如何让控件的背景透明(100分)

我想做一个图像显示的控件，比如说一个透明的Gif文件，我想让它放到窗体或者是
其他程序如Office中可以透明显示，我想用ActiveForm来做，不知道可不可以，再有
如果直接选择ActiveX控件，一定要从那些控件继承吗？我没有发现我能用的，这个怎么办？

gz

这里有个控件的源代码，非常好用，可惜焦点在这个控件上时不透明，你可以试着改一下。
unit RbsWiredEdit;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;

const
TWM_RbsInvalidate=WM_USER+1;

type
TRbsWiredEdit = class(TEdit)
private
{ Private declarations }
procedure RbsInvalidate(var Message:TMessage)
message
TWM_RbsInvalidate;
procedure CNCTLCOLOREDIT(var Message:TWMCTLCOLOREDIT)
message
CN_CTLCOLOREDIT;
procedure WMEraseBkgnd(var Message: TWMEraseBkgnd)
message WM_ERASEBKGND;
procedure WMMove(var Message: TMessage)
message WM_MOVE;

protected
{ Protected declarations }
FTransparent: boolean;
procedure CreateWnd
override;
procedure CreateParams(var Params: TCreateParams)
override;
procedure DoExit
override;
procedure DoEnter
override;
public
{ Public declarations }
constructor Create(AOwner: TComponent)
override;
procedure Invalidate
override;

published
{ Published declarations }
end;

procedure Register;

implementation

constructor TRbsWiredEdit.Create(AOwner:TComponent);
begin
inherited create(AOwner);
ftransparent:=true;
end;

procedure TRbsWiredEdit.CreateWnd;
begin
inherited CreateWnd;
if fTransparent then
begin
SetWindowLong(Parent.Handle, GWL_STYLE,
GetWindowLong(Parent.Handle, GWL_STYLE) and not WS_CLIPCHILDREN);
end;
end;

procedure TRbsWiredEdit.RbsInvalidate(var Message:TMessage);
var r:TRect;
begin
if (Parent<>nil) and FTransparent then
begin
r:=ClientRect;
r.TopLeft:=Parent.ScreenToClient(ClientToScreen(r.TopLeft));
r.BottomRight:=Parent.ScreenToClient(ClientToScreen(r.BottomRight));
RedrawWindow(Handle,nil,0,RDW_FRAME+RDW_INVALIDATE);
end;
end;

procedure TRbsWiredEdit.CNCTLCOLOREDIT(var Message:TWMCTLCOLOREDIT);
begin
if FTransparent then
with Message do
begin
SetBkMode(ChildDC,Windows.TRANSPARENT);
Result:=GetStockObject(HOLLOW_BRUSH)
end
else inherited;
end;



procedure TRbsWiredEdit.WMEraseBkgnd(var Message:TWMERASEBKGND);
begin
if FTransparent and not (csDesigning in ComponentState) then
PostMessage(Handle,TWM_RbsInvalidate,0,0)
else inherited;
end;

procedure TRbsWiredEdit.WMMove(var message:TMessage);
begin
inherited;
if FTransparent then SendMessage(Handle,TWM_RbsInvalidate,0,0)
else Invalidate;
end;

procedure TRbsWiredEdit.CreateParams(var Params:TCreateParams);
begin
inherited CreateParams(Params);
if (CsDesigning in ComponentState) then exit;
with Params do
begin
ExStyle:=ExStyle or WS_EX_TRANSPARENT;
end;
end;

procedure TRbsWiredEdit.DoExit;
begin
inherited;
FTransparent:=true;
SetCursor(0);
RecreateWnd;
end;

procedure TRbsWiredEdit.DoEnter;
var exstyle,stdstyle:longint;
begin
inherited;
Ftransparent:=false;
StdStyle:= Windows.GetWindowLong(handle, GWL_EXSTYLE);
exStyle:= StdStyle and not WS_EX_TRANSPARENT;
Windows.SetWindowLong(handle, GWL_EXSTYLE, exStyle);
invalidate;
end;

procedure TRbsWiredEdit.Invalidate;
begin
if FTransparent then SendMessage(Handle,TWM_RbsInvalidate,0,0)
else inherited;
end;

procedure Register;
begin
RegisterComponents('Rombest', [TRbsWiredEdit]);
end


end.

如果直接选择ActiveX控件，一定要从那些控件继承吗？
->不一定，可以通过delphi activex(DAX)框架来手工编写，不过可能较复杂。
我没有发现我能用的，这个怎么办？
->delphi编写activex控件受到的限制太多，可以考虑用vb来开发。

GZ