Why is my customized Windows Forms panel cant handle child controls? - windows

Question

I want extend an System.Windows.Forms.Panel(just inherit) and using a custom ControlDesigner.
I use a very minimalistic ControlDesigner implementation, just overwrite GetHitTest.
The problem is my custom panel instance is not ready to contains child controls any longer.
I play a little bit with AssociatedComponents but without effect. Remove custom designer attribute and it works great.
can someone help me to pin point whats wrong ???
[Designer(typeof(MyPanelDesigner)), ToolboxItem(true)]
public class MyPanel : System.Windows.Forms.Panel
{
// empty except for OnPaint
}
internal class DrawPanelDesigner : ControlDesigner
{
private MyPanel ParentControl
{
get
{
return Control as MyPanel;
}
}
public override System.Collections.ICollection AssociatedComponents
{
get
{
return ParentControl.Controls;
}
}
protected override bool GetHitTest(System.Drawing.Point point)
{
// hit detection for some owner drawed items in OnPaint
point = ParentControl.PointToClient(point);
var item = ParentControl.View.GetItemFromViewPoint(point.X, point.Y, true);
return null != item;
}

Answer 1

You are using the wrong designer. Try inheriting from the ScrollableControlDesigner instead:
internal class DrawPanelDesigner : ScrollableControlDesigner {
public DrawPanelDesigner() {
AutoResizeHandles = true;
}
private MyPanel ParentControl {
get {
return Control as MyPanel;
}
}
protected Pen BorderPen {
get {
Color penColor = Control.BackColor.GetBrightness() < .5 ?
ControlPaint.Light(Control.BackColor) :
ControlPaint.Dark(Control.BackColor);
Pen pen = new Pen(penColor);
pen.DashStyle = DashStyle.Dash;
return pen;
}
}
protected virtual void DrawBorder(Graphics graphics) {
Panel panel = (Panel)Component;
if (panel == null || !panel.Visible) {
return;
}
Pen pen = BorderPen;
Rectangle rc = Control.ClientRectangle;
rc.Width--;
rc.Height--;
graphics.DrawRectangle(pen, rc);
pen.Dispose();
}
protected override void OnPaintAdornments(PaintEventArgs pe) {
Panel panel = (Panel)Component;
if (panel.BorderStyle == BorderStyle.None) {
DrawBorder(pe.Graphics);
}
base.OnPaintAdornments(pe);
}
}