Delphi: How to use ShowWindow properly on external application [duplicate]

Answer 1

The following works well for me. I'm not 100% certain I have fully understood the question though, so do let me know if I've got it wrong.

var
  _PreviousHandle: HWND;
  WindowPlacement: TWindowPlacement;
....
WindowPlacement.length := SizeOf(WindowPlacement);
GetWindowPlacement(_PreviousHandle, WindowPlacement);
if WindowPlacement.flags and WPF_RESTORETOMAXIMIZED<>0 then
  WindowPlacement.showCmd := SW_MAXIMIZE
else
  WindowPlacement.showCmd := SW_RESTORE;
SetWindowPlacement(_PreviousHandle, WindowPlacement);
SetForegroundWindow(_PreviousHandle);

Note that the correct type for _PreviousHandle is HWND and not THandle.