unit Unit1;

{The transparent form effect is done with Regions.

First create a region that encompasses the entire form.

Then, find the client area of the form (Client vs. non-Client) and

combine with the full region with RGN_DIFF to make the borders

and title bar visible.  Then create a region for each of the

controls and combine them with the original (FullRgn) region.}

{From various posts in the newsgroups - based on some famous

author I'm sure, but I first saw the post by Kerstin Thaler...}

interface

uses

 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

 ExtCtrls, StdCtrls;

type

 TForm1 = class(TForm)

   Button1: TButton;

   Panel1: TPanel;

   Button2: TButton;

   procedure FormDestroy(Sender: TObject);

   procedure FormCreate(Sender: TObject);

   procedure Button1Click(Sender: TObject);

   procedure Button2Click(Sender: TObject);

   procedure FormResize(Sender: TObject);

 private

   { Private declarations }

   procedure DoVisible;

   procedure DoInvisible;

 public

   { Public declarations }

 end;

var

 Form1: TForm1;

 FullRgn, ClientRgn, CtlRgn : THandle;

implementation

{$R *.DFM}

procedure TForm1.DoInvisible;

var

 AControl : TControl;

 A, Margin, X, Y, CtlX, CtlY : Integer;

begin

 Margin := ( Width - ClientWidth ) div 2;

 //First, get form region

 FullRgn := CreateRectRgn(0, 0, Width, Height);

 //Find client area region

 X := Margin;

 Y := Height - ClientHeight - Margin;

 ClientRgn := CreateRectRgn( X, Y, X + ClientWidth, Y + ClientHeight );

 //'Mask' out all but non-client areas

 CombineRgn( FullRgn, FullRgn, ClientRgn, RGN_DIFF );

 //Now, walk through all the controls on the form and 'OR' them

 // into the existing Full region.

 for A := 0 to ControlCount - 1 do begin

   AControl := Controls[A];

   if ( AControl is TWinControl ) or ( AControl is TGraphicControl )

       then with AControl do begin

     if Visible then begin

       CtlX := X + Left;

       CtlY := Y + Top;

       CtlRgn := CreateRectRgn( CtlX, CtlY, CtlX + Width, CtlY + Height );

       CombineRgn( FullRgn, FullRgn, CtlRgn, RGN_OR );

     end;

   end;

 end;

 //When the region is all ready, put it into effect:

 SetWindowRgn(Handle, FullRgn, TRUE);

end;

procedure TForm1.FormDestroy(Sender: TObject);

begin

 //Clean up the regions we created

 DeleteObject(ClientRgn);

 DeleteObject(FullRgn);

 DeleteObject(CtlRgn);

end;

procedure TForm1.DoVisible;

begin

 //To restore complete visibility:

 FullRgn := CreateRectRgn(0, 0, Width, Height);

 CombineRgn(FullRgn, FullRgn, FullRgn, RGN_COPY);

 SetWindowRgn(Handle, FullRgn, TRUE);

end;

procedure TForm1.FormCreate(Sender: TObject);

begin

 //We start out as a transparent form....

 DoInvisible;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

 //This button just toggles between transparent and not trans..

 if Button1.Caption = 'Show Form' then begin

   DoVisible;

   Button1.Caption := 'Hide Form';

 end

 else begin

   DoInvisible;

   Button1.Caption := 'Show Form';

 end;

end;

procedure TForm1.Button2Click(Sender: TObject);

begin

 Application.Terminate;

end;

procedure TForm1.FormResize(Sender: TObject);

begin

 //Need to address the transparency if the form gets re-sized.

 //Also, note that Form1 scroll bars are set to VISIBLE/FALSE.

 //I did that to save a little coding here....

 if Button1.Caption = 'Show Form' then

   DoInvisible

 else

   DoVisible;

end;

end.