Avoid breaking Arabic shaping in 'window-text-pixel-size'

* src/xdisp.c (CHAR_COMPOSED_P): If the bidi_p flag is not set,
pass -1 to composition_reseat_it, so that the shaping engine will
figure out the directionality of the text.  This is important,
e.g., when using move_it_* functions in some context that is not
redisplay, such as 'window-text-pixel-size'.  (Bug#44521)

1 files changed, 9 insertions, 2 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 60864c2671c..ac706d08414 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -7221,14 +7221,21 @@ static next_element_function const get_next_element[NUM_IT_METHODS] =
 
 
 /* Return true iff a character at CHARPOS (and BYTEPOS) is composed
-   (possibly with the following characters).  */
+   (possibly with the following characters).
+
+  Note: we pass -1 as the "resolved bidi level" when the iterator
+  doesn't have the bidi_p flag set, because in that case we really
+  don't know what is the directionality of the text, so we leave it to
+  the shaping engine to figure that out.  */
 
 #define CHAR_COMPOSED_P(IT,CHARPOS,BYTEPOS,END_CHARPOS)                 \
   ((IT)->cmp_it.id >= 0                                                 \
    || ((IT)->cmp_it.stop_pos == (CHARPOS)                               \
        && composition_reseat_it (&(IT)->cmp_it, CHARPOS, BYTEPOS,       \
                                  END_CHARPOS, (IT)->w,                  \
-                                 (IT)->bidi_it.resolved_level,          \
+                                 (IT)->bidi_p                           \
+                                 ? (IT)->bidi_it.resolved_level         \
+                                 : -1,                                  \
                                  FACE_FROM_ID_OR_NULL ((IT)->f,         \
                                                        (IT)->face_id),  \
                                  (IT)->string)))