Part of Bug 325714 – Pango should respect $LANGUAGE

2007-05-13  Behdad Esfahbod  <behdad@gnome.org>

        Part of Bug 325714 – Pango should respect $LANGUAGE

        * pango/pango-ot.h:
        * pango/pango-ot-private.h:
        * pango/pango-ot-tag.c (pango_ot_tag_from_script),
        (pango_ot_tag_from_language):
        * pango/pango-ot-info.c (pango_ot_info_find_script),
        (pango_ot_info_find_language), (pango_ot_info_find_feature),
        (pango_ot_info_list_languages), (pango_ot_info_list_features):
        * pango/pango-ot-ruleset.c (pango_ot_ruleset_new),
        (pango_ot_ruleset_new_for), (pango_ot_ruleset_add_feature),
        (pango_ot_ruleset_maybe_add_feature),
        (pango_ot_ruleset_maybe_add_features):
        Add new engine API:

                PANGO_OT_NO_FEATURE
                PANGO_OT_NO_SCRIPT
                PANGO_OT_TAG_DEFAULT_SCRIPT
                PANGO_OT_TAG_DEFAULT_LANGUAGE
                pango_ot_ruleset_new_for()
                pango_ot_ruleset_maybe_add_feature()
                pango_ot_ruleset_maybe_add_features()

        Using pango_ot_ruleset_new_for() and
        pango_ot_ruleset_maybe_add_features() drastically simplifies ruleset
        building in modules, and does correct script and language selection
        too.  Modules need to be updated to use it though.

        * docs/pango-docs.sgml:
        * docs/pango-sections.txt:
        * docs/tmpl/opentype.sgml:
        Update.


svn path=/trunk/; revision=2284

1 files changed, 184 insertions, 0 deletions

diff --git a/pango/pango-ot-ruleset.c b/pango/pango-ot-ruleset.c
index a54c87ef..75896f56 100644
--- a/pango/pango-ot-ruleset.c
+++ b/pango/pango-ot-ruleset.c
@@ -115,6 +115,94 @@ pango_ot_ruleset_new (PangoOTInfo *info)
   ruleset->info = info;
   g_object_add_weak_pointer (ruleset->info, &ruleset->info);
 
+  ruleset->script_index[0]   = PANGO_OT_NO_SCRIPT;
+  ruleset->script_index[1]   = PANGO_OT_NO_SCRIPT;
+  ruleset->language_index[0] = PANGO_OT_DEFAULT_LANGUAGE;
+  ruleset->language_index[1] = PANGO_OT_DEFAULT_LANGUAGE;
+
+  return ruleset;
+}
+
+/**
+ * pango_ot_ruleset_new_for:
+ * @info: a #PangoOTInfo.
+ * @script: a #PangoScript.
+ * @language: a #PangoLanguage.
+ *
+ * Creates a new #PangoOTRuleset for the given OpenType info, script, and
+ * language.
+ *
+ * This function is part of a convenience scheme that highly simplifies
+ * using a #PangoOTRuleset to represent features for a specific pair of script
+ * and language.  So one can use this function passing in the script and
+ * language of interest, and later try to add features to the ruleset by just
+ * specifying the feature name or tag, without having to deal with finding
+ * script, language, or feature indices manually.
+ *
+ * In excess to what pango_ot_ruleset_new() does, this function will:
+ * <itemizedlist>
+ *   <listitem>
+ *   Find the #PangoOTTag script and language tags associated with
+ *   @script and @language using pango_ot_tag_from_script() and
+ *   pango_ot_tag_from_language(),
+ *   </listitem>
+ *   <listitem>
+ *   For each of table types %PANGO_OT_TABLE_GSUB and %PANGO_OT_TABLE_GPOS,
+ *   find the script index of the script tag found and the language
+ *   system index of the language tag found in that script system, using
+ *   pango_ot_info_find_script() and pango_ot_info_find_language(),
+ *   </listitem>
+ *   <listitem>
+ *   For found language-systems, if they have required feature
+ *   index, add that feature to the ruleset using
+ *   pango_ot_ruleset_add_feature(),
+ *   </listitem>
+ *   <listitem>
+ *   Remember found script and language indices for both table types,
+ *   and use them in future pango_ot_ruleset_maybe_add_feature() and
+ *   pango_ot_ruleset_maybe_add_features().
+ *   </listitem>
+ * </itemizedlist>
+ *
+ * Because of the way return values of pango_ot_info_find_script() and
+ * pango_ot_info_find_language() are ignored, this function automatically
+ * finds and uses the 'DFLT' script and the default language-system.
+ *
+ * Return value: the newly allocated #PangoOTRuleset, which
+ *               should be freed with g_object_unref().
+ *
+ * Since: 1.18
+ **/
+PangoOTRuleset *
+pango_ot_ruleset_new_for (PangoOTInfo       *info,
+			  PangoScript        script,
+			  PangoLanguage     *language)
+{
+  PangoOTRuleset *ruleset = pango_ot_ruleset_new (info);
+  PangoOTTag script_tag, language_tag;
+  PangoOTTableType table_type;
+
+  script_tag   = pango_ot_tag_from_script (script);
+  language_tag = pango_ot_tag_from_language (language);
+
+  for (table_type = PANGO_OT_TABLE_GSUB; table_type <= PANGO_OT_TABLE_GPOS; table_type++)
+    {
+      guint script_index, language_index, feature_index;
+
+      pango_ot_info_find_script   (ruleset->info, table_type,
+				   script_tag, &script_index);
+      pango_ot_info_find_language (ruleset->info, table_type, script_index,
+				   language_tag, &language_index,
+				   &feature_index);
+
+      ruleset->script_index[table_type] = script_index;
+      ruleset->language_index[table_type] = language_index;
+
+      /* add required feature of the language */
+      pango_ot_ruleset_add_feature (ruleset, table_type,
+				    feature_index, PANGO_OT_ALL_GLYPHS);
+    }
+
   return ruleset;
 }
 
