Eli Zaretskii <eliz@gnu.org> writes:

> The difference is that window-text-pixel-size already exists, we just
> extend it for another use case.

> Well, then this is equivalent to telling window-text-pixel-size to
> stop at the visual left edge of a screen line, right?  That is,
> interpret TO not as a literal buffer position, but as the visual
> beginning of the line which shows position TO.

Yes, I think the two meanings are equivalent.  I documented it as the
former, but it wouldn't hurt to document it like this instead.

Anyway, here are two patches that implement the extensions to
`window-text-pixel-size', along with the code in
pixel-scroll-precision-mode that makes use of them.  I tried to update
the documentation, but to be frank I'm not good at writing documentation
and couldn't word it very well, so someone else should take a look at
it.

Thanks a lot!