To get a control instance from a control handle

Create a Delphi project, place a tedit and TButton, and enter some text in Edit1.

{---------------Gets the control instance through the control handle-----------------------------------------------------------principle, see Classes.pas Unit, 13045 line <Delphi7>---------------------------------------principles see Classes.pas Unit, 11613 lines <Delphi2007>-------- ----------------------------principle See Classes.pas Unit, 13045 lines <Delphi2010>------------------------------------principles See Classes.pas unit, 13512 rows <DelphiXE>-----------------------} function Getinstancefromhwnd (const hwnd:cardinal):
Twincontrol;

  Type pobjectinstance = ^tobjectinstance;            tobjectinstance = packed record code:byte;
    {Short Jump $E 8}       Offset:integer; {Calcjmpoffset (Instance, @Block ^. Code); } next:pobjectinstance;
    {Mainwndproc Address}         Self:pointer;
{Control object address} end;
var wc:pobjectinstance;
  Begin Result: = nil;
  WC: = Pointer (GetWindowLong (HWnd, GWL_WNDPROC)); If WC <> nil then begin Result: = WC.
  Self;
End

End
Procedure Tform1.btn1click (Sender:tobject); Begin BTN1. Caption: = Tedit (Getinstancefromhwnd (edt1. Handle)).
Text;
 End

See how we got the text in the Edit1. Very magical, understand the VCL code, it is not so magical.