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

10 files changed, 481 insertions, 45 deletions

diff --git a/docs/pango-docs.sgml b/docs/pango-docs.sgml
index b8670dec..3c82eeec 100644
--- a/docs/pango-docs.sgml
+++ b/docs/pango-docs.sgml
@@ -18,7 +18,7 @@
 <!ENTITY pango-Win32-Fonts-and-Rendering SYSTEM "xml/win32-fonts.xml">
 <!ENTITY pango-FreeType-Fonts-and-Rendering SYSTEM "xml/freetype-fonts.xml">
 <!ENTITY pango-Xft-Fonts-and-Rendering SYSTEM "xml/xft-fonts.xml">
-<!ENTITY pango-ATSUI-Fonts-and-Rendering SYSTEM "xml/atsui-fonts.xml">
+<!ENTITY pango-ATSUI-Fonts SYSTEM "xml/atsui-fonts.xml">
 <!ENTITY pangocairo SYSTEM "xml/pangocairo.xml">
 <!ENTITY PangoFcFontMap SYSTEM "xml/pangofc-fontmap.xml">
 <!ENTITY PangoFcFont SYSTEM "xml/pangofc-font.xml">
@@ -57,7 +57,7 @@
     &pango-FreeType-Fonts-and-Rendering;
     &pango-Xft-Fonts-and-Rendering;
     &pangocairo;
-    &pango-ATSUI-Fonts-and-Rendering;
+    &pango-ATSUI-Fonts;
     &pango-X-Fonts-and-Rendering;
   </chapter>
 
@@ -87,36 +87,38 @@
     <title>Object Hierarchy</title>
     &pango-tree-index;
   </chapter>
-  <index/>
 
-  <index role="deprecated">
+  <index id="index-all">
+    <title>Index</title>
+  </index>
+  <index id="index-deprecated" role="deprecated">
     <title>Index of deprecated symbols</title>
   </index>
-  <index role="1.2">
+  <index id="index-1.2" role="1.2">
     <title>Index of new symbols in 1.2</title>
   </index>
-  <index role="1.4">
+  <index id="index-1.4" role="1.4">
     <title>Index of new symbols in 1.4</title>
   </index>
-  <index role="1.6">
+  <index id="index-1.6" role="1.6">
     <title>Index of new symbols in 1.6</title>
   </index>
-  <index role="1.8">
+  <index id="index-1.8" role="1.8">
     <title>Index of new symbols in 1.8</title>
   </index>
-  <index role="1.10">
+  <index id="index-1.10" role="1.10">
     <title>Index of new symbols in 1.10</title>
   </index>
-  <index role="1.12">
+  <index id="index-1.12" role="1.12">
     <title>Index of new symbols in 1.12</title>
   </index>
-  <index role="1.14">
+  <index id="index-1.14" role="1.14">
     <title>Index of new symbols in 1.14</title>
   </index>
-  <index role="1.16">
+  <index id="index-1.16" role="1.16">
     <title>Index of new symbols in 1.16</title>
   </index>
-  <index role="1.18">
+  <index id="index-1.18" role="1.18">
     <title>Index of new symbols in 1.18</title>
   </index>
 </book>
diff --git a/docs/pango-sections.txt b/docs/pango-sections.txt
index e7348d31..e016407e 100644
--- a/docs/pango-sections.txt
+++ b/docs/pango-sections.txt
@@ -941,9 +941,13 @@ PangoOTBuffer
 PangoOTGlyph
 PangoOTRuleset
 PangoOTTableType
+PangoOTFeatureMap
 PANGO_OT_ALL_GLYPHS
+PANGO_OT_NO_FEATURE
+PANGO_OT_NO_SCRIPT
 PANGO_OT_DEFAULT_LANGUAGE
-PANGO_OT_DEFAULT_SCRIPT
+PANGO_OT_TAG_DEFAULT_LANGUAGE
+PANGO_OT_TAG_DEFAULT_SCRIPT
 pango_ot_info_get
 pango_ot_info_find_script
 pango_ot_info_find_language
@@ -960,7 +964,10 @@ pango_ot_buffer_set_zero_width_marks
 pango_ot_buffer_get_glyphs
 pango_ot_buffer_output
 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
 pango_ot_ruleset_substitute
 pango_ot_ruleset_position
 pango_ot_tag_from_language
diff --git a/docs/tmpl/atsui-fonts.sgml b/docs/tmpl/atsui-fonts.sgml
index f838f998..d711d4c3 100644
--- a/docs/tmpl/atsui-fonts.sgml
+++ b/docs/tmpl/atsui-fonts.sgml
@@ -2,7 +2,7 @@
 ATSUI Fonts
 
