允许自定义控件正确滚动出视野

我有一个自定义控件，其中包含带有文本的填充圆角矩形。（实际控件更加复杂，但是此处显示的代码具有相同的症状。）我将控件的实例附加到Panel，并使用AutoScroll = true使Panel成为另一个Panel的子级。我认为这对于正确的滚动行为就足够了，但是如果您滚动以使控件的左侧偏离面板的左侧，则它会粘住并且控件会收缩。与滚动相同，因此控件应在顶部关闭。（底部和右侧似乎没有问题。）这是示例代码（需要对System.Windows.Forms和System.Drawing的引用。）我在Windows上将Visual Studio 2010与.NET 4客户端一起使用。

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;


namespace CustomControlScrollTest
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }

    // Form with a Dock = Fill panel with autoscroll turned on, and a nested panel
    // with few custom roundRectControls.
    public class Form1 : Form
    {
        Panel autoScrollPanel;
        Panel rectPanel;

        public Form1()
        {
            Size = new Size(300, 200);

            autoScrollPanel = new Panel();
            autoScrollPanel.Dock = DockStyle.Fill;
            autoScrollPanel.AutoScroll = true;
            autoScrollPanel.AutoScrollMinSize = new Size(600, 450);

            autoScrollPanel.Resize += autoScrollPanel_Resize;
            autoScrollPanel.Scroll += autoScrollPanel_Scroll;

            Controls.Add(autoScrollPanel);

            rectPanel = new Panel();
            rectPanel.Size = autoScrollPanel.AutoScrollMinSize;
            rectPanel.Controls.AddRange(new RoundRectControl[] {
                new RoundRectControl(),
                new RoundRectControl(),
                new RoundRectControl(),
                new RoundRectControl(),
                new RoundRectControl()
            });

            foreach (Control c in rectPanel.Controls)
            {
                c.Click += c_Click;
            }

            autoScrollPanel.Controls.Add(rectPanel);

            placeBoxes();
        }

        // we want to be able to recalculate the boxes position at any time
        // in the real program this occurs due to model changes
        void c_Click(object sender, EventArgs e)
        {
            placeBoxes();
        }

        void autoScrollPanel_Scroll(object sender, ScrollEventArgs e)
        {
            Refresh();
        }

        void autoScrollPanel_Resize(object sender, EventArgs e)
        {
            Refresh();
        }

        private void placeBoxes()
        {
            for (int i = 0; i < rectPanel.Controls.Count; ++i)
            {
                int j = i + 1;
                var node = rectPanel.Controls[i] as RoundRectControl;
                if (node != null)
                {
                    node.Title = "Hello (" + j + ")";
                    node.Location = new Point(i * 100, j * 75);
                    node.Visible = true;                   
                }
            }
        }
    }

    // A rounded rectangle filled blue with a black border and white text
    // the size is determined by the text
    public class RoundRectControl : Control
    {
        public RoundRectControl()
        {
            var f = SystemFonts.MessageBoxFont;
            titleFont = new Font(f.Name, f.SizeInPoints + 2, FontStyle.Bold, GraphicsUnit.Point);
            ResizeRedraw = true;
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            var g = e.Graphics;

            var left = e.ClipRectangle.X;
            var right = left + titleWidth + 2 * radius;
            var top = e.ClipRectangle.Y;
            var bottom = top + nodeHeight + 2 * radius;

            var r2 = 2 * radius;

            using (var path = new GraphicsPath())
            {
                path.AddArc(left,       bottom - r2, r2,  r2, 90,  90);
                path.AddArc(left,       top,         r2,  r2, 180, 90);
                path.AddArc(right - r2, top,         r2,  r2, 270, 90);
                path.AddArc(right - r2, bottom - r2, r2,  r2, 0,   90);
                path.CloseFigure();

                g.FillPath(titleBrush, path);
                g.DrawPath(borderPen, path);
            }

            g.DrawString(title, titleFont, titleTextBrush, left + radius, top + radius);
        }

        private string title;
        public string Title
        {
            get { return title; }
            set
            {
                title = value;
                Size = getSize();
                Invalidate();
            }
        }

        private Brush titleBrush = Brushes.Blue;

        private Brush titleTextBrush = Brushes.White;

        private Pen borderPen = Pens.Black;

        private Size getSize()
        {
            var g = CreateGraphics();
            var titleSize = g.MeasureString(title, titleFont);
            titleWidth = (int)titleSize.Width;
            nodeHeight = (int)titleSize.Height;
            return new Size(titleWidth + 2 * radius + 1, nodeHeight + 2 * radius + 1);
        }

        public override Size GetPreferredSize(Size proposedSize)
        {
            return getSize();
        }

        private int titleWidth;
        private int nodeHeight;

        private Font titleFont;

        private int radius = 5;
    }
}