public void OnMessage(ref Message m)
{
// If the designer has jumped ship, the continue partying on messages, but send them back to the original control.
if (_designer.Component is null)
{
OldWindowTarget.OnMessage(ref m);
return;
}
// We want these messages to go through the designer's WndProc method, and we want people to be able
// to do default processing with the designer's DefWndProc. So, we stuff the old window target into
// the designer's target and then call their WndProc.
IDesignerTarget designerTarget = _designer.DesignerTarget;
_designer.DesignerTarget = this;
try
{
_designer.WndProc(ref m);
}
catch (Exception ex)
{
_designer.SetUnhandledException(_childControl, ex);
}
finally
{
// If the designer disposed us, then we should follow suit.
if (_designer.DesignerTarget is null)
{
designerTarget.Dispose();
}
else
{
_designer.DesignerTarget = designerTarget;
}
// Controls (primarily RichEdit) will register themselves as drag-drop source/targets when they
// are instantiated. Normally, when they are being designed, we will RevokeDragDrop() in their
// designers. The problem occurs when these controls are inside a UserControl. At that time, we
// do not have a designer for these controls, and they prevent the ParentControlDesigner's
// drag-drop from working. What we do is to loop through all child controls that do not have a
// designer (in HookChildControls()), and RevokeDragDrop() after their handles have been created.
if (m.Msg == (int)User32.WM.CREATE)
{
Debug.Assert(_handle != IntPtr.Zero, "Handle for control not created");
Ole32.RevokeDragDrop(_handle);
}
}
}
