Re: notmuch-show-mode: slowdown due to redisplay

[Rainer Gemulla <hqn1@gmx.de>]

>> Navigating certain messages (e.g., with many attachments or images)
>> may become very slow in notmuch-show-mode. I see this rarely, but when
>> it happens, it takes >1s to simply move the point so that the buffer
>> is barely usable. The CPU profiler shows that
>> notmuch-show-command-hook calls redisplay and that's that all where
>> the time goes. Not sure if anything can be done about this.
>
> Hmm. Hard to debug without a sample message, or a more definite
> pattern. Do you notice a threshold in terms of numbers of attachements?
> I can imagine there is some bad behaviour involving large numbers of
> buttons when running redisplay.

I've tracked it down: it happens when multiple large images are attached to the email (and displayed inline) and global-hl-line-mode is turned on. The former slows down redisplay, the latter makes redisplay do something with every cursor movement.