追踪CM_CONTROLCHANGE消息的流向，可以较好的
测试代码：
procedure TForm1.Button1Click(Sender: TObject);
var
Image2 : TImage;
begin
Image2 := TImage.Create(self);
Image2.Left := 100;
Image2.Top := 50;
Image2.Picture.LoadFromFile(‘c:\pic.jpg‘);
Image2.Parent := Form1;
end;
procedure TWinControl.InsertControl(AControl: TControl);
begin
AControl.ValidateContainer(Self);
Perform(CM_CONTROLLISTCHANGE, Integer(AControl), Integer(True));
Insert(AControl);
if not (csReading in AControl.ComponentState) then
begin
AControl.Perform(CM_PARENTCOLORCHANGED, 0, 0);
AControl.Perform(CM_PARENTFONTCHANGED, 0, 0);
AControl.Perform(CM_PARENTSHOWHINTCHANGED, 0, 0);
AControl.Perform(CM_PARENTBIDIMODECHANGED, 0, 0);
if AControl is TWinControl then
begin
AControl.Perform(CM_PARENTCTL3DCHANGED, 0, 0);
UpdateControlState;
end else
if HandleAllocated then AControl.Invalidate;
AlignControl(AControl);
end;
Perform(CM_CONTROLCHANGE, Integer(AControl), Integer(True));
end;
追踪CM_CONTROLCHANGE消息的产生和执行过程，可以较好的领会VCL的思想（就是到处通知，但耦合性很弱）
原文：http://www.cnblogs.com/findumars/p/4758446.html