Add a simple Thai shaper. (Reasonably complete but intended mostly for an

Mon May  8 16:19:22 2000  Owen Taylor  <otaylor@redhat.com>

	* modules/thai/* modules/Makefile.am configure.in:
	Add a simple Thai shaper. (Reasonably complete but
	intended mostly for an example for the shape docs
	right now.)

	* pango/pangox.h (PANGO_X_GLYPH_INDEX): Protect
	arguments to macros.

5 files changed, 884 insertions, 1 deletions

diff --git a/modules/Makefile.am b/modules/Makefile.am
index 90cb1513..e2ba627f 100644
--- a/modules/Makefile.am
+++ b/modules/Makefile.am
@@ -5,7 +5,8 @@ SUBDIRS = 		\
 	devanagari 	\
 	basic 		\
 	hangul 		\
-	tamil 
+	tamil 		\
+	thai
 
 install-data-local:
 	$(mkinstalldirs) $(DESTDIR)$(localstatedir)/lib/pango
diff --git a/modules/thai/.cvsignore b/modules/thai/.cvsignore
new file mode 100644
index 00000000..6e5ca7ed
--- /dev/null
+++ b/modules/thai/.cvsignore
@@ -0,0 +1,6 @@
+Makefile
+Makefile.in
+.deps
+.libs
+*.lo
+*.la
diff --git a/modules/thai/Makefile.am b/modules/thai/Makefile.am
new file mode 100644
index 00000000..38d4fc0e
--- /dev/null
+++ b/modules/thai/Makefile.am
@@ -0,0 +1,20 @@
+## Process this file with automake to create Makefile.in.
+
+sources = thai.c
+
+if INCLUDE_THAI
+noinst_LTLIBRARIES = libpango-thai.la
+moddefine = -DMODULE_PREFIX
+else
+moduledir = $(libdir)/pango/modules
+module_LTLIBRARIES = pango-thai.la
+endif
+
+INCLUDES = -I$(top_srcdir) -I$(top_srcdir)/pango/ $(moddefine)
+
+pango_thai_la_LDFLAGS = -rpath $(libdir) -export-dynamic -avoid-version -module
+pango_thai_la_LIBADD = $(UNICODE_LIBS)
+pango_thai_la_SOURCES = $(sources)
+
+libpango_thai_la_SOURCES = $(sources)
+
diff --git a/modules/thai/thai-x.c b/modules/thai/thai-x.c
new file mode 100644
index 00000000..17d1d024
--- /dev/null
+++ b/modules/thai/thai-x.c
@@ -0,0 +1,428 @@
+/* Pango
+ * thai.c:
+ *
+ * Copyright (C) 1999 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.
+ */
+
+#include <iconv.h>
+
+#include <glib.h>
+#include "pango.h"
+#include "pangox.h"
+#include "utils.h"
+#include <unicode.h>
+#include <fribidi/fribidi.h>
+
+/* We handle the range U+0e01 to U+0e5b exactly
+ */
+static PangoEngineRange thai_ranges[] = {
+  { 0x0e01, 0x0e5b, "*" },  /* Thai */
+};
+
+static PangoEngineInfo script_engines[] = {
+  {
+    "ThaiScriptEngineLang",
+    PANGO_ENGINE_TYPE_LANG,
+    PANGO_RENDER_TYPE_NONE,
+    thai_ranges, G_N_ELEMENTS(thai_ranges)
+  },
+  {
+    "ThaiScriptEngineX",
+    PANGO_ENGINE_TYPE_SHAPE,
+    PANGO_RENDER_TYPE_X,
+    thai_ranges, G_N_ELEMENTS(thai_ranges)
+  }
+};
+
+/*
+ * Language script engine
+ */
+
+static void 
+thai_engine_break (const char     *text,
+		    gint            len,
+		    PangoAnalysis  *analysis,
+		    PangoLogAttr   *attrs)
+{
+}
+
+static PangoEngine *
+thai_engine_lang_new ()
+{
+  PangoEngineLang *result;
+  
+  result = g_new (PangoEngineLang, 1);
+
+  result->engine.id = "ThaiScriptEngine";
+  result->engine.type = PANGO_ENGINE_TYPE_LANG;
+  result->engine.length = sizeof (result);
+  result->script_break = thai_engine_break;
+
+  return (PangoEngine *)result;
+}
+
+/*
+ * X window system script engine portion
+ */
+
+typedef struct _ThaiFontInfo ThaiFontInfo;
+
+/* The type of encoding that we will use
+ */
+typedef enum {
+  THAI_FONT_NONE,
+  THAI_FONT_XTIS,
+  THAI_FONT_TIS,
+  THAI_FONT_ISO10646
+} ThaiFontType;
+
+struct _ThaiFontInfo
+{
+  PangoFont   *font;
+  ThaiFontType type;
+  PangoXSubfont subfont;
+};
+
+/* All combining marks for Thai fall in the range U+0E30-U+0E50,
+ * so we confine our data tables to that range, and use
+ * default values for characters outside those ranges.
