Further fix for bug #11860 with Arabic display on Windows.

 src/w32uniscribe.c (uniscribe_shape): Handle correctly the case of
 more than one grapheme cluster passed to the shaper: compute the
 offset adjustment values separately for each cluster.

2 files changed, 30 insertions, 16 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 5b58d77e54a..e186b8af87f 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,9 @@
 2012-09-01  Eli Zaretskii  <eliz@gnu.org>
 
+        * w32uniscribe.c (uniscribe_shape): Handle correctly the case of
+        more than one grapheme cluster passed to the shaper: compute the
+        offset adjustment values separately for each cluster.  (Bug#11860)
+
         * image.c: Restore mistakenly removed inclusion of w32.h.  Without
         it, GCC doesn't see prototypes of w32_delayed_load, and complains
         about implicit conversions from integer to pointer.
diff --git a/src/w32uniscribe.c b/src/w32uniscribe.c
index 50532acaff3..bc45e2c648c 100644
--- a/src/w32uniscribe.c
+++ b/src/w32uniscribe.c
@@ -322,22 +322,6 @@ uniscribe_shape (Lisp_Object lgstring)
             {
               int j, from, to, adj_offset = 0;
 
-              /* For RTL text, the Uniscribe shaper prepares the
-                 values in ADVANCES array for layout in reverse order,
-                 whereby "advance width" is applied to move the pen in
-                 reverse direction and _before_ drawing the glyph.
-                 Since we draw glyphs in their normal left-to-right
-                 order, we need to adjust the coordinates of each
-                 non-base glyph in a grapheme cluster via X-OFF
-                 component of the gstring's ADJUSTMENT sub-vector.
-                 This loop computes the initial value of the
-                 adjustment for the base character, which is then
-                 updated for each successive glyph in the grapheme
-                 cluster.  */
-              if (items[i].a.fRTL)
-                for (j = 1; j < nglyphs; j++)
-                  adj_offset += advances[j];
-
               from = 0;
               to = from;
 
@@ -380,6 +364,32 @@ uniscribe_shape (Lisp_Object lgstring)
                                 }
                             }
                         }
+
+                      /* For RTL text, the Uniscribe shaper prepares
+                         the values in ADVANCES array for layout in
+                         reverse order, whereby "advance width" is
+                         applied to move the pen in reverse direction
+                         and _before_ drawing the glyph.  Since we
+                         draw glyphs in their normal left-to-right
+                         order, we need to adjust the coordinates of
+                         each non-base glyph in a grapheme cluster via
+                         X-OFF component of the gstring's ADJUSTMENT
+                         sub-vector.  This loop computes, for each
+                         grapheme cluster, the initial value of the
+                         adjustment for the base character, which is
+                         then updated for each successive glyph in the
+                         grapheme cluster.  */
+                      if (items[i].a.fRTL)
+                        {
+                          int j1 = j;
+
+                          adj_offset = 0;
+                          while (j1 < nglyphs && !attributes[j1].fClusterStart)
+                            {
+                              adj_offset += advances[j1];
+                              j1++;
+                            }
+                        }
                     }
 
                   LGLYPH_SET_CHAR (lglyph, chars[items[i].iCharPos