@@ -140,6 +228,9 @@ pango_ot_ruleset_add_feature (PangoOTRuleset   *ruleset,
   g_return_if_fail (PANGO_IS_OT_RULESET (ruleset));
   g_return_if_fail (PANGO_IS_OT_INFO (ruleset->info));
 
+  if (feature_index == PANGO_OT_NO_FEATURE)
+    return;
+
   tmp_rule.table_type = table_type;
   tmp_rule.feature_index = feature_index;
   tmp_rule.property_bit = property_bit;
@@ -148,6 +239,99 @@ pango_ot_ruleset_add_feature (PangoOTRuleset   *ruleset,
 }
 
 /**
+ * pango_ot_ruleset_maybe_add_feature:
+ * @ruleset: a #PangoOTRuleset.
+ * @table_type: the table type to add a feature to.
+ * @feature_tag: the tag of the feature to add.
+ * @property_bit: the property bit to use for this feature. Used to identify
+ *                the glyphs that this feature should be applied to, or
+ *                %PANGO_OT_ALL_GLYPHS if it should be applied to all glyphs.
+ *
+ * This is a convenience function that first tries to find the feature
+ * using pango_ot_info_find_feature() and the ruleset script and language
+ * passed to pango_ot_ruleset_new_for(),
+ * and if the feature is found, adds it to the ruleset.
+ *
+ * If @ruleset was not created using pango_ot_ruleset_new_for(), this function
+ * does nothing.
+ *
+ * Return value: %TRUE if the feature was found and added to ruleset,
+ *               %FALSE otherwise.
+ *
+ * Since: 1.18
+ **/
+gboolean
+pango_ot_ruleset_maybe_add_feature (PangoOTRuleset          *ruleset,
+				    PangoOTTableType         table_type,
+				    PangoOTTag               feature_tag,
+				    gulong                   property_bit)
+{
+  guint feature_index;
+
+  g_return_val_if_fail (PANGO_IS_OT_RULESET (ruleset), FALSE);
+  g_return_val_if_fail (PANGO_IS_OT_INFO (ruleset->info), FALSE);
+
+  pango_ot_info_find_feature (ruleset->info, table_type,
+			      feature_tag,
+			      ruleset->script_index[table_type],
+			      ruleset->language_index[table_type],
+			      &feature_index);
+
+  if (feature_index != PANGO_OT_NO_FEATURE)
+    {
+      pango_ot_ruleset_add_feature (ruleset, table_type,
+				    feature_index, property_bit);
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
+/**
+ * pango_ot_ruleset_maybe_add_features:
+ * @ruleset: a #PangoOTRuleset.
+ * @table_type: the table type to add features to.
+ * @features: array of feature name and property bits to add.
+ * @n_features: number of feature records in @features array.
+ *
+ * This is a convenience function that 
+ * for each feature in the feature map array @features
+ * converts the feature name to a #PangoOTTag feature tag using FT_MAKE_TAG()
+ * and calls pango_ot_ruleset_maybe_add_feature() on it.
+ *
+ * Return value: The number of features in @features that were found
+ *               and added to @ruleset.
+ *
+ * Since: 1.18
+ **/
+int
+pango_ot_ruleset_maybe_add_features (PangoOTRuleset          *ruleset,
+				     PangoOTTableType         table_type,
+				     const PangoOTFeatureMap *features,
+				     int                      n_features)
+{
+  int i, n_found_features = 0;
+
+  g_return_val_if_fail (PANGO_IS_OT_RULESET (ruleset), 0);
+  g_return_val_if_fail (PANGO_IS_OT_INFO (ruleset->info), 0);
+
+  for (i = 0; i < n_features; i++)
+    {
+      PangoOTTag feature_tag = FT_MAKE_TAG (features[i].feature_name[0],
+					    features[i].feature_name[1],
+					    features[i].feature_name[2],
+					    features[i].feature_name[3]);
+
+      n_found_features += pango_ot_ruleset_maybe_add_feature (ruleset,
+							      table_type,
+							      feature_tag,
+							      features[i].property_bit);
+    }
+
+  return n_found_features;
+}
+
+/**
  * pango_ot_ruleset_substitute:
  * @ruleset: a #PangoOTRuleset.
  * @buffer: a #PangoOTBuffer.