+ */
+
+/* Map from code point to group used for rendering with XTIS fonts
+ * (0 == base character)
+ */
+static const char groups[32] = {
+  0, 1, 0, 0, 1, 1, 1, 1,
+  1, 1, 1, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 2,
+  2, 2, 2, 2, 2, 2, 1, 0
+};
+
+/* Map from code point to index within group 1
+ * (0 == no combining mark from group 1)
+ */   
+static const char group1_map[32] = {
+  0, 1, 0, 0, 2, 3, 4, 5,
+  6, 7, 8, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0
+};
+
+/* Map from code point to index within group 2
+ * (0 == no combining mark from group 2)
+ */   
+static const char group2_map[32] = {
+  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 1,
+  2, 3, 4, 5, 6, 7, 1, 0
+};
+
+/* Returns a structure with information we will use to rendering given the
+ * #PangoFont. This is computed once per font and cached for later retrieval.
+ */
+static ThaiFontInfo *
+get_font_info (PangoFont *font)
+{
+  static const char *charsets[] = {
+    "xtis620.2529-1",
+    "xtis-0",
+    "tis620.2529-1",
+    "iso10646-1",
+  };
+
+  static const int charset_types[] = {
+    THAI_FONT_XTIS,
+    THAI_FONT_XTIS,
+    THAI_FONT_TIS,
+    THAI_FONT_ISO10646
+  };
+  
+  ThaiFontInfo *font_info;
+  
+  font_info = pango_font_get_data (font, "thai-font-info");
+  if (!font_info)
+    {
+      /* No cached information not found, so we need to compute it
+       * from scratch
+       */
+      PangoXSubfont *subfont_ids;
+      int *subfont_charsets;
+      int n_subfonts, i;
+
+      font_info = g_new (ThaiFontInfo, 1);
+      font_info->font = font;
+      font_info->type = THAI_FONT_NONE;
+      
+      pango_font_set_data (font, "thai-font-info", font_info, (GDestroyNotify)g_free);
+      
+      n_subfonts = pango_x_list_subfonts (font, (char **)charsets, G_N_ELEMENTS (charsets),
+					  &subfont_ids, &subfont_charsets);
+
+      for (i=0; i < n_subfonts; i++)
+	{
+	  ThaiFontType font_type = charset_types[subfont_charsets[i]];
+	  
+	  if (font_type != THAI_FONT_ISO10646 ||
+	      pango_x_has_glyph (font, PANGO_X_MAKE_GLYPH (subfont_ids[i], 0xe01)))
+	    {
+	      font_info->type = font_type;
+	      font_info->subfont = subfont_ids[i];
+	      
+	      break;
+	    }
+	}
+
+      g_free (subfont_ids);
+      g_free (subfont_charsets);
+    }
+
+  return font_info;
+}
+
+static void
+add_glyph (ThaiFontInfo     *font_info, 
+	   PangoGlyphString *glyphs, 
+	   int               cluster_start, 
+	   PangoGlyph        glyph,
+	   gboolean          combining)
+{
+  PangoRectangle ink_rect, logical_rect;
+  int index = glyphs->num_glyphs;
+
+  pango_glyph_string_set_size (glyphs, index + 1);
+  
+  glyphs->glyphs[index].glyph = glyph;
+  glyphs->glyphs[index].attr.is_cluster_start = combining ? 0 : 1;
+  
+  glyphs->log_clusters[index] = cluster_start;
+
+  pango_font_get_glyph_extents (font_info->font,
