How To Capture a Text Size Change Within an ActiveX Control (260578)

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Microsoft Foundation Classes (MFC) Control

In an MFC control, the AmbientPropertyChange's dispatch ID (DISPID) will be DISPID_UNKNOWN. The following steps show how you can tell if the font changed.

1. Declare a Private variable in the control:

   LPFONTDISP orgFont;
   					

2. In the constructor of the control, for example, CMFCControlCtrl, add the following code:

   	if (0 != GetAmbientProperty(DISPID_AMBIENT_FONT, VT_FONT , &orgFont))
   		AfxMessageBox("Ambient property is supported in this container");
   					

3. Modify OnAmbientPropertyChange as follows:

   void CMFCControlCtrl::OnAmbientPropertyChange(DISPID dispid) 
   {
   
       if (DISPID_UNKNOWN == dispid)
   	{
   		LPFONTDISP pFont = AmbientFont();
   		if (pFont != orgFont)
   			AfxMessageBox("Font Changed");
   	}
   	
   	COleControl::OnAmbientPropertyChange(dispid);
   }
   					

Microsoft Visual Basic Control

In a Visual Basic control, the PropertyName of the AmbientChanged event is an empty string. The following code demonstrates how you can use code to create the empty string with Visual Basic.

Option Explicit
Private orgFontSize As Currency

Private Sub UserControl_AmbientChanged(PropertyName As String)
   If PropertyName = "" Then
       If orgFontSize <> Ambient.Font.Size Then
           MsgBox orgFontSize & " font changed to " & Ambient.Font.Size
           orgFontSize = Ambient.Font.Size
       End If
   End If
       
End Sub

Private Sub UserControl_Show()
   orgFontSize = Ambient.Font.Size
End Sub