1 /* 2 * Copyright (C) 2006 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef SkFontHost_DEFINED 18 #define SkFontHost_DEFINED 19 20 #include "SkScalerContext.h" 21 #include "SkTypeface.h" 22 23 class SkDescriptor; 24 class SkStream; 25 class SkWStream; 26 27 typedef uint32_t SkFontTableTag; 28 29 /** \class SkFontHost 30 31 This class is ported to each environment. It is responsible for bridging 32 the gap between the (sort of) abstract class SkTypeface and the 33 platform-specific implementation that provides access to font files. 34 35 One basic task is for each create (subclass of) SkTypeface, the FontHost is 36 resonsible for assigning a uniqueID. The ID should be unique for the 37 underlying font file/data, not unique per typeface instance. Thus it is 38 possible/common to request a typeface for the same font more than once 39 (e.g. asking for the same font by name several times). The FontHost may 40 return seperate typeface instances in that case, or it may choose to use a 41 cache and return the same instance (but calling typeface->ref(), since the 42 caller is always responsible for calling unref() on each instance that is 43 returned). Either way, the fontID for those instance(s) will be the same. 44 In addition, the fontID should never be set to 0. That value is used as a 45 sentinel to indicate no-font-id. 46 47 The major aspects are: 48 1) Given either a name/style, return a subclass of SkTypeface that 49 references the closest matching font available on the host system. 50 2) Given the data for a font (either in a stream or a file name), return 51 a typeface that allows access to that data. 52 3) Each typeface instance carries a 32bit ID for its corresponding font. 53 SkFontHost turns that ID into a stream to access the font's data. 54 4) Given a font ID, return a subclass of SkScalerContext, which connects a 55 font scaler (e.g. freetype or other) to the font's data. 56 5) Utilites to manage the font cache (budgeting) and gamma correction 57 */ 58 class SK_API SkFontHost { 59 public: 60 /** Return a new, closest matching typeface given either an existing family 61 (specified by a typeface in that family) or by a familyName and a 62 requested style, or by a set of Unicode codepoitns to cover in a given 63 style. 64 1) If familyFace is null, use familyName. 65 2) If familyName is null, use data (UTF-16 to cover). 66 3) If all are null, return the default font that best matches style 67 */ 68 static SkTypeface* CreateTypeface(const SkTypeface* familyFace, 69 const char familyName[], 70 const void* data, size_t bytelength, 71 SkTypeface::Style style); 72 73 /** Return a new typeface given the data buffer. If the data does not 74 represent a valid font, returns null. 75 76 If a typeface instance is returned, the caller is responsible for 77 calling unref() on the typeface when they are finished with it. 78 79 The returned typeface may or may not have called ref() on the stream 80 parameter. If the typeface has not called ref(), then it may have made 81 a copy of the releveant data. In either case, the caller is still 82 responsible for its refcnt ownership of the stream. 83 */ 84 static SkTypeface* CreateTypefaceFromStream(SkStream*); 85 86 /** Return a new typeface from the specified file path. If the file does not 87 represent a valid font, this returns null. If a typeface is returned, 88 the caller is responsible for calling unref() when it is no longer used. 89 */ 90 static SkTypeface* CreateTypefaceFromFile(const char path[]); 91 92 /////////////////////////////////////////////////////////////////////////// 93 94 /** Returns true if the specified unique ID matches an existing font. 95 Returning false is similar to calling OpenStream with an invalid ID, 96 which will return NULL in that case. 97 */ 98 static bool ValidFontID(SkFontID uniqueID); 99 100 /** Return a new stream to read the font data, or null if the uniqueID does 101 not match an existing typeface. .The caller must call stream->unref() 102 when it is finished reading the data. 103 */ 104 static SkStream* OpenStream(SkFontID uniqueID); 105 106 /** Some fonts are stored in files. If that is true for the fontID, then 107 this returns the byte length of the full file path. If path is not null, 108 then the full path is copied into path (allocated by the caller), up to 109 length bytes. If index is not null, then it is set to the truetype 110 collection index for this font, or 0 if the font is not in a collection. 111 112 Note: GetFileName does not assume that path is a null-terminated string, 113 so when it succeeds, it only copies the bytes of the file name and 114 nothing else (i.e. it copies exactly the number of bytes returned by the 115 function. If the caller wants to treat path[] as a C string, it must be 116 sure that it is allocated at least 1 byte larger than the returned size, 117 and it must copy in the terminating 0. 118 119 If the fontID does not correspond to a file, then the function returns 120 0, and the path and index parameters are ignored. 121 122 @param fontID The font whose file name is being queried 123 @param path Either NULL, or storage for receiving up to length bytes 124 of the font's file name. Allocated by the caller. 125 @param length The maximum space allocated in path (by the caller). 126 Ignored if path is NULL. 127 @param index Either NULL, or receives the TTC index for this font. 128 If the font is not a TTC, then will be set to 0. 129 @return The byte length of th font's file name, or 0 if the font is not 130 baked by a file. 131 */ 132 static size_t GetFileName(SkFontID fontID, char path[], size_t length, 133 int32_t* index); 134 135 /////////////////////////////////////////////////////////////////////////// 136 137 /** Write a unique identifier to the stream, so that the same typeface can 138 be retrieved with Deserialize(). 