 <!-- ##### SECTION Short_Description ##### -->
-Font handling and rendering with ATSUI fonts
+Font handling with ATSUI fonts
 
 <!-- ##### SECTION Long_Description ##### -->
 <para>
diff --git a/docs/tmpl/opentype.sgml b/docs/tmpl/opentype.sgml
index 1bc78474..6c4f7be0 100644
--- a/docs/tmpl/opentype.sgml
+++ b/docs/tmpl/opentype.sgml
@@ -86,6 +86,17 @@ identify the various OpenType tables in the
 @PANGO_OT_TABLE_GSUB: The GSUB table.
 @PANGO_OT_TABLE_GPOS: The GPOS table.
 
+<!-- ##### STRUCT PangoOTFeatureMap ##### -->
+<para>
+The <type>PangoOTFeatureMap</type> typedef is used to represent an OpenType
+feature with the property bit associated with it.  The feature tag is
+represented as a char array instead of a #PangoOTTag for convenience.
+</para>
+
+@feature_name: feature tag in represented as four-letter ASCII string.
+@property_bit: the property bit to use for this feature.  See
+	       pango_ot_ruleset_add_feature() for details.
+
 <!-- ##### MACRO PANGO_OT_ALL_GLYPHS ##### -->
 <para>
 This is used as the property bit in pango_ot_ruleset_add_feature() when a
@@ -94,18 +105,60 @@ feature should be applied to all glyphs.
 
 
 
+<!-- ##### MACRO PANGO_OT_NO_FEATURE ##### -->
+<para>
+This is used as a feature index that represent no feature, that is, should be
+skipped.  It may be returned as feature index by pango_ot_info_find_feature()
+if the feature is not found, and pango_ot_rulset_add_feature() function
+automatically skips this value, so no special handling is required by the
+user.
+</para>
+
+
+
+<!-- ##### MACRO PANGO_OT_NO_SCRIPT ##### -->
+<para>
+This is used as a script index that represent no script, that is, when the
+requested script was not found, and a default ('DFLT') script was not found
+either.  It may be returned as script index by pango_ot_info_find_script()
+if the script or a default script are not found, all other functions
+taking a script index essentially return if the input script index is
+this value, so no special handling is required by the user.
+</para>
+
+
+
 <!-- ##### MACRO PANGO_OT_DEFAULT_LANGUAGE ##### -->
 <para>
 This is used as the language index in pango_ot_info_find_feature() when
 the default language system of the script is desired.
+
+It is also returned by pango_ot_info_find_language() if the requested language
+is not found, or the requested language tag was PANGO_OT_TAG_DEFAULT_LANGUAGE.
+The end result is that one can always call pango_ot_tag_from_language()
+followed by pango_ot_info_find_language() and pass the result to
+pango_ot_info_find_feature() without having to worry about falling back to
+default language system explicitly.
+</para>
+
+
+
+<!-- ##### MACRO PANGO_OT_TAG_DEFAULT_LANGUAGE ##### -->
+<para>
+This is a #PangoOTTag representing a special language tag 'dflt'.  It is
+returned as language tag by pango_ot_tag_from_language() if the requested
+language is not found.  It is safe to pass this value to
+pango_ot_info_find_language() as that function falls back to returning default
+language-system if the requested language tag is not found.
 </para>
 
