File: pango-context.c

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/* Pango
 * pango-context.c: Contexts for itemization and shaping
 *
 * Copyright (C) 2000, 2006 Red Hat Software
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/**
 * SECTION:main
 * @title:Rendering
 * @short_description:Functions to run the rendering pipeline
 *
 * The Pango rendering pipeline takes a string of
 * Unicode characters and converts it into glyphs.
 * The functions described in this section accomplish
 * various steps of this process.
 */
#include "config.h"
#include <string.h>
#include <stdlib.h>

#include "pango-context.h"
#include "pango-impl-utils.h"

#include "pango-engine-private.h"
#include "pango-script-private.h"
#include "pango-emoji-private.h"

/**
 * PangoContext:
 *
 * The #PangoContext structure stores global information
 * used to control the itemization process.
 */
struct _PangoContext
{
  GObject parent_instance;
  guint serial;
  guint fontmap_serial;

  PangoLanguage *set_language;
  PangoLanguage *language;
  PangoDirection base_dir;
  PangoGravity base_gravity;
  PangoGravity resolved_gravity;
  PangoGravityHint gravity_hint;

  PangoFontDescription *font_desc;

  PangoMatrix *matrix;

  PangoFontMap *font_map;
};

struct _PangoContextClass
{
  GObjectClass parent_class;

};

static void pango_context_finalize    (GObject       *object);
static void context_changed           (PangoContext  *context);

G_DEFINE_TYPE (PangoContext, pango_context, G_TYPE_OBJECT)

static void
pango_context_init (PangoContext *context)
{
  context->base_dir = PANGO_DIRECTION_WEAK_LTR;
  context->resolved_gravity = context->base_gravity = PANGO_GRAVITY_SOUTH;
  context->gravity_hint = PANGO_GRAVITY_HINT_NATURAL;

  context->serial = 1;
  context->set_language = NULL;
  context->language = pango_language_get_default ();
  context->font_map = NULL;

  context->font_desc = pango_font_description_new ();
  pango_font_description_set_family_static (context->font_desc, "serif");
  pango_font_description_set_style (context->font_desc, PANGO_STYLE_NORMAL);
  pango_font_description_set_variant (context->font_desc, PANGO_VARIANT_NORMAL);
  pango_font_description_set_weight (context->font_desc, PANGO_WEIGHT_NORMAL);
  pango_font_description_set_stretch (context->font_desc, PANGO_STRETCH_NORMAL);
  pango_font_description_set_size (context->font_desc, 12 * PANGO_SCALE);
}

static void
pango_context_class_init (PangoContextClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);

  object_class->finalize = pango_context_finalize;
}

static void
pango_context_finalize (GObject *object)
{
  PangoContext *context;

  context = PANGO_CONTEXT (object);

  if (context->font_map)
    g_object_unref (context->font_map);

  pango_font_description_free (context->font_desc);
  if (context->matrix)
    pango_matrix_free (context->matrix);

  G_OBJECT_CLASS (pango_context_parent_class)->finalize (object);
}

/**
 * pango_context_new:
 *
 * Creates a new #PangoContext initialized to default values.
 *
 * This function is not particularly useful as it should always
 * be followed by a pango_context_set_font_map() call, and the
 * function pango_font_map_create_context() does these two steps
 * together and hence users are recommended to use that.
 *
 * If you are using Pango as part of a higher-level system,
 * that system may have it's own way of create a #PangoContext.
 * For instance, the GTK+ toolkit has, among others,
 * gdk_pango_context_get_for_screen(), and
 * gtk_widget_get_pango_context().  Use those instead.
 *
 * Return value: the newly allocated #PangoContext, which should
 *               be freed with g_object_unref().
 **/
PangoContext *
pango_context_new (void)
{
  PangoContext *context;

  context = g_object_new (PANGO_TYPE_CONTEXT, NULL);

  return context;
}

static void
update_resolved_gravity (PangoContext *context)
{
  if (context->base_gravity == PANGO_GRAVITY_AUTO)
    context->resolved_gravity = pango_gravity_get_for_matrix (context->matrix);
  else
    context->resolved_gravity = context->base_gravity;
}

/**
 * pango_context_set_matrix:
 * @context: a #PangoContext
 * @matrix: (allow-none): a #PangoMatrix, or %NULL to unset any existing
 * matrix. (No matrix set is the same as setting the identity matrix.)
 *
 * Sets the transformation matrix that will be applied when rendering
 * with this context. Note that reported metrics are in the user space
 * coordinates before the application of the matrix, not device-space
 * coordinates after the application of the matrix. So, they don't scale
 * with the matrix, though they may change slightly for different
 * matrices, depending on how the text is fit to the pixel grid.
 *
 * Since: 1.6
 **/
void
pango_context_set_matrix (PangoContext       *context,
			  const PangoMatrix  *matrix)
{
  g_return_if_fail (PANGO_IS_CONTEXT (context));

  if (context->matrix || matrix)
    context_changed (context);

  if (context->matrix)
    pango_matrix_free (context->matrix);
  if (matrix)
    context->matrix = pango_matrix_copy (matrix);
  else
    context->matrix = NULL;

  update_resolved_gravity (context);
}

/**
 * pango_context_get_matrix:
 * @context: a #PangoContext
 *
 * Gets the transformation matrix that will be applied when
 * rendering with this context. See pango_context_set_matrix().
 *
 * Return value: (nullable): the matrix, or %NULL if no matrix has
 *  been set (which is the same as the identity matrix). The returned
 *  matrix is owned by Pango and must not be modified or freed.
 *
 * Since: 1.6
 **/
const PangoMatrix *
pango_context_get_matrix (PangoContext *context)
{
  g_return_val_if_fail (PANGO_IS_CONTEXT (context), NULL);

  return context->matrix;
}

/**
 * pango_context_set_font_map:
 * @context: a #PangoContext
 * @font_map: the #PangoFontMap to set.
 *
 * Sets the font map to be searched when fonts are looked-up in this context.
 * This is only for internal use by Pango backends, a #PangoContext obtained
 * via one of the recommended methods should already have a suitable font map.
 **/
void
pango_context_set_font_map (PangoContext *context,
			    PangoFontMap *font_map)
{
  g_return_if_fail (PANGO_IS_CONTEXT (context));
  g_return_if_fail (!font_map || PANGO_IS_FONT_MAP (font_map));

  if (font_map == context->font_map)
    return;

  context_changed (context);

  if (font_map)
    g_object_ref (font_map);

  if (context->font_map)
    g_object_unref (context->font_map);

  context->font_map = font_map;
  context->fontmap_serial = pango_font_map_get_serial (font_map);
}

