Autoresize a form and its controls when the user changes the font

Automatically resize the form and controls when the user changes the font.

The use of the common dialog control in VB5/6 allowes the programer to easly give the user the ability to change font characterists. However resizing the controls and the form to accommodate the changes in the font characteristics poses some problems for the programmer. The problem is that there is no way to know in advance which font characterists the user will change. If you want to change the size of a control, for example a textbox, to a size that will accommodate a given font then you must know the height and width of the characters when that font is applied.

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The windows API GETTEXTMETRICS will supply this information. This API call requires a handle to the device context for the control. Unfortunately many of the commonly used controls supplied with VB5/6 do not have a hDC property. As the form does have a hDC property the solution to this problem is to set the font for the form and then set the fonts for the controls to the same font as the form. This way you can use the hDC of the form in the call to GETTEXTMETRICS.

I have written a class that will use this API call to collect the information necessary for resizing the controls and the form to accommodate changes in the font.

This class sets the fonts of all controls to the same font and then read the text height and average text width. These values are used to compute the ratio of change between the new text height and average text width and the current text height and average text width. This ratio is then used to resize the form and the controls. The class contains an event that will fire after changing the form. This event can be used to reset any default values you do not want the user to change. For example setting the font to bold for all labels.

Assumptions

The form Border style is set to 1-Fixed Single.

Testing:

Load and run the prjResizeTest or

With an existing project:

1. Add a menu item with the Name: mnu_ChangeFont, Caption: Change Font.
2. Add a common dialog control to the form. Use the default name.
3. Add the cAutoResize class to the project.
4. In the decelerations section add the following:

   
   private withevents cResize as cAutoResize
   

5. In the Form_Load event:

   
   private Sub Form_Load()
       set cResize = new cAutoResize
   End sub
   

6. In the mnu_ChangeFont_Click event:

private Sub  mnu_ChangeFont_Click()
  Dim msg as string
  
  CommonDialog1.Flags = cdlCFBoth
  CommonDialog1.ShowFont

'get the current font info
'on error show err msg then exit
  msg = cResize.GetOldFontInfo(me)
  If msg <> "OK" then
    MsgBox msg, vbOKOnly, "error"
    Exit Sub
  End If

'set the font for the form
  With CommonDialog1
    me.FontBold = .FontBold
    me.FontItalic = .FontItalic
    me.FontName = .FontName
    me.FontSize = .FontSize
    me.FontStrikethru = .FontStrikethru
    me.FontUnderline = .FontUnderline
  End With

'set the form
  msg = cResize.SetForm(me)

'Check for errors
'If error then show msg then out of here

  If msg <> "OK" then
    MsgBox msg, vbOKOnly, "error"
    Exit Sub
  End If

End sub

7. In the form_activate event:

private Sub Form_Activate()
  Dim msg as string
'Init cAutoresize and set the form
  
  msg = cResize.Init(me)
  If msg <> "OK" then
    MsgBox msg, vbOKOnly, "error"
    Exit Sub
  End If

'Center form
  msg = cResize.SetForm(me)
  If msg <> "OK" then
    MsgBox msg, vbOKOnly, "error"
    Exit Sub
  End If
End Sub

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