 
 
-<!-- ##### MACRO PANGO_OT_DEFAULT_SCRIPT ##### -->
+<!-- ##### MACRO PANGO_OT_TAG_DEFAULT_SCRIPT ##### -->
 <para>
-Expands to the #PangoOTTag corresponding to the special OpenType
-script tag 'DFLT'.
+This is a #PangoOTTag representing the special script tag 'DFLT'.  It is
+returned as script tag by pango_ot_tag_from_script() if the requested script
+is not found.
 </para>
 
 
@@ -276,6 +329,17 @@ script tag 'DFLT'.
 @Returns: 
 
 
+<!-- ##### FUNCTION pango_ot_ruleset_new_for ##### -->
+<para>
+
+</para>
+
+@info: 
+@script: 
+@language: 
+@Returns: 
+
+
 <!-- ##### FUNCTION pango_ot_ruleset_add_feature ##### -->
 <para>
 
@@ -287,6 +351,30 @@ script tag 'DFLT'.
 @property_bit: 
 
 
+<!-- ##### FUNCTION pango_ot_ruleset_maybe_add_feature ##### -->
+<para>
+
+</para>
+
+@ruleset: 
+@table_type: 
+@feature_tag: 
+@property_bit: 
+@Returns: 
+
+
+<!-- ##### FUNCTION pango_ot_ruleset_maybe_add_features ##### -->
+<para>
+
+</para>
+
+@ruleset: 
+@table_type: 
+@features: 
+@n_features: 
+@Returns: 
+
+
 <!-- ##### FUNCTION pango_ot_ruleset_substitute ##### -->
 <para>
 
diff --git a/docs/tmpl/pangocairo.sgml b/docs/tmpl/pangocairo.sgml
index 1a07574d..0299893d 100644
--- a/docs/tmpl/pangocairo.sgml
+++ b/docs/tmpl/pangocairo.sgml
@@ -132,7 +132,7 @@ int main (int argc, char **argv)
 }
 </programlisting>
 </example>
-<figure>
+<figure id="rotated-example-output">
   <title>Output of <xref linkend="rotated-example"/></title>
   <graphic fileref="rotated-text.png" format="PNG"/>
 </figure>
diff --git a/pango/pango-ot-info.c b/pango/pango-ot-info.c
index 5f3ff33f..75d14e2b 100644
--- a/pango/pango-ot-info.c
+++ b/pango/pango-ot-info.c
@@ -404,7 +404,15 @@ get_tables (PangoOTInfo      *info,
  * @script_tag: the tag of the script to find.
  * @script_index: location to store the index of the script, or %NULL.
  *
- * Finds the index of a script.
+ * Finds the index of a script.  If not found, tries to find the 'DFLT'
+ * and then 'dflt' scripts and return the index of that in @script_index.
+ * If none of those is found either, %PANGO_OT_NO_SCRIPT is placed in
+ * @script_index.
+ *
+ * All other functions taking an input script_index parameter know
+ * how to handle %PANGO_OT_NO_SCRIPT, so one can ignore the return
+ * value of this function completely and proceed, to enjoy the automatic
+ * fallback to the 'DFLT'/'dflt' script.
  *
  * Return value: %TRUE if the script was found.
  **/
@@ -417,6 +425,9 @@ pango_ot_info_find_script (PangoOTInfo      *info,
   HB_ScriptList *script_list;
   int i;
 
+  if (script_index)
+    *script_index = PANGO_OT_NO_SCRIPT;
+
   g_return_val_if_fail (PANGO_IS_OT_INFO (info), FALSE);
 
   if (!get_tables (info, table_type, &script_list, NULL))
@@ -433,6 +444,34 @@ pango_ot_info_find_script (PangoOTInfo      *info,
 	}
     }
 
