BIDI question

BIDI question

[Dmitry Antipov]

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There is a text with a mix of Arabic and ASCII characters (attached), and it is
displayed correctly (first screenshot a.k.a top.png). But, when I concatenate
this text with itself (cat /tmp/uthmani.txt /tmp/uthmani.txt > 1.txt) and view
the result, second Arabic fragment is rendered L2R (second screenshot a.k.a
next.png). Why it is different from the first Arabic fragment, and isn't it a bug?

Dmitry

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بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ تَبَّتْ يَدَآ أَبِى لَهَبٍۢ وَتَبَّ
مَآ أَغْنَىٰ عَنْهُ مَالُهُۥ وَمَا كَسَبَ
سَيَصْلَىٰ نَارًۭا ذَاتَ لَهَبٍۢ
وَٱمْرَأَتُهُۥ حَمَّالَةَ ٱلْحَطَبِ
فِى جِيدِهَا حَبْلٌۭ مِّن مَّسَدٍۭ
بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ قُلْ هُوَ ٱللَّهُ أَحَدٌ
ٱللَّهُ ٱلصَّمَدُ
لَمْ يَلِدْ وَلَمْ يُولَدْ
وَلَمْ يَكُن لَّهُۥ كُفُوًا أَحَدٌۢ
بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ قُلْ أَعُوذُ بِرَبِّ ٱلْفَلَقِ
مِن شَرِّ مَا خَلَقَ
وَمِن شَرِّ غَاسِقٍ إِذَا وَقَبَ
وَمِن شَرِّ ٱلنَّفَّٰثَٰتِ فِى ٱلْعُقَدِ
وَمِن شَرِّ حَاسِدٍ إِذَا حَسَدَ
بِسْمِ ٱللَّهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ قُلْ أَعُوذُ بِرَبِّ ٱلنَّاسِ
مَلِكِ ٱلنَّاسِ
إِلَٰهِ ٱلنَّاسِ
مِن شَرِّ ٱلْوَسْوَاسِ ٱلْخَنَّاسِ
ٱلَّذِى يُوَسْوِسُ فِى صُدُورِ ٱلنَّاسِ
مِنَ ٱلْجِنَّةِ وَٱلنَّاسِ


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Re: BIDI question

[Eli Zaretskii]

> Date: Mon, 07 Oct 2013 21:25:54 +0400
> From: Dmitry Antipov <dmantipov@yandex.ru>
> CC: Eli Zaretskii <eliz@gnu.org>
> 
> There is a text with a mix of Arabic and ASCII characters (attached), and it is
> displayed correctly (first screenshot a.k.a top.png). But, when I concatenate
> this text with itself (cat /tmp/uthmani.txt /tmp/uthmani.txt > 1.txt) and view
> the result, second Arabic fragment is rendered L2R (second screenshot a.k.a
> next.png). Why it is different from the first Arabic fragment, and isn't it a bug?

It's a feature: a paragraph starts after at least one empty line (or
at point-min).  In this case, there's no empty line between the
English text (which is an L2R paragraph) and the second Arabic
fragment, so the second Arabic fragment is rendered as a continuation
of the L2R paragraph that starts with the English text.

IOW, Emacs does not recognize the second Arabic fragment as a new
paragraph, and does not recompute the base paragraph direction for it,
instead it continues using the base paragraph direction computed for
the English text.