When applying attribute to a glyph item, handle attributes that split

Thu May 29 18:37:58 2003  Owen Taylor  <otaylor@redhat.com>

        * pango/pango-glyph-item.c (pango_glyph_item_apply_attrs):
        When applying attribute to a glyph item, handle attributes
        that split clusters by giving the cluster all the attributes
        that apply to it. (Previously caused a crash, #104976
        Taneem Ahmed, Sunil Mohan Adapa)

1 files changed, 226 insertions, 29 deletions

diff --git a/pango/pango-glyph-item.c b/pango/pango-glyph-item.c
index a941f650..a18dd0d9 100644
--- a/pango/pango-glyph-item.c
+++ b/pango/pango-glyph-item.c
@@ -24,6 +24,8 @@
 
 #include "pango-glyph-item.h"
 
+#define LTR(glyph_item) (((glyph_item)->item->analysis.level % 2) == 0)
+
 /**
  * pango_glyph_item_split:
  * @orig: a #PangoItem
@@ -53,14 +55,13 @@ pango_glyph_item_split (PangoGlyphItem *orig,
   int num_glyphs;
   int num_remaining;
   int split_offset;
-  gboolean ltr = (orig->item->analysis.level % 2) == 0;
 
   g_return_val_if_fail (orig != NULL, NULL);
   g_return_val_if_fail (orig->item->length > 0, NULL);
   g_return_val_if_fail (split_index > 0, NULL);
   g_return_val_if_fail (split_index < orig->item->length, NULL);
 
-  if (ltr)
+  if (LTR (orig))
     {
       for (i = 0; i < orig->glyphs->num_glyphs; i++)
 	{
@@ -99,7 +100,7 @@ pango_glyph_item_split (PangoGlyphItem *orig,
   new->glyphs = pango_glyph_string_new ();
   pango_glyph_string_set_size (new->glyphs, num_glyphs);
 
-  if (ltr)
+  if (LTR (orig))
     {
       memcpy (new->glyphs->glyphs, orig->glyphs->glyphs, num_glyphs * sizeof (PangoGlyphInfo));
       memcpy (new->glyphs->log_clusters, orig->glyphs->log_clusters, num_glyphs * sizeof (int));
@@ -123,6 +124,26 @@ pango_glyph_item_split (PangoGlyphItem *orig,
   return new;
 }
 
+/* Structure holding state when we're iterating over a GlyphItem for
+ * pango_glyph_item_apply_attrs(). cluster_start/cluster_end (and
+ * range_start/range_end in apply_attrs()) are offsets into the
+ * text, so note the difference of glyph_item->item->offset between
+ * them and clusters in the log_clusters[] array.
+ */
+typedef struct 
+{
+  PangoGlyphItem *glyph_item;
+  const gchar *text;
+  
+  int glyph_index;
+  int cluster_start;
+  int cluster_end;
+  
+  GSList *segment_attrs;
+} ApplyAttrsState;
+
+/* Tack @attrs onto the attributes of glyph_item
+ */
 static void
 append_attrs (PangoGlyphItem *glyph_item,
 	      GSList         *attrs)
@@ -131,6 +152,101 @@ append_attrs (PangoGlyphItem *glyph_item,
     g_slist_concat (glyph_item->item->analysis.extra_attrs, attrs);
 }
 
