint | ControlStyles.SupportsTransparentBackColor, true);
        BackColor = Color.Transparent;
    }
    void timer_Tick(object sender, EventArgs e)
    {
        Invalidate();
    }
    protected override void OnPaint(PaintEventArgs e)
    {
        if (fullTransparency)
        {
            Transparencer.MakeTransparent(this, e.Graphics);
        }
        e.Graphics.SmoothingMode = SmoothingMode.HighQuality;
        int length = Math.Min(Width, Height);
        PointF center = new PointF(length / 2, length / 2);
        int bigRadius = length / 2 - radius - (n - 1) * increment;
        float unitAngle = 360 / n;
        next++;
        next = next >= n ? 0 : next;
        int a = 0;
        for (int i = next; i < next + n; i++)
        {
            int factor = i % n;
            float c1X = center.X + (float)(bigRadius * Math.Cos(unitAngle * factor * Math.PI / 180));
            float c1Y = center.Y + (float)(bigRadius * Math.Sin(unitAngle * factor * Math.PI / 180));
            int currRad = radius + a * increment;
            PointF c1 = new PointF(c1X - currRad, c1Y - currRad);
            e.Graphics.FillEllipse(Brushes.Black, c1.X, c1.Y, 2 * currRad, 2 * currRad);
            using (Pen pen = new Pen(Color.White, 2))
                e.Graphics.DrawEllipse(pen, c1.X, c1.Y, 2 * currRad, 2 * currRad);
            a++;
        }
    }
    protected override void OnVisibleChanged(EventArgs e)
    {
        timer.Enabled = Visible;
        base.OnVisibleChanged(e);
    }
    public bool FullTransparent
    {
        get
        {
            return fullTransparency;
        }
        set
        {
            fullTransparency = value;
        }
    }
}
public class Transparencer
{
    public static void MakeTransparent(Control cont, Graphics g)
    {
        if (cont.Parent != null)
        {
            Bitmap behind = new Bitmap(cont.Parent.Width, cont.Parent.Height);
            foreach (Control c in cont.Parent.Controls)
                if (c.Bounds.IntersectsWith(c.Bounds) & c != cont)
                    c.DrawToBitmap(behind, c.Bounds);
            g.DrawImage(behind, -cont.Left, -cont.Top);
            behind.Dispose();
        }
    }
}

Answer 1

Why does this problem occurs and how can I fix it?

该问题与设计时间和计时器没有任何共同之处，而是您的 MakeTransparent 方法的错误实现。

首先，条件有一个明显的bug

c.Bounds.IntersectsWith(c.Bounds)

此错误的影响是它为每个控件调用 c.DrawToBitmap 而不是调用者。但是 DrawToBitmap 会触发 OnPaint，所以当另一个控件也是 SpinningCircles 时，它也会做同样的事情，所以它会命中当前的调用者，你最终会陷入无限的 OnPaint 循环.

根据预期修复条件

c.Bounds.IntersectsWith(cont.Bounds)

只要两个自定义控件不重叠，就会解决此问题。

整个实现是不正确的。你一开始不应该这样做，但一旦你这样做了，它至少应该只为与调用者 相交并且具有较低 ZOrder 的控件调用 DrawToBitmap .像这样：

public static void MakeTransparent(Control control, Graphics g)
{
    var parent = control.Parent;
    if (parent == null) return;
    var bounds = control.Bounds;
    var siblings = parent.Controls;
    int index = siblings.IndexOf(control);
    Bitmap behind = null;
    for (int i = siblings.Count - 1; i > index; i--)
    {
        var c = siblings[i];
        if (!c.Bounds.IntersectsWith(bounds)) continue;
        if (behind == null)
            behind = new Bitmap(control.Parent.ClientSize.Width, control.Parent.ClientSize.Height);
        c.DrawToBitmap(behind, c.Bounds);
    }
    if (behind == null) return;
    g.DrawImage(behind, control.ClientRectangle, bounds, GraphicsUnit.Pixel);
    behind.Dispose();
}

为什么当两个自定义控件添加了计时器时设计器会变慢？

Why does the designer slowing when two custom controls has timer added?

c#

timer

custom-controls

winforms

busyindicator