🚀 go-pugleaf

MS wrote:
> Hi,
> we can use GetWindowLong(AHandle,GWL_WNDPROC) and
> SetWindowLong(AHandle,GWL_WNDPROC,AWndProc) to Hook an window wndproc in our
> owner program,But how to do it for other program window?
> Example,I want to hook NOTEPAD's main window WNDPROC,the under code can't do
> it:
> 
> var
>   OldWndProc:Pointer;
> 
> function
> NewWndProc(AHwnd:HWND;uMsg:UINT;wParam:WPARAM;lParam:LPARAM):UINT;stdcall;
> begin
>   ////Do myself something....
>   CallWindowProc(OldWndProc,AHwnd,uMsg,wParam,lParam);
> end;
> 
> procedure TForm1.Button1Click(Sender:TObject);
> var
>   H:HWND;
> begin
>   h:=FindWindow('Notepad',nil);
>   if h=0 then exit;
>   OldWndProc:=GetWindowLong(h,GWL_WNDPROC);  /////Error : Access denied
>   SetWindowLong(h,GWL_WNDPROC,integer(@NewWndProc));
> end;
> 
> ......
> 
> I'm sorry for my english.
> 
> Thanks in advance.
> 
> 
SetWindowLong must be executed in the context of the process that 
contains the window thread, so you cannot subclass Notepad's main window 
using it.

Instead, use SetWindowsHookEx, with the hook procedure being called from 
a DLL you have written.

Regards,
Scott