bug#38013: [PATCH] Rectangular region selection with mouse

[Mattias Engdegård]

16 nov. 2019 kl. 13.35 skrev Eli Zaretskii <eliz@gnu.org>:

> Did you try this with stretch glyphs generated by the likes of
> :align-to display 'space' properties?  Also, what about stretch glyphs
> generated by the display engine in R2L screen lines (you can get those
> easily by visiting TUTORIAL.he: each line that has white space at its
> left end has a stretch glyph there)?

I didn't try right-to-left text until now --- thanks for prodding --- and the 
behaviour was predictably awful. An updated patch (attached) tries to do better 
(up to what is possible with the underlying rect.el machinery).

> IOW, it might be necessary to add more conditions here, and just the
> mouse_movement_in_tab thingy you added in a later version might not be
> enough.  E.g., we may need a condition that verifies that this is a
> TAB (should be easy by looking at glyph->object, I think).

After some false starts, I settled on the simpler 'fine-grained-mouse-movement' 
solution, giving pixel-wise events no matter what the mouse is pointing at. The 
extra cost for this is imperceptibly slight, and it feels more generally useful 
than the 'mouse-movement-in-tab' thingy.

0001-Mouse-rectangular-region-selection-bug-38013.patch
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