Traverse the global list of all windows

Problem/Question/Abstract:

Traverse the global list of all windows

Answer:

Sometimes you may want to do something with all windows (and controls) on the screen, including non-Delphi windows.

For such a purpose, you will use the API function EnumWindows. The following code includes the calls MakeProcInstance/ FreeProcInstance, which are needed in 16bit-Windows (including Delphi 1 under Win95).

This sample code hides every existing window.. a rather useless example, but after all, it's just an example.


function NextWindow(Wnd: HWnd; Form: TForm1): Boolean; export;
{$IFDEF Win32} stdcall;
{$ENDIF}
begin
  ShowWindow(Wnd, SW_HIDE);
  NextWindow := true; { next window, please }
end;

procedure TForm1.Sample;
var
  EnumProc: TFarProc;
begin
  { this works in Win32 }
  EnumWindows(@NextWindow, LongInt(Self));

  { MakeProcInstance for Win16 }
  EnumProc := MakeProcInstance(@NextWindow, HInstance);
  EnumWindows(EnumProc, 0);
  FreeProcInstance(EnumProc);
end;