+				glyphs->glyphs[index].glyph, &ink_rect, &logical_rect);
+
+  if (combining)
+    {
+      glyphs->glyphs[index].geometry.width = 
+	MAX (logical_rect.width, glyphs->glyphs[index - 1].geometry.width);
+      glyphs->glyphs[index - 1].geometry.width = 0;
+      glyphs->glyphs[index].geometry.x_offset = 0;
+    }
+  else
+    {
+      glyphs->glyphs[index].geometry.x_offset = 0;
+      glyphs->glyphs[index].geometry.width = logical_rect.width;
+    }
+  
+  glyphs->glyphs[index].geometry.y_offset = 0;
+}
+
+/* Return the glyph code within the font for the given Unicode Thai 
+ * code pointer
+ */
+static int
+get_glyph (ThaiFontInfo *font_info, unicode_char_t wc)
+{
+  switch (font_info->type)
+    {
+    case THAI_FONT_NONE:
+      return pango_x_get_unknown_glyph (font_info->font);
+    case THAI_FONT_XTIS:
+      return PANGO_X_MAKE_GLYPH (font_info->subfont, 0x100 * (wc - 0xe00 + 0x20) + 0x30);
+    case THAI_FONT_TIS:
+      return PANGO_X_MAKE_GLYPH (font_info->subfont, wc - 0xe00 + 0xA0);
+    case THAI_FONT_ISO10646:
+      return PANGO_X_MAKE_GLYPH (font_info->subfont, wc);
+    }
+  return 0;			/* Quiet GCC */
+}
+
+static void
+add_cluster (ThaiFontInfo *font_info,
+	     PangoGlyphString *glyphs,
+	     int cluster_start,
+	     unicode_char_t base, 
+	     unicode_char_t group1,
+	     unicode_char_t group2)
+{
+  /* If we are rendering with an XTIS font, we try to find a precomposed
+   * glyph for the cluster.
+   */
+  if (font_info->type == THAI_FONT_XTIS)
+    {
+      PangoGlyph glyph;
+      int xtis_index = 0x100 * (base - 0xe00 + 0x20) + 0x30;
+      if (group1)
+	xtis_index +=8 * group1_map[group1 - 0xe30];
+      if (group2)
+	xtis_index += group2_map[group2 - 0xe30];
+      
+      glyph = PANGO_X_MAKE_GLYPH (font_info->subfont, xtis_index);
+
+      if (pango_x_has_glyph (font_info->font, glyph))
+	{
+	  add_glyph (font_info, glyphs, cluster_start, glyph, FALSE);
+	  return;
+	}
+    }
+
+  /* If that failed, then we add compose the cluster out of three 
+   * individual glyphs
+   */
+  add_glyph (font_info, glyphs, cluster_start, get_glyph (font_info, base), FALSE);
+  if (group1)
+    add_glyph (font_info, glyphs, cluster_start, get_glyph (font_info, group1), TRUE);
+  if (group2)
+    add_glyph (font_info, glyphs, cluster_start, get_glyph (font_info, group2), TRUE);
+}
+
+static void 
+thai_engine_shape (PangoFont        *font,
+		   const char       *text,
+		   gint              length,
+		   PangoAnalysis    *analysis,
+		   PangoGlyphString *glyphs)
+{
+  ThaiFontInfo *font_info;
+  const char *p, *next;
+
+  unicode_char_t base = 0;
+  unicode_char_t group1 = 0;
+  unicode_char_t group2 = 0;
+  int cluster_start = 0;
+
+  pango_glyph_string_set_size (glyphs, 0);
+
+  font_info = get_font_info (font);
+  
+  p = text;
+  while (p < text + length)
+    {
+      int group;
