pango arabic ft2 module

[Christian <chri ascensit com>]

Hi, I adapted the arabic-ot to be used with ft2. I need this in the
context of an application displaying arabic text on linux framebuffer.
GTK2fb/Pango works great, thanks! I'm attaching the code if it's
useful to someone else. I just have a question about the subindex font
of ft2 interface. I had to add the following kludge (if
subfont_index==0 ....) in pangoft2.c:


pango_ft2_get_face (PangoFont      *font,
                    PangoFT2Subfont subfont_index)
{

....

  if (subfont_index==0) subfont_index++;
  if (subfont_index < 1 || subfont_index > ft2font->n_fonts)

......
  

may you point me to the right solution?

Thanks for the great stuff that is pango .... it's amazing to sit
down and look at the anti-aliased rendering of strange foreing
languages! :-)

-------------8<--------arabic-ft2.c-----------------------

/* Pango - Arabic module 
 * arabic module
 *
 * (C) 2001 Christian Pellegrin <chri ascensit com>
 *          ported to FT2 with small modifications
 * (C) 2000 Karl Koehler<koehler or uni-bonn de>
 *          Owen Taylor <otaylor redhat com> 
 * 
 */

#include <stdio.h>
#include <glib.h>
#include <string.h>


#include "pango-layout.h"
#include "pango-engine.h"
#include "pangoft2.h"
#include "pango-utils.h"
#include "arabic-ot.h"


// #define DEBUG 
#ifdef DEBUG
#include <stdio.h>
#endif

#define SCRIPT_ENGINE_NAME "ArabicScriptEngineFT2" 

/* taken from arabic-xft */

static PangoEngineRange arabic_ranges[] = {
  /* Language characters */
  { 0x060c, 0x06f9, "*" }, /* Arabic */
};

static PangoEngineInfo script_engines[] = {
  {
    SCRIPT_ENGINE_NAME,
    PANGO_ENGINE_TYPE_SHAPE,
    PANGO_RENDER_TYPE_FT2,
    arabic_ranges, G_N_ELEMENTS(arabic_ranges)
  }
};

static gint n_script_engines = G_N_ELEMENTS (script_engines);

void
maybe_add_feature (PangoOTRuleset *ruleset,
		   PangoOTInfo    *info,
		   guint           script_index,
		   PangoOTTag      tag,
		   gulong          property_bit)
{
  guint feature_index;
  
  /* 0xffff == default language system */
  if (pango_ot_info_find_feature (info, PANGO_OT_TABLE_GSUB,
				  tag, script_index, 0xffff, &feature_index))
    pango_ot_ruleset_add_feature (ruleset, PANGO_OT_TABLE_GSUB, feature_index,
				  property_bit);
}

static PangoOTRuleset *
get_ruleset (PangoFont *font)
{
  PangoOTRuleset *ruleset;
  static GQuark ruleset_quark = 0;

//  PangoOTInfo *info = pango_xft_font_get_ot_info (font);
  PangoOTInfo *info = pango_ot_info_new(pango_ft2_get_face(font,1));

  if (!ruleset_quark)
    ruleset_quark = g_quark_from_string ("pango-arabic-ruleset");
  
  if (!info)
    return NULL;

  ruleset = g_object_get_qdata (G_OBJECT (font), ruleset_quark);

  if (!ruleset)
    {
      PangoOTTag arab_tag = FT_MAKE_TAG ('a', 'r', 'a', 'b');
      guint script_index;

      ruleset = pango_ot_ruleset_new (info);

      if (pango_ot_info_find_script (info, PANGO_OT_TABLE_GSUB,
				     arab_tag, &script_index))
	{
	  maybe_add_feature (ruleset, info, script_index, FT_MAKE_TAG ('i','s','o','l'), isolated);
	  maybe_add_feature (ruleset, info, script_index, FT_MAKE_TAG ('i','n','i','t'), initial);
	  maybe_add_feature (ruleset, info, script_index, FT_MAKE_TAG ('m','e','d','i'), medial);
	  maybe_add_feature (ruleset, info, script_index, FT_MAKE_TAG ('f','i','n','a'), final);
	  maybe_add_feature (ruleset, info, script_index, FT_MAKE_TAG ('l','i','g','a'), 0xFFFF);
	}

