Subject: bug#23801: 25.0.95; term.el redraws extremely slow with bidi support enabled, and large buffers

From: Phil Sainty <[email-masked]>
Date: Tue, 21 Jun 2016 03:07:58 +1200

On 21/06/16 02:28, Eli Zaretskii wrote:
>> I suspect you'll need to do something which repaints the entire
>> terminal.
>
> I don't understand what that means.  The output from "ls" repaints the
> entire terminal as well, as it produces 1500 lines, much more than is
> shown in the window.

Yes, in hindsight the slow redraws with a background colour were so
blatantly drawing every single character in the terminal that I was
imagining that other kinds of command output (with less colourful
results) did not need to do that; and that the problem was therefore
connected to the slow redraws processing many more characters than
was necessary for other kinds of screen update. Now that I've (AFAICS)
isolated the issue to whitespace, I can see that my earlier presumption
doesn't actually make much sense. Apologies for the confusion.

Let me know if you'd still like me to provide profiler or elp results?
I'm well and truly done for the night, but I can follow up tomorrow.
(I'm hoping that with the prior email you're now able to replicate
the issue, though?)