+      unicode_char_t wc;
+
+      next = unicode_get_utf8 (p, &wc);
+
+      if (wc >= 0xe30 && wc < 0xe50)
+	group = groups[wc - 0xe30];
+      else
+	group = 0;
+
+      switch (group)
+	{
+	case 0:
+	  if (base)
+	    {
+	      add_cluster (font_info, glyphs, cluster_start, base, group1, group2);
+	      group1 = 0;
+	      group2 = 0;
+	    }
+	  cluster_start = p - text;
+	  base = wc;
+	  break;
+	case 1:
+	  group1 = wc;
+	  break;
+	case 2:
+	  group2 = wc;
+	  break;
+	}
+      
+      p = next;
+    }
+
+  if (base)
+    add_cluster (font_info, glyphs, cluster_start, base, group1, group2);
+}
+
+static PangoCoverage *
+thai_engine_get_coverage (PangoFont  *font,
+			   const char *lang)
+{
+  PangoCoverage *result = pango_coverage_new ();
+  
+  ThaiFontInfo *font_info = get_font_info (font);
+  
+  if (font_info->type != THAI_FONT_NONE)
+    {
+      unicode_char_t wc;
+      
+      for (wc = 0xe01; wc <= 0xe3a; wc++)
+	pango_coverage_set (result, wc, PANGO_COVERAGE_EXACT);
+      for (wc = 0xe3f; wc <= 0xe5b; wc++)
+	pango_coverage_set (result, wc, PANGO_COVERAGE_EXACT);
+    }
+
+  return result;
+}
+
+static PangoEngine *
+thai_engine_x_new ()
+{
+  PangoEngineShape *result;
+  
+  result = g_new (PangoEngineShape, 1);
+
+  result->engine.id = "ThaiScriptEngine";
+  result->engine.type = PANGO_ENGINE_TYPE_LANG;
+  result->engine.length = sizeof (result);
+  result->script_shape = thai_engine_shape;
+  result->get_coverage = thai_engine_get_coverage;
+
+  return (PangoEngine *)result;
+}
+
+/* The following three functions provide the public module API for
+ * Pango. If we are compiling it is a module, then we name the
+ * entry points script_engine_list, etc. But if we are compiling
+ * it for inclusion directly in Pango, then we need them to
+ * to have distinct names for this module, so we prepend
+ * _pango_thai_
+ */
+#ifdef MODULE_PREFIX
+#define MODULE_ENTRY(func) _pango_thai_##func
+#else
+#define MODULE_ENTRY(func) func
+#endif
+
+/* List the engines contained within this module
+ */
+void 
+MODULE_ENTRY(script_engine_list) (PangoEngineInfo **engines, gint *n_engines)
+{
+  *engines = script_engines;
+  *n_engines = G_N_ELEMENTS (script_engines);
+}
+
+/* Load a particular engine given the ID for the engine
+ */
+PangoEngine *
+MODULE_ENTRY(script_engine_load) (const char *id)
+{
+  if (!strcmp (id, "ThaiScriptEngineLang"))
+    return thai_engine_lang_new ();
+  else if (!strcmp (id, "ThaiScriptEngineX"))
+    return thai_engine_x_new ();
+  else
+    return NULL;
+}
+
+void 
+MODULE_ENTRY(script_engine_unload) (PangoEngine *engine)
+{
+}
+
diff --git a/modules/thai/thai.c b/modules/thai/thai.c
new file mode 100644
index 00000000..17d1d024
--- /dev/null
+++ b/modules/thai/thai.c
@@ -0,0 +1,428 @@
+/* Pango
+ * thai.c:
+ *
+ * Copyright (C) 1999 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.