/**
 * pango_context_get_font_map:
 * @context: a #PangoContext
 *
 * Gets the #PangoFontMap used to look up fonts for this context.
 *
 * Return value: (transfer none): the font map for the #PangoContext.
 *               This value is owned by Pango and should not be unreferenced.
 *
 * Since: 1.6
 **/
PangoFontMap *
pango_context_get_font_map (PangoContext *context)
{
  g_return_val_if_fail (PANGO_IS_CONTEXT (context), NULL);

  return context->font_map;
}

/**
 * pango_context_list_families:
 * @context: a #PangoContext
 * @families: (out) (array length=n_families) (transfer container): location to store a pointer to
 *            an array of #PangoFontFamily *. This array should be freed
 *            with g_free().
 * @n_families: (out): location to store the number of elements in @descs
 *
 * List all families for a context.
 **/
void
pango_context_list_families (PangoContext          *context,
			     PangoFontFamily     ***families,
			     int                   *n_families)
{
  g_return_if_fail (context != NULL);
  g_return_if_fail (families == NULL || n_families != NULL);

  if (n_families == NULL)
    return;

  if (context->font_map == NULL)
    {
      *n_families = 0;
      if (families)
	*families = NULL;

      return;
    }
  else
    pango_font_map_list_families (context->font_map, families, n_families);
}

/**
 * pango_context_load_font:
 * @context: a #PangoContext
 * @desc: a #PangoFontDescription describing the font to load
 *
 * Loads the font in one of the fontmaps in the context
 * that is the closest match for @desc.
 *
 * Returns: (transfer full) (nullable): the newly allocated #PangoFont
 *          that was loaded, or %NULL if no font matched.
 **/
PangoFont *
pango_context_load_font (PangoContext               *context,
			 const PangoFontDescription *desc)
{
  g_return_val_if_fail (context != NULL, NULL);
  g_return_val_if_fail (context->font_map != NULL, NULL);

  return pango_font_map_load_font (context->font_map, context, desc);
}

/**
 * pango_context_load_fontset:
 * @context: a #PangoContext
 * @desc: a #PangoFontDescription describing the fonts to load
 * @language: a #PangoLanguage the fonts will be used for
 *
 * Load a set of fonts in the context that can be used to render
 * a font matching @desc.
 *
 * Returns: (transfer full) (nullable): the newly allocated
 *          #PangoFontset loaded, or %NULL if no font matched.
 **/
PangoFontset *
pango_context_load_fontset (PangoContext               *context,
			    const PangoFontDescription *desc,
			    PangoLanguage             *language)
{
  g_return_val_if_fail (context != NULL, NULL);

  return pango_font_map_load_fontset (context->font_map, context, desc, language);
}

/**
 * pango_context_set_font_description:
 * @context: a #PangoContext
 * @desc: the new pango font description
 *
 * Set the default font description for the context
 **/
void
pango_context_set_font_description (PangoContext               *context,
				    const PangoFontDescription *desc)
{
  g_return_if_fail (context != NULL);
  g_return_if_fail (desc != NULL);

  if (desc != context->font_desc &&
      (!desc || !context->font_desc || !pango_font_description_equal(desc, context->font_desc)))
    {
      context_changed (context);

      pango_font_description_free (context->font_desc);
      context->font_desc = pango_font_description_copy (desc);
    }
}

/**
 * pango_context_get_font_description:
 * @context: a #PangoContext
 *
 * Retrieve the default font description for the context.
 *
 * Return value: (transfer none): a pointer to the context's default font
 *               description. This value must not be modified or freed.
 **/
PangoFontDescription *
pango_context_get_font_description (PangoContext *context)
{
  g_return_val_if_fail (context != NULL, NULL);

  return context->font_desc;
}

/**
 * pango_context_set_language:
 * @context: a #PangoContext
 * @language: the new language tag.
 *
 * Sets the global language tag for the context.  The default language
 * for the locale of the running process can be found using
 * pango_language_get_default().
 **/
void
pango_context_set_language (PangoContext *context,
			    PangoLanguage    *language)
{
  g_return_if_fail (context != NULL);

  if (language != context->language)
    context_changed (context);

  context->set_language = language;
  if (language)
    context->language = language;
  else
    context->language = pango_language_get_default ();
}

/**
 * pango_context_get_language:
 * @context: a #PangoContext
 *
 * Retrieves the global language tag for the context.
 *
 * Return value: the global language tag.
 **/
PangoLanguage *
pango_context_get_language (PangoContext *context)
{
  g_return_val_if_fail (context != NULL, NULL);

  return context->set_language;
}

/**
 * pango_context_set_base_dir:
 * @context: a #PangoContext
 * @direction: the new base direction
 *
 * Sets the base direction for the context.
 *
 * The base direction is used in applying the Unicode bidirectional
 * algorithm; if the @direction is %PANGO_DIRECTION_LTR or
 * %PANGO_DIRECTION_RTL, then the value will be used as the paragraph
 * direction in the Unicode bidirectional algorithm.  A value of
 * %PANGO_DIRECTION_WEAK_LTR or %PANGO_DIRECTION_WEAK_RTL is used only
 * for paragraphs that do not contain any strong characters themselves.
 **/
void
pango_context_set_base_dir (PangoContext  *context,
			    PangoDirection direction)
{
  g_return_if_fail (context != NULL);

  if (direction != context->base_dir)
    context_changed (context);

  context->base_dir = direction;
}

/**
 * pango_context_get_base_dir:
 * @context: a #PangoContext
 *
 * Retrieves the base direction for the context. See
 * pango_context_set_base_dir().
 *
 * Return value: the base direction for the context.
 **/
PangoDirection
pango_context_get_base_dir (PangoContext *context)
{
  g_return_val_if_fail (context != NULL, PANGO_DIRECTION_LTR);

  return context->base_dir;
}

/**
 * pango_context_set_base_gravity:
 * @context: a #PangoContext
 * @gravity: the new base gravity
 *
 * Sets the base gravity for the context.
 *
 * The base gravity is used in laying vertical text out.
 *
 * Since: 1.16
 **/
void
pango_context_set_base_gravity (PangoContext  *context,
				PangoGravity gravity)
{
  g_return_if_fail (context != NULL);

  if (gravity != context->base_gravity)
    context_changed (context);

  context->base_gravity = gravity;

  update_resolved_gravity (context);
}

/**
 * pango_context_get_base_gravity:
 * @context: a #PangoContext
 *
 * Retrieves the base gravity for the context. See
 * pango_context_set_base_gravity().
 *
 * Return value: the base gravity for the context.
 *
 * Since: 1.16
 **/
PangoGravity
pango_context_get_base_gravity (PangoContext *context)
{
  g_return_val_if_fail (context != NULL, PANGO_GRAVITY_SOUTH);

