MessageDialog Sheets by Seth Willits June 25, 2005 Printer Version

Using a New Feature From REALbasic 2005!
In this tutorial, we're going to use a new feature of the MessageDialog class, the ShowModalWithin method, to show the dialog as a sheet within a parent window. This is something that was sorely lacking in REALbasic 5.5. Without this feature, developers (such as myself) had to resort to using declares to implement a standard message alert that could be shown as a sheet.

The MessageDialog class is an important user interface element that if not done correctly, sticks out like a sore thumb on Mac OS X. Users expect a consistent message interface between applications, so it is critical that developers adopt and embrace the MessageDialog class as a part of becoming a good Mac OS X citizen. See the tutorial "Using MessageDialogs" to learn about the other features of this class.

It's a Sheet!
This tutorial isn't exactly the most indepth of them all. In the code below, you simply have a chunk which sets up a MessageDialog in the CancelClose event of a Window and displays it using ShowModalWithin.

Function CancelClose(appQuitting as Boolean) As Boolean
  dim dlog as MessageDialog
  
  // Create Dialog
  dlog = New MessageDialog
  dlog.Message = "Do you want to save the changes you made in the document """ + self.Title + """?"
  dlog.Explanation = "Your changes will be lost if you don't save them."
  dlog.ActionButton.Caption = "&Save..."
  dlog.CancelButton.Caption = "Cancel"
  dlog.AlternateActionButton.Caption = "&Don't Save"
  dlog.ActionButton.Visible = true
  dlog.CancelButton.Visible = true
  dlog.AlternateActionButton.Visible = true
  
  // Show Dialog
  Select Case dlog.ShowModalWithin(self).Caption
  Case "&Save..."
     MsgBox "Pretend this is a save dialog..."
     return false
  Case "&Don't Save"
     return false
  Case "Cancel"
     return true
  end Select
End Function