[pango] Use grapheme boundaries in justify_clusters()

[Khaled Hosny <khaledh src gnome org>]

commit 25976af86f2db722eb75c8d3015888cd5cad2efb
Author: Khaled Hosny <khaledhosny eglug org>
Date:   Tue Aug 18 16:04:16 2015 +0200

    Use grapheme boundaries in justify_clusters()
    
    Instead of relying on the fact that marks have the same cluster number
    as their bases, which will change in the next commit.

 pango/pango-layout.c |   77 ++++++++++++++++++++++++++++++--------------------
 1 files changed, 46 insertions(+), 31 deletions(-)
---
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index 862ae8b..fa6fbc5 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -5167,6 +5167,10 @@ static void
 justify_clusters (PangoLayoutLine *line,
                  ParaBreakState  *state)
 {
+  const gchar *text = line->layout->text;
+  const PangoLogAttr *log_attrs = line->layout->log_attrs;
+
+  int offset;
   int total_remaining_width, total_gaps = 0;
   int added_so_far, gaps_so_far;
   gboolean is_hinted;
@@ -5188,52 +5192,63 @@ justify_clusters (PangoLayoutLine *line,
       added_so_far = 0;
       gaps_so_far = 0;
 
+      offset = state->line_start_offset;
       for (run_iter = line->runs; run_iter; run_iter = run_iter->next)
        {
          PangoLayoutRun *run = run_iter->data;
          PangoGlyphString *glyphs = run->glyphs;
          gboolean is_first_gap = TRUE;
+         PangoGlyphItemIter cluster_iter;
+         gboolean have_cluster;
 
-         int i;
-
-         for (i = 0; i < glyphs->num_glyphs; i++)
+         for (have_cluster = pango_glyph_item_iter_init_start (&cluster_iter, run, text);
+              have_cluster;
+              have_cluster = pango_glyph_item_iter_next_cluster (&cluster_iter))
            {
-             if (!glyphs->glyphs[i].attr.is_cluster_start)
-               continue;
+             int i;
+             int dir;
 
-             /* also don't expand zero-width spaces at the end of runs */
-             if (glyphs->glyphs[i].geometry.width == 0)
-               {
-                 if (i == glyphs->num_glyphs -1)
-                   continue;
+             /* don't expand in the middle of graphemes */
+             if (!log_attrs[offset + cluster_iter.start_char].is_cursor_position)
+               continue;
 
-                 if (i == 0 && glyphs->num_glyphs > 1 && glyphs->glyphs[i+1].attr.is_cluster_start)
-                   continue;
-               }
+             dir = (cluster_iter.start_glyph < cluster_iter.end_glyph) ? 1 : -1;
+             for (i = cluster_iter.start_glyph; i != cluster_iter.end_glyph; i += dir)
+               {
+                 /* also don't expand zero-width spaces at the end of runs */
+                 if (glyphs->glyphs[i].geometry.width == 0)
+                   {
+                     if (i == glyphs->num_glyphs -1)
+                       continue;
 
-             if (is_first_gap)
-               {
-                 is_first_gap = FALSE;
-                 continue;
-               }
+                     if (i == 0 && glyphs->num_glyphs > 1 && glyphs->glyphs[i+1].attr.is_cluster_start)
+                       continue;
+                   }
+
+                 if (is_first_gap)
+                   {
+                     is_first_gap = FALSE;
+                     continue;
+                   }
 
-             gaps_so_far++;
+                 gaps_so_far++;
 
-             if (mode == ADJUST)
-               {
-                 int adjustment, space_left, space_right;
+                 if (mode == ADJUST)
+                   {
+                     int adjustment, space_left, space_right;
 
-                 adjustment = (gaps_so_far * total_remaining_width) / total_gaps - added_so_far;
-                 if (is_hinted)
-                   adjustment = PANGO_UNITS_ROUND (adjustment);
-                 /* distribute to before/after */
-                 distribute_letter_spacing (adjustment, &space_left, &space_right);
+                     adjustment = (gaps_so_far * total_remaining_width) / total_gaps - added_so_far;
+                     if (is_hinted)
+                       adjustment = PANGO_UNITS_ROUND (adjustment);
+                     /* distribute to before/after */
+                     distribute_letter_spacing (adjustment, &space_left, &space_right);
 
-                 glyphs->glyphs[i-1].geometry.width    += space_left ;
-                 glyphs->glyphs[i  ].geometry.width    += space_right;
-                 glyphs->glyphs[i  ].geometry.x_offset += space_right;
+                     glyphs->glyphs[i-1].geometry.width    += space_left ;
+                     glyphs->glyphs[i  ].geometry.width    += space_right;
+                     glyphs->glyphs[i  ].geometry.x_offset += space_right;
 
-                 added_so_far += adjustment;
+                     added_so_far += adjustment;
+                   }
                }
            }
        }