TextArea.SelectionFontSize
From Xojo Documentation
Property (As Single )
aTextArea.SelectionFontSize = newSingleValue
or
SingleValue = aTextArea.SelectionFontSize
New in 2019r2
Supported for all project types and targets.
or
SingleValue = aTextArea.SelectionFontSize
New in 2019r2
Supported for all project types and targets.
Used to get and set the font size of the selected text.
Notes
When used in an unstyled TextArea it changes the font size of all the text in the TextArea.