  return context->base_gravity;
}

/**
 * pango_context_get_gravity:
 * @context: a #PangoContext
 *
 * Retrieves the gravity for the context. This is similar to
 * pango_context_get_base_gravity(), except for when the base gravity
 * is %PANGO_GRAVITY_AUTO for which pango_gravity_get_for_matrix() is used
 * to return the gravity from the current context matrix.
 *
 * Return value: the resolved gravity for the context.
 *
 * Since: 1.16
 **/
PangoGravity
pango_context_get_gravity (PangoContext *context)
{
  g_return_val_if_fail (context != NULL, PANGO_GRAVITY_SOUTH);

  return context->resolved_gravity;
}

/**
 * pango_context_set_gravity_hint:
 * @context: a #PangoContext
 * @hint: the new gravity hint
 *
 * Sets the gravity hint for the context.
 *
 * The gravity hint is used in laying vertical text out, and is only relevant
 * if gravity of the context as returned by pango_context_get_gravity()
 * is set %PANGO_GRAVITY_EAST or %PANGO_GRAVITY_WEST.
 *
 * Since: 1.16
 **/
void
pango_context_set_gravity_hint (PangoContext    *context,
				PangoGravityHint hint)
{
  g_return_if_fail (context != NULL);

  if (hint != context->gravity_hint)
    context_changed (context);

  context->gravity_hint = hint;
}

/**
 * pango_context_get_gravity_hint:
 * @context: a #PangoContext
 *
 * Retrieves the gravity hint for the context. See
 * pango_context_set_gravity_hint() for details.
 *
 * Return value: the gravity hint for the context.
 *
 * Since: 1.16
 **/
PangoGravityHint
pango_context_get_gravity_hint (PangoContext *context)
{
  g_return_val_if_fail (context != NULL, PANGO_GRAVITY_HINT_NATURAL);

  return context->gravity_hint;
}

/**********************************************************************/

static gboolean
advance_attr_iterator_to (PangoAttrIterator *iterator,
			  int                start_index)
{
  int start_range, end_range;

  pango_attr_iterator_range (iterator, &start_range, &end_range);

  while (start_index >= end_range)
    {
      if (!pango_attr_iterator_next (iterator))
	return FALSE;
      pango_attr_iterator_range (iterator, &start_range, &end_range);
    }

  if (start_range > start_index)
    g_warning ("In pango_itemize(), the cached iterator passed in "
	       "had already moved beyond the start_index");

  return TRUE;
}

/***************************************************************************
 * We cache the results of character,fontset => font,shaper in a hash table
 ***************************************************************************/

typedef struct {
  GHashTable *hash;
} FontCache;

typedef struct {
  PangoFont *font;
} FontElement;

static void
font_cache_destroy (FontCache *cache)
{
  g_hash_table_destroy (cache->hash);
  g_slice_free (FontCache, cache);
}

static void
font_element_destroy (FontElement *element)
{
  if (element->font)
    g_object_unref (element->font);
  g_slice_free (FontElement, element);
}

static FontCache *
get_font_cache (PangoFontset *fontset)
{
  FontCache *cache;

  static GQuark cache_quark = 0; /* MT-safe */
  if (G_UNLIKELY (!cache_quark))
    cache_quark = g_quark_from_static_string ("pango-shaper-font-cache");

retry:
  cache = g_object_get_qdata (G_OBJECT (fontset), cache_quark);
  if (G_UNLIKELY (!cache))
    {
      cache = g_slice_new (FontCache);
      cache->hash = g_hash_table_new_full (g_direct_hash, NULL,
					   NULL, (GDestroyNotify)font_element_destroy);
      if (!g_object_replace_qdata (G_OBJECT (fontset), cache_quark, NULL,
                                   cache, (GDestroyNotify)font_cache_destroy,
                                   NULL))
        {
          font_cache_destroy (cache);
          goto retry;
        }
    }

  return cache;
}

static gboolean
font_cache_get (FontCache   *cache,
		gunichar     wc,
		PangoFont  **font)
{
  FontElement *element;

  element = g_hash_table_lookup (cache->hash, GUINT_TO_POINTER (wc));
  if (element)
    {
      *font = element->font;

      return TRUE;
    }
  else
    return FALSE;
}

static void
font_cache_insert (FontCache   *cache,
		   gunichar           wc,
		   PangoFont         *font)
{
  FontElement *element = g_slice_new (FontElement);
  element->font = font ? g_object_ref (font) : NULL;

  g_hash_table_insert (cache->hash, GUINT_TO_POINTER (wc), element);
}

/**********************************************************************/

typedef enum {
  EMBEDDING_CHANGED    = 1 << 0,
  SCRIPT_CHANGED       = 1 << 1,
  LANG_CHANGED         = 1 << 2,
  FONT_CHANGED         = 1 << 3,
  DERIVED_LANG_CHANGED = 1 << 4,
  WIDTH_CHANGED        = 1 << 5,
  EMOJI_CHANGED        = 1 << 6,
} ChangedFlags;



typedef struct _PangoWidthIter PangoWidthIter;

struct _PangoWidthIter
{
	const gchar *text_start;
	const gchar *text_end;
	const gchar *start;
	const gchar *end;
	gboolean wide;
};

typedef struct _ItemizeState ItemizeState;



struct _ItemizeState
{
  PangoContext *context;
  const char *text;
  const char *end;

  const char *run_start;
  const char *run_end;

  GList *result;
  PangoItem *item;

  guint8 *embedding_levels;
  int embedding_end_offset;
  const char *embedding_end;
  guint8 embedding;

  PangoGravity gravity;
  PangoGravityHint gravity_hint;
  PangoGravity resolved_gravity;
  PangoGravity font_desc_gravity;
  gboolean centered_baseline;

  PangoAttrIterator *attr_iter;
  gboolean free_attr_iter;
  const char *attr_end;
  PangoFontDescription *font_desc;
  PangoFontDescription *emoji_font_desc;
  PangoLanguage *lang;
  GSList *extra_attrs;
  gboolean copy_extra_attrs;

  ChangedFlags changed;

  PangoScriptIter script_iter;
  const char *script_end;
  PangoScript script;

  PangoWidthIter width_iter;
  PangoEmojiIter emoji_iter;

  PangoLanguage *derived_lang;
  PangoEngineLang *lang_engine;