      g_object_set_qdata_full (G_OBJECT (font), ruleset_quark, ruleset,
			       (GDestroyNotify)g_object_unref);
    }

  return ruleset;
}

static void
swap_range (PangoGlyphString *glyphs, int start, int end)
{
  int i, j;
  
  for (i = start, j = end - 1; i < j; i++, j--)
    {
      PangoGlyphInfo glyph_info;
      gint log_cluster;
      
      glyph_info = glyphs->glyphs[i];
      glyphs->glyphs[i] = glyphs->glyphs[j];
      glyphs->glyphs[j] = glyph_info;
      
      log_cluster = glyphs->log_clusters[i];
      glyphs->log_clusters[i] = glyphs->log_clusters[j];
      glyphs->log_clusters[j] = log_cluster;
    }
}

static void
set_glyph (PangoFont *font, PangoGlyphString *glyphs, int i, int offset, PangoGlyph glyph)
{
  glyphs->glyphs[i].glyph = glyph;
  glyphs->log_clusters[i] = offset;
}

static guint
find_char (FT_Face face, PangoFont *font, gunichar wc)
{
  int index = FT_Get_Char_Index (face, wc);

  if (index && index <= face->num_glyphs)
    return index;
  else
    return 0;
}


static void 
arabic_engine_shape (PangoFont        *font,
		    const char       *text,
		    gint              length,
		    PangoAnalysis    *analysis,
		    PangoGlyphString *glyphs)
{
  int n_chars;
  int i;
  const char *p;
  gulong *properties = NULL;
  gunichar *wcs = NULL;
  FT_Face face;
  PangoOTRuleset *ruleset;

  g_return_if_fail (font != NULL);
  g_return_if_fail (text != NULL);
  g_return_if_fail (length >= 0);
  g_return_if_fail (analysis != NULL);

  face = pango_ft2_get_face (font,1);
  g_assert (face);

  n_chars = g_utf8_strlen (text, length);
  pango_glyph_string_set_size (glyphs, n_chars);

  ruleset = get_ruleset (font);
  if (ruleset)
    {
      wcs = g_utf8_to_ucs4_fast (text, length, NULL);
      properties = g_new0 (gulong, n_chars);
      
      Assign_Arabic_Properties (wcs, properties, n_chars);
    }
  
  p = text;
  for (i=0; i < n_chars; i++)
    {
      gunichar wc;
      gunichar mirrored_ch;
      PangoGlyph index;
      char buf[6];
      const char *input;

      wc = g_utf8_get_char (p);

      input = p;
      if (analysis->level % 2)
	if (pango_get_mirror_char (wc, &mirrored_ch))
	  {
	    wc = mirrored_ch;
	    
	    g_unichar_to_utf8 (wc, buf);
	    input = buf;
	  }

      if (wc >= 0x200B && wc <= 0x200F)	/* Zero-width characters */
	{
	  set_glyph (font, glyphs, i, p - text, 0);
	}
      else
	{
	  /* Hack - Microsoft fonts are strange and don't contain the
	   * correct rules to shape ARABIC LETTER FARSI YEH in
	   * medial/initial position. It looks identical to ARABIC LETTER
	   * YEH in these positions, so we substitute
	   */
	  if (wc == 0x6cc && ruleset &&
	      ((properties[i] & (initial | medial)) != (initial | medial)))
	    wc = 0x64a;
	  
	  index = find_char (face, font, wc);

	  if (!index)
	    {
	      set_glyph (font, glyphs, i, p - text,
			 //pango_xft_font_get_unknown_glyph (font, wc));
			 pango_ft2_get_unknown_glyph(font));
	    }
	  else
	    {
	      set_glyph (font, glyphs, i, p - text, index);
	      
	      if (g_unichar_type (wc) == G_UNICODE_NON_SPACING_MARK)
		{
		  if (i > 0)
		    {
		      glyphs->log_clusters[i] = glyphs->log_clusters[i-1];
#if 0		      
		      PangoRectangle logical_rect, ink_rect;
		      
		      glyphs->glyphs[i].geometry.width = MAX (glyphs->glyphs[i-1].geometry.width,
							      glyphs->glyphs[i].geometry.width);
		      glyphs->glyphs[i-1].geometry.width = 0;
		      
