Windows窗体：允许重叠控件的正确方法是什么？

Question

我正在制作测试程序，以了解我可以将事件添加到自定义绘制的System.Windows.Form.Control对象中。如果我能做得好，那么我可以为以后做一些更高级的事。

我正在处理附加图像的问题。我有目的地画了两个圈子。目标是让一个圆圈与另一个圆圈重叠。出于本测试程序的目的，我不关心哪个圆圈重叠哪个。但是，我确实关心角落。

上图显示中心圆被左圆圈掩埋，但左圆也是绘制角落并用它们覆盖中心圆。我希望隐藏这些角落，或者至少让它们变得透明。我确实读到有make a control transparent的方法，但是在BackColor上使用Color.Transparent会因为某些原因而给我黑色，而不是与油漆面板的颜色相匹配。

下面是GUI的代码部分（设计师不包括在内，但关键部分应该很明显）。

namespace PaintingFirstAttempt
{
    using System;
    using System.Drawing;
    using System.Windows.Forms;

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void BtnExit_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void BtnClear_Click(object sender, EventArgs e)
        {
            Graphics g1 = this.paintPanel.CreateGraphics();
            g1.Clear(this.paintPanel.BackColor);
            g1.Dispose();
        }

        private void PaintPanel_MouseDown(object sender, MouseEventArgs e)
        {
            this.paintPanel.Controls.Add(new EventableCircle { Location = new Point(e.X - 16, e.Y - 16), Size = new Size(32, 32) });
        }
    }
}

以下是自定义圈子。

namespace PaintingFirstAttempt
{
    using System;
    using System.Drawing;
    using System.Windows.Forms;

    public class EventableCircle : Control
    {
        public EventableCircle()
        {
            this.SetStyle(ControlStyles.SupportsTransparentBackColor, true);
            // this.BackColor = Color.Transparent;
        }

        private static SolidBrush fillColor = new SolidBrush(Color.Red);
        protected override void OnClick(EventArgs e)
        {
            MessageBox.Show("TODO: Bring up a combo box on right click.");
        }

        private void DrawCircle(Pen pen)
        {
            Graphics g = this.CreateGraphics();
            g.Clear(this.BackColor);
            g.FillRectangle(new SolidBrush(Color.Transparent), 0, 0, 32, 32);
            g.FillEllipse(fillColor, 0, 0, 32, 32);
            g.DrawEllipse(pen, 0, 0, 32, 32);
            g.Dispose();

        }

        protected override void OnPaint(PaintEventArgs e)
        {
            this.DrawCircle(Pens.Black);
        }

        protected override void OnMouseEnter(EventArgs e)
        {
            base.OnMouseEnter(e);
            this.DrawCircle(Pens.Blue);
        }

        protected override void OnMouseLeave(EventArgs e)
        {
            base.OnMouseLeave(e);
            this.DrawCircle(Pens.Black);
        }
    }
}

考虑到这些信息，我如何才能让圈子的角落不显示，或者找到一种方法来解决这个问题？

Answer 1

确定只需输入一个mainform form1，不需要任何代码。这是用户控件的代码，表单上的Draw 3或4，如果它们向右移动，它们可以重叠。

然后点击它们！效率低下，但宝宝哭了，我得走了，它打败了你自己的保留对象编辑器！

Public Class linectl   

    Public Sub DrawMe(ByVal g As Graphics, ByVal otherctl As Control)
        Dim where As New Rectangle(otherctl.Left - Left, otherctl.Top - Top, otherctl.Width - 1, otherctl.Height - 1)
        g.FillEllipse(Brushes.Red, where)
        g.DrawEllipse(Pens.Black, where)
    End Sub

    Protected Overrides Sub OnPaintBackground(ByVal e As System.Windows.Forms.PaintEventArgs)
        MyBase.OnPaintBackground(e)
        DrawMe(e.Graphics, Me)
        drawneighbors()
    End Sub

    Private Sub linectl_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Click
        Me.Left += 10
    End Sub

    Private Sub linectl_MoveResize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Move, Me.Resize
        If Parent IsNot Nothing Then
            For Each c In From ctl In Parent.Controls Where TypeOf ctl Is linectl Select CType(ctl, linectl)
                Using g = c.CreateGraphics
                    g.Clear(c.BackColor)
                    c.DrawMe(g, c)
                    c.drawneighbors()
                End Using
            Next
        End If
    End Sub

    Public Sub drawneighbors()
        If Parent IsNot Nothing Then
            Dim ctls = (From ctl In Parent.Controls Where TypeOf ctl Is linectl Let c = CType(ctl, linectl) _
                        Select New With {.ctl = c, _
                            .rect = New Rectangle(c.Left, c.Top, c.Width, c.Height)}).ToArray.Reverse
            For Each ctl In ctls
                Dim ctl_unclosed = ctl
                For Each ictl In (From c In ctls Where ctl_unclosed.rect.IntersectsWith(c.rect))
                    Using g = ictl.ctl.CreateGraphics
                        ictl.ctl.DrawMe(g, Me)
                    End Using
                    Using g = Me.CreateGraphics
                        Me.DrawMe(g, ictl.ctl)
                    End Using
                Next
            Next
        End If
    End Sub

End Class