How do I get another application's window handle passed to Delphi via a mouse click

Question

How can I get the handle of a window to be passed to Delphi by the user selecting the window (could be any other aplication\'s window) by clicking with the mouse on it. In m

Answer 1

if you know what text is in the title of the window, this code will do the trick for you:

var
  WindowList: TList;

function GetHandle (windowtitle: string): HWND;
var
  h, TopWindow: HWND;
  Dest: array[0..80] of char;
  i: integer;
  s: string;

  function getWindows(Handle: HWND; Info: Pointer): BOOL; stdcall;
    begin
      Result:= True;
      WindowList.Add(Pointer(Handle));
    end;

begin
  result:= 0;

  try
    WindowList:= TList.Create;
    TopWindow:= Application.Handle;
    EnumWindows(@getWindows, Longint(@TopWindow));
    i:= 0;
    while (i < WindowList.Count) and (result = 0) do
      begin
        GetWindowText(HWND(WindowList[i]), Dest, sizeof(Dest) - 1);
        s:= dest;
        if length(s) > 0 then
          begin
            if (Pos(UpperCase(Windowtitle), UpperCase(s)) >= 1) then
              begin
                h:= HWND(WindowList[i]);
                if IsWindow(h) then
                  result:= h
             end
           end;
        inc(i)
      end
    finally
      WindowList.Free;
    end;
end;

Usage in your example (notepad puts the name of the opened file in the window caption):

h:= getHandle('text.txt');
if (h = 0)
  // Oops not found
else 
  begin
    // you got the handle!
  end;

I used this code to check if my application was already up and running. But it can be used on any launched application.