+  /* try finding 'DFLT' */
+  script_tag = PANGO_OT_TAG_DEFAULT_SCRIPT;
+
+  for (i=0; i < script_list->ScriptCount; i++)
+    {
+      if (script_list->ScriptRecord[i].ScriptTag == script_tag)
+	{
+	  if (script_index)
+	    *script_index = i;
+
+	  return FALSE;
+	}
+    }
+
+  /* try with 'dflt'; MS site has had typos and many fonts use it now :( */
+  script_tag = FT_MAKE_TAG ('d', 'f', 'l', 't');
+
+  for (i=0; i < script_list->ScriptCount; i++)
+    {
+      if (script_list->ScriptRecord[i].ScriptTag == script_tag)
+	{
+	  if (script_index)
+	    *script_index = i;
+
+	  return FALSE;
+	}
+    }
+
   return FALSE;
 }
 
@@ -447,6 +486,13 @@ pango_ot_info_find_script (PangoOTInfo      *info,
  *    the language, or %NULL.
  *
  * Finds the index of a language and its required feature index.
+ * If the language is not found, sets @language_index to
+ * PANGO_OT_DEFAULT_LANGUAGE and the required feature of the default language
+ * system is returned in required_feature_index.  For best compatibility with
+ * some fonts, also searches the language system tag 'dflt' before falling
+ * back to the default language system, but that is transparent to the user.
+ * The user can simply ignore the return value of this function to
+ * automatically fall back to the default language system.
  *
  * Return value: %TRUE if the language was found.
  **/
@@ -462,8 +508,16 @@ pango_ot_info_find_language (PangoOTInfo      *info,
   HB_Script *script;
   int i;
 
+  if (language_index)
+    *language_index = PANGO_OT_DEFAULT_LANGUAGE;
+  if (required_feature_index)
+    *required_feature_index = PANGO_OT_NO_FEATURE;
+
   g_return_val_if_fail (PANGO_IS_OT_INFO (info), FALSE);
 
+  if (script_index == PANGO_OT_NO_SCRIPT)
+    return FALSE;
+
   if (!get_tables (info, table_type, &script_list, NULL))
     return FALSE;
 
@@ -483,6 +537,27 @@ pango_ot_info_find_language (PangoOTInfo      *info,
 	}
     }
 
+  /* try with 'dflt'; MS site has had typos and many fonts use it now :( */
+  language_tag = FT_MAKE_TAG ('d', 'f', 'l', 't');
+
+  for (i = 0; i < script->LangSysCount; i++)
+    {
+      if (script->LangSysRecord[i].LangSysTag == language_tag)
+	{
+	  if (language_index)
+	    *language_index = i;
+	  if (required_feature_index)
+	    *required_feature_index = script->LangSysRecord[i].LangSys.ReqFeatureIndex;
+	  return FALSE;
+	}
+    }
+
+  /* DefaultLangSys */
+  if (language_index)
+    *language_index = PANGO_OT_DEFAULT_LANGUAGE;
+  if (required_feature_index)
+    *required_feature_index = script->DefaultLangSys.ReqFeatureIndex;
+
   return FALSE;
 }
 
@@ -496,7 +571,15 @@ pango_ot_info_find_language (PangoOTInfo      *info,
  *     or %PANGO_OT_DEFAULT_LANGUAGE to use the default language of the script.
  * @feature_index: location to store the index of the feature, or %NULL.
  *
- * Finds the index of a feature.
+ * Finds the index of a feature.  If the feature is not found, sets
+ * @feature_index to PANGO_OT_NO_FEATURE, which is safe to pass to
+ * pango_ot_ruleset_add_feature() and similar functions.
+ *
+ * In the future, this may set @feature_index to an special value that if used
+ * in pango_ot_ruleset_add_feature() will ask Pango to synthesize the
+ * requested feature based on Unicode properties and data.  However, this
+ * function will still return %FALSE in those cases.  So, users may want to
+ * ignore the return value of this function in certain cases.
  *
  * Return value: %TRUE if the feature was found.
  **/
@@ -515,8 +598,14 @@ pango_ot_info_find_feature  (PangoOTInfo      *info,
 
   int i;
 
