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I have a largish Delphi 6 app that I have ported to Delphi XE3. At one point the main form launches another non-modal form. Sometimes (say 50%) after a second or two the newly created form moves behind the main form. Even thought it is now at the back, the newly created form still has focus so there are no activate/deactivate events. There are a few Timer controls and I have disabled them. It still happens.

I can accept my code is doing this -- but how can I find out what is happening? Is there a way to intercept when then new form moves to the back?

Just to be clear: I want both forms to be used separately. Any of them can appear behind the other. What is happening at the moment is that the z-order seems to be changing.

Rob
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  • Please can you supply a complete program the demonstrates the problem. – David Heffernan Apr 11 '13 at 12:13
  • Ok - I have tried to give out a few answer ticks. – Rob Apr 11 '13 at 12:36
  • This is a classic delphi issue and the name for the problem was the reason why the `PopupMode` and `PopupParent` were added to Delphi 2007. I seriously suggest moving up to 2007 if not to the latest unicode version. – Warren P Apr 13 '13 at 02:00
  • This problem was in XE3 - I converted from 6. We used the TNT Unicode controls previously for Unicode - which worked well. – Rob Apr 13 '13 at 09:10

2 Answers2

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I had the same problem and I fixed it this way: Project - View source and setted Application.MainFormOnTaskbar to False.

begin
  Application.Initialize;
  Application.MainFormOnTaskbar:=**False**;
  Application.CreateForm(Tdm, dm);
  Application.CreateForm(TLogin, Login);
  Application.Run;
end.
Renato Braz
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I have found the answer to this. I discovered I had added a CreateParams override that did this:

  // make a taskbar window
 inherited CreateParams( params );
 params.ExStyle := params.ExStyle or WS_EX_APPWINDOW;
 params.WndParent := GetDesktopwindow; // this line caused the problem

Commenting the WndParent solved it. The effect is bizarre though. It is as if there is a timer that goes off about a second after any key or mouse event that forces the window behind others. Thanks to David Heffernan whose comments about stepping CreateParam made me notice it.

Rob
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    Raymond Chen has written about the perils of making the desktop window be your owner. You don't need to add app window style either. Simply set WndParent to 0. Unowned top level windows appear on the taskbar. – David Heffernan Apr 11 '13 at 13:35