Drawing dirty rectangles with expose_window: row->clip = fr

[Keith David Bershatsky]

I am working on feature requests #22873 (multiple fake cursors) and #17684 
(crosshairs that track the cursor position).

Even though ns_clip_to_rect returns TRUE, "row->clip = fr;" in expose_window 
can sometimes prevent glyphs from being drawn within the rectangle that is 
passed as an argument of ns_clip_to_rect.  This has the effect of permitting 
fake cursors to be drawn, but then glyphs cannot be drawn on top of hollow/box 
fake cursors.

How can I reconcile a false_positive with ns_clip_to_rect?

Or, perhaps "row->clip = fr;" in expose_window needs to be adjusted to permit 
the drawing of glyphs?

If I comment out "row->clip = fr;" in expose_window, the problem goes away.

Keith