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bug#33944: 27.0.50; harfbuzz: Noto Sans Mandaic not rendered correctly
From: |
Eli Zaretskii |
Subject: |
bug#33944: 27.0.50; harfbuzz: Noto Sans Mandaic not rendered correctly |
Date: |
Tue, 01 Jan 2019 17:28:42 +0200 |
> From: Benjamin Riefenstahl <b.riefenstahl@turtle-trading.net>
> Date: Tue, 01 Jan 2019 15:36:40 +0100
>
> This may be a more general problem, but Noto Sans Mandaic reproduces it
> for me:
You mean, with other fonts that support Arabic shaping the problem
doesn't happen?
> I save this code in a file "reproduce.el" and execute it with "emacs -Q
> -l reproduce.el":
>
> (set-fontset-font t '(?\u0840 . ?\u085B) "Noto Sans Mandaic 20")
>
> (set-char-table-range
> composition-function-table '(?\u0840 . ?\u085B)
> (list ["[\u0840-\u085B]+" 0 arabic-shape-gstring]))
>
> (setq bidi-paragraph-direction t)
>From the doc string of bidi-paragraph-direction:
If this is nil (the default), the direction of each paragraph is
determined by the first strong directional character of its text.
The values of ‘right-to-left’ and ‘left-to-right’ override that.
Any other value is treated as nil.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Did you set it to t on purpose? If so, can you explain why?
> (insert "\u0856\u0844\u0845")
>
> The problem is that the second and third character from the right are
> not combined as they should. This works in hb-view and it also works,
> if I remove the setting of bidi-paragraph-direction.
What happens if bidi-paragraph-direction is set to one of the valid
values?
> The commit that breaks this is the last one, 48776b7011 "Provide text
> directionality and language to HarfBuzz shaper". Before that commit it
> works for me.
Can you run Emacs under a debugger and see what value of 'dir' do we
come up with in this snippet from ftfont.c:
hb_direction_t dir = HB_DIRECTION_INVALID;
if (EQ (direction, QL2R))
dir = HB_DIRECTION_LTR;
else if (EQ (direction, QR2L))
dir = HB_DIRECTION_RTL;
/* If the caller didn't provide a meaningful DIRECTION, let HarfBuzz
guess it. */
if (dir != HB_DIRECTION_INVALID)
hb_buffer_set_direction (hb_buffer, dir);
Do we call hb_buffer_set_direction, and if so, with what value?
Thanks.