ellipsize.c

GTK+-2.0源码之pango-1.15.6.tar.gz

		     int                new_index)
{
  int start, end;

  do
    {
      pango_attr_iterator_range (iter, &start, &end);
      if (end > new_index)
	break;
    }
  while (pango_attr_iterator_next (iter));
}

/* Updates the shaping of the ellipsis if necessary when we move the
 * position of the start of the gap.
 *
 * The shaping of the ellipsis is determined by two things:
 *
 * - The font attributes applied to the first character in the gap
 * - Whether the first character in the gap is wide or not. If the
 *   first character is wide, then we assume that we are ellipsizing
 *   East-Asian text, so prefer a mid-line ellipsizes to a baseline
 *   ellipsis, since that's typical practice for Chinese/Japanese/Korean.
 */
static void
update_ellipsis_shape (EllipsizeState *state)
{
  gboolean recompute = FALSE;
  gunichar start_wc;
  gboolean is_cjk;

  /* Unfortunately, we can only advance PangoAttrIterator forward; so each
   * time we back up we need to go forward to find the new position. To make
   * this not utterly slow, we cache an iterator at the start of the line
   */
  if (!state->line_start_attr)
    {
      state->line_start_attr = pango_attr_list_get_iterator (state->attrs);
      advance_iterator_to (state->line_start_attr, state->run_info[0].run->item->offset);
    }

  if (state->gap_start_attr)
    {
      /* See if the current attribute range contains the new start position
       */
      int start, end;

      pango_attr_iterator_range (state->gap_start_attr, &start, &end);

      if (state->gap_start_iter.run_iter.start_index < start)
	{
	  pango_attr_iterator_destroy (state->gap_start_attr);
	  state->gap_start_attr = NULL;
	}
    }

  /* Check whether we need to recompute the ellipsis because of new font attributes
   */
  if (!state->gap_start_attr)
    {
      state->gap_start_attr = pango_attr_iterator_copy (state->line_start_attr);
      advance_iterator_to (state->gap_start_attr,
			   state->run_info[state->gap_start_iter.run_index].run->item->offset);

      recompute = TRUE;
    }

  /* Check whether we need to recompute the ellipsis because we switch from CJK to not
   * or vice-versa
   */
  start_wc = g_utf8_get_char (state->layout->text + state->gap_start_iter.run_iter.start_index);
  is_cjk = g_unichar_iswide (start_wc);

  if (is_cjk != state->ellipsis_is_cjk)
    {
      state->ellipsis_is_cjk = is_cjk;
      recompute = TRUE;
    }

  if (recompute)
    shape_ellipsis (state);
}

/* Computes the position of the gap center and finds the smallest span containing it
 */
static void
find_initial_span (EllipsizeState *state)
{
  PangoGlyphItem *glyph_item;
  PangoGlyphItemIter *run_iter;
  gboolean have_cluster;
  int i;
  int x;
  int cluster_width;

  switch (state->layout->ellipsize)
    {
    case PANGO_ELLIPSIZE_NONE:
    default:
      g_assert_not_reached ();
    case PANGO_ELLIPSIZE_START:
      state->gap_center = 0;
      break;
    case PANGO_ELLIPSIZE_MIDDLE:
      state->gap_center = state->total_width / 2;
      break;
    case PANGO_ELLIPSIZE_END:
      state->gap_center = state->total_width;
      break;
    }

  /* Find the run containing the gap center
   */
  x = 0;
  for (i = 0; i < state->n_runs; i++)
    {
      if (x + state->run_info[i].width > state->gap_center)
	break;

      x += state->run_info[i].width;
    }

  if (i == state->n_runs)	/* Last run is a closed interval, so back off one run */
    {
      i--;
      x -= state->run_info[i].width;
    }