  PangoFontset *current_fonts;
  FontCache *cache;
  PangoFont *base_font;
  gboolean enable_fallback;
};

static void
update_embedding_end (ItemizeState *state)
{
  state->embedding = state->embedding_levels[state->embedding_end_offset];
  while (state->embedding_end < state->end &&
	 state->embedding_levels[state->embedding_end_offset] == state->embedding)
    {
      state->embedding_end_offset++;
      state->embedding_end = g_utf8_next_char (state->embedding_end);
    }

  state->changed |= EMBEDDING_CHANGED;
}

static PangoAttribute *
find_attribute (GSList        *attr_list,
		PangoAttrType  type)
{
  GSList *node;

  for (node = attr_list; node; node = node->next)
    if (((PangoAttribute *) node->data)->klass->type == type)
      return (PangoAttribute *) node->data;

  return NULL;
}

static void
update_attr_iterator (ItemizeState *state)
{
  PangoLanguage *old_lang;
  PangoAttribute *attr;
  int end_index;

  pango_attr_iterator_range (state->attr_iter, NULL, &end_index);
  if (end_index < state->end - state->text)
    state->attr_end = state->text + end_index;
  else
    state->attr_end = state->end;

  if (state->emoji_font_desc)
    {
      pango_font_description_free (state->emoji_font_desc);
      state->emoji_font_desc = NULL;
    }

  old_lang = state->lang;
  if (state->font_desc)
    pango_font_description_free (state->font_desc);
  state->font_desc = pango_font_description_copy_static (state->context->font_desc);
  pango_attr_iterator_get_font (state->attr_iter, state->font_desc,
				&state->lang, &state->extra_attrs);
  if (pango_font_description_get_set_fields (state->font_desc) & PANGO_FONT_MASK_GRAVITY)
    state->font_desc_gravity = pango_font_description_get_gravity (state->font_desc);
  else
    state->font_desc_gravity = PANGO_GRAVITY_AUTO;

  state->copy_extra_attrs = FALSE;

  if (!state->lang)
    state->lang = state->context->language;

  attr = find_attribute (state->extra_attrs, PANGO_ATTR_FALLBACK);
  state->enable_fallback = (attr == NULL || ((PangoAttrInt *)attr)->value);

  attr = find_attribute (state->extra_attrs, PANGO_ATTR_GRAVITY);
  state->gravity = attr == NULL ? PANGO_GRAVITY_AUTO : ((PangoAttrInt *)attr)->value;

  attr = find_attribute (state->extra_attrs, PANGO_ATTR_GRAVITY_HINT);
  state->gravity_hint = attr == NULL ? state->context->gravity_hint : (PangoGravityHint)((PangoAttrInt *)attr)->value;

  state->changed |= FONT_CHANGED;
  if (state->lang != old_lang)
    state->changed |= LANG_CHANGED;
}

static void
update_end (ItemizeState *state)
{
  state->run_end = state->embedding_end;
  if (state->attr_end < state->run_end)
    state->run_end = state->attr_end;
  if (state->script_end < state->run_end)
    state->run_end = state->script_end;
  if (state->width_iter.end < state->run_end)
    state->run_end = state->width_iter.end;
  if (state->emoji_iter.end < state->run_end)
    state->run_end = state->emoji_iter.end;
}

/* g_unichar_iswide() uses EastAsianWidth, which is broken.
 * We should switch to using VerticalTextLayout:
 * http://www.unicode.org/reports/tr50/#Data50
 *
 * In the mean time, fixup Hangul jamo to be all wide so we
 * don't break run in the middle.  The EastAsianWidth has
 * 'W' for L-jamo, and 'N' for T and V jamo!
 *
 * https://bugzilla.gnome.org/show_bug.cgi?id=705727
 */
static gboolean
width_iter_iswide (gunichar ch)
{
  if ((0x1100u <= ch && ch <= 0x11FFu) ||
      (0xA960u <= ch && ch <= 0xA97Cu) ||
      (0xD7B0u <= ch && ch <= 0xD7FBu))
    return TRUE;

  return g_unichar_iswide (ch);
}

static void
width_iter_next(PangoWidthIter* iter)
{
  gboolean met_joiner = FALSE;
  iter->start = iter->end;

  if (iter->end < iter->text_end)
    {
      gunichar ch = g_utf8_get_char (iter->end);
      iter->wide = width_iter_iswide (ch);
    }

  while (iter->end < iter->text_end)
    {
      gunichar ch = g_utf8_get_char (iter->end);

      /* for zero width joiner */
      if (ch == 0x200D)
        {
          iter->end = g_utf8_next_char (iter->end);
          met_joiner = TRUE;
          continue;
        }

      /* ignore the wide check if met joiner */
      if (met_joiner)
        {
          iter->end = g_utf8_next_char (iter->end);
          met_joiner = FALSE;
          continue;
        }

      /* for variation selector, tag and emoji modifier. */
      if (G_UNLIKELY(ch == 0xFE0EU || ch == 0xFE0FU
                    || (ch >= 0xE0020 && ch <= 0xE007F)
                    || (ch >= 0x1F3FB && ch <= 0x1F3FF)))
        {
          iter->end = g_utf8_next_char (iter->end);
          continue;
        }

      if (width_iter_iswide (ch) != iter->wide)
        break;
      iter->end = g_utf8_next_char (iter->end);
    }
}

static void
width_iter_init (PangoWidthIter* iter, const char* text, int length)
{
  iter->text_start = text;
  iter->text_end = text + length;
  iter->start = iter->end = text;

  width_iter_next (iter);
}

static void
width_iter_fini (PangoWidthIter* iter)
{
}

static void
itemize_state_init (ItemizeState      *state,
		    PangoContext      *context,
		    const char        *text,
		    PangoDirection     base_dir,
		    int                start_index,
		    int                length,
		    PangoAttrList     *attrs,
		    PangoAttrIterator *cached_iter,
		    const PangoFontDescription *desc)
{

  state->context = context;
  state->text = text;
  state->end = text + start_index + length;

  state->result = NULL;
  state->item = NULL;

  state->run_start = text + start_index;

  /* First, apply the bidirectional algorithm to break
   * the text into directional runs.
   */
  state->embedding_levels = pango_log2vis_get_embedding_levels (text + start_index, length, &base_dir);

  state->embedding_end_offset = 0;
  state->embedding_end = text + start_index;
  update_embedding_end (state);

