To create a shape mask
from text, use the Curves > Text 
tool to write the text.
To create a text mask shape
- Choose Paint > Shape > Make Mask Shape
from the tool palette, and
select each letter, curve by curve.
- Click Accept after
selecting all letters if you want to create a single mask shape.
or
Click Accept after
selecting each letter if you want to create separate mask shapes
for each letter.
- To protect the text area on the canvas
from being over-painted, no further action is necessary. To modify
the paint on the text area only, click on the MaskShape-# layer
in the Canvas Layer Editor, and choose Invert
layer from the editor’s Edit menu.
