Re: Low redisplay performance (23 regression)

[Tassilo Horn]

David Reitter <address@hidden> writes:

Hi David,

>> And on yet another related note, today I've found out that after
>> changing the font scale for the current buffer using `C-x C-+' or
>> `C-x C--' line-by-line scrolling slows down considerably.
>
> As said earlier, I found that using face-remapping is highly
> correlated with this slow-down.

Ah, sorry, I must have missed that.

>> Oh, yet another observation: While writing this mail I enlarged the
>> text scale with `C-x C-+' and if I press and hold the up or down key,
>> point hangs for very short periods of time at some positions and then
>> jumps over some lines without visible redisplay, even though no
>> scrolling at all is done.
>
> I see the same thing.  Did you (setq redisplay-dont-pause t) ?

No, but setting it doesn't make a big difference here.

> Either way, it suggests that drawing takes much longer with a change
> of faces. (E.g., M-x list-faces-display ?)

Ouch!  Without remapping it scrolls with some minor hangs (tenth of a
second), but with face-remapping it starts fine, but then slows down
very quickly.  From the middle of the buffer to the last line (with
pressing and holding down, ~200 lines) it's basically a 5-10 seconds
hang followed by a jump to the last line -- nothing in between.
redisplay-dont-pause doesn't make a (noticeable) difference for me.

Bye,
Tassilo