+  if (feature_index)
+    *feature_index = PANGO_OT_NO_FEATURE;
+
   g_return_val_if_fail (PANGO_IS_OT_INFO (info), FALSE);
 
+  if (script_index == PANGO_OT_NO_SCRIPT)
+    return FALSE;
+
   if (!get_tables (info, table_type, &script_list, &feature_list))
     return FALSE;
 
@@ -555,8 +644,8 @@ pango_ot_info_find_feature  (PangoOTInfo      *info,
  *
  * Obtains the list of available scripts.
  *
- * Return value: a newly-allocated array containing the tags of the
- *   available scripts.
+ * Return value: a newly-allocated zero-terminated array containing the tags of the
+ *   available scripts that should be freed using g_free().
  **/
 PangoOTTag *
 pango_ot_info_list_scripts (PangoOTInfo      *info,
@@ -590,8 +679,8 @@ pango_ot_info_list_scripts (PangoOTInfo      *info,
  *
  * Obtains the list of available languages for a given script.
  *
- * Return value: a newly-allocated array containing the tags of the
- *   available languages.
+ * Return value: a newly-allocated zero-terminated array containing the tags of the
+ *   available languages that should be freed using g_free().
  **/
 PangoOTTag *
 pango_ot_info_list_languages (PangoOTInfo      *info,
@@ -606,6 +695,13 @@ pango_ot_info_list_languages (PangoOTInfo      *info,
 
   g_return_val_if_fail (PANGO_IS_OT_INFO (info), NULL);
 
+  if (script_index == PANGO_OT_NO_SCRIPT)
+    {
+      result = g_new (PangoOTTag, 1);
+      result[0] = 0;
+      return result;
+    }
+
   if (!get_tables (info, table_type, &script_list, NULL))
     return NULL;
 
@@ -635,8 +731,8 @@ pango_ot_info_list_languages (PangoOTInfo      *info,
  *
  * Obtains the list of features for the given language of the given script.
  *
- * Return value: a newly-allocated array containing the tags of the
- * available features.
+ * Return value: a newly-allocated zero-terminated array containing the tags of the
+ * available features that should be freed using g_free().
  **/
 PangoOTTag *
 pango_ot_info_list_features  (PangoOTInfo      *info,
@@ -656,6 +752,13 @@ pango_ot_info_list_features  (PangoOTInfo      *info,
 
   g_return_val_if_fail (PANGO_IS_OT_INFO (info), NULL);
 
+  if (script_index == PANGO_OT_NO_SCRIPT)
+    {
+      result = g_new (PangoOTTag, 1);
+      result[0] = 0;
+      return result;
+    }
+
   if (!get_tables (info, table_type, &script_list, &feature_list))
     return NULL;
 
diff --git a/pango/pango-ot-private.h b/pango/pango-ot-private.h
index c301a56f..089c57c9 100644
--- a/pango/pango-ot-private.h
+++ b/pango/pango-ot-private.h
@@ -71,6 +71,9 @@ struct _PangoOTRuleset
 
   GArray *rules;
   PangoOTInfo *info;
+
+  guint script_index[2];
+  guint language_index[2];
 };
 
