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.

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.