  /* Initialize the attribute iterator
   */
  if (cached_iter)
    {
      state->attr_iter = cached_iter;
      state->free_attr_iter = FALSE;
    }
  else if (attrs)
    {
      state->attr_iter = pango_attr_list_get_iterator (attrs);
      state->free_attr_iter = TRUE;
    }
  else
    {
      state->attr_iter = NULL;
      state->free_attr_iter = FALSE;
    }

  state->emoji_font_desc = NULL;
  if (state->attr_iter)
    {
      state->font_desc = NULL;
      state->lang = NULL;

      advance_attr_iterator_to (state->attr_iter, start_index);
      update_attr_iterator (state);
    }
  else
    {
      state->font_desc = pango_font_description_copy_static (desc ? desc : state->context->font_desc);
      state->lang = state->context->language;
      state->extra_attrs = NULL;
      state->copy_extra_attrs = FALSE;

      state->attr_end = state->end;
      state->enable_fallback = TRUE;
    }

  /* Initialize the script iterator
   */
  _pango_script_iter_init (&state->script_iter, text + start_index, length);
  pango_script_iter_get_range (&state->script_iter, NULL,
			       &state->script_end, &state->script);

  width_iter_init (&state->width_iter, text + start_index, length);
  _pango_emoji_iter_init (&state->emoji_iter, text + start_index, length);

  update_end (state);

  if (pango_font_description_get_set_fields (state->font_desc) & PANGO_FONT_MASK_GRAVITY)
    state->font_desc_gravity = pango_font_description_get_gravity (state->font_desc);
  else
    state->font_desc_gravity = PANGO_GRAVITY_AUTO;

  state->gravity = PANGO_GRAVITY_AUTO;
  state->centered_baseline = PANGO_GRAVITY_IS_VERTICAL (state->context->resolved_gravity);
  state->gravity_hint = state->context->gravity_hint;
  state->resolved_gravity = PANGO_GRAVITY_AUTO;
  state->derived_lang = NULL;
  state->lang_engine = NULL;
  state->current_fonts = NULL;
  state->cache = NULL;
  state->base_font = NULL;

  state->changed = EMBEDDING_CHANGED | SCRIPT_CHANGED | LANG_CHANGED | FONT_CHANGED | WIDTH_CHANGED | EMOJI_CHANGED;
}

static gboolean
itemize_state_next (ItemizeState *state)
{
  if (state->run_end == state->end)
    return FALSE;

  state->changed = 0;

  state->run_start = state->run_end;

  if (state->run_end == state->embedding_end)
    {
      update_embedding_end (state);
    }

  if (state->run_end == state->attr_end)
    {
      pango_attr_iterator_next (state->attr_iter);
      update_attr_iterator (state);
    }

  if (state->run_end == state->script_end)
    {
      pango_script_iter_next (&state->script_iter);
      pango_script_iter_get_range (&state->script_iter, NULL,
				   &state->script_end, &state->script);
      state->changed |= SCRIPT_CHANGED;
    }
  if (state->run_end == state->width_iter.end)
    {
      width_iter_next (&state->width_iter);
      state->changed |= WIDTH_CHANGED;
    }
  if (state->run_end == state->emoji_iter.end)
    {
      _pango_emoji_iter_next (&state->emoji_iter);
      state->changed |= EMOJI_CHANGED;
    }

  update_end (state);

  return TRUE;
}

static GSList *
copy_attr_slist (GSList *attr_slist)
{
  GSList *new_list = NULL;
  GSList *l;

  for (l = attr_slist; l; l = l->next)
    new_list = g_slist_prepend (new_list, pango_attribute_copy (l->data));

  return g_slist_reverse (new_list);
}

static void
itemize_state_fill_shaper (ItemizeState     *state,
			   PangoEngineShape *shape_engine,
			   PangoFont        *font)
{
  GList *l;

  for (l = state->result; l; l = l->next)
    {
      PangoItem *item = l->data;
      if (item->analysis.shape_engine)
	break;
      if (font)
	item->analysis.font = g_object_ref (font);
      else
	item->analysis.font = NULL;
      item->analysis.shape_engine = shape_engine;
    }
}

static void
itemize_state_add_character (ItemizeState     *state,
			     PangoEngineShape *shape_engine,
			     PangoFont        *font,
			     gboolean          force_break,
			     const char       *pos)
{
  if (state->item)
    {
      if (!state->item->analysis.shape_engine && shape_engine)
	{
	  itemize_state_fill_shaper (state, shape_engine, font);
	}
      else if (state->item->analysis.shape_engine && !shape_engine)
	{
	  font = state->item->analysis.font;
	  shape_engine = state->item->analysis.shape_engine;
	}

      if (!force_break &&
	  state->item->analysis.lang_engine == state->lang_engine &&
	  state->item->analysis.shape_engine == shape_engine &&
	  state->item->analysis.font == font)
	{
	  state->item->num_chars++;
	  return;
	}

      state->item->length = (pos - state->text) - state->item->offset;
    }

  state->item = pango_item_new ();
  state->item->offset = pos - state->text;
  state->item->length = 0;
  state->item->num_chars = 1;
  state->item->analysis.shape_engine = shape_engine;
  state->item->analysis.lang_engine = state->lang_engine;

  if (font)
    g_object_ref (font);
  state->item->analysis.font = font;

  state->item->analysis.level = state->embedding;
  state->item->analysis.gravity = state->resolved_gravity;

  /* The level vs. gravity dance:
   *	- If gravity is SOUTH, leave level untouched.
   *	- If gravity is NORTH, step level one up, to
   *	  not get mirrored upside-down text.
   *	- If gravity is EAST, step up to an even level, as
   *	  it's a clockwise-rotated layout, so the rotated
   *	  top is unrotated left.
   *	- If gravity is WEST, step up to an odd level, as
   *	  it's a counter-clockwise-rotated layout, so the rotated
   *	  top is unrotated right.
   *
   * A similar dance is performed in pango-layout.c:
   * line_set_resolved_dir().  Keep in synch.
   */
  switch (state->item->analysis.gravity)
    {
      case PANGO_GRAVITY_SOUTH:
      default:
	break;
      case PANGO_GRAVITY_NORTH:
	state->item->analysis.level++;
	break;
      case PANGO_GRAVITY_EAST:
	state->item->analysis.level += 1;
	state->item->analysis.level &= ~1;
	break;
      case PANGO_GRAVITY_WEST:
	state->item->analysis.level |= 1;
	break;
    }

  state->item->analysis.flags = state->centered_baseline ? PANGO_ANALYSIS_FLAG_CENTERED_BASELINE : 0;

  state->item->analysis.script = state->script;
  state->item->analysis.language = state->derived_lang;

  if (state->copy_extra_attrs)
    {
      state->item->analysis.extra_attrs = copy_attr_slist (state->extra_attrs);
    }
  else
    {
      state->item->analysis.extra_attrs = state->extra_attrs;
      state->copy_extra_attrs = TRUE;
    }

  state->result = g_list_prepend (state->result, state->item);
}

typedef struct {
  PangoLanguage *lang;
  gunichar wc;
  PangoFont *font;
} GetFontInfo;

static gboolean
get_font_foreach (PangoFontset *fontset,
		  PangoFont    *font,
		  gpointer      data)
{
  GetFontInfo *info = data;
  PangoEngineShape *engine;
  PangoCoverageLevel level;

  if (G_UNLIKELY (!font))
    return FALSE;

  engine = pango_font_find_shaper (font, info->lang, info->wc),
  level = _pango_engine_shape_covers (engine, font, info->lang, info->wc);
  if (level != PANGO_COVERAGE_NONE)
    {
      info->font = font;
      return TRUE;
    }

  if (!fontset)
    {
      info->font = font;
      return TRUE;
    }

  return FALSE;
}

static PangoFont *
get_base_font (ItemizeState *state)
{
  if (!state->base_font)
    state->base_font = pango_font_map_load_font (state->context->font_map,
						 state->context,
						 state->font_desc);
  return state->base_font;
}

static PangoScript
get_script (ItemizeState      *state)
{
  /* Always use a basic shaper for vertical layout (ie, east/west gravity)
   * as none of our script shapers support vertical shaping right now.
   *
   * XXX Should move the knowledge into the shaper interface.
   */

  if (PANGO_GRAVITY_IS_VERTICAL (state->resolved_gravity))
    return PANGO_SCRIPT_COMMON;
  else
    return state->script;
}

static gboolean
get_shaper_and_font (ItemizeState      *state,
		     gunichar           wc,
		     PangoEngineShape **shape_engine,
		     PangoFont        **font)
{
  GetFontInfo info;

