Question

How to get ClassName of active form (may be from another application) on Delphi?

It seems Application.ActiveFormHandle returns active form of Application only.

Answer 1

The window handle that you are looking for is, I believe, returned by GetForegroundWindow.

To get the class name, pass that window handle to the Windows API function GetClassName. Here’s a Delphi wrapper to that API function:

function GetWindowClassName(Window: HWND): string;
const
  MaxClassNameLength = 257;//256 plus null terminator
var
  Buffer: array [0..MaxClassNameLength-1] of Char;
  len: Integer;
begin
  len := GetClassName(Window, Buffer, Length(Buffer));
  if len=0 then
    RaiseLastOSError;
  SetString(Result, Buffer, len);
end;

I used a buffer of length 256 because window class names are not allowed to be longer than that.