+/* Make a deep copy of a GSlist of PangoAttribute
+ */
+static GSList *
+attr_slist_copy (GSList *attrs)
+{
+  GSList *tmp_list;
+  GSList *new_attrs;
+  
+  new_attrs = g_slist_copy (attrs);
+  
+  for (tmp_list = new_attrs; tmp_list; tmp_list = tmp_list->next)
+    tmp_list->data = pango_attribute_copy (tmp_list->data);
+
+  return new_attrs;
+}
+
+/* Advance to the next logical cluster
+ */
+static gboolean
+next_cluster (ApplyAttrsState *state)
+{
+  int glyph_index = state->glyph_index;
+  PangoGlyphString *glyphs = state->glyph_item->glyphs;
+  PangoItem *item = state->glyph_item->item;
+    
+  state->cluster_start = state->cluster_end;
+  
+  if (LTR (state->glyph_item))
+    {
+      if (glyph_index == glyphs->num_glyphs)
+	return FALSE;
+      
+      while (TRUE)
+	{
+	  glyph_index++;
+	  
+	  if (glyph_index == glyphs->num_glyphs)
+	    {
+	      state->cluster_end = item->offset + item->length;
+	      break;
+	    }
+	  
+	  if (item->offset + glyphs->log_clusters[glyph_index] >= state->cluster_start)
+	    {
+	      state->cluster_end = item->offset + glyphs->log_clusters[glyph_index];
+	      break; 
+	    }
+	}
+    }
+  else			/* RTL */
+    {
+      if (glyph_index < 0)
+	return FALSE;
+      
+      while (TRUE)
+	{
+	  glyph_index--;
+	  
+	  if (glyph_index < 0)
+	    {
+	      state->cluster_end = item->offset + item->length;
+	      break;
+	    }
+	  
+	  if (item->offset + glyphs->log_clusters[glyph_index] >= state->cluster_start)
+	    {
+	      state->cluster_end = item->offset + glyphs->log_clusters[glyph_index];
+	      break; 
+	    }
+	}
+    }
+
+  state->glyph_index = glyph_index;
+  return TRUE;
+}
+
+/* Split the glyph item at the start of the current cluster
+ */
+static PangoGlyphItem *
+split_before_cluster_start (ApplyAttrsState *state)
+{
+  PangoGlyphItem *split_item;
+  int split_len = state->cluster_start - state->glyph_item->item->offset;
+
+  split_item = pango_glyph_item_split (state->glyph_item, state->text, split_len);
+  append_attrs (split_item, state->segment_attrs);
+
+  /* Adjust iteration to account for the split
+   */
+  if (LTR (state->glyph_item))
+    state->glyph_index -= split_item->glyphs->num_glyphs;
+ 
+  return split_item;
+}
+
 /**
  * pango_glyph_item_apply_attrs:
  * @glyph_item: a shaped item 
@@ -144,6 +260,13 @@ append_attrs (PangoGlyphItem *glyph_item,
  * apply the shaping process and then reapply them to the result using
  * this function.
  *
+ * All attributes that start or end inside a cluster are applied
+ * to that cluster; for instance, if half of a cluster is underlined
+ * and the other-half strikethough, then the cluster will end
+ * up with both underline and strikethrough attributes. In these
+ * cases, it may happen that item->extra_attrs for some of the
+ * result items can have multiple attributes of the same type.
+ *
  * This function takes ownership of @glyph_item; it will be reused
  * as one of the elements in the list.
  * 
@@ -157,51 +280,125 @@ pango_glyph_item_apply_attrs (PangoGlyphItem   *glyph_item,
 			      PangoAttrList    *list)
 {
   PangoAttrIterator *iter = pango_attr_list_get_iterator (list);
-  PangoGlyphItem *new;
   GSList *result = NULL;
-  int start;
-  int end;
+  ApplyAttrsState state;
+  gboolean start_new_segment = FALSE;
+  int range_start, range_end;
 
-  gboolean ltr = (glyph_item->item->analysis.level % 2) == 0;
+  /* This routine works by iterating through the item cluster by
+   * cluster; we accumulate the attributes that we need to
+   * add to the next output item, and decide when to split
+   * off an output item based on two criteria:
+   *
+   * A) If cluster_start < attribute_start < cluster_end
+   *    (attribute starts within cluster) then we need
+   *    to split between the last cluster and this cluster.
+   * B) If cluster_start < attribute_end <= cluster_end,
+   *    (attribute ends within cluster) then we need to
+   *    split between this cluster and the next one.
+   */
+
+  state.glyph_item = glyph_item;
+  state.text = text;
+  
+  if (LTR (glyph_item))
+    state.glyph_index = 0;
+  else
+    state.glyph_index = glyph_item->glyphs->num_glyphs - 1;
+
+  state.cluster_end = glyph_item->item->offset;
+  
+  /* Advance the attr iterator to the start of the item
+   */
+  while (TRUE)
+    {
+      pango_attr_iterator_range (iter, &range_start, &range_end);
+      if (range_end > state.cluster_end)
+	break;
+      
+      g_assert (pango_attr_iterator_next (iter));
+    }
 
