bug#57367: [PATCH v3] Speed up em-smart

[Morgan Smith]

Stefan Kangas <stefankangas@gmail.com> writes:

> Jim Porter <jporterbugs@gmail.com> writes:
>
>> On 9/6/2022 6:30 PM, Morgan Smith wrote:
>>> I've attached my patch V2.
>>> This restores some more of the original logic that I have now realized
>>> was indeed necessary.  Again, this patch should not actually change
>>> anything with respect to program logic, flow, or user experience.  In my
>>> limited testing, it seems to act just as it did before (but
>>> significantly more performant).
>>
>> Thanks, this does indeed seem a lot faster. I do notice one small change in
>> behavior though: after starting Eshell with the em-smart module loaded, run
>> "echo hi" and then split the window vertically with 'C-x 2'. Before the 
>> patch,
>> the window doesn't scroll. After the patch, the window is scrolled so that 
>> the
>> "echo hi" block is at the top (i.e. the "Welcome to the Emacs shell" banner 
>> is
>> hidden).
>>
>> The same sort of thing happens if you run a command with a lot of output 
>> first
>> and then run "echo hi". Before splitting, the "echo hi" block is at the
>> bottom. Without this patch, 'C-x 2' maintains that position (i.e. it scrolls 
>> the
>> minimum amount of the previous command out of view so that you can see the
>> most-recent command). With the patch, 'C-x 2' scrolls *all* of the previous
>> command out of view, so the "echo hi" block is at the top.
>>
>> I think the pre-patch behavior is the most-usable: if you can fit all of the
>> last command in the window, it should be at the bottom so that you can see 
>> (some
>> of) the previous command.
>>
>> (I also saw some strange issue with resizing the windows via the mouse, but I
>> can't reproduce it anymore. If I can figure out how trigger this reliably, 
>> I'll
>> send an update. Sorry that's not very helpful at present...)
>
> That was one year ago.
>
> Morgan, did you get a chance to look into the issues Jim pointed out
> above?

Thanks for the ping.  Reading the documentation for
`window-configuration-change-hook' I found out I can run the scroll
command only on updated windows.  Furthermore, that hook selects the
window which is nice.  I believe the problems pointed out above stem
from using `(point)` to scroll a window that wasn't actually selected.

Anyways here is V3

v3-0001-Speed-up-em-smart.patch
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