pango-glyph-item.c

Pango is a library for layout and rendering of text, with an emphasis on internationalization. Pang

	}
    }

  iter->start_glyph = glyph_index;
  return TRUE;
}

/**
 * _pango_glyph_item_iter_init_start:
 * @iter: pointer to a #PangoGlyphItemIter structure
 * @glyph_item: the glyph item that @iter points into
 * @text: text corresponding to the glyph item
 *
 * Initializes a #PangoGlyphItemIter structure to point to the
 * first cluster in a glyph item.
 *
 * Return value: %FALSE if there are no clusters in the glyph item;
 *  in this case, the state of @iter is undefined.
 **/
gboolean
_pango_glyph_item_iter_init_start (PangoGlyphItemIter  *iter,
				   PangoGlyphItem      *glyph_item,
				   const char          *text)
{
  iter->glyph_item = glyph_item;
  iter->text = text;

  if (LTR (glyph_item))
    iter->end_glyph = 0;
  else
    iter->end_glyph = glyph_item->glyphs->num_glyphs - 1;

  iter->end_index = glyph_item->item->offset;
  iter->end_char = 0;

  /* Advance onto the first cluster of the glyph item */
  return _pango_glyph_item_iter_next_cluster (iter);
}

/**
 * _pango_glyph_item_iter_init_end:
 * @iter: pointer to a #PangoGlyphItemIter structure
 * @glyph_item: the glyph item that @iter points into
 * @text: text corresponding to the glyph item
 *
 * Initializes a #PangoGlyphItemIter structure to point to the
 * last cluster in a glyph item.
 *
 * Return value: %FALSE if there are no clusters in the glyph item;
 *  in this case, the state of @iter is undefined.
 **/
gboolean
_pango_glyph_item_iter_init_end (PangoGlyphItemIter  *iter,
				 PangoGlyphItem      *glyph_item,
				 const char          *text)
{
  iter->glyph_item = glyph_item;
  iter->text = text;

  if (LTR (glyph_item))
    iter->start_glyph = glyph_item->glyphs->num_glyphs;
  else
    iter->start_glyph = -1;

  iter->start_index = glyph_item->item->offset + glyph_item->item->length;
  iter->start_char = glyph_item->item->num_chars;

  /* Advance onto the first cluster of the glyph item */
  return _pango_glyph_item_iter_prev_cluster (iter);
}

typedef struct
{
  PangoGlyphItemIter iter;

  GSList *segment_attrs;
} ApplyAttrsState;

/* Tack @attrs onto the attributes of glyph_item
 */
static void
append_attrs (PangoGlyphItem *glyph_item,
	      GSList         *attrs)
{
  glyph_item->item->analysis.extra_attrs =
    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;
}

/* 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->iter.start_index - state->iter.glyph_item->item->offset;

  split_item = pango_glyph_item_split (state->iter.glyph_item, state->iter.text, split_len);
  append_attrs (split_item, state->segment_attrs);

  /* Adjust iteration to account for the split
   */
  if (LTR (state->iter.glyph_item))
    {
      state->iter.start_glyph -= split_item->glyphs->num_glyphs;
      state->iter.end_glyph -= split_item->glyphs->num_glyphs;
    }

  state->iter.start_char -= split_item->item->num_chars;
  state->iter.end_char -= split_item->item->num_chars;

  return split_item;
}

/**
 * pango_glyph_item_apply_attrs:
 * @glyph_item: a shaped item
 * @text: text that @list applies to
 * @list: a #PangoAttrList
 *
 * Splits a shaped item (PangoGlyphItem) into multiple items based
 * on an attribute list. The idea is that if you have attributes
 * that don't affect shaping, such as color or underline, to avoid
 * affecting shaping, you filter them out (pango_attr_list_filter()),
 * 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 strikethrough, 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.
 *
 * Return value: a list of glyph items resulting from splitting
 *   @glyph_item. Free the elements using pango_glyph_item_free(),
 *   the list using g_slist_free().
 *
 * Since: 1.2
 **/
GSList *
pango_glyph_item_apply_attrs (PangoGlyphItem   *glyph_item,
			      const char       *text,
			      PangoAttrList    *list)
{
  PangoAttrIterator *iter = pango_attr_list_get_iterator (list);
  GSList *result = NULL;
  ApplyAttrsState state;
  gboolean start_new_segment = FALSE;
  gboolean have_cluster;
  int range_start, range_end;

  /* 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 start_index < attribute_start < end_index
   *    (attribute starts within cluster) then we need
   *    to split between the last cluster and this cluster.
   * B) If start_index < attribute_end <= end_index,
   *    (attribute ends within cluster) then we need to
   *    split between this cluster and the next one.
   */

