VB3 Adjust Form Size for Different Video Screen Resolutions

SUMMARY

Different display devices can have different resolutions (twips per pixel ratios). These differences can cause form and control sizes and locations to appear differently than when they were created. Two solutions to this problem are:

• Adjust your form and control sizes and locations at run time to match visual elements which are not affected by the screen resolution. For example, the sample program given below adjusts the width of the client area of a form to match a bitmap which is a fixed number of pixels wide and is therefore not affected by screen resolution.

In addition, the following techniques will prove useful when creating forms that are "resolution independent."

• Design your forms for a VGA mode resolution, that is, for the "least common denominator." Forms created at higher resolution may not size well at smaller resolutions.
• You can make use of the TwipsPerPixelX and TwipsPerPixelY properties of both the printer and the screen for positioning controls correctly. The TextWidth and TextHeight methods are also handy for calculating the size of text to be displayed. They return the size of a given piece of text for the current scale mode of the object they are called with; that is, form or printer--and for the current font and size. The code below demonstrates how to calculate the size of a single character:

       Dim FontHeight%, FontWidth%
       FontWidth%  = TextWidth ( "X"  )
       FontHeight% = TextHeight( "Xg" )
  
  						

• Beware of resizing your form in the form's resize event. This can create a cascading resize event, which will quickly exhaust stack space and crash your program. The code fragment below demonstrates how to avoid this:

       Sub Form1_Resize()
          If InResize% <> -1 Then
             InResize% = -1
             ' Sample code which would trigger a resize event
             form1.Width = frmWidth%
             form1.Height = frmHeight%
             InResize% = 0
          End If
       End Sub
  
  						

• Make use of the form's move method to minimize calls to the resize event. The following code issues four separate calls to the resize event

       form1.Top = 0
       form1.left = 0
       form1.Width = 100
       form1.Height = 100
  
  						

  as opposed to this code which triggers only one resize event:

       Dim bTop%, bLeft%, bWidth%, bHeight%
       bTop% = 0
       bleft% = 0
       bWidth% = 100
       bHeight% = 100
       form1.move bLeft%, bTop%, bWidth%, bHeight%