+  /* Short circuit the case when we don't actually need to
+   * split the item
+   */
+  if (range_start <= glyph_item->item->offset &&
+      range_end >= glyph_item->item->offset + glyph_item->item->length)
+    goto out;
+  
+  state.segment_attrs = pango_attr_iterator_get_attrs (iter);
+  
   while (TRUE)
     {
-      pango_attr_iterator_range (iter, &start, &end);
+      /* Find the next logical cluster; [range_start,range_end]
+       * is the first range that intersects the new cluster.
+       */
+      if (!next_cluster (&state))
+	break;
 
-      if (start > glyph_item->item->offset)
+      /* Split item into two, if this cluster isn't a continuation
+       * of the last cluster
+       */
+      if (start_new_segment)
 	{
-	  if (start >= glyph_item->item->offset + glyph_item->item->length)
-	    break;
-
-	  new = pango_glyph_item_split (glyph_item, text,
-					start - glyph_item->item->offset);
-	  
-	  result = g_slist_prepend (result, new);
+	  result = g_slist_prepend (result,
+				    split_before_cluster_start (&state));
+	  state.segment_attrs = pango_attr_iterator_get_attrs (iter);
 	}
+      
+      start_new_segment = FALSE;
 
-      if (end > glyph_item->item->offset)
+      /* Loop over all ranges that intersect this cluster; exiting
+       * leaving [range_start,range_end] being the first range that
+       * intersects the next cluster.
+       */
+      while (TRUE)
 	{
-	  if (end >= glyph_item->item->offset + glyph_item->item->length)
+	  /* If any ranges end in this cluster, then the next cluster
+	   * goes into a separate segment
+	   */
+	  if (range_end <= state.cluster_end)
+	    start_new_segment = TRUE;
+
+	  if (range_end > state.cluster_end) /* Range intersects next cluster */
+	    break;
+
+	  g_assert (pango_attr_iterator_next (iter));
+	  pango_attr_iterator_range (iter, &range_start, &range_end);
+
+	  if (range_start >= state.cluster_end) /* New range doesn't intersect this cluster */
 	    {
-	      append_attrs (glyph_item, pango_attr_iterator_get_attrs (iter));
+	      /* No gap between ranges, so previous range must of ended
+	       * at cluster boundary.
+	       */
+	      g_assert (range_start == state.cluster_end && start_new_segment);
 	      break;
 	    }
 
-	  new = pango_glyph_item_split (glyph_item, text,
-					end - glyph_item->item->offset);
-
-	  append_attrs (new, pango_attr_iterator_get_attrs (iter));
-
-	  result = g_slist_prepend (result, new);
+	  /* If any ranges start *inside* this cluster, then we need
+	   * to split the previous cluster into a separate segment
+	   */
+	  if (range_start > state.cluster_start &&
+	      state.cluster_start != glyph_item->item->offset)
+	    {
+	      GSList *new_attrs = attr_slist_copy (state.segment_attrs);
+	      result = g_slist_prepend (result, 
+					split_before_cluster_start (&state));
+	      state.segment_attrs = new_attrs;
+	    }
+	  
+	  state.segment_attrs = g_slist_concat (state.segment_attrs,
+						pango_attr_iterator_get_attrs (iter));
 	}
-
-      if (!pango_attr_iterator_next (iter))
-	  break;
     }
 
+ out:
+  /* What's left in glyph_item is the remaining portion
+   */
+  append_attrs (glyph_item, state.segment_attrs);
   result = g_slist_prepend (result, glyph_item);
 
-  if (ltr)
+  if (LTR (glyph_item))
     result = g_slist_reverse (result);
 
   pango_attr_iterator_destroy (iter);