  /* We'd need a separate cache when fallback is disabled, but since lookup
   * with fallback disabled is faster anyways, we just skip caching */
  if (state->enable_fallback && font_cache_get (state->cache, wc, font))
  {
    *shape_engine = pango_font_find_shaper (*font, state->derived_lang, wc);
    return TRUE;
  }

  info.lang = state->derived_lang;
  info.wc = wc;
  info.font = NULL;

  if (state->enable_fallback)
    pango_fontset_foreach (state->current_fonts, get_font_foreach, &info);
  else
    get_font_foreach (NULL, get_base_font (state), &info);

  *font = info.font;
  *shape_engine = pango_font_find_shaper (*font, state->derived_lang, wc);

  /* skip caching if fallback disabled (see above) */
  if (state->enable_fallback)
    font_cache_insert (state->cache, wc, *font);

  return TRUE;
}

static PangoLanguage *
compute_derived_language (PangoLanguage *lang,
			  PangoScript    script)
{
  PangoLanguage *derived_lang;

  /* Make sure the language tag is consistent with the derived
   * script. There is no point in marking up a section of
   * Arabic text with the "en" language tag.
   */
  if (lang && pango_language_includes_script (lang, script))
    derived_lang = lang;
  else
    {
      derived_lang = pango_script_get_sample_language (script);
      /* If we don't find a sample language for the script, we
       * use a language tag that shouldn't actually be used
       * anywhere. This keeps fontconfig (for the PangoFc*
       * backend) from using the language tag to affect the
       * sort order. I don't have a reference for 'xx' being
       * safe here, though Keith Packard claims it is.
       */
      if (!derived_lang)
	derived_lang = pango_language_from_string ("xx");
    }

  return derived_lang;
}

static void
itemize_state_update_for_new_run (ItemizeState *state)
{
  /* This block should be moved to update_attr_iterator, but I'm too lazy to
   * do it right now */
  if (state->changed & (FONT_CHANGED | SCRIPT_CHANGED | WIDTH_CHANGED))
    {
      /* Font-desc gravity overrides everything */
      if (state->font_desc_gravity != PANGO_GRAVITY_AUTO)
	{
	  state->resolved_gravity = state->font_desc_gravity;
	}
      else
	{
	  PangoGravity gravity = state->gravity;
	  PangoGravityHint gravity_hint = state->gravity_hint;

	  if (G_LIKELY (gravity == PANGO_GRAVITY_AUTO))
	    gravity = state->context->resolved_gravity;

	  state->resolved_gravity = pango_gravity_get_for_script_and_width (state->script,
									    state->width_iter.wide,
									    gravity,
									    gravity_hint);
	}

      if (state->font_desc_gravity != state->resolved_gravity)
	{
	  pango_font_description_set_gravity (state->font_desc, state->resolved_gravity);
	  state->changed |= FONT_CHANGED;
	}
    }

  if (state->changed & (SCRIPT_CHANGED | LANG_CHANGED))
    {
      PangoLanguage *old_derived_lang = state->derived_lang;
      state->derived_lang = compute_derived_language (state->lang, state->script);
      if (old_derived_lang != state->derived_lang)
	state->changed |= DERIVED_LANG_CHANGED;
    }

  if ((state->changed & DERIVED_LANG_CHANGED) || !state->lang_engine)
    {
      state->lang_engine = _pango_get_language_engine ();
    }

  if (state->changed & (EMOJI_CHANGED))
    {
      state->changed |= FONT_CHANGED;
    }

  if (state->changed & (FONT_CHANGED | DERIVED_LANG_CHANGED) &&
      state->current_fonts)
    {
      g_object_unref (state->current_fonts);
      state->current_fonts = NULL;
      state->cache = NULL;
    }

  if (!state->current_fonts)
    {
      gboolean is_emoji = state->emoji_iter.is_emoji;
      if (is_emoji && !state->emoji_font_desc)
      {
        state->emoji_font_desc = pango_font_description_copy_static (state->font_desc);
        pango_font_description_set_family_static (state->emoji_font_desc, "emoji");
      }
      state->current_fonts = pango_font_map_load_fontset (state->context->font_map,
							  state->context,
							  is_emoji ? state->emoji_font_desc : state->font_desc,
							  state->derived_lang);
      state->cache = get_font_cache (state->current_fonts);
    }

  if ((state->changed & FONT_CHANGED) && state->base_font)
    {
      g_object_unref (state->base_font);
      state->base_font = NULL;
    }
}

static const char *
string_from_script (PangoScript script)
{
  static GEnumClass *class = NULL; /* MT-safe */
  GEnumValue *value;
  if (g_once_init_enter (&class))
    g_once_init_leave(&class, (gpointer)g_type_class_ref (PANGO_TYPE_SCRIPT));

  value = g_enum_get_value (class, script);
  if (!value)
    return string_from_script (PANGO_SCRIPT_INVALID_CODE);

  return value->value_nick;
}

static void
itemize_state_process_run (ItemizeState *state)
{
  const char *p;
  gboolean last_was_forced_break = FALSE;

  /* Only one character has type G_UNICODE_LINE_SEPARATOR in Unicode 4.0;
   * update this if that changes. */
#define LINE_SEPARATOR 0x2028

  itemize_state_update_for_new_run (state);

  /* We should never get an empty run */
  g_assert (state->run_end != state->run_start);

  for (p = state->run_start;
       p < state->run_end;
       p = g_utf8_next_char (p))
    {
      gunichar wc = g_utf8_get_char (p);
      gboolean is_forced_break = (wc == '\t' || wc == LINE_SEPARATOR);
      PangoEngineShape *shape_engine;
      PangoFont *font;
      GUnicodeType type;