 struct _PangoOTRulesetClass
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.
diff --git a/pango/pango-ot-tag.c b/pango/pango-ot-tag.c
index c3d853d4..eb6a19d3 100644
--- a/pango/pango-ot-tag.c
+++ b/pango/pango-ot-tag.c
@@ -106,21 +106,21 @@ static const char ot_scripts[][4] = {
  * The %PANGO_SCRIPT_COMMON, %PANGO_SCRIPT_INHERITED, and
  * %PANGO_SCRIPT_UNKNOWN scripts are mapped to the OpenType
  * 'DFLT' script tag that is also defined as
- * %PANGO_OT_DEFAULT_SCRIPT.
+ * %PANGO_OT_TAG_DEFAULT_SCRIPT.
  *
  * Note that multiple #PangoScript values may map to the same
  * OpenType script tag.  In particular, %PANGO_SCRIPT_HIRAGANA
  * and %PANGO_SCRIPT_KATAKANA both map to the OT tag 'kana'.
  *
  * Return value: #PangoOTTag corresponding to @script or
- * %PANGO_OT_DEFAULT_SCRIPT if none found.
+ * %PANGO_OT_TAG_DEFAULT_SCRIPT if none found.
  *
  * Since: 1.18
  **/
 PangoOTTag
 pango_ot_tag_from_script (PangoScript script)
 {
-  g_return_val_if_fail (script >= 0 && (guint)script < G_N_ELEMENTS (ot_scripts), PANGO_OT_DEFAULT_SCRIPT);
+  g_return_val_if_fail (script >= 0 && (guint)script < G_N_ELEMENTS (ot_scripts), PANGO_OT_TAG_DEFAULT_SCRIPT);
 