+ */
+
+#include <iconv.h>
+
+#include <glib.h>
+#include "pango.h"
+#include "pangox.h"
+#include "utils.h"
+#include <unicode.h>
+#include <fribidi/fribidi.h>
+
+/* We handle the range U+0e01 to U+0e5b exactly
+ */
+static PangoEngineRange thai_ranges[] = {
+  { 0x0e01, 0x0e5b, "*" },  /* Thai */
+};
+
+static PangoEngineInfo script_engines[] = {
+  {
+    "ThaiScriptEngineLang",
+    PANGO_ENGINE_TYPE_LANG,
+    PANGO_RENDER_TYPE_NONE,
+    thai_ranges, G_N_ELEMENTS(thai_ranges)
+  },
+  {
+    "ThaiScriptEngineX",
+    PANGO_ENGINE_TYPE_SHAPE,
+    PANGO_RENDER_TYPE_X,
+    thai_ranges, G_N_ELEMENTS(thai_ranges)
+  }
+};
+
+/*
+ * Language script engine
+ */
+
+static void 
+thai_engine_break (const char     *text,
+		    gint            len,
+		    PangoAnalysis  *analysis,
+		    PangoLogAttr   *attrs)
+{
+}
+
+static PangoEngine *
+thai_engine_lang_new ()
+{
+  PangoEngineLang *result;
+  
+  result = g_new (PangoEngineLang, 1);
+
+  result->engine.id = "ThaiScriptEngine";
+  result->engine.type = PANGO_ENGINE_TYPE_LANG;
+  result->engine.length = sizeof (result);
+  result->script_break = thai_engine_break;
+
+  return (PangoEngine *)result;
+}
+
+/*
+ * X window system script engine portion
+ */
+
+typedef struct _ThaiFontInfo ThaiFontInfo;
+
+/* The type of encoding that we will use
+ */
+typedef enum {
+  THAI_FONT_NONE,
+  THAI_FONT_XTIS,
+  THAI_FONT_TIS,
+  THAI_FONT_ISO10646
+} ThaiFontType;
+
+struct _ThaiFontInfo
+{
+  PangoFont   *font;
+  ThaiFontType type;
+  PangoXSubfont subfont;
+};
+
+/* All combining marks for Thai fall in the range U+0E30-U+0E50,
+ * so we confine our data tables to that range, and use
+ * default values for characters outside those ranges.
+ */
+
+/* Map from code point to group used for rendering with XTIS fonts
+ * (0 == base character)
+ */
+static const char groups[32] = {
+  0, 1, 0, 0, 1, 1, 1, 1,
+  1, 1, 1, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 2,
+  2, 2, 2, 2, 2, 2, 1, 0
+};
+
+/* Map from code point to index within group 1
+ * (0 == no combining mark from group 1)
+ */   
+static const char group1_map[32] = {
+  0, 1, 0, 0, 2, 3, 4, 5,
+  6, 7, 8, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0
+};
+
+/* Map from code point to index within group 2
+ * (0 == no combining mark from group 2)
+ */   
+static const char group2_map[32] = {
+  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 1,
+  2, 3, 4, 5, 6, 7, 1, 0
+};
+
+/* Returns a structure with information we will use to rendering given the
+ * #PangoFont. This is computed once per font and cached for later retrieval.
+ */
+static ThaiFontInfo *
+get_font_info (PangoFont *font)
+{
+  static const char *charsets[] = {
+    "xtis620.2529-1",
+    "xtis-0",
+    "tis620.2529-1",
+    "iso10646-1",
+  };
+
+  static const int charset_types[] = {
+    THAI_FONT_XTIS,
+    THAI_FONT_XTIS,
+    THAI_FONT_TIS,
+    THAI_FONT_ISO10646
+  };
+  
+  ThaiFontInfo *font_info;
+  
+  font_info = pango_font_get_data (font, "thai-font-info");
