1 2 /* 3 * Copyright 2006 The Android Open Source Project 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #ifndef SkFontHost_DEFINED 11 #define SkFontHost_DEFINED 12 13 #include "SkScalerContext.h" 14 #include "SkTypeface.h" 15 16 class SkDescriptor; 17 class SkStream; 18 class SkWStream; 19 20 typedef uint32_t SkFontTableTag; 21 22 /** \class SkFontHost 23 24 This class is ported to each environment. It is responsible for bridging 25 the gap between the (sort of) abstract class SkTypeface and the 26 platform-specific implementation that provides access to font files. 27 28 One basic task is for each create (subclass of) SkTypeface, the FontHost is 29 resonsible for assigning a uniqueID. The ID should be unique for the 30 underlying font file/data, not unique per typeface instance. Thus it is 31 possible/common to request a typeface for the same font more than once 32 (e.g. asking for the same font by name several times). The FontHost may 33 return seperate typeface instances in that case, or it may choose to use a 34 cache and return the same instance (but calling typeface->ref(), since the 35 caller is always responsible for calling unref() on each instance that is 36 returned). Either way, the fontID for those instance(s) will be the same. 37 In addition, the fontID should never be set to 0. That value is used as a 38 sentinel to indicate no-font-id. 39 40 The major aspects are: 41 1) Given either a name/style, return a subclass of SkTypeface that 42 references the closest matching font available on the host system. 43 2) Given the data for a font (either in a stream or a file name), return 44 a typeface that allows access to that data. 45 3) Each typeface instance carries a 32bit ID for its corresponding font. 46 SkFontHost turns that ID into a stream to access the font's data. 47 4) Given a font ID, return a subclass of SkScalerContext, which connects a 48 font scaler (e.g. freetype or other) to the font's data. 49 5) Utilites to manage the font cache (budgeting) and gamma correction 50 */ 51 class SK_API SkFontHost { 52 public: 53 /** Return a new, closest matching typeface given either an existing family 54 (specified by a typeface in that family) or by a familyName and a 55 requested style, or by a set of Unicode codepoitns to cover in a given 56 style. 57 1) If familyFace is null, use familyName. 58 2) If familyName is null, use data (UTF-16 to cover). 59 3) If all are null, return the default font that best matches style 60 */ 61 static SkTypeface* CreateTypeface(const SkTypeface* familyFace, 62 const char familyName[], 63 const void* data, size_t bytelength, 64 SkTypeface::Style style); 65 66 /** Return a new typeface given the data buffer. If the data does not 67 represent a valid font, returns null. 68 69 If a typeface instance is returned, the caller is responsible for 70 calling unref() on the typeface when they are finished with it. 71 72 The returned typeface may or may not have called ref() on the stream 73 parameter. If the typeface has not called ref(), then it may have made 74 a copy of the releveant data. In either case, the caller is still 75 responsible for its refcnt ownership of the stream. 76 */ 77 static SkTypeface* CreateTypefaceFromStream(SkStream*); 78 79 /** Return a new typeface from the specified file path. If the file does not 80 represent a valid font, this returns null. If a typeface is returned, 81 the caller is responsible for calling unref() when it is no longer used. 82 */ 83 static SkTypeface* CreateTypefaceFromFile(const char path[]); 84 85 /////////////////////////////////////////////////////////////////////////// 86 87 /** Return a new stream to read the font data, or null if the uniqueID does 88 not match an existing typeface. .The caller must call stream->unref() 89 when it is finished reading the data. 90 */ 91 static SkStream* OpenStream(SkFontID uniqueID); 92 93 /** Some fonts are stored in files. If that is true for the fontID, then 94 this returns the byte length of the full file path. If path is not null, 95 then the full path is copied into path (allocated by the caller), up to 96 length bytes. If index is not null, then it is set to the truetype 97 collection index for this font, or 0 if the font is not in a collection. 98 99 Note: GetFileName does not assume that path is a null-terminated string, 100 so when it succeeds, it only copies the bytes of the file name and 101 nothing else (i.e. it copies exactly the number of bytes returned by the 102 function. If the caller wants to treat path[] as a C string, it must be 103 sure that it is allocated at least 1 byte larger than the returned size, 104 and it must copy in the terminating 0. 105 106 If the fontID does not correspond to a file, then the function returns 107 0, and the path and index parameters are ignored. 108 109 @param fontID The font whose file name is being queried 110 @param path Either NULL, or storage for receiving up to length bytes 111 of the font's file name. Allocated by the caller. 112 @param length The maximum space allocated in path (by the caller). 113 Ignored if path is NULL. 114 @param index Either NULL, or receives the TTC index for this font. 115 If the font is not a TTC, then will be set to 0. 116 @return The byte length of th font's file name, or 0 if the font is not 117 baked by a file. 118 */ 119 static size_t GetFileName(SkFontID fontID, char path[], size_t length, 120 int32_t* index); 121 122 /////////////////////////////////////////////////////////////////////////// 123 124 /** Write a unique identifier to the stream, so that the same typeface can 125 be retrieved with Deserialize(). 126 */ 127 static void Serialize(const SkTypeface*, SkWStream*); 128 129 /** Given a stream created by Serialize(), return a new typeface (like 130 CreateTypeface) or return NULL if no match is found. 131 */ 132 static SkTypeface* Deserialize(SkStream*); 133 134 /////////////////////////////////////////////////////////////////////////// 135 136 /** Return a subclass of SkScalarContext 137 */ 138 static SkScalerContext* CreateScalerContext(const SkDescriptor* desc); 139 140 /** 141 * Given a "current" fontID, return the next logical fontID to use 142 * when searching fonts for a given unicode value. Typically the caller 143 * will query a given font, and if a unicode value is not supported, they 144 * will call this, and if 0 is not returned, will search that font, and so 145 * on. This process must be finite, and when the fonthost sees a 146 * font with no logical successor, it must return 0. 147 * 148 * The original fontID is also provided. This is the initial font that was 149 * stored in the typeface of the caller. It is provided as an aid to choose 150 * the best next logical font. e.g. If the original font was bold or serif, 151 * but the 2nd in the logical chain was plain, then a subsequent call to 152 * get the 3rd can still inspect the original, and try to match its 153 * stylistic attributes. 154 */ 155 static SkFontID NextLogicalFont(SkFontID currFontID, SkFontID origFontID); 156 157 #ifdef SK_BUILD_FOR_ANDROID 158 /* 159 * This Android-only version of NextLogicalFont allows us to pass in an 160 * entire Rec structure so that a caller can change fallback behavior 161 */ 162 static SkFontID NextLogicalFont(const SkScalerContext::Rec& rec); 163 #endif 164 165 166 /////////////////////////////////////////////////////////////////////////// 167 168 /** Given a filled-out rec, the fonthost may decide to modify it to reflect 169 what the host is actually capable of fulfilling. For example, if the 170 rec is requesting a level of hinting that, for this host, maps some 171 other level (e.g. kFull -> kNormal), it should update the rec to reflect 172 what will actually be done. This is an optimization so that the font 173 cache does not contain different recs (i.e. keys) that in reality map to 174 the same output. 175 176 A lazy (but valid) fonthost can do nothing in its FilterRec routine. 177 */ 178 static void FilterRec(SkScalerContext::Rec* rec); 179 180 /////////////////////////////////////////////////////////////////////////// 181 182 /** Retrieve detailed typeface metrics. Used by the PDF backend. 183 @param perGlyphInfo Indicate what glyph specific information (advances, 184 names, etc.) should be populated. 185 @return The returned object has already been referenced. NULL is 186 returned if the font is not found. 187 @param glyphIDs For per-glyph info, specify subset of the font by 188 giving glyph ids. Each integer represents a glyph 189 id. Passing NULL means all glyphs in the font. 190 @param glyphIDsCount Number of elements in subsetGlyphIds. Ignored if 191 glyphIDs is NULL. 192 */ 193 static SkAdvancedTypefaceMetrics* GetAdvancedTypefaceMetrics( 194 SkFontID fontID, 195 SkAdvancedTypefaceMetrics::PerGlyphInfo perGlyphInfo, 196 const uint32_t* glyphIDs, 197 uint32_t glyphIDsCount); 198 199 /** Return the number of tables in the font 200 */ 201 static int CountTables(SkFontID); 202 203 /** Copy into tags[] (allocated by the caller) the list of table tags in 204 the font, and return the number. This will be the same as CountTables() 205 or 0 if an error occured. 206 */ 207 static int GetTableTags(SkFontID, SkFontTableTag[]); 208 209 /** Given a table tag, return the size of its contents, or 0 if not present 210 */ 211 static size_t GetTableSize(SkFontID, SkFontTableTag); 212 213 /** Copy the contents of a table into data (allocated by the caller). Note 214 that the contents of the table will be in their native endian order 215 (which for most truetype tables is big endian). If the table tag is 216 not found, or there is an error copying the data, then 0 is returned. 217 If this happens, it is possible that some or all of the memory pointed 218 to by data may have been written to, even though an error has occured. 219 220 @param fontID the font to copy the table from 221 @param tag The table tag whose contents are to be copied 222 @param offset The offset in bytes into the table's contents where the 223 copy should start from. 224 @param length The number of bytes, starting at offset, of table data 225 to copy. 226 @param data storage address where the table contents are copied to 227 @return the number of bytes actually copied into data. If offset+length 228 exceeds the table's size, then only the bytes up to the table's 229 size are actually copied, and this is the value returned. If 230 offset > the table's size, or tag is not a valid table, 231 then 0 is returned. 232 */ 233 static size_t GetTableData(SkFontID fontID, SkFontTableTag tag, 234 size_t offset, size_t length, void* data); 235 236 /////////////////////////////////////////////////////////////////////////// 237 238 /** DEPRECATED -- only called by SkFontHost_FreeType internally 239 240 Return NULL or a pointer to 256 bytes for the black (table[0]) and 241 white (table[1]) gamma tables. 242 */ 243 static void GetGammaTables(const uint8_t* tables[2]); 244 245 /////////////////////////////////////////////////////////////////////////// 246 247 /** LCDs either have their color elements arranged horizontally or 248 vertically. When rendering subpixel glyphs we need to know which way 249 round they are. 250 251 Note, if you change this after startup, you'll need to flush the glyph 252 cache because it'll have the wrong type of masks cached. 253 */ 254 enum LCDOrientation { 255 kHorizontal_LCDOrientation = 0, //!< this is the default 256 kVertical_LCDOrientation = 1, 257 }; 258 259 static void SetSubpixelOrientation(LCDOrientation orientation); 260 static LCDOrientation GetSubpixelOrientation(); 261 262 /** LCD color elements can vary in order. For subpixel text we need to know 263 the order which the LCDs uses so that the color fringes are in the 264 correct place. 265 266 Note, if you change this after startup, you'll need to flush the glyph 267 cache because it'll have the wrong type of masks cached. 268 269 kNONE_LCDOrder means that the subpixel elements are not spatially 270 separated in any usable fashion. 271 */ 272 enum LCDOrder { 273 kRGB_LCDOrder = 0, //!< this is the default 274 kBGR_LCDOrder = 1, 275 kNONE_LCDOrder = 2, 276 }; 277 278 static void SetSubpixelOrder(LCDOrder order); 279 static LCDOrder GetSubpixelOrder(); 280 281 #ifdef SK_BUILD_FOR_ANDROID 282 /////////////////////////////////////////////////////////////////////////// 283 284 /** 285 * Return the number of font units per em. 286 * 287 * @param fontID the font to query. 288 * @return the number of font units per em or 0 on error. 289 */ 290 static uint32_t GetUnitsPerEm(SkFontID fontID); 291 #endif 292 293 /** If Skia is running in a constrained environment and the typeface 294 implementation is handle based, the typeface data may become 295 unavailable asynchronously. If a font host or scaler context method is 296 unable to access font data, it may call this function as a request to 297 make the handle contained in the typeface useable. 298 */ 299 static void EnsureTypefaceAccessible(const SkTypeface& typeface); 300 }; 301 302 #endif 303