  /* Find the cluster containing the gap center
   */
  state->gap_start_iter.run_index = i;
  run_iter = &state->gap_start_iter.run_iter;
  glyph_item = state->run_info[i].run;

  cluster_width = 0;		/* Quiet GCC, the line must have at least one cluster */
  for (have_cluster = _pango_glyph_item_iter_init_start (run_iter, glyph_item, state->layout->text);
       have_cluster;
       have_cluster = _pango_glyph_item_iter_next_cluster (run_iter))
    {
      cluster_width = get_cluster_width (&state->gap_start_iter);

      if (x + cluster_width > state->gap_center)
	break;

      x += cluster_width;
    }

  if (!have_cluster)	/* Last cluster is a closed interval, so back off one cluster */
    x -= cluster_width;

  state->gap_end_iter = state->gap_start_iter;

  state->gap_start_x = x;
  state->gap_end_x = x + cluster_width;

  /* Expand the gap to a full span
   */
  while (!starts_at_ellipsization_boundary (state, &state->gap_start_iter))
    {
      line_iter_prev_cluster (state, &state->gap_start_iter);
      state->gap_start_x -= get_cluster_width (&state->gap_start_iter);
    }

  while (!ends_at_ellipsization_boundary (state, &state->gap_end_iter))
    {
      line_iter_next_cluster (state, &state->gap_end_iter);
      state->gap_end_x += get_cluster_width (&state->gap_end_iter);
    }

  update_ellipsis_shape (state);
}

/* Removes one run from the start or end of the gap. Returns FALSE
 * if there's nothing left to remove in either direction.
 */
static gboolean
remove_one_span (EllipsizeState *state)
{
  LineIter new_gap_start_iter;
  LineIter new_gap_end_iter;
  int new_gap_start_x;
  int new_gap_end_x;
  int width;

  /* Find one span backwards and forward from the gap
   */
  new_gap_start_iter = state->gap_start_iter;
  new_gap_start_x = state->gap_start_x;
  do
    {
      if (!line_iter_prev_cluster (state, &new_gap_start_iter))
	break;
      width = get_cluster_width (&new_gap_start_iter);
      new_gap_start_x -= width;
    }
  while (!starts_at_ellipsization_boundary (state, &new_gap_start_iter) ||
	 width == 0);

  new_gap_end_iter = state->gap_end_iter;
  new_gap_end_x = state->gap_end_x;
  do
    {
      if (!line_iter_next_cluster (state, &new_gap_end_iter))
	break;
      width = get_cluster_width (&new_gap_end_iter);
      new_gap_end_x += width;
    }
  while (!ends_at_ellipsization_boundary (state, &new_gap_end_iter) ||
	 width == 0);

  if (state->gap_end_x == new_gap_end_x && state->gap_start_x == new_gap_start_x)
    return FALSE;

  /* In the case where we could remove a span from either end of the
   * gap, we look at which causes the smaller increase in the
   * MAX (gap_end - gap_center, gap_start - gap_center)
   */
  if (state->gap_end_x == new_gap_end_x ||
      (state->gap_start_x != new_gap_start_x &&
       state->gap_center - new_gap_start_x < new_gap_end_x - state->gap_center))
    {
      state->gap_start_iter = new_gap_start_iter;
      state->gap_start_x = new_gap_start_x;

      update_ellipsis_shape (state);
    }
  else
    {
      state->gap_end_iter = new_gap_end_iter;
      state->gap_end_x = new_gap_end_x;
    }

  return TRUE;
}

/* Fixes up the properties of the ellipsis run once we've determined the final extents
 * of the gap
 */
static void
fixup_ellipsis_run (EllipsizeState *state)
{
  PangoGlyphString *glyphs = state->ellipsis_run->glyphs;
  PangoItem *item = state->ellipsis_run->item;
  int level;
  int i;

  /* Make the entire glyphstring into a single logical cluster */
  for (i = 0; i < glyphs->num_glyphs; i++)
    {
      glyphs->log_clusters[i] = 0;
      glyphs->glyphs[i].attr.is_cluster_start = FALSE;
    }

  glyphs->glyphs[0].attr.is_cluster_start = TRUE;

  /* Fix up the item to point to the entire elided text */
  item->offset = state->gap_start_iter.run_iter.start_index;
  item->length = state->gap_end_iter.run_iter.end_index - item->offset;
  item->num_chars = g_utf8_strlen (state->layout->text + item->offset, item->length);

