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center a form within another form

Posted on 1998-08-18
Last Modified: 2010-04-04
I have small dialog/form that is started from the main form. I want this small form to always come up centered within the main form no matter where it is on the screen. How can I do this in Delphi 4.0?
Question by:Kmiller
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Accepted Solution

Matvey earned 50 total points
ID: 1337202
I doubt there is some automatic method for it. There's nothing to it - just set the dialog form position according to the other form position:

frmDialog.Left := frmMain.Left + frmMain.Width div 2 - frmDialog.Width div 2;
frmDialog.Top := frmMain.Top + frmMain.Height div 2 - frmDialog.Height div 2;

-Then show it.

c u, Matvey

Expert Comment

ID: 1337203
I use something like this in the FormShow method on the dialog form (where frmMain is the main form):

  (* Center dialog on mainform *)
  PWidth := frmMain.Width;
  PHeight := frmMain.Height;
  Left := ((PWidth - Width) Div 2) + frmMain.ClientOrigin.X;
  Top := ((PHeight - Height) Div 2) + frmMain.ClientOrigin.Y;


Expert Comment

ID: 1337204
Ok Matvey, you were the fastest! But mine works better (I guess)with MDI forms!
LVL 10

Expert Comment

ID: 1337205
In the main form that sits behind not the dialog form, enter this in OnShow...

procedure MainForm.OnShow......
  DialogForm.Top := ( MainForm.Height div 2 ) - ( DialogForm.Height div 2 );
  DialogForm.left := ( MainForm.Width div 2 ) - ( DialogForm.Width div 2 );

That's all you need to do! ;)

Viktor Ivanov
LVL 10

Expert Comment

ID: 1337206
Wow, you were very fast... ;)

Matvey did you see the comp I sent you the other day? Is it cool?

Viktor Ivanov

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