      /* We don't want space characters to affect font selection; in general,
       * it's always wrong to select a font just to render a space.
       * We assume that all fonts have the ASCII space, and for other space
       * characters if they don't, HarfBuzz will compatibility-decompose them
       * to ASCII space...
       * See bugs #355987 and #701652.
       *
       * We don't want to change fonts just for variation selectors.
       * See bug #781123.
       */
      type = g_unichar_type (wc);
      if (G_UNLIKELY (type == G_UNICODE_CONTROL ||
                      type == G_UNICODE_FORMAT ||
                      type == G_UNICODE_SURROGATE ||
                      (type == G_UNICODE_SPACE_SEPARATOR && wc != 0x1680u /* OGHAM SPACE MARK */) ||
                      (wc >= 0xfe00u && wc <= 0xfe0fu) ||
                      (wc >= 0xe0100u && wc <= 0xe01efu)))
        {
	  shape_engine = NULL;
	  font = NULL;
        }
      else
        {
	  get_shaper_and_font (state, wc, &shape_engine, &font);
	}

      itemize_state_add_character (state,
				   shape_engine, font,
				   is_forced_break || last_was_forced_break,
				   p);

      last_was_forced_break = is_forced_break;
    }

  /* Finish the final item from the current segment */
  state->item->length = (p - state->text) - state->item->offset;
  if (!state->item->analysis.shape_engine)
    {
      PangoEngineShape *shape_engine;
      PangoFont *font;

      if (G_UNLIKELY (!get_shaper_and_font (state, ' ', &shape_engine, &font)))
	{
	  /* If no shaper was found, warn only once per fontmap/script pair */
	  PangoFontMap *fontmap = state->context->font_map;
	  const char *script_name = string_from_script (get_script (state));

	  if (!g_object_get_data (G_OBJECT (fontmap), script_name))
	    {
G_GNUC_BEGIN_IGNORE_DEPRECATIONS
	      g_warning ("failed to choose a font, expect ugly output. engine-type='%s', script='%s'",
			 pango_font_map_get_shape_engine_type (fontmap),
			 script_name);
G_GNUC_END_IGNORE_DEPRECATIONS

	      g_object_set_data_full (G_OBJECT (fontmap), script_name,
				      GINT_TO_POINTER (1), NULL);
	    }

	  shape_engine = _pango_get_fallback_shaper ();
	  font = NULL;
	}

      itemize_state_fill_shaper (state, shape_engine, font);
    }
  state->item = NULL;
}

static void
itemize_state_finish (ItemizeState *state)
{
  g_free (state->embedding_levels);
  if (state->free_attr_iter)
    pango_attr_iterator_destroy (state->attr_iter);
  _pango_script_iter_fini (&state->script_iter);
  pango_font_description_free (state->font_desc);
  pango_font_description_free (state->emoji_font_desc);
  width_iter_fini (&state->width_iter);
  _pango_emoji_iter_fini (&state->emoji_iter);

  if (state->current_fonts)
    g_object_unref (state->current_fonts);
  if (state->base_font)
    g_object_unref (state->base_font);
}

/**
 * pango_itemize_with_base_dir:
 * @context:   a structure holding information that affects
 *             the itemization process.
 * @base_dir:  base direction to use for bidirectional processing
 * @text:      the text to itemize.
 * @start_index: first byte in @text to process
 * @length:    the number of bytes (not characters) to process
 *             after @start_index. This must be >= 0.
 * @attrs:     the set of attributes that apply to @text.
 * @cached_iter: (allow-none): Cached attribute iterator, or %NULL
 *
 * Like pango_itemize(), but the base direction to use when
 * computing bidirectional levels (see pango_context_set_base_dir ()),
 * is specified explicitly rather than gotten from the #PangoContext.
 *
 * Return value: (transfer full) (element-type Pango.Item): a #GList of
 *               #PangoItem structures.  The items should be freed using
 *               pango_item_free() probably in combination with
 *               g_list_foreach(), and the list itself using g_list_free().
 *
 * Since: 1.4
 */
GList *
pango_itemize_with_base_dir (PangoContext      *context,
			     PangoDirection     base_dir,
			     const char        *text,
			     int                start_index,
			     int                length,
			     PangoAttrList     *attrs,
			     PangoAttrIterator *cached_iter)
{
  ItemizeState state;

  g_return_val_if_fail (context != NULL, NULL);
  g_return_val_if_fail (start_index >= 0, NULL);
  g_return_val_if_fail (length >= 0, NULL);
  g_return_val_if_fail (length == 0 || text != NULL, NULL);

  if (length == 0)
    return NULL;

  itemize_state_init (&state, context, text, base_dir, start_index, length,
		      attrs, cached_iter, NULL);

  do
    itemize_state_process_run (&state);
  while (itemize_state_next (&state));

  itemize_state_finish (&state);

  return g_list_reverse (state.result);
}

static GList *
itemize_with_font (PangoContext               *context,
		   const char                 *text,
		   int                         start_index,
		   int                         length,
		   const PangoFontDescription *desc)
{
  ItemizeState state;

  if (length == 0)
    return NULL;

  itemize_state_init (&state, context, text, context->base_dir, start_index, length,
		      NULL, NULL, desc);

  do
    itemize_state_process_run (&state);
  while (itemize_state_next (&state));

  itemize_state_finish (&state);

  return g_list_reverse (state.result);
}

/**
 * pango_itemize:
 * @context:   a structure holding information that affects
	       the itemization process.
 * @text:      the text to itemize.
 * @start_index: first byte in @text to process
 * @length:    the number of bytes (not characters) to process
 *             after @start_index.
 *             This must be >= 0.
 * @attrs:     the set of attributes that apply to @text.
 * @cached_iter: (allow-none): Cached attribute iterator, or %NULL
 *
 * Breaks a piece of text into segments with consistent
 * directional level and shaping engine. Each byte of @text will
 * be contained in exactly one of the items in the returned list;
 * the generated list of items will be in logical order (the start
 * offsets of the items are ascending).
 *
 * @cached_iter should be an iterator over @attrs currently positioned at a
 * range before or containing @start_index; @cached_iter will be advanced to
 * the range covering the position just after @start_index + @length.
 * (i.e. if itemizing in a loop, just keep passing in the same @cached_iter).
 *
 * Return value: (transfer full) (element-type Pango.Item): a #GList of #PangoItem
 *               structures. The items should be freed using pango_item_free()
 *               probably in combination with g_list_foreach(), and the list itself
 *               using g_list_free().
 */
GList *
pango_itemize (PangoContext      *context,
	       const char        *text,
	       int                start_index,
	       int                length,
	       PangoAttrList     *attrs,
	       PangoAttrIterator *cached_iter)
{
  g_return_val_if_fail (context != NULL, NULL);
  g_return_val_if_fail (start_index >= 0, NULL);
  g_return_val_if_fail (length >= 0, NULL);
  g_return_val_if_fail (length == 0 || text != NULL, NULL);

  return pango_itemize_with_base_dir (context, context->base_dir,
				      text, start_index, length, attrs, cached_iter);
}

static gboolean
get_first_metrics_foreach (PangoFontset  *fontset,
			   PangoFont     *font,
			   gpointer       data)
{
  PangoFontMetrics *fontset_metrics = data;
  PangoLanguage *language = PANGO_FONTSET_GET_CLASS (fontset)->get_language (fontset);
  PangoFontMetrics *font_metrics = pango_font_get_metrics (font, language);
  guint save_ref_count;