   return GUINT32_FROM_BE (* (PangoOTTag *) ot_scripts[script]);
 }
@@ -189,7 +189,9 @@ static const LangTag ot_languages[] = {
   {"ay",	"AYM "},
   {"az",	"AZE "},
   {"ba",	"BSH "},
+  {"bal",	"BLI "},
   {"bem",	"BEM "},
+  {"ber",	"BBR "},
   {"bg",	"BGR "},
   {"bho",	"BHO "},
   {"bik",	"BIK "},
@@ -198,6 +200,7 @@ static const LangTag ot_languages[] = {
   {"bn",	"BEN "},
   {"bo",	"TIB "},
   {"br",	"BRE "},
+  {"brh",	"BRH "},
   {"ca",	"CAT "},
   {"ce",	"CHE "},
   {"ceb",	"CEB "},
@@ -212,18 +215,22 @@ static const LangTag ot_languages[] = {
   {"cy",	"WEL "},
   {"da",	"DAN "},
   {"dar",	"DAR "},
+  {"de",	"DEU "},
   {"din",	"DNK "},
   {"doi",	"DGR "},
+  {"dsb",	"LSB "},
   {"dv",	"DHV "},
   {"dz",	"DZN "},
   {"ee",	"EWE "},
   {"efi",	"EFI "},
+  {"el",	"ELL "},
   {"en",	"ENG "},
   {"eo",	"NTO "},
   {"es",	"ESP "},
   {"et",	"ETI "},
   {"eu",	"EUQ "},
   {"fa",	"FAR "},
+  {"ff",	"FUL "},
   {"fi",	"FIN "},
   {"fil",	"PIL "},
   {"fj",	"FJI "},
@@ -231,6 +238,7 @@ static const LangTag ot_languages[] = {
   {"fon",	"FON "},
   {"fr",	"FRA "},
   {"fur",	"FRL "},
+  {"fy",	"FRI "},
   {"ga",	"IRI "},
   {"gaa",	"GAD "},
   {"gd",	"GAE "},
@@ -249,6 +257,8 @@ static const LangTag ot_languages[] = {
   {"hy",	"HYE "},
   {"id",	"IND "},
   {"ig",	"IBO "},
+  {"inc",	"SRK "},
+  {"ine",	"KHW "},
   {"inh",	"ING "},
   {"is",	"ISL "},
   {"it",	"ITA "},
@@ -262,6 +272,7 @@ static const LangTag ot_languages[] = {
   {"ki",	"KIK "},
   {"kk",	"KAZ "},
   {"kl",	"GRN "},
+  {"km",	"KHM "},
   {"kn",	"KAN "},
   {"ko",	"KOR "},
   {"kok",	"KOK "},
@@ -273,15 +284,23 @@ static const LangTag ot_languages[] = {
   {"ku",	"KUR "},
   {"kum",	"KUM "},
   {"ky",	"KIR "},
+  {"la",	"LAT "},
+  {"lad",	"JUD "},
+  {"lbj",	"LDK "},
   {"ln",	"LIN "},
+  {"lo",	"LAO "},
   {"lt",	"LTH "},
+  {"lv",	"LVI "},
   {"mai",	"MTH "},
   {"mdf",	"MOK "},
   {"men",	"MDE "},
   {"mg",	"MLG "},
   {"mi",	"MRI "},
+  {"mkh",	"KUY "},
+  {"ml",	"MLR "},
   {"mnc",	"MCH "},
   {"mni",	"MNI "},
+  {"mnk",	"MND "},
   {"mo",	"MOL "},
   {"mr",	"MAR "},
   {"ms",	"MLY "},
@@ -289,10 +308,11 @@ static const LangTag ot_languages[] = {
   {"mwr",	"MAW "},
   {"my",	"BRM "},
   {"myv",	"ERZ "},
-  {"nl",	"FLE "},
+  {"ne",	"NEP "},
   {"nl",	"NLD "},
   {"no",	"NOR "},
   {"ny",	"CHI "},
+  {"oc",	"PRO "},
   {"om",	"ORO "},
   {"or",	"ORI "},
   {"os",	"OSS "},
@@ -326,7 +346,10 @@ static const LangTag ot_languages[] = {
   {"sv",	"SVE "},
   {"sw",	"SWK "},
   {"syr",	"SYR "},
+  {"ta",	"TAM "},
+  {"te",	"TEL "},
   {"tg",	"TAJ "},
+  {"th",	"THA "},
   {"ti",	"TGY "},
   {"tig",	"TGR "},
   {"tk",	"TKM "},
@@ -344,6 +367,7 @@ static const LangTag ot_languages[] = {
   {"wo",	"WLF "},
   {"xal",	"KLM "},
   {"xh",	"XHS "},
+  {"yi",	"JII "},
   {"yo",	"YBA "},
   {"zh-cn",	"ZHS "},
   {"zh-hk",	"ZHH "},
@@ -377,19 +401,24 @@ lang_compare_first_component (gconstpointer pa,
  * Finds the OpenType language-system tag best describing @language.
  *
  * Return value: #PangoOTTag best matching @language or
- * %PANGO_OT_DEFAULT_LANGUAGE if none found.
+ * %PANGO_OT_TAG_DEFAULT_LANGUAGE if none found.
  *
  * Since: 1.18
  **/
 PangoOTTag
 pango_ot_tag_from_language (PangoLanguage *language)
 {
-  const char *lang_str = pango_language_to_string (language);
+  const char *lang_str;
+  LangTag *lang_tag;
+
+  g_return_val_if_fail (language != NULL, PANGO_OT_TAG_DEFAULT_LANGUAGE);
+
+  lang_str = pango_language_to_string (language);
 
   /* find a language matching in the first component */
-  LangTag *lang_tag = bsearch (lang_str, ot_languages,
-			       G_N_ELEMENTS (ot_languages), sizeof (LangTag),
-			       lang_compare_first_component);
+  lang_tag = bsearch (lang_str, ot_languages,
+		      G_N_ELEMENTS (ot_languages), sizeof (LangTag),
+		      lang_compare_first_component);
 
   /* we now need to find the best language matching */
   if (lang_tag)
@@ -421,7 +450,7 @@ pango_ot_tag_from_language (PangoLanguage *language)
   if (lang_tag)
     return GUINT32_FROM_BE (* (PangoOTTag *) lang_tag->tag);
 
-  return PANGO_OT_DEFAULT_LANGUAGE;
+  return PANGO_OT_TAG_DEFAULT_LANGUAGE;
 }
 
 /**
diff --git a/pango/pango-ot.h b/pango/pango-ot.h
index ce8778f3..df049378 100644
--- a/pango/pango-ot.h
+++ b/pango/pango-ot.h
@@ -34,10 +34,11 @@ G_BEGIN_DECLS
 
 typedef guint32 PangoOTTag;
 