		      /* Some heuristics to try to guess how overstrike glyphs are
		       * done and compensate
		       */
		      pango_font_get_glyph_extents (font, glyphs->glyphs[i].glyph, &ink_rect, &logical_rect);
		      if (logical_rect.width == 0 && ink_rect.x == 0)
			glyphs->glyphs[i].geometry.x_offset = (glyphs->glyphs[i].geometry.width - ink_rect.width) / 2;
#endif
		    }
		}
	    }
	}
      
      p = g_utf8_next_char (p);
    }

  ruleset = get_ruleset (font);

  if (ruleset)
    {
      pango_ot_ruleset_shape (ruleset, glyphs, properties);

      g_free (wcs);
      g_free (properties);

    }

  for (i = 0; i < glyphs->num_glyphs; i++)
    {

      if (glyphs->glyphs[i].glyph)
	{
	  PangoRectangle logical_rect;
	  
	  pango_font_get_glyph_extents (font, glyphs->glyphs[i].glyph, NULL, &logical_rect);
	  glyphs->glyphs[i].geometry.width = logical_rect.width;
	}
      else
	glyphs->glyphs[i].geometry.width = 0;
  
      glyphs->glyphs[i].geometry.x_offset = 0;
      glyphs->glyphs[i].geometry.y_offset = 0;
    }

  /* Simple bidi support */

  if (analysis->level % 2)
    {
      int start, end;

      /* Swap all glyphs */
      swap_range (glyphs, 0, glyphs->num_glyphs);
      
      /* Now reorder glyphs within each cluster back to LTR */
      for (start=0; start<glyphs->num_glyphs;)
	{
	  end = start;
	  while (end < glyphs->num_glyphs &&
		 glyphs->log_clusters[end] == glyphs->log_clusters[start])
	    end++;

	  if (end > start + 1)
	    swap_range (glyphs, start, end);
	  start = end;
	}
    }
}

static PangoCoverage *
arabic_engine_get_coverage (PangoFont  *font,
			   PangoLanguage *lang)
{
  gunichar i;
  PangoCoverage *result = pango_coverage_new ();
  
  for (i = 0x60B; i <= 0x66D; i++)
    pango_coverage_set (result, i, PANGO_COVERAGE_EXACT);
  for (i = 0x670; i <= 0x6D3; i++)
    pango_coverage_set (result, i, PANGO_COVERAGE_EXACT);
  
  return result;
}

static PangoEngine *
arabic_engine_ft2_new ()
{
  PangoEngineShape *result;
  
  result = g_new (PangoEngineShape, 1);

  result->engine.id = SCRIPT_ENGINE_NAME;
  result->engine.type = PANGO_ENGINE_TYPE_SHAPE;
  result->engine.length = sizeof (result);
  result->script_shape = arabic_engine_shape;
  result->get_coverage = arabic_engine_get_coverage;

  return (PangoEngine *)result;
}

/* end */


/* The following three functions provide the public module API for
 * Pango
 */
#ifdef X_MODULE_PREFIX
#define MODULE_ENTRY(func) _pango_arabic_ft2_##func
#else
#define MODULE_ENTRY(func) func
#endif

void 
MODULE_ENTRY(script_engine_list) (PangoEngineInfo **engines, int *n_engines)
{
    *engines   = script_engines;
    *n_engines = n_script_engines;
}

PangoEngine *
MODULE_ENTRY(script_engine_load) (const char *id)
{
  if (!strcmp (id, SCRIPT_ENGINE_NAME))
    return arabic_engine_ft2_new ();
  else
    return NULL;
}

void 
MODULE_ENTRY(script_engine_unload) (PangoEngine *engine)
{
}

-------------8<--------Makefile.am------------------------
## Process this file with automake to create Makefile.in.

