Put Canvas behind TextArea?

Is there no way to put a Canvas behind a TextArea so it shows through the TextArea instead of covering it up?

I want the background of a TextArea to be a giant (but subtle) progress bar.

I have the graphics part for creating the image all figured out, I just can’t get the image to go behind a transparent TextArea.

which OS ?

macOS Catalina

Put it over the TextArea instead, and use transparent colors for the bar.

Is this “true”?
I have a custom control I built a while back that “fakes” highlighting text by drawing on a canvas under a text area. Problem with putting it OVER the textarea is not only catching some events, but the colors tend to be muted due to being transparent

Putting the canvas over the TextArea will reduce contrast between the text and its background making it harder to read for people who are blind or have low vision so I need a way to put it behind the TextArea - and have it the same size as the TextArea.

It is not that difficult.