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bug#28312: 25.2; Arabic script changes when scrolling
From: |
Eli Zaretskii |
Subject: |
bug#28312: 25.2; Arabic script changes when scrolling |
Date: |
Fri, 01 Sep 2017 09:45:08 +0300 |
> From: Nick Helm <nick@tenpoint.co.nz>
> Date: Fri, 01 Sep 2017 13:03:02 +1200
>
> With bidi enabled, Arabic text changes unexpectedly when scrolling or
> moving point with the mouse.
>
> Recipe:
> Emacs -Q
> C-h h ;visit HELLO file
> ;use the mouse to scroll slowly
>
> Observe the text on the line that starts with the word Arabic. As the
> buffer scrolls, some of the characters in the Arabic representations of
> the words "Arabic" and "Hello" change between at least two glyphs.
I don't see this here, but I'm not on Darwin. Can anyone reproduce
this on GNU/Linux?
Does the character also change its shape if you move cursor across
that line, especially when the cursor moves across the character?
> Here's a quick screen cap to show what I mean:
> https://ln.sync.com/dl/22d37f320/fwujc85a-dhb63yfw-cv5vhzj5-5qsis2h8
I cannot watch this movie with the software I have installed.
> The problem goes away when I change the file local variable:
> ;;; bidi-display-reordering: nil
Not much sense in doing that for displaying Arabic!
> My system defaults to Geeza Pro to display Arabic script, but the
> problem also occurs with other fonts, such as Arial Unicode MS. I don't
> see the problem with other RTL scripts in the HELLO file, such as
> Hebrew.
Arabic needs shaping support from the underlying font back-end, so
(unless this will be reproduced on GNU/Linux) it sounds like something
is wrong with either the back-end Emacs uses on Darwin, or its version
you have installed, or with the support code in Emacs which is needed
for displaying complex RTL scripts such as Arabic.
FWIW, I tried Arial Unicode here, and saw no problem with that,
either.
- bug#28312: 25.2; Arabic script changes when scrolling,
Eli Zaretskii <=