Re: emacs rendering comparisson between emacs23 and emacs26.3

[martin rudalics]

> Can you tell how many times you turn the wheel until Emacs gets stuck?

Five or six times where a "turn of the wheel" means to put the finger at
one end of the opening of the wheel and turn the wheel until the finger
is at the opposite end, approximately.  Each such turn seems to provoke
between 5 and 7 subsequent calls of 'mwheel-scroll' here so it
apparently takes 30 to 35 calls to get into those ~10 second freezes.
33 is a typical number I've seen, using a simple counter within
'mwheel-scroll'.  A typical value of the cumulative number of lines to
scroll (AMT in 'mwheel-scroll') then seems to be about 3000.  I would
have to run this more often to get better values.

The first five or so of such turns are seemingly processed normally.
After that, input apparently arrives faster than Emacs is able to
process it and no redisplay takes place until all input has been
consumed.

I cannot nearly simulate the problem using a simple loop that steadily
invokes say (forward-line 50) followed by a (sit-for 0).  50 such
invocations take 16.7 seconds here, 22.7 with (forward-line -50).  And
redisplay takes place as expected here.  So it's likely the mouse wheel
input mounting up that inhibits redisplay.

Do you at least see CPU activity significantly go up when you do such
mouse wheel scrolling?  I rarely use mouse wheel scrolling in Emacs so I
cannot say what is typical and what isn't.

martin