Moving-Controls-over-the-form


            Title: Moving Controls over the form
Question: How is it possiple to move an control over the form ?
Answer:
It's very simple - so don't try to write hundreds of lines to solve this problem
just take a look at this small source-snip
all what we need to do is to override the dynamic MouseDown method of the TControl-BaseClass and fire an WM_SysCommand event with the magicKey $F012.
best regards 
Boris Benjamin Wittfoth
{-----------------------------------------------------------------------------
 hEaDRoOm Development
 29.10.2002
 Unit Name: HREdit
 Author: Benjamin Benjamin Wittfoth
 Purpose:
 History:
-----------------------------------------------------------------------------}
unit HREdit;
interface
uses
 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
 StdCtrls;
type
 THREdit = class(TEdit)
 private
 fDragable:Boolean;
 protected
 procedure MouseDown(Button: TMouseButton;Shift: TShiftState; X, Y: Integer);override;
 public
 Constructor Create(AOwner:TComponent);override;
 Destructor Destroy;override;
 published
 property Dragable:Boolean read fDragable write fDragable;
 end;
procedure Register;
implementation
procedure Register;
begin
 RegisterComponents('HEADROOM DEVELOPMENT', [THREdit]);
end;
{ THREdit }
constructor THREdit.Create(AOwner: TComponent);
begin
 inherited Create(AOwner);
end;
destructor THREdit.Destroy;
begin
 inherited;
end;
procedure THREdit.MouseDown(Button: TMouseButton; Shift: TShiftState; X,
 Y: Integer);
const
 SC_DragMove = $F012; // important key !!
begin
 inherited;
 if assigned(onMouseDown)then
 OnMouseDown(self,Button,Shift,x,y);
 if fDragable then
 begin
 ReleaseCapture;
 (self as TControl).perform(WM_SysCommand, SC_DragMove, 0); // this is the key !
 end;
end;
end.
Forms Delphi