+  if (!font_info)
+    {
+      /* No cached information not found, so we need to compute it
+       * from scratch
+       */
+      PangoXSubfont *subfont_ids;
+      int *subfont_charsets;
+      int n_subfonts, i;
+
+      font_info = g_new (ThaiFontInfo, 1);
+      font_info->font = font;
+      font_info->type = THAI_FONT_NONE;
+      
+      pango_font_set_data (font, "thai-font-info", font_info, (GDestroyNotify)g_free);
+      
+      n_subfonts = pango_x_list_subfonts (font, (char **)charsets, G_N_ELEMENTS (charsets),
+					  &subfont_ids, &subfont_charsets);
+
+      for (i=0; i < n_subfonts; i++)
+	{
+	  ThaiFontType font_type = charset_types[subfont_charsets[i]];
+	  
+	  if (font_type != THAI_FONT_ISO10646 ||
+	      pango_x_has_glyph (font, PANGO_X_MAKE_GLYPH (subfont_ids[i], 0xe01)))
+	    {
+	      font_info->type = font_type;
+	      font_info->subfont = subfont_ids[i];
+	      
+	      break;
+	    }
+	}
+
+      g_free (subfont_ids);
+      g_free (subfont_charsets);
+    }
+
+  return font_info;
+}
+
+static void
+add_glyph (ThaiFontInfo     *font_info, 
+	   PangoGlyphString *glyphs, 
+	   int               cluster_start, 
+	   PangoGlyph        glyph,
+	   gboolean          combining)
+{
+  PangoRectangle ink_rect, logical_rect;
+  int index = glyphs->num_glyphs;
+
+  pango_glyph_string_set_size (glyphs, index + 1);
+  
+  glyphs->glyphs[index].glyph = glyph;
+  glyphs->glyphs[index].attr.is_cluster_start = combining ? 0 : 1;
+  
+  glyphs->log_clusters[index] = cluster_start;
+
+  pango_font_get_glyph_extents (font_info->font,
+				glyphs->glyphs[index].glyph, &ink_rect, &logical_rect);
+
+  if (combining)
+    {
+      glyphs->glyphs[index].geometry.width = 
+	MAX (logical_rect.width, glyphs->glyphs[index - 1].geometry.width);
+      glyphs->glyphs[index - 1].geometry.width = 0;
+      glyphs->glyphs[index].geometry.x_offset = 0;
+    }
+  else
+    {
+      glyphs->glyphs[index].geometry.x_offset = 0;
+      glyphs->glyphs[index].geometry.width = logical_rect.width;
+    }
+  
+  glyphs->glyphs[index].geometry.y_offset = 0;
+}
+
+/* Return the glyph code within the font for the given Unicode Thai 
+ * code pointer
+ */
+static int
+get_glyph (ThaiFontInfo *font_info, unicode_char_t wc)
+{
+  switch (font_info->type)
+    {
+    case THAI_FONT_NONE:
+      return pango_x_get_unknown_glyph (font_info->font);
+    case THAI_FONT_XTIS:
+      return PANGO_X_MAKE_GLYPH (font_info->subfont, 0x100 * (wc - 0xe00 + 0x20) + 0x30);
+    case THAI_FONT_TIS:
+      return PANGO_X_MAKE_GLYPH (font_info->subfont, wc - 0xe00 + 0xA0);
+    case THAI_FONT_ISO10646:
+      return PANGO_X_MAKE_GLYPH (font_info->subfont, wc);
+    }
+  return 0;			/* Quiet GCC */
+}
+
+static void
+add_cluster (ThaiFontInfo *font_info,
+	     PangoGlyphString *glyphs,
+	     int cluster_start,
+	     unicode_char_t base, 
+	     unicode_char_t group1,
+	     unicode_char_t group2)
+{
+  /* If we are rendering with an XTIS font, we try to find a precomposed
+   * glyph for the cluster.
