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Dialog window size

V245 asked
Medium Priority
Last Modified: 2013-12-03
I create a dialog window by using CreateIndirect(). And I have a problem.
I want to create the window with a certain size, for example with a client
rectangle size of a parent window. I can get wanted size by using GetClientRect().
But the values I get are measured in pixels. At the same time I have to set
x, y, cx and cy parameters of DLGTEMPLATE in dialog box units, not in pixels.
I make the following:

CRect MainWndClientRect;
LONG  DlgBaseUnit = GetDialogBaseUnits();
UINT  DlgBaseUnitX = (UINT)( ( DlgBaseUnit << 16 ) >> 16 );
UINT  DlgBaseUnitY = (UINT)( DlgBaseUnit >> 16 );

dlgTempl.x  = (short)( ( MainWndClientRect.left     * 4 ) / DlgBaseUnitX );
dlgTempl.y  = (short)( ( MainWndClientRect.top      * 8 ) / DlgBaseUnitY );
dlgTempl.cx = (short)( ( MainWndClientRect.Width()  * 4 ) / DlgBaseUnitX );
dlgTempl.cy = (short)( ( MainWndClientRect.Height() * 8 ) / DlgBaseUnitY );
CreateIndirect( &dlgTempl, &pParentWnd );

As a result I have the dialog window with a wrong size. Why?
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I'm not sure why that doesn't work.  But I can suggest an improvement.  (Yes that's right a change that will make it not work even faster.)

instead of

UINT  DlgBaseUnitX = (UINT)( ( DlgBaseUnit << 16 ) >> 16 );
UINT  DlgBaseUnitY = (UINT)( DlgBaseUnit >> 16 );


UINT  DlgBaseUnitX = (UINT)( DlgBaseUnit && 0x0000FFFF );
UINT  DlgBaseUnitY = (UINT)( DlgBaseUnit >> 16 );

How far are you off by?  like could this be a rounding thing?  
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The calculation you make is only valid if you're using the system font.
There is a workaround.  See KB articles Q145994 and Q74280 for details.


I'm using system font. So I accept the Duneram answer also at common I don't like such solutions. To my mind it isn't a problem solution but it is a trick for go around the problem. In any case it works.
Thanks for Nietod and Alexo for your advices.

I'm still curious, how far off was the positioning using your formulas?  was it close?


Sorry for my delay, I was in leave. Well, at the time I know that   GetDialogBaseUnits() is cause of my problem. This function returns wrong value (¬†DlgBaseUnitX=10 and ¬†DlgBaseUnitY=20 instead of 8 and 16 ). I tried 'Method Two' from article Q145994 - it works correct.
Thanks for all.

Well, seems I was able to help after all :-)


'Method Two' can be used for calculating dialog units instead GetDialogBaseUnits(). But in my case I can't use it because I need the dialog units values before the window is created. So I can't call MapDialogRect(). In my program I implemented Duneram's solution: I create the window with wrong size and then call SetWindowPos() in OnInitDialog(). I guess His Majesty Bill Gates didn't let me any choice ;-)
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