bug#74430: 30.0.92; pixel-scroll-precision-mode hiding Eshell prompt after some commands

[Jim Porter <jporterbugs@gmail.com>]

On 11/21/2024 2:53 AM, Eli Zaretskii wrote:
>> From: Ashton Wiersdorf <ashton@wiersdorfmail.net>
>> Date: Mon, 18 Nov 2024 10:52:27 -0700
>>
>> When the command finished, the Eshell prompt was almost entirely
>> obscured by the modeline.
>>
>> The bug does not manifest when I turn off
>> `pixel-scroll-precision-mode`.
>> It returns when I turn `pixel-scroll-precision-mode` back on.
> 
> Po Lu and Jim, could you look into this, please?

I'm only dimly aware of how 'pixel-scroll-precision-mode' works, but I 
seem to recall that it sets the window's vscroll to allow scrolling past 
*part* of a line. On the Eshell side, I believe the relevant function is 
'eshell-postoutput-scroll-to-bottom', which calls 'recenter' to scroll 
the window.

I'm guessing these interact badly, and what we actually want to do is to 
reset the vscroll when Eshell calls 'recenter'. However, I'm not sure 
what the best way to do this would be. Is there some better function 
Eshell can call that would handle this case correctly?