+   */
+  if (font_info->type == THAI_FONT_XTIS)
+    {
+      PangoGlyph glyph;
+      int xtis_index = 0x100 * (base - 0xe00 + 0x20) + 0x30;
+      if (group1)
+	xtis_index +=8 * group1_map[group1 - 0xe30];
+      if (group2)
+	xtis_index += group2_map[group2 - 0xe30];
+      
+      glyph = PANGO_X_MAKE_GLYPH (font_info->subfont, xtis_index);
+
+      if (pango_x_has_glyph (font_info->font, glyph))
+	{
+	  add_glyph (font_info, glyphs, cluster_start, glyph, FALSE);
+	  return;
+	}
+    }
+
+  /* If that failed, then we add compose the cluster out of three 
+   * individual glyphs
+   */
+  add_glyph (font_info, glyphs, cluster_start, get_glyph (font_info, base), FALSE);
+  if (group1)
+    add_glyph (font_info, glyphs, cluster_start, get_glyph (font_info, group1), TRUE);
+  if (group2)
+    add_glyph (font_info, glyphs, cluster_start, get_glyph (font_info, group2), TRUE);
+}
+
+static void 
+thai_engine_shape (PangoFont        *font,
+		   const char       *text,
+		   gint              length,
+		   PangoAnalysis    *analysis,
+		   PangoGlyphString *glyphs)
+{
+  ThaiFontInfo *font_info;
+  const char *p, *next;
+
+  unicode_char_t base = 0;
+  unicode_char_t group1 = 0;
+  unicode_char_t group2 = 0;
+  int cluster_start = 0;
+
+  pango_glyph_string_set_size (glyphs, 0);
+
+  font_info = get_font_info (font);
+  
+  p = text;
+  while (p < text + length)
+    {
+      int group;
+      unicode_char_t wc;
+
+      next = unicode_get_utf8 (p, &wc);
+
+      if (wc >= 0xe30 && wc < 0xe50)
+	group = groups[wc - 0xe30];
+      else
+	group = 0;
+
+      switch (group)
+	{
+	case 0:
+	  if (base)
+	    {
+	      add_cluster (font_info, glyphs, cluster_start, base, group1, group2);
+	      group1 = 0;
+	      group2 = 0;
+	    }
+	  cluster_start = p - text;
+	  base = wc;
+	  break;
+	case 1:
+	  group1 = wc;
+	  break;
+	case 2:
+	  group2 = wc;
+	  break;
+	}
+      
+      p = next;
+    }
+
+  if (base)
+    add_cluster (font_info, glyphs, cluster_start, base, group1, group2);
+}
+
+static PangoCoverage *
+thai_engine_get_coverage (PangoFont  *font,
+			   const char *lang)
+{
+  PangoCoverage *result = pango_coverage_new ();
+  
+  ThaiFontInfo *font_info = get_font_info (font);
+  
+  if (font_info->type != THAI_FONT_NONE)
+    {
+      unicode_char_t wc;
+      
+      for (wc = 0xe01; wc <= 0xe3a; wc++)
+	pango_coverage_set (result, wc, PANGO_COVERAGE_EXACT);
+      for (wc = 0xe3f; wc <= 0xe5b; wc++)
+	pango_coverage_set (result, wc, PANGO_COVERAGE_EXACT);
+    }
+
+  return result;
+}
+
+static PangoEngine *
+thai_engine_x_new ()
+{
+  PangoEngineShape *result;
+  
+  result = g_new (PangoEngineShape, 1);
+
+  result->engine.id = "ThaiScriptEngine";
+  result->engine.type = PANGO_ENGINE_TYPE_LANG;
+  result->engine.length = sizeof (result);
+  result->script_shape = thai_engine_shape;
+  result->get_coverage = thai_engine_get_coverage;
+
+  return (PangoEngine *)result;
+}
+
+/* The following three functions provide the public module API for
+ * Pango. If we are compiling it is a module, then we name the
+ * entry points script_engine_list, etc. But if we are compiling
+ * it for inclusion directly in Pango, then we need them to
+ * to have distinct names for this module, so we prepend
+ * _pango_thai_
+ */
+#ifdef MODULE_PREFIX
+#define MODULE_ENTRY(func) _pango_thai_##func
+#else
+#define MODULE_ENTRY(func) func
+#endif
+
+/* List the engines contained within this module
+ */
+void 
+MODULE_ENTRY(script_engine_list) (PangoEngineInfo **engines, gint *n_engines)
+{
+  *engines = script_engines;
+  *n_engines = G_N_ELEMENTS (script_engines);
+}
+
+/* Load a particular engine given the ID for the engine
+ */
+PangoEngine *
+MODULE_ENTRY(script_engine_load) (const char *id)
+{
+  if (!strcmp (id, "ThaiScriptEngineLang"))
+    return thai_engine_lang_new ();
+  else if (!strcmp (id, "ThaiScriptEngineX"))
+    return thai_engine_x_new ();
+  else
+    return NULL;
+}
+
+void 
+MODULE_ENTRY(script_engine_unload) (PangoEngine *engine)
+{
+}
+