Author: Jean Claude Servaye

How to convert dialogs units in pixels if the dialog do not use system font

Answer:
1   
2   function DialogUnitsToPixels(DialogUnits: Integer; Canvas: TCanvas; Font: TFont):
3     Integer;
4   var
5     A: array[0..52] of char;
6     Z: Integer;
7     U: Word;
8   begin
9     // select the current font
10    SelectObject(Canvas.Handle, Font.Handle);
11    // Get DialogBaseUnit for system font
12    U := HiWord(GetDialogBaseUnits) div 4;
13    // compute mean width of characters in current font
14    // as recommended by Microsoft
15    A := 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
16    Z := (Canvas.TextWidth(A) div 26 + 1) div 2;
17    // Compute result and adjust for screen resolution
18    Result := DialogUnits * Z div U * Screen.PixelsPerInch div 96;
19  end;