pangolibs = $(top_builddir)/pango/libpango.la $(FRIBIDI_LIBS) $(GLIB_LIBS)
pangoxlibs = $(top_builddir)/pango/libpangox.la $(X_LIBS) $(pangolibs)
pangoxftlibs = $(top_builddir)/pango/libpangoxft.la $(pangolibs)
pangoft2libs = $(top_builddir)/pango/libpangoft2.la $(FREETYPE_LIBS) $(top_builddir)/pango/opentype/libpango-ot.la $(pangolibs)

if HAVE_XFT
if INCLUDE_ARABIC_XFT
XFT_MODULES=
XFT_INCLUDED=libpango-arabic-xft.la
XFT_PREFIX=-DXFT_MODULE_PREFIX
else
XFT_MODULES=pango-arabic-xft.la
XFT_INCLUDED=
XFT_PREFIX=
arabic_xft_libadd=$(pangoxftlibs)
endif
else
XFT_MODULES=
XFT_INCLUDED=
XFT_PREFIX=
endif

if HAVE_FREETYPE
if INCLUDE_ARABIC_FT2
FT2_MODULES=
FT2_INCLUDED=libpango-arabic-ft2.la
FT2_PREFIX=-DFT2_MODULE_PREFIX
else
FT2_MODULES=pango-arabic-ft2.la
FT2_INCLUDED=
FT2_PREFIX=
arabic_ft2_libadd=$(pangoft2libs)
endif
else
FT2_MODULES=
FT2_INCLUDED=
FT2_PREFIX=
endif


x_sources = \
	arabic-x.c \
	arconv.c \
	mulefont.c \
	mulefont.h \
	langboxfont.c \
	langboxfont.h \
	naqshfont.c \
	naqshfont.h \
	arconv.h 

xft_sources = \
	arabic-xft.c \
	arabic-ot.c \
	arabic-ot.h

ft2_sources = \
	arabic-ft2.c \
	arabic-ot.c \
	arabic-ot.h

if HAVE_X
if INCLUDE_ARABIC_X
X_MODULES=
X_INCLUDED=libpango-arabic-x.la
X_PREFIX=-DX_MODULE_PREFIX
else
X_MODULES=pango-arabic-x.la
X_INCLUDED=
X_PREFIX=
arabic_x_libadd=$(pangoxlibs)
endif
else
X_MODULES=
X_INCLUDED=
X_PREFIX=
endif

noinst_LTLIBRARIES = $(X_INCLUDED) $(XFT_INCLUDED) $(FT2_INCLUDED) 
module_LTLIBRARIES = $(X_MODULES) $(XFT_MODULES) $(FT2_MODULES)
moddefine = $(X_PREFIX) $(XFT_PREFIX) $(FT2_PREFIX) 
moduledir = $(libdir)/pango/modules

INCLUDES = -I$(top_srcdir) -I$(top_srcdir)/pango/ $(moddefine) $(X_CFLAGS) $(FREETYPE_CFLAGS)

pango_arabic_x_la_LDFLAGS = -export-dynamic -avoid-version -module
pango_arabic_x_la_LIBADD = $(arabic_x_libadd)
pango_arabic_x_la_SOURCES = $(x_sources)

libpango_arabic_x_la_SOURCES = $(x_sources)

pango_arabic_xft_la_LDFLAGS = -export-dynamic -avoid-version -module
pango_arabic_xft_la_LIBADD = $(arabic_xft_libadd)
pango_arabic_xft_la_SOURCES = $(xft_sources)

libpango_arabic_xft_la_SOURCES = $(xft_sources)

pango_arabic_ft2_la_LDFLAGS = -export-dynamic -avoid-version -module
pango_arabic_ft2_la_LIBADD = $(arabic_ft2_libadd)
pango_arabic_ft2_la_SOURCES = $(ft2_sources)

libpango_arabic_ft2_la_SOURCES = $(ft2_sources)

included-modules: $(noinst_LTLIBRARIES)

.PHONY: included-modules