  /* The level for the item is the minimum level of the elided text */
  level = G_MAXINT;
  for (i = state->gap_start_iter.run_index; i <= state->gap_end_iter.run_index; i++)
    level = MIN (level, state->run_info[i].run->item->analysis.level);

  item->analysis.level = level;
}

/* Computes the new list of runs for the line
 */
static GSList *
get_run_list (EllipsizeState *state)
{
  PangoGlyphItem *partial_start_run = NULL;
  PangoGlyphItem *partial_end_run = NULL;
  GSList *result = NULL;
  RunInfo *run_info;
  PangoGlyphItemIter *run_iter;
  int i;

  /* We first cut out the pieces of the starting and ending runs we want to
   * preserve; we do the end first in case the end and the start are
   * the same. Doing the start first would disturb the indices for the end.
   */
  run_info = &state->run_info[state->gap_end_iter.run_index];
  run_iter = &state->gap_end_iter.run_iter;
  if (run_iter->end_char != run_info->run->item->num_chars)
    {
      partial_end_run = run_info->run;
      run_info->run = pango_glyph_item_split (run_info->run, state->layout->text,
					      run_iter->end_index - run_info->run->item->offset);
    }

  run_info = &state->run_info[state->gap_start_iter.run_index];
  run_iter = &state->gap_start_iter.run_iter;
  if (run_iter->start_char != 0)
    {
      partial_start_run = pango_glyph_item_split (run_info->run, state->layout->text,
						  run_iter->start_index - run_info->run->item->offset);
    }

  /* Now assemble the new list of runs
   */
  for (i = 0; i < state->gap_start_iter.run_index; i++)
    result = g_slist_prepend (result, state->run_info[i].run);

  if (partial_start_run)
    result = g_slist_prepend (result, partial_start_run);

  result = g_slist_prepend (result, state->ellipsis_run);

  if (partial_end_run)
    result = g_slist_prepend (result, partial_end_run);

  for (i = state->gap_end_iter.run_index + 1; i < state->n_runs; i++)
    result = g_slist_prepend (result, state->run_info[i].run);

  /* And free the ones we didn't use
   */
  for (i = state->gap_start_iter.run_index; i <= state->gap_end_iter.run_index; i++)
    pango_glyph_item_free (state->run_info[i].run);

  return g_slist_reverse (result);
}

/* Computes the width of the line as currently ellipsized
 */
static int
current_width (EllipsizeState *state)
{
  return state->total_width - (state->gap_end_x - state->gap_start_x) + state->ellipsis_width;
}

/**
 * _pango_layout_line_ellipsize:
 * @line: a #PangoLayoutLine
 * @attrs: Attributes being used for itemization/shaping
 *
 * Given a #PangoLayoutLine with the runs still in logical order, ellipsize
 * it according the layout's policy to fit within the set width of the layout.
 *
 * Return value: whether the line had to be ellipsized
 **/
gboolean
_pango_layout_line_ellipsize (PangoLayoutLine *line,
			      PangoAttrList   *attrs)
{
  EllipsizeState state;
  int goal_width;
  gboolean is_ellipsized = FALSE;

  if (line->layout->ellipsize == PANGO_ELLIPSIZE_NONE ||
      line->layout->width < 0)
    goto ret;

  init_state (&state, line, attrs);

  goal_width = state.layout->width;
  if (state.layout->indent > 0 && state.layout->alignment != PANGO_ALIGN_CENTER)
    goal_width -= state.layout->indent;

  if (state.total_width <= goal_width)
    goto out;

  find_initial_span (&state);

  while (current_width (&state) > goal_width)
    {
      if (!remove_one_span (&state))
	break;
    }

  fixup_ellipsis_run (&state);

  g_slist_free (line->runs);
  line->runs = get_run_list (&state);
  is_ellipsized = TRUE;

 out:
  free_state (&state);
 ret:
  return is_ellipsized;
}