139 */ 140 static void Serialize(const SkTypeface*, SkWStream*); 141 142 /** Given a stream created by Serialize(), return a new typeface (like 143 CreateTypeface) or return NULL if no match is found. 144 */ 145 static SkTypeface* Deserialize(SkStream*); 146 147 /////////////////////////////////////////////////////////////////////////// 148 149 /** Return a subclass of SkScalarContext 150 */ 151 static SkScalerContext* CreateScalerContext(const SkDescriptor* desc); 152 153 /** 154 * Given a "current" fontID, return the next logical fontID to use 155 * when searching fonts for a given unicode value. Typically the caller 156 * will query a given font, and if a unicode value is not supported, they 157 * will call this, and if 0 is not returned, will search that font, and so 158 * on. This process must be finite, and when the fonthost sees a 159 * font with no logical successor, it must return 0. 160 * 161 * The original fontID is also provided. This is the initial font that was 162 * stored in the typeface of the caller. It is provided as an aid to choose 163 * the best next logical font. e.g. If the original font was bold or serif, 164 * but the 2nd in the logical chain was plain, then a subsequent call to 165 * get the 3rd can still inspect the original, and try to match its 166 * stylistic attributes. 167 */ 168 static SkFontID NextLogicalFont(SkFontID currFontID, SkFontID origFontID); 169 170 /////////////////////////////////////////////////////////////////////////// 171 172 /** Given a filled-out rec, the fonthost may decide to modify it to reflect 173 what the host is actually capable of fulfilling. For example, if the 174 rec is requesting a level of hinting that, for this host, maps some 175 other level (e.g. kFull -> kNormal), it should update the rec to reflect 176 what will actually be done. This is an optimization so that the font 177 cache does not contain different recs (i.e. keys) that in reality map to 178 the same output. 179 180 A lazy (but valid) fonthost can do nothing in its FilterRec routine. 181 */ 182 static void FilterRec(SkScalerContext::Rec* rec); 183 184 /////////////////////////////////////////////////////////////////////////// 185 186 /** Retrieve detailed typeface metrics. Used by the PDF backend. 187 @param perGlyphInfo Indicate what glyph specific information (advances, 188 names, etc.) should be populated. 189 @return The returned object has already been referenced. NULL is 190 returned if the font is not found. 191 */ 192 static SkAdvancedTypefaceMetrics* GetAdvancedTypefaceMetrics( 193 SkFontID fontID, 194 SkAdvancedTypefaceMetrics::PerGlyphInfo perGlyphInfo); 195 196 /** Return the number of tables in the font 197 */ 198 static int CountTables(SkFontID); 199 200 /** Copy into tags[] (allocated by the caller) the list of table tags in 201 the font, and return the number. This will be the same as CountTables() 202 or 0 if an error occured. 203 */ 204 static int GetTableTags(SkFontID, SkFontTableTag[]); 205 206 /** Given a table tag, return the size of its contents, or 0 if not present 207 */ 208 static size_t GetTableSize(SkFontID, SkFontTableTag); 209 210 /** Copy the contents of a table into data (allocated by the caller). Note 211 that the contents of the table will be in their native endian order 212 (which for most truetype tables is big endian). If the table tag is 213 not found, or there is an error copying the data, then 0 is returned. 214 If this happens, it is possible that some or all of the memory pointed 215 to by data may have been written to, even though an error has occured. 216 217 @param fontID the font to copy the table from 218 @param tag The table tag whose contents are to be copied 219 @param offset The offset in bytes into the table's contents where the 220 copy should start from. 221 @param length The number of bytes, starting at offset, of table data 222 to copy. 223 @param data storage address where the table contents are copied to 224 @return the number of bytes actually copied into data. If offset+length 225 exceeds the table's size, then only the bytes up to the table's 226 size are actually copied, and this is the value returned. If 227 offset > the table's size, or tag is not a valid table, 228 then 0 is returned. 229 */ 230 static size_t GetTableData(SkFontID fontID, SkFontTableTag tag, 231 size_t offset, size_t length, void* data); 232 233 /////////////////////////////////////////////////////////////////////////// 234 235 /** Return the number of bytes (approx) that should be purged from the font 236 cache. The input parameter is the cache's estimate of how much as been 237 allocated by the cache so far. 238 To purge (basically) everything, return the input parameter. 239 To purge nothing, return 0 240 */ 241 static size_t ShouldPurgeFontCache(size_t sizeAllocatedSoFar); 242 243 /** Return SkScalerContext gamma flag, or 0, based on the paint that will be 244 used to draw something with antialiasing. 245 */ 246 static int ComputeGammaFlag(const SkPaint& paint); 247 248 /** Return NULL or a pointer to 256 bytes for the black (table[0]) and 249 white (table[1]) gamma tables. 250 */ 251 static void GetGammaTables(const uint8_t* tables[2]); 252 253 /////////////////////////////////////////////////////////////////////////// 254 255 /** LCDs either have their color elements arranged horizontally or 256 vertically. When rendering subpixel glyphs we need to know which way 257 round they are. 258 259 Note, if you change this after startup, you'll need to flush the glyph 260 cache because it'll have the wrong type of masks cached. 261 */ 262 enum LCDOrientation { 263 kHorizontal_LