src/ports/SkFontHost_fontconfig.cpp - platform/external/skia - Git at Google

 /* libs/graphics/ports/SkFontHost_fontconfig.cpp
 **
 ** Copyright 2008, Google Inc.
 **
 ** Licensed under the Apache License, Version 2.0 (the "License");
 ** you may not use this file except in compliance with the License.
 ** You may obtain a copy of the License at
 **
 **     http://www.apache.org/licenses/LICENSE-2.0
 **
 ** Unless required by applicable law or agreed to in writing, software
 ** distributed under the License is distributed on an "AS IS" BASIS,
 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 ** See the License for the specific language governing permissions and
 ** limitations under the License.
 */

 // -----------------------------------------------------------------------------
 // This file provides implementations of the font resolution members of
 // SkFontHost by using the fontconfig[1] library. Fontconfig is usually found
 // on Linux systems and handles configuration, parsing and caching issues
 // involved with enumerating and matching fonts.
 //
 // [1] http://fontconfig.org
 // -----------------------------------------------------------------------------

 #include <map>
 #include <string>

 #include <fontconfig/fontconfig.h>

 #include "SkFontHost.h"
 #include "SkStream.h"

 // This is an extern from SkFontHost_FreeType
 SkTypeface::Style find_name_and_style(SkStream* stream, SkString* name);

 // -----------------------------------------------------------------------------
 // The rest of Skia requires that fonts be identified by a unique unsigned id
 // and that we be able to load them given the id. What we actually get from
 // fontconfig is the filename of the font so we keep a locked map from
 // filenames to fileid numbers and back.
 //
 // Note that there's also a unique id in the SkTypeface. This is unique over
 // both filename and style. Thus we encode that id as (fileid << 8) | style.
 // Although truetype fonts can support multiple faces in a single file, at the
 // moment Skia doesn't.
 // -----------------------------------------------------------------------------
 static SkMutex global_fc_map_lock;
 static std::map<std::string, unsigned> global_fc_map;
 static std::map<unsigned, std::string> global_fc_map_inverted;
 static std::map<uint32_t, SkTypeface *> global_fc_typefaces;
 static unsigned global_fc_map_next_id = 0;

 // This is the maximum size of the font cache.
 static const unsigned kFontCacheMemoryBudget = 2 * 1024 * 1024;  // 2MB

 static unsigned UniqueIdToFileId(unsigned uniqueid)
 {
     return uniqueid >> 8;
 }

 static SkTypeface::Style UniqueIdToStyle(unsigned uniqueid)
 {
     return static_cast<SkTypeface::Style>(uniqueid & 0xff);
 }

 static unsigned FileIdAndStyleToUniqueId(unsigned fileid,
                                          SkTypeface::Style style)
 {
     SkASSERT((style & 0xff) == style);
     return (fileid << 8) | static_cast<int>(style);
 }

 // -----------------------------------------------------------------------------
 // Normally we only return exactly the font asked for. In last-resort cases,
 // the request is for one of the basic font names "Sans", "Serif" or
 // "Monospace". This function tells you whether a given request is for such a
 // fallback.
 // -----------------------------------------------------------------------------
 static bool IsFallbackFontAllowed(const char* request)
 {
     return strcmp(request, "Sans") == 0 ||
            strcmp(request, "Serif") == 0 ||
            strcmp(request, "Monospace") == 0;
 }

 class FontConfigTypeface : public SkTypeface {
 public:
     FontConfigTypeface(Style style, uint32_t id)
         : SkTypeface(style, id)
     { }
 };

 // -----------------------------------------------------------------------------
 // Find a matching font where @type (one of FC_*) is equal to @value. For a
 // list of types, see http://fontconfig.org/fontconfig-devel/x19.html#AEN27.
 // The variable arguments are a list of triples, just like the first three
 // arguments, and must be NULL terminated.
 //
 // For example,
 //   FontMatchString(FC_FILE, FcTypeString, "/usr/share/fonts/myfont.ttf",
 //                   NULL);
 // -----------------------------------------------------------------------------
 static FcPattern* FontMatch(const char* type, FcType vtype, const void* value,
                             ...)
 {
     va_list ap;
     va_start(ap, value);

     FcPattern* pattern = FcPatternCreate();
     const char* family_requested = NULL;

     for (;;) {
         FcValue fcvalue;
         fcvalue.type = vtype;
         switch (vtype) {
             case FcTypeString:
                 fcvalue.u.s = (FcChar8*) value;
                 break;
             case FcTypeInteger:
                 fcvalue.u.i = (int)(intptr_t)value;
                 break;
             default:
                 SkASSERT(!"FontMatch unhandled type");
         }
         FcPatternAdd(pattern, type, fcvalue, 0);

         if (vtype == FcTypeString && strcmp(type, FC_FAMILY) == 0)
             family_requested = (const char*) value;

         type = va_arg(ap, const char *);
         if (!type)
             break;
         // FcType is promoted to int when passed through ...
         vtype = static_cast<FcType>(va_arg(ap, int));
         value = va_arg(ap, const void *);
     };
     va_end(ap);

     FcConfigSubstitute(0, pattern, FcMatchPattern);
     FcDefaultSubstitute(pattern);

     // Font matching:
     // CSS often specifies a fallback list of families:
     //    font-family: a, b, c, serif;
     // However, fontconfig will always do its best to find *a* font when asked
     // for something so we need a way to tell if the match which it has found is
     // "good enough" for us. Otherwise, we can return NULL which gets piped up
     // and lets WebKit know to try the next CSS family name. However, fontconfig
     // configs allow substitutions (mapping "Arial -> Helvetica" etc) and we
     // wish to support that.
     //
     // Thus, if a specific family is requested we set @family_requested. Then we
     // record two strings: the family name after config processing and the
     // family name after resolving. If the two are equal, it's a good match.
     //
     // So consider the case where a user has mapped Arial to Helvetica in their
     // config.
     //    requested family: "Arial"
     //    post_config_family: "Helvetica"
     //    post_match_family: "Helvetica"
     //      -> good match
     //
     // and for a missing font:
     //    requested family: "Monaco"
     //    post_config_family: "Monaco"
     //    post_match_family: "Times New Roman"
     //      -> BAD match
     //
     // However, we special-case fallback fonts; see IsFallbackFontAllowed().
     FcChar8* post_config_family;
     FcPatternGetString(pattern, FC_FAMILY, 0, &post_config_family);

     FcResult result;
     FcPattern* match = FcFontMatch(0, pattern, &result);
     if (!match) {
         FcPatternDestroy(pattern);
         return NULL;
     }

     FcChar8* post_match_family;
     FcPatternGetString(match, FC_FAMILY, 0, &post_match_family);
     const bool family_names_match =
         !family_requested ?
         true :
         strcasecmp((char *)post_config_family, (char *)post_match_family) == 0;

     FcPatternDestroy(pattern);

     if (!family_names_match && !IsFallbackFontAllowed(family_requested)) {
         FcPatternDestroy(match);
         return NULL;
     }

     return match;
 }

 // -----------------------------------------------------------------------------
 // Check to see if the filename has already been assigned a fileid and, if so,
 // use it. Otherwise, assign one. Return the resulting fileid.
 // -----------------------------------------------------------------------------
 static unsigned FileIdFromFilename(const char* filename)
 {
     SkAutoMutexAcquire ac(global_fc_map_lock);

     std::map<std::string, unsigned>::const_iterator i =
         global_fc_map.find(filename);
     if (i == global_fc_map.end()) {
         const unsigned fileid = global_fc_map_next_id++;
         global_fc_map[filename] = fileid;
         global_fc_map_inverted[fileid] = filename;
         return fileid;
     } else {
         return i->second;
     }
 }

 // static
 SkTypeface* SkFontHost::CreateTypeface(const SkTypeface* familyFace,
                                        const char familyName[],
                                        const void* data, size_t bytelength,
                                        SkTypeface::Style style)
 {
     const char* resolved_family_name = NULL;
     FcPattern* face_match = NULL;

     {
         SkAutoMutexAcquire ac(global_fc_map_lock);
         FcInit();
     }

     if (familyFace) {
         // Here we use the inverted global id map to find the filename from the
         // SkTypeface object. Given the filename we can ask fontconfig for the
         // familyname of the font.
         SkAutoMutexAcquire ac(global_fc_map_lock);

         const unsigned fileid = UniqueIdToFileId(familyFace->uniqueID());
         std::map<unsigned, std::string>::const_iterator i =
             global_fc_map_inverted.find(fileid);
         if (i == global_fc_map_inverted.end())
             return NULL;

         FcInit();
         face_match = FontMatch(FC_FILE, FcTypeString, i->second.c_str(),
                                NULL);

         if (!face_match)
             return NULL;
         FcChar8* family;
         if (FcPatternGetString(face_match, FC_FAMILY, 0, &family)) {
             FcPatternDestroy(face_match);
             return NULL;
         }
         // At this point, @family is pointing into the @face_match object so we
         // cannot release it yet.

         resolved_family_name = reinterpret_cast<char*>(family);
     } else if (familyName) {
         resolved_family_name = familyName;
     } else {
         return NULL;
     }

     // At this point, we have a resolved_family_name from somewhere
     SkASSERT(resolved_family_name);

     const int bold = style & SkTypeface::kBold ?
                      FC_WEIGHT_BOLD : FC_WEIGHT_NORMAL;
     const int italic = style & SkTypeface::kItalic ?
                        FC_SLANT_ITALIC : FC_SLANT_ROMAN;
     FcPattern* match = FontMatch(FC_FAMILY, FcTypeString, resolved_family_name,
                                  FC_WEIGHT, FcTypeInteger, bold,
                                  FC_SLANT, FcTypeInteger, italic,
                                  NULL);
     if (face_match)
         FcPatternDestroy(face_match);

     if (!match)
         return NULL;

     FcChar8* filename;
     if (FcPatternGetString(match, FC_FILE, 0, &filename) != FcResultMatch) {
         FcPatternDestroy(match);
         return NULL;
     }
     // Now @filename is pointing into @match

     const unsigned fileid = FileIdFromFilename(reinterpret_cast<char*>(filename));
     const unsigned id = FileIdAndStyleToUniqueId(fileid, style);
     SkTypeface* typeface = SkNEW_ARGS(FontConfigTypeface, (style, id));
     FcPatternDestroy(match);

     {
         SkAutoMutexAcquire ac(global_fc_map_lock);
         global_fc_typefaces[id] = typeface;
     }

     return typeface;
 }

 // static
 SkTypeface* SkFontHost::CreateTypefaceFromStream(SkStream* stream)
 {
     SkASSERT(!"SkFontHost::CreateTypefaceFromStream unimplemented");
     return NULL;
 }

 // static
 SkTypeface* SkFontHost::CreateTypefaceFromFile(const char path[])
 {
     SkASSERT(!"SkFontHost::CreateTypefaceFromFile unimplemented");
     return NULL;
 }

 // static
 bool SkFontHost::ValidFontID(SkFontID uniqueID) {
     SkAutoMutexAcquire ac(global_fc_map_lock);
     return global_fc_typefaces.find(uniqueID) != global_fc_typefaces.end();
 }

 // static
 SkStream* SkFontHost::OpenStream(uint32_t id)
 {
     SkAutoMutexAcquire ac(global_fc_map_lock);
     const unsigned fileid = UniqueIdToFileId(id);

     std::map<unsigned, std::string>::const_iterator i =
         global_fc_map_inverted.find(fileid);
     if (i == global_fc_map_inverted.end())
         return NULL;

     return SkNEW_ARGS(SkFILEStream, (i->second.c_str()));
 }

 size_t SkFontHost::GetFileName(SkFontID fontID, char path[], size_t length,
                                int32_t* index) {
     SkAutoMutexAcquire ac(global_fc_map_lock);
     const unsigned fileid = UniqueIdToFileId(fontID);

     std::map<unsigned, std::string>::const_iterator i =
     global_fc_map_inverted.find(fileid);
     if (i == global_fc_map_inverted.end()) {
         return 0;
     }

     const std::string& str = i->second;
     if (path) {
         memcpy(path, str.c_str(), SkMin32(str.size(), length));
     }
     if (index) {    // TODO: check if we're in a TTC
         *index = 0;
     }
     return str.size();
 }

 void SkFontHost::Serialize(const SkTypeface*, SkWStream*) {
     SkASSERT(!"SkFontHost::Serialize unimplemented");
 }

 SkTypeface* SkFontHost::Deserialize(SkStream* stream) {
     SkASSERT(!"SkFontHost::Deserialize unimplemented");
     return NULL;
 }

 SkFontID SkFontHost::NextLogicalFont(SkFontID currFontID, SkFontID origFontID) {
     // We don't handle font fallback, WebKit does.
     return 0;
 }

 ///////////////////////////////////////////////////////////////////////////////

 size_t SkFontHost::ShouldPurgeFontCache(size_t sizeAllocatedSoFar)
 {
     if (sizeAllocatedSoFar > kFontCacheMemoryBudget)
         return sizeAllocatedSoFar - kFontCacheMemoryBudget;
     else
         return 0;   // nothing to do
 }
	/* libs/graphics/ports/SkFontHost_fontconfig.cpp
	**
	** Copyright 2008, Google Inc.
	**
	** Licensed under the Apache License, Version 2.0 (the "License");
	** you may not use this file except in compliance with the License.
	** You may obtain a copy of the License at
	**
	** http://www.apache.org/licenses/LICENSE-2.0
	**
	** Unless required by applicable law or agreed to in writing, software
	** distributed under the License is distributed on an "AS IS" BASIS,
	** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	** See the License for the specific language governing permissions and
	** limitations under the License.
	*/

	// -----------------------------------------------------------------------------
	// This file provides implementations of the font resolution members of
	// SkFontHost by using the fontconfig[1] library. Fontconfig is usually found
	// on Linux systems and handles configuration, parsing and caching issues
	// involved with enumerating and matching fonts.
	//
	// [1] http://fontconfig.org
	// -----------------------------------------------------------------------------

	#include <map>
	#include <string>

	#include <fontconfig/fontconfig.h>

	#include "SkFontHost.h"
	#include "SkStream.h"

	// This is an extern from SkFontHost_FreeType
	SkTypeface::Style find_name_and_style(SkStream* stream, SkString* name);

	// -----------------------------------------------------------------------------
	// The rest of Skia requires that fonts be identified by a unique unsigned id
	// and that we be able to load them given the id. What we actually get from
	// fontconfig is the filename of the font so we keep a locked map from
	// filenames to fileid numbers and back.
	//
	// Note that there's also a unique id in the SkTypeface. This is unique over
	// both filename and style. Thus we encode that id as (fileid << 8) \| style.
	// Although truetype fonts can support multiple faces in a single file, at the
	// moment Skia doesn't.
	// -----------------------------------------------------------------------------
	static SkMutex global_fc_map_lock;
	static std::map<std::string, unsigned> global_fc_map;
	static std::map<unsigned, std::string> global_fc_map_inverted;
	static std::map<uint32_t, SkTypeface *> global_fc_typefaces;
	static unsigned global_fc_map_next_id = 0;

	// This is the maximum size of the font cache.
	static const unsigned kFontCacheMemoryBudget = 2 * 1024 * 1024; // 2MB

	static unsigned UniqueIdToFileId(unsigned uniqueid)
	{
	return uniqueid >> 8;
	}

	static SkTypeface::Style UniqueIdToStyle(unsigned uniqueid)
	{
	return static_cast<SkTypeface::Style>(uniqueid & 0xff);
	}

	static unsigned FileIdAndStyleToUniqueId(unsigned fileid,
	SkTypeface::Style style)
	{
	SkASSERT((style & 0xff) == style);
	return (fileid << 8) \| static_cast<int>(style);
	}

	// -----------------------------------------------------------------------------
	// Normally we only return exactly the font asked for. In last-resort cases,
	// the request is for one of the basic font names "Sans", "Serif" or
	// "Monospace". This function tells you whether a given request is for such a
	// fallback.
	// -----------------------------------------------------------------------------
	static bool IsFallbackFontAllowed(const char* request)
	{
	return strcmp(request, "Sans") == 0 \|\|
	strcmp(request, "Serif") == 0 \|\|
	strcmp(request, "Monospace") == 0;
	}

	class FontConfigTypeface : public SkTypeface {
	public:
	FontConfigTypeface(Style style, uint32_t id)
	: SkTypeface(style, id)
	{ }
	};

	// -----------------------------------------------------------------------------
	// Find a matching font where @type (one of FC_*) is equal to @value. For a
	// list of types, see http://fontconfig.org/fontconfig-devel/x19.html#AEN27.
	// The variable arguments are a list of triples, just like the first three
	// arguments, and must be NULL terminated.
	//
	// For example,
	// FontMatchString(FC_FILE, FcTypeString, "/usr/share/fonts/myfont.ttf",
	// NULL);
	// -----------------------------------------------------------------------------
	static FcPattern* FontMatch(const char* type, FcType vtype, const void* value,
	...)
	{
	va_list ap;
	va_start(ap, value);

	FcPattern* pattern = FcPatternCreate();
	const char* family_requested = NULL;

	for (;;) {
	FcValue fcvalue;
	fcvalue.type = vtype;
	switch (vtype) {
	case FcTypeString:
	fcvalue.u.s = (FcChar8*) value;
	break;
	case FcTypeInteger:
	fcvalue.u.i = (int)(intptr_t)value;
	break;
	default:
	SkASSERT(!"FontMatch unhandled type");
	}
	FcPatternAdd(pattern, type, fcvalue, 0);

	if (vtype == FcTypeString && strcmp(type, FC_FAMILY) == 0)
	family_requested = (const char*) value;

	type = va_arg(ap, const char *);
	if (!type)
	break;
	// FcType is promoted to int when passed through ...
	vtype = static_cast<FcType>(va_arg(ap, int));
	value = va_arg(ap, const void *);
	};
	va_end(ap);

	FcConfigSubstitute(0, pattern, FcMatchPattern);
	FcDefaultSubstitute(pattern);

	// Font matching:
	// CSS often specifies a fallback list of families:
	// font-family: a, b, c, serif;
	// However, fontconfig will always do its best to find a font when asked
	// for something so we need a way to tell if the match which it has found is
	// "good enough" for us. Otherwise, we can return NULL which gets piped up
	// and lets WebKit know to try the next CSS family name. However, fontconfig
	// configs allow substitutions (mapping "Arial -> Helvetica" etc) and we
	// wish to support that.
	//
	// Thus, if a specific family is requested we set @family_requested. Then we
	// record two strings: the family name after config processing and the
	// family name after resolving. If the two are equal, it's a good match.
	//
	// So consider the case where a user has mapped Arial to Helvetica in their
	// config.
	// requested family: "Arial"
	// post_config_family: "Helvetica"
	// post_match_family: "Helvetica"
	// -> good match
	//
	// and for a missing font:
	// requested family: "Monaco"
	// post_config_family: "Monaco"
	// post_match_family: "Times New Roman"
	// -> BAD match
	//
	// However, we special-case fallback fonts; see IsFallbackFontAllowed().
	FcChar8* post_config_family;
	FcPatternGetString(pattern, FC_FAMILY, 0, &post_config_family);

	FcResult result;
	FcPattern* match = FcFontMatch(0, pattern, &result);
	if (!match) {
	FcPatternDestroy(pattern);
	return NULL;
	}

	FcChar8* post_match_family;
	FcPatternGetString(match, FC_FAMILY, 0, &post_match_family);
	const bool family_names_match =
	!family_requested ?
	true :
	strcasecmp((char )post_config_family, (char )post_match_family) == 0;

	FcPatternDestroy(pattern);

	if (!family_names_match && !IsFallbackFontAllowed(family_requested)) {
	FcPatternDestroy(match);
	return NULL;
	}

	return match;
	}

	// -----------------------------------------------------------------------------
	// Check to see if the filename has already been assigned a fileid and, if so,
	// use it. Otherwise, assign one. Return the resulting fileid.
	// -----------------------------------------------------------------------------
	static unsigned FileIdFromFilename(const char* filename)
	{
	SkAutoMutexAcquire ac(global_fc_map_lock);

	std::map<std::string, unsigned>::const_iterator i =
	global_fc_map.find(filename);
	if (i == global_fc_map.end()) {
	const unsigned fileid = global_fc_map_next_id++;
	global_fc_map[filename] = fileid;
	global_fc_map_inverted[fileid] = filename;
	return fileid;
	} else {
	return i->second;
	}
	}

	// static
	SkTypeface* SkFontHost::CreateTypeface(const SkTypeface* familyFace,
	const char familyName[],
	const void* data, size_t bytelength,
	SkTypeface::Style style)
	{
	const char* resolved_family_name = NULL;
	FcPattern* face_match = NULL;

	{
	SkAutoMutexAcquire ac(global_fc_map_lock);
	FcInit();
	}

	if (familyFace) {
	// Here we use the inverted global id map to find the filename from the
	// SkTypeface object. Given the filename we can ask fontconfig for the
	// familyname of the font.
	SkAutoMutexAcquire ac(global_fc_map_lock);

	const unsigned fileid = UniqueIdToFileId(familyFace->uniqueID());
	std::map<unsigned, std::string>::const_iterator i =
	global_fc_map_inverted.find(fileid);
	if (i == global_fc_map_inverted.end())
	return NULL;

	FcInit();
	face_match = FontMatch(FC_FILE, FcTypeString, i->second.c_str(),
	NULL);

	if (!face_match)
	return NULL;
	FcChar8* family;
	if (FcPatternGetString(face_match, FC_FAMILY, 0, &family)) {
	FcPatternDestroy(face_match);
	return NULL;
	}
	// At this point, @family is pointing into the @face_match object so we
	// cannot release it yet.

	resolved_family_name = reinterpret_cast<char*>(family);
	} else if (familyName) {
	resolved_family_name = familyName;
	} else {
	return NULL;
	}

	// At this point, we have a resolved_family_name from somewhere
	SkASSERT(resolved_family_name);

	const int bold = style & SkTypeface::kBold ?
	FC_WEIGHT_BOLD : FC_WEIGHT_NORMAL;
	const int italic = style & SkTypeface::kItalic ?
	FC_SLANT_ITALIC : FC_SLANT_ROMAN;
	FcPattern* match = FontMatch(FC_FAMILY, FcTypeString, resolved_family_name,
	FC_WEIGHT, FcTypeInteger, bold,
	FC_SLANT, FcTypeInteger, italic,
	NULL);
	if (face_match)
	FcPatternDestroy(face_match);

	if (!match)
	return NULL;

	FcChar8* filename;
	if (FcPatternGetString(match, FC_FILE, 0, &filename) != FcResultMatch) {
	FcPatternDestroy(match);
	return NULL;
	}
	// Now @filename is pointing into @match

	const unsigned fileid = FileIdFromFilename(reinterpret_cast<char*>(filename));
	const unsigned id = FileIdAndStyleToUniqueId(fileid, style);
	SkTypeface* typeface = SkNEW_ARGS(FontConfigTypeface, (style, id));
	FcPatternDestroy(match);

	{
	SkAutoMutexAcquire ac(global_fc_map_lock);
	global_fc_typefaces[id] = typeface;
	}

	return typeface;
	}

	// static
	SkTypeface* SkFontHost::CreateTypefaceFromStream(SkStream* stream)
	{
	SkASSERT(!"SkFontHost::CreateTypefaceFromStream unimplemented");
	return NULL;
	}

	// static
	SkTypeface* SkFontHost::CreateTypefaceFromFile(const char path[])
	{
	SkASSERT(!"SkFontHost::CreateTypefaceFromFile unimplemented");
	return NULL;
	}

	// static
	bool SkFontHost::ValidFontID(SkFontID uniqueID) {
	SkAutoMutexAcquire ac(global_fc_map_lock);
	return global_fc_typefaces.find(uniqueID) != global_fc_typefaces.end();
	}

	// static
	SkStream* SkFontHost::OpenStream(uint32_t id)
	{
	SkAutoMutexAcquire ac(global_fc_map_lock);
	const unsigned fileid = UniqueIdToFileId(id);

	std::map<unsigned, std::string>::const_iterator i =
	global_fc_map_inverted.find(fileid);
	if (i == global_fc_map_inverted.end())
	return NULL;

	return SkNEW_ARGS(SkFILEStream, (i->second.c_str()));
	}

	size_t SkFontHost::GetFileName(SkFontID fontID, char path[], size_t length,
	int32_t* index) {
	SkAutoMutexAcquire ac(global_fc_map_lock);
	const unsigned fileid = UniqueIdToFileId(fontID);

	std::map<unsigned, std::string>::const_iterator i =
	global_fc_map_inverted.find(fileid);
	if (i == global_fc_map_inverted.end()) {
	return 0;
	}

	const std::string& str = i->second;
	if (path) {
	memcpy(path, str.c_str(), SkMin32(str.size(), length));
	}
	if (index) { // TODO: check if we're in a TTC
	*index = 0;
	}
	return str.size();
	}

	void SkFontHost::Serialize(const SkTypeface, SkWStream) {
	SkASSERT(!"SkFontHost::Serialize unimplemented");
	}

	SkTypeface* SkFontHost::Deserialize(SkStream* stream) {
	SkASSERT(!"SkFontHost::Deserialize unimplemented");
	return NULL;
	}

	SkFontID SkFontHost::NextLogicalFont(SkFontID currFontID, SkFontID origFontID) {
	// We don't handle font fallback, WebKit does.
	return 0;
	}

	///////////////////////////////////////////////////////////////////////////////

	size_t SkFontHost::ShouldPurgeFontCache(size_t sizeAllocatedSoFar)
	{
	if (sizeAllocatedSoFar > kFontCacheMemoryBudget)
	return sizeAllocatedSoFar - kFontCacheMemoryBudget;
	else
	return 0; // nothing to do
	}