[pango/non-breaking-attrs: 4/6] layout: Don't break runs for font_features

[Matthias Clasen <matthiasc src gnome org>]

commit a0483fc2157a7efbf153effec0b241583e43e047
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Jul 11 11:32:22 2019 -0400

    layout: Don't break runs for font_features
    
    Don't pass font_features attributes into the itemize
    run, since we don't need to break runs for this.
    Split them off, and reapply them after itemization.
    We rapply them before line breaking, since we want
    them to affect the shaping.
    
    Closes: https://gitlab.gnome.org/GNOME/pango/issues/242

 pango/pango-layout.c | 84 ++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 65 insertions(+), 19 deletions(-)
---
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index 2384d6b0..97beccc8 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -4006,11 +4006,6 @@ no_shape_filter_func (PangoAttribute *attribute,
     PANGO_ATTR_UNDERLINE,
     PANGO_ATTR_STRIKETHROUGH,
     PANGO_ATTR_RISE
-    /* Ideally we want font-features here, because we don't
-     * want it to break shaping runs.  But if we put it here,
-     * it won't show up in the shaper anymore :(.  To be
-     * fixed later. */
-    /* PANGO_ATTR_FONT_FEATURES */
   };
 
   int i;
@@ -4032,33 +4027,76 @@ filter_no_shape_attributes (PangoAttrList *attrs)
 
 static void
 apply_no_shape_attributes (PangoLayout   *layout,
-                          PangoAttrList *no_shape_attrs)
+                           PangoAttrList *no_shape_attrs)
 {
-  GSList *line_list;
+  GSList *ll;
 
-  for (line_list = layout->lines; line_list; line_list = line_list->next)
+  for (ll = layout->lines; ll; ll = ll->next)
     {
-      PangoLayoutLine *line = line_list->data;
+      PangoLayoutLine *line = ll->data;
       GSList *old_runs = g_slist_reverse (line->runs);
-      GSList *run_list;
+      GSList *rl;
 
       line->runs = NULL;
-      for (run_list = old_runs; run_list; run_list = run_list->next)
-       {
-         PangoGlyphItem *glyph_item = run_list->data;
-         GSList *new_runs;
+      for (rl = old_runs; rl; rl = rl->next)
+        {
+          PangoGlyphItem *glyph_item = rl->data;
+          GSList *new_runs;
 
-         new_runs = pango_glyph_item_apply_attrs (glyph_item,
-                                                  layout->text,
-                                                  no_shape_attrs);
+          new_runs = pango_glyph_item_apply_attrs (glyph_item,
+          layout->text,
+          no_shape_attrs);
 
-         line->runs = g_slist_concat (new_runs, line->runs);
-       }
+          line->runs = g_slist_concat (new_runs, line->runs);
+        }
 
       g_slist_free (old_runs);
     }
 }
 
+static gboolean
+no_break_filter_func (PangoAttribute *attribute,
+                     gpointer        data G_GNUC_UNUSED)
+{
+  static const PangoAttrType no_break_types[] = {
+    PANGO_ATTR_FONT_FEATURES
+  };
+
+  int i;
+
+  for (i = 0; i < (int)G_N_ELEMENTS (no_break_types); i++)
+    if (attribute->klass->type == no_break_types[i])
+      return TRUE;
+
+  return FALSE;
+}
+
+static PangoAttrList *
+filter_no_break_attributes (PangoAttrList *attrs)
+{
+  return pango_attr_list_filter (attrs,
+                                no_break_filter_func,
+                                NULL);
+}
+
+static void
+apply_no_break_attributes (GList         *items,
+                          PangoAttrList *no_break_attrs)
+{
+  GList *l;
+  PangoAttrIterator *iter;
+
+  iter = pango_attr_list_get_iterator (no_break_attrs);
+
+  for (l = items; l; l = l->next)
+    {
+      PangoItem *item = l->data;
+      pango_item_apply_attrs (item, iter);
+    }
+
+  pango_attr_iterator_destroy (iter);
+}
+
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 
@@ -4070,6 +4108,7 @@ pango_layout_check_lines (PangoLayout *layout)
   int start_offset;
   PangoAttrList *attrs;
   PangoAttrList *no_shape_attrs;
+  PangoAttrList *no_break_attrs;
   PangoAttrIterator *iter;
   PangoDirection prev_base_dir = PANGO_DIRECTION_NEUTRAL, base_dir = PANGO_DIRECTION_NEUTRAL;
   ParaBreakState state;
@@ -4089,6 +4128,7 @@ pango_layout_check_lines (PangoLayout *layout)
 
   attrs = pango_layout_get_effective_attributes (layout);
   no_shape_attrs = filter_no_shape_attributes (attrs);
+  no_break_attrs = filter_no_break_attributes (attrs);
   iter = pango_attr_list_get_iterator (attrs);
 
   layout->log_attrs = g_new (PangoLogAttr, layout->n_chars + 1);
@@ -4169,6 +4209,12 @@ pango_layout_check_lines (PangoLayout *layout)
                                                 attrs,
                                                 iter);
 
+      if (no_break_attrs)
+        {
+          apply_no_break_attributes (state.items, no_break_attrs);
+          pango_attr_list_unref (no_break_attrs);
+        }
+
       get_items_log_attrs (start, state.items,
                           layout->log_attrs + start_offset,
                           delim_len);