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Activating an application and correctly setting the focus

Posted on 2007-11-14
Last Modified: 2013-11-22
I've a series of applications which can be used concurrently. The user can switch between the applications without alt-tabbing, from within each application.

This works fine, but...

If application A switches to application B, and application B has a modal dialog open, it's the main form which is shown - not the modal dialog. The user then clicks on the main form and of course nothing happens other than a series of beeps. The user has to alt tab to bring the modal dialog into view and then close this to allow access to the application.

How can I achieve the same result as alt-tabbing? This is how I'm doing it at the moment...

     Result := FindWindow(Pchar(ThisWindowClass), nil);
     ShowWindow(Result, SW_RESTORE);
     ShowWindow(Result, SW_SHOWMAXIMIZED);
     SendMessage(Result, WM_ACTIVATEAPP, 1, 0);

Thanks for any help.

Question by:steve-west
  • 2
  • 2
LVL 21

Expert Comment

ID: 20283097
I found some code that does this, here is the link.  check out the section on how to steal focus.


If you need me to provide a Delphi example, I will see what I can do.

Let me know.

Author Comment

ID: 20287767
Thank you for this, but I don't see any topics within the link which are relevant.

There is a section which relates to setting the focus to a KNOWN modal dialog but this is not what I'm after.

Application A switches to application B.

Application B could have nth number of Modal dialog boxes opened on top of each other. The way I'm currently doing this results in only the main form of application B showing, but with the dialog boxes open, the application is effectively disabled.

I need to do exactly what Alt-tabbing does - i.e. show the topmost dialog. I could send a message to the application telling it to show the topmost dialog, but how do I do this (showing the window that is, not the messagey part).


LVL 21

Accepted Solution

developmentguru earned 500 total points
ID: 20291463
I used code directly off the link in my example.  I created one program that just had a buton that brought up the modal file open dialog.  I called the form TLaunchDialog and the title was LaunchDialog.  I left it running.  In my second application I used the following code and it works as you stated you wanted it to.

procedure TForm2.Button1Click(Sender: TObject);
  WindowHandle : THandle;

  WindowHandle := FindWindow('TLaunchDialog', 'LaunchDialog');

  if WindowHandle <> 0 then
        GetCurrentThreadID(), true);


        GetCurrentThreadID(), false);

Let me know if you need more.

Author Comment

ID: 20297014
I agree, the solution you propose will return focus to an application with an open modal dialog.

The problem with this method, you have to know the class of the form you are bringing to the front. The applications that the user can switch between them hold over 3000 forms so it's not practical to code for each class type.

I've eventually managed to implement this successfully with the following approach.

1. Switch to application B from A by finding application's B main window and showing that.

2. Send application B a user defined message

3. When Application B receives this, it runs through the list of all open screens and for any screen which itself has an open screen, then bring the topmost screen to the front.

Since your solution does work, although not really suitable for my situation, I'll award the points.

Thanks fro your help


procedure TPRIAMCoreMainF.UMEnsureRestored(var Msg: TMessage);
  iCounter : integer;
  ComCounter: Integer;
  HasScreens : boolean;
  // Restore application
  if IsIconic(Application.Handle) then
  if not Visible then
    Visible := True;
  // Ensure all TOPMOST modal screens are brought to the front
  for iCounter := 0 to Screen.FormCount - 1  do
    if Screen.Forms[iCounter].Visible and
      (Screen.Forms[iCounter].FormStyle = fsNormal) and
      // ignore embedded forms
      (not (Screen.Forms[iCounter] is TPriamConnF))  then
        HasScreens := false;
        for ComCounter := 0 to Screen.Forms[iCounter].ComponentCount - 1 do
          if Screen.Forms[iCounter].Components[ComCounter] is TForm then
            HasScreens := true;
        if not HasScreens then

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