Re: Changes in frame/window code

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 16 Aug 2014 15:46:04 +0200
> From: martin rudalics <rudalics@gmx.at>
> CC: emacs-devel@gnu.org
> 
>  > At
>  > least the scroll bar is on the wrong side here.
> 
> You mean the slider/thumb for hscroll equal zero?  That is the crucial
> point.  Moving it to the other side causes all problems I've seen so
> far.

Understood, but I cannot say anything about how the scroll bar works
until it gets that initial position right.  The current state of
affairs is a non-starter.

>  > Commit the changes we were discussing, and we could then talk
>  > meaningfully about whatever problems are left.  Right now, I cannot
>  > even try reproducing those problems.
> 
> I'll do that as soon as you fixed bug#18277.

I don't see the relevance of 18277 to this issue.  That bug is about
clicking inside the text area, not about clicking on the scroll bar or
hscrolling.  Why do you think they are related?

> I see three problems currently:
> 
> (1) When dragging I cannot move the slider entirely to the right and
>      make the first column of R2L lines visible until I release the mouse
>      button.  I suppose this is due to some off-by-one failure here but
>      there might be more to it.
> 
> (2) Sometimes during dragging the slider starts moving for-/backward in
>      some erratic fashion.  I'm not yet sure whether this is caused by an
>      hmargin issue or something else.
> 
> (3) Line 121 (written backwards as)
> 
> אם הסמן נמצא באמצע מילה, M-f זז לסוף המילה. אם הסמן נמצא בין שתי מלים,
> 
>     of the tutorial presents a special problem: When I'm repeatedly doing
>     `next-line' on the rightmost column before that line and are about
>     to move to that line I enter some strange sort of loop with the
>     slider in the center of the scroll bar trying to move back- and
>     forward.  C-g gets me out of it but I can't tell so far why I'm stuck
>     there.
> 
> If (2) or (3) are caused by bug#18277 (or a common underlying problem)
> it should be easier to resolve the remaining issues.

I could be wrong, but I don't think they are related to 18277 at all.
E.g., there's nothing in common between vertical-motion (which is what
you do in (3)) and moving point by clicking the mouse.

As for 2, does this happen around line 655?  That line, and the one
that follows, are L2R, and so are lines 918 and 919.  This could
confuse the code.  Another possible reason could be short lines that
disappear entirely under some large enough hscroll.

To summarize, I think you should commit your changes, and we should
deal with the fallout with later commits.  After all, these problems
went unnoticed until now, and they only happen if one turns on
truncate-lines in the tutorial, which sounds an unlikely situation.
It makes little sense to me to delay the horizontal scroll-bar fixes
due to these anomalies, which are unlikely to be related to your
un-installed changes.

But it's your call.