  /* Initialize the fontset metrics to metrics of the first font in the
   * fontset; saving the refcount and restoring it is a bit of hack but avoids
   * having to update this code for each metrics addition.
   */
  save_ref_count = fontset_metrics->ref_count;
  *fontset_metrics = *font_metrics;
  fontset_metrics->ref_count = save_ref_count;

  pango_font_metrics_unref (font_metrics);

  return TRUE;			/* Stops iteration */
}

static PangoFontMetrics *
get_base_metrics (PangoFontset *fontset)
{
  PangoFontMetrics *metrics = pango_font_metrics_new ();

  /* Initialize the metrics from the first font in the fontset */
  pango_fontset_foreach (fontset, get_first_metrics_foreach, metrics);

  return metrics;
}

static void
update_metrics_from_items (PangoFontMetrics *metrics,
			   PangoLanguage    *language,
			   const char       *text,
			   unsigned int      text_len,
			   GList            *items)

{
  GHashTable *fonts_seen = g_hash_table_new (NULL, NULL);
  PangoGlyphString *glyphs = pango_glyph_string_new ();
  GList *l;
  glong text_width;

  /* This should typically be called with a sample text string. */
  g_return_if_fail (text_len > 0);

  metrics->approximate_char_width = 0;

  for (l = items; l; l = l->next)
    {
      PangoItem *item = l->data;
      PangoFont *font = item->analysis.font;

      if (font != NULL && g_hash_table_lookup (fonts_seen, font) == NULL)
	{
	  PangoFontMetrics *raw_metrics = pango_font_get_metrics (font, language);
	  g_hash_table_insert (fonts_seen, font, font);

	  /* metrics will already be initialized from the first font in the fontset */
	  metrics->ascent = MAX (metrics->ascent, raw_metrics->ascent);
	  metrics->descent = MAX (metrics->descent, raw_metrics->descent);
	  pango_font_metrics_unref (raw_metrics);
	}

      pango_shape_full (text + item->offset, item->length,
			text, text_len,
			&item->analysis, glyphs);
      metrics->approximate_char_width += pango_glyph_string_get_width (glyphs);
    }

  pango_glyph_string_free (glyphs);
  g_hash_table_destroy (fonts_seen);

  text_width = pango_utf8_strwidth (text);
  g_assert (text_width > 0);
  metrics->approximate_char_width /= text_width;
}

/**
 * pango_context_get_metrics:
 * @context: a #PangoContext
 * @desc: (allow-none): a #PangoFontDescription structure.  %NULL means that the
 *            font description from the context will be used.
 * @language: (allow-none): language tag used to determine which script to get
 *            the metrics for. %NULL means that the language tag from the context
 *            will be used. If no language tag is set on the context, metrics
 *            for the default language (as determined by pango_language_get_default())
 *            will be returned.
 *
 * Get overall metric information for a particular font
 * description.  Since the metrics may be substantially different for
 * different scripts, a language tag can be provided to indicate that
 * the metrics should be retrieved that correspond to the script(s)
 * used by that language.
 *
 * The #PangoFontDescription is interpreted in the same way as
 * by pango_itemize(), and the family name may be a comma separated
 * list of figures. If characters from multiple of these families
 * would be used to render the string, then the returned fonts would
 * be a composite of the metrics for the fonts loaded for the
 * individual families.
 *
 * Return value: a #PangoFontMetrics object. The caller must call pango_font_metrics_unref()
 *   when finished using the object.
 **/
PangoFontMetrics *
pango_context_get_metrics (PangoContext                 *context,
			   const PangoFontDescription   *desc,
			   PangoLanguage                *language)
{
  PangoFontset *current_fonts = NULL;
  PangoFontMetrics *metrics;
  const char *sample_str;
  unsigned int text_len;
  GList *items;

  g_return_val_if_fail (PANGO_IS_CONTEXT (context), NULL);

  if (!desc)
    desc = context->font_desc;

  if (!language)
    language = context->language;

  current_fonts = pango_font_map_load_fontset (context->font_map, context, desc, language);
  metrics = get_base_metrics (current_fonts);

  sample_str = pango_language_get_sample_string (language);
  text_len = strlen (sample_str);
  items = itemize_with_font (context, sample_str, 0, text_len, desc);

  update_metrics_from_items (metrics, language, sample_str, text_len, items);

  g_list_foreach (items, (GFunc)pango_item_free, NULL);
  g_list_free (items);

  g_object_unref (current_fonts);

  return metrics;
}

static void
context_changed  (PangoContext *context)
{
  context->serial++;
  if (context->serial == 0)
    context->serial++;
}

/**
 * pango_context_changed:
 * @context: a #PangoContext
 *
 * Forces a change in the context, which will cause any #PangoLayout
 * using this context to re-layout.
 *
 * This function is only useful when implementing a new backend
 * for Pango, something applications won't do. Backends should
 * call this function if they have attached extra data to the context
 * and such data is changed.
 *
 * Since: 1.32.4
 **/
void
pango_context_changed  (PangoContext *context)
{
  context_changed (context);
}

static void
check_fontmap_changed (PangoContext *context)
{
  guint old_serial = context->fontmap_serial;

  if (!context->font_map)
    return;

  context->fontmap_serial = pango_font_map_get_serial (context->font_map);

  if (old_serial != context->fontmap_serial)
    context_changed (context);
}

/**
 * pango_context_get_serial:
 * @context: a #PangoContext
 *
 * Returns the current serial number of @context.  The serial number is
 * initialized to an small number larger than zero when a new context
 * is created and is increased whenever the context is changed using any
 * of the setter functions, or the #PangoFontMap it uses to find fonts has
 * changed. The serial may wrap, but will never have the value 0. Since it
 * can wrap, never compare it with "less than", always use "not equals".
 *
 * This can be used to automatically detect changes to a #PangoContext, and
 * is only useful when implementing objects that need update when their
 * #PangoContext changes, like #PangoLayout.
 *
 * Return value: The current serial number of @context.
 *
 * Since: 1.32.4
 **/
guint
pango_context_get_serial (PangoContext *context)
{
  check_fontmap_changed (context);
  return context->serial;
}