GNU bug report logs - #14582
24.3.50.1; Strange overlay behavior, when window-start is inside an overlay.

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From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: larsi <at> gnus.org, esabof <at> gmail.com, 14582 <at> debbugs.gnu.org
Subject: bug#14582: 24.3.50.1; Strange overlay behavior, when window-start is inside an overlay.
Date: Mon, 28 Feb 2022 00:19:36 +0100

Eli Zaretskii <eliz <at> gnu.org> writes:

> In the context of redisplay, any change of the window-start point is
> referred to as "scrolling the window".  So when you tell the display
> engine to make sure the window-start is visible, and the last used
> window-start isn't, you cannot at the same time ask it not to scroll,
> because that's a contradiction.

But when I said that using the new variable makes Emacs really scroll,
visually, not only in an abstract sense, didn't you say mean that was
unavoidable?

> > And tell me that a solution without scrolling involved
> > is not possible, and why, or why you think that scrolling is
> > unavoidable.  You said it can't be avoided when we do something in the
> > display engine.
>
> That's not what I said.  Quote:
>
>   It isn't unavoidable, but doing something more sophisticated would
>   call for a significantly more complex code.  The current solution for
>   when this variable is set and the window-start point is invisible is
>   very simple: we recenter the window around point.  The recentering
>   method is safe, because it always succeeds, which is why it also
>   serves as the fallback method of finding the suitable window-start for
>   redisplaying a window.  The code that implements the recentering was
>   already there, so the introduction of this new variable boiled down to
>   recognizing the conditions under which we should go directly to
>   recentering, bypassing all the other methods.

Recenter means actual, not only per definition scroll - right?

> I need a more concrete proposal to answer these questions.  IOW, I
> don't think I understand what kind of solution do you have in mind
> here.

I didn't make one since my knowledge here in inferior.  Personally I
would adjust window-start from a hook and call `redisplay', which is
probably not the best solution.

> That was an (obviously failed) attempt to joke about the practice not
> to close bug reports where there's nothing left to do, that's all.
> Why you saw that as unfriendly, and against you on top of that, I
> don't think I understand; I certainly didn't mean that.

Ok..ok.  Then I misinterpreted your intention.  Didn't sound at all like
a joke to me.  Then let's try to get back to the issue.


Michael.

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