  /* Advance the attr iterator to the start of the item
   */
  do
    {
      pango_attr_iterator_range (iter, &range_start, &range_end);
      if (range_end > glyph_item->item->offset)
	break;
    }
  while (pango_attr_iterator_next (iter));

  state.segment_attrs = pango_attr_iterator_get_attrs (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;

  for (have_cluster = _pango_glyph_item_iter_init_start (&state.iter, glyph_item, text);
       have_cluster;
       have_cluster = _pango_glyph_item_iter_next_cluster (&state.iter))
    {
      gboolean have_next;

      /* [range_start,range_end] is the first range that intersects
       * the current cluster.
       */

      /* Split item into two, if this cluster isn't a continuation
       * of the last cluster
       */
      if (start_new_segment)
	{
	  result = g_slist_prepend (result,
				    split_before_cluster_start (&state));
	  state.segment_attrs = pango_attr_iterator_get_attrs (iter);
	}

      start_new_segment = FALSE;

      /* Loop over all ranges that intersect this cluster; exiting
       * leaving [range_start,range_end] being the first range that
       * intersects the next cluster.
       */
      do
	{
	  if (range_end > state.iter.end_index) /* Range intersects next cluster */
	    break;

	  /* Since ranges end in this cluster, the next cluster goes into a
	   * separate segment
	   */
	  start_new_segment = TRUE;

	  have_next = pango_attr_iterator_next (iter);
	  pango_attr_iterator_range (iter, &range_start, &range_end);

	  if (range_start >= state.iter.end_index) /* New range doesn't intersect this cluster */
	    {
	      /* No gap between ranges, so previous range must of ended
	       * at cluster boundary.
	       */
	      g_assert (range_start == state.iter.end_index && start_new_segment);
	      break;
	    }

	  /* If any ranges start *inside* this cluster, then we need
	   * to split the previous cluster into a separate segment
	   */
	  if (range_start > state.iter.start_index &&
	      state.iter.start_index != 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));
	}
      while (have_next);
    }

 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 (glyph_item))
    result = g_slist_reverse (result);

  pango_attr_iterator_destroy (iter);

  return result;
}

/**
 * pango_glyph_item_letter_space:
 * @glyph_item: a #PangoGlyphItem
 * @text: text that @glyph_item corresponds to
 *   (glyph_item->item->offset is an offset from the
 *    start of @text)
 * @log_attrs: logical attributes for the item (the
 *   first logical attribute refers to the position
 *   before the first character in the item)
 * @letter_spacing: amount of letter spacing to add
 *   in Pango units. May be negative, though too large
 *   negative values will give ugly results.
 *
 * Adds spacing between the graphemes of @glyph_item to
 * give the effect of typographic letter spacing.
 *
 * Since: 1.6
 **/
void
pango_glyph_item_letter_space (PangoGlyphItem *glyph_item,
			       const char     *text,
			       PangoLogAttr   *log_attrs,
			       int             letter_spacing)
{
  PangoGlyphItemIter iter;
  PangoGlyphInfo *glyphs = glyph_item->glyphs->glyphs;
  gboolean have_cluster;
  int space_left, space_right;

  space_left = letter_spacing / 2;

  /* hinting */
  if ((letter_spacing & (PANGO_SCALE - 1)) == 0)
    {
      space_left = PANGO_UNITS_ROUND (space_left);
    }

  space_right = letter_spacing - space_left;

  for (have_cluster = _pango_glyph_item_iter_init_start (&iter, glyph_item, text);
       have_cluster;
       have_cluster = _pango_glyph_item_iter_next_cluster (&iter))
    {
      if (!log_attrs[iter.start_char].is_cursor_position)
        continue;

      if (iter.start_glyph < iter.end_glyph) /* LTR */
	{
	  if (iter.start_char > 0)
	    {
	      glyphs[iter.start_glyph].geometry.width    += space_left ;
	      glyphs[iter.start_glyph].geometry.x_offset += space_left ;
	    }
	  if (iter.end_char < glyph_item->item->num_chars)
	    {
	      glyphs[iter.end_glyph-1].geometry.width    += space_right;
	    }
	}
      else			                 /* RTL */
	{
	  if (iter.start_char > 0)
	    {
	      glyphs[iter.start_glyph].geometry.width    += space_right;
	    }
	  if (iter.end_char < glyph_item->item->num_chars)
	    {
	      glyphs[iter.end_glyph+1].geometry.x_offset += space_left ;
	      glyphs[iter.end_glyph+1].geometry.width    += space_left ;
	    }
	}
    }
}