How to create transparent control with TCustomTransparentControl? - delphi

Question

I want to create a transparent panel that holds an PNG image that has transparency in it. I want to put this panel on top of other panels and see trough.
I have the code below but it won't accept controls. If I uncomment the commented lines the IDE raises an exception when I put the controls on the form.
unit TransparentPanel5;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Vcl.Controls, ExtCtrls;
type
TTransparentPanel5 = class(TCustomTransparentControl)
private
public
constructor Create(AOwner: TComponent); override;
procedure CreateParams(var Params: TCreateParams); override;
end;
procedure Register;
implementation
constructor TTransparentPanel5.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
//ControlStyle := ControlStyle - [csSetCaption]+ [csAcceptsControls];
end;
procedure TTransparentPanel5.CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(Params);
// Params.ExStyle := Params.ExStyle + WS_EX_Transparent;
// ControlStyle := ControlStyle - [csOpaque] + [csAcceptsControls]
end;
procedure Register;
begin
RegisterComponents('His', [TTransparentPanel5]);
end;
end.

Answer 1

You've got two unrelated questions. I chose to answer the second one.
The IDE raise an AV because you fail to apply extended styles properly. You have to use or operator to set a bit. When you use + you add up the value of the style bit and end up with an entirely different meaning, in this case with some WS_EX_MDICHILD which causes the CreateWindowEx call to fail.
Should be like this:
procedure TTransparentPanel5.CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(Params);
Params.ExStyle := Params.ExStyle or WS_EX_Transparent;
// ControlStyle := ControlStyle - [csOpaque] + [csAcceptsControls]
end;
Note that it won't have any effect since the TCustomTransparentControl already sets that extended style.