-typedef struct _PangoOTInfo    PangoOTInfo;
-typedef struct _PangoOTBuffer  PangoOTBuffer;
-typedef struct _PangoOTGlyph   PangoOTGlyph;
-typedef struct _PangoOTRuleset PangoOTRuleset;
+typedef struct _PangoOTInfo       PangoOTInfo;
+typedef struct _PangoOTBuffer     PangoOTBuffer;
+typedef struct _PangoOTGlyph      PangoOTGlyph;
+typedef struct _PangoOTRuleset    PangoOTRuleset;
+typedef struct _PangoOTFeatureMap PangoOTFeatureMap;
 
 typedef enum
 {
@@ -47,8 +48,12 @@ typedef enum
 
 
 #define PANGO_OT_ALL_GLYPHS		((guint) 0xFFFF)
-#define PANGO_OT_DEFAULT_LANGUAGE	((PangoOTTag) 0xFFFF)
-#define PANGO_OT_DEFAULT_SCRIPT		((PangoOTTag) FT_MAKE_TAG ('D', 'F', 'L', 'T'))
+#define PANGO_OT_NO_FEATURE		((guint) 0xFFFF)
+#define PANGO_OT_NO_SCRIPT		((guint) 0xFFFF)
+#define PANGO_OT_DEFAULT_LANGUAGE	((guint) 0xFFFF)
+
+#define PANGO_OT_TAG_DEFAULT_SCRIPT		((PangoOTTag) (FT_MAKE_TAG ('D', 'F', 'L', 'T')))
+#define PANGO_OT_TAG_DEFAULT_LANGUAGE		((PangoOTTag) (FT_MAKE_TAG ('d', 'f', 'l', 't')))
 
 /* Note that this must match HB_GlyphItem */
 struct _PangoOTGlyph
@@ -61,6 +66,12 @@ struct _PangoOTGlyph
   gushort  property_cache;    /* Internal */
 };
 
+struct _PangoOTFeatureMap
+{
+  char     feature_name[5];
+  gulong   property_bit;
+};
+
 PangoOTInfo *pango_ot_info_get (FT_Face face);
 
 gboolean pango_ot_info_find_script   (PangoOTInfo      *info,
@@ -111,16 +122,25 @@ void           pango_ot_buffer_set_zero_width_marks (PangoOTBuffer     *buffer,
 						     gboolean           zero_width_marks);
 
 PangoOTRuleset *pango_ot_ruleset_new (PangoOTInfo       *info);
-
+PangoOTRuleset *pango_ot_ruleset_new_for (PangoOTInfo       *info,
+					  PangoScript        script,
+					  PangoLanguage     *language);
 void            pango_ot_ruleset_add_feature (PangoOTRuleset   *ruleset,
 					      PangoOTTableType  table_type,
 					      guint             feature_index,
 					      gulong            property_bit);
+gboolean        pango_ot_ruleset_maybe_add_feature (PangoOTRuleset   *ruleset,
+						    PangoOTTableType  table_type,
+						    PangoOTTag        feature_tag,
+						    gulong            property_bit);
+int             pango_ot_ruleset_maybe_add_features (PangoOTRuleset          *ruleset,
+						     PangoOTTableType         table_type,
+						     const PangoOTFeatureMap *features,
+						     int                      n_features);
 void            pango_ot_ruleset_substitute  (PangoOTRuleset   *ruleset,
 					      PangoOTBuffer    *buffer);
 void            pango_ot_ruleset_position    (PangoOTRuleset   *ruleset,
 					      PangoOTBuffer    *buffer);
-
 PangoScript     pango_ot_tag_to_script     (PangoOTTag     script_tag);
 PangoOTTag      pango_ot_tag_from_script   (PangoScript    script);
 PangoLanguage*  pango_ot_tag_to_language   (PangoOTTag     language_tag);