Delphi - How to prevent Forms/MsgBoxes to move under prior form?

Question

Hi!

Many times we experienced after Windows 98 era that some dialogs are lost their Z-Order, and moved back to prior form.

For example:

Dialog1.ShowModal;

Dialog1.OnClickButton() : ShowMessage('anything');

When MessageBox appears, sometimes not got focus, it is moved under Dialog1. The users confused on it, because they are say: application freezed!!! But if they are uses AltTab to move another app and back, the focus return to the MessageBox, and it will be the foreground Window.

We experienced this with ShowMessage, MessageBox, normal forms, QuickReport forms also.

Is anyone knows about this? Is it Windows bug? How to prevent it? How to catch this?

Thanks for your help: dd

Answer 1

That's what the PopupMode and PopupParent properties are for.

E.g., you can do:

Dialog1.PopupMode := pmExplicit;
Dialog1.PopupParent := self;
Dialog1.ShowModal;

This tells Windows the correct Z-order.

Answer 2

For old versions of delphi (prior to Delphi 2007), on forms OTHER than your main form:

interface
  TMyForm = Class(TForm)
  protected
    procedure CreateParams(var Para: TCreateParams); override;
  end;
...
implementation
...
procedure TMyForm.CreateParams(var Para: TCreateParams);
begin
  inherited;
  Para.Style := Para.Style or WS_POPUP;
  { WinXP Window manager requires this for proper Z-Ordering }
  // Para.WndParent:=GetActiveWindow;
  Para.WndParent := Application.MainForm.Handle;
end;

For message boxes include MB_TOPMOST in your flags:

Application.MessageBox(PChar(amessage), PChar(atitle),    otherflags or MB_TOPMOST);

Answer 3

I looked at this page and the FAQ for half an hour and still can't find how to post a comment, so forgive me for this breach of protocol.

First of all I'd like to make clear that the poster, IMHO, is not using Windows 98. He writes "after Windows 98 era" which I understand means he is having this problem with Windows versions after 98.

As I am having this problem too (CB2009), I'd like to emphasize the poster's question "Is it Windows bug?", which I have not seen answered. If it's a Delphi/Builder bug, maybe there is a way to avoid it? I can't see how intercepting all potential dialogs is a workable solution, nor avoid using fsStayOnTop. I have a settings form that needs to stay on top of my main form, but the settings form can and will popup dialogs that under certain conditions will disappear under the settings form.

It would be very helpful if I would understand where the support of z-order goes wrong, as it may offer a clue on how to avoid it.

Answer 4

Hi!

I really said that AFTER Win98, so it is all OS (Win7 also) affected by this problem. We used Delphi 6 Prof, so the properties are not working with Default forms.

Somebody spoken the message dialogs are controllable with MessageBox + MB_APPLMODAL. This is good news, but we have many of old forms, and components, third party tools.

So it is hard work to making a completely new application with substitution of the forms.

But we will trying with it.

I think the answer is this in a half application problem, in a half Windows problem. If Windows sometimes handle this, and sometimes not - that is seems to be Windows bug. But if we can force the good modal window making then it is programming bug.

Somebody can explain me what is the meaning of the WS_POPUP flag? Is it have some side effect or not?

Thanks: dd