I have not used with StyledText for a long time and started playing with it to see if an idea I have in mind might work. To that end I put the code below in the Open event of a Window that has a TextArea on it (OSX 10.14.6, Xojo2019R1).
To my eye the 3rd run does not look to be italic if I use Geneva as the font... But does if I change it to Arial or Helvetica... Have I found a bug or is there some other reason Geneva does not render in italic... At one time in the past (though it may have been LONG ago) I'm pretty sure it did.
Dim X as StyleRun X= New StyleRun X.Text = "The first Run" X.Size = 12 X.Font = "Helvetica" ST.AppendStyleRun X X= New StyleRun X.Text = " The 2nd Run" X.Size = 16 X.Font = "Times" X.TextColor = &CFF0000 ST.AppendStyleRun X X= New StyleRun X.Text = " The 3rd Run" X.Size = 14 X.Font = "Geneva" X.TextColor = &C0000FF X.Italic = True X.Underline = True ST.AppendStyleRun X X= New StyleRun X.Text = " The 4rd Run" X.Size = 24 X.Font = "Arial" X.TextColor = &C00FF00 X.Bold = True ST.AppendStyleRun X TextArea1.StyledText = St