bug#14616: 24.3.50; Excessive cursor movement on non-X Emacs

[Lars Magne Ingebrigtsen <larsi@gnus.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> It doesn't actually redraw the lines, at least not on my system.  What
> it does is examine each screen line in the 'desired' glyph matrix (a
> structure that describes what _should_ be on the screen) with the
> corresponding line in the 'current' glyph matrix (which describes what
> _is_ on the screen).

I see.  Is there a better place to put the trace so that it'll only
trigger when something is actually redrawn?  That would make poking
around trying to trigger the bug easier...

> Do you see on your system any writes to the terminal, e.g., in strace?

I tried stracing it now, but couldn't see anything to indicate that it
actually writes anything to the terminal.

> (If you wonder why each iteration through your recipe causes Emacs to
> enter redisplay, then this is caused by delete-process: you will see
> that it calls redisplay_preserve_echo_area, which enters redisplay.
> Presumably, this is because deleting a process or a network connection
> constitutes a status change, and we always call redisplay in that
> case, I think for sentinels' sake.  So this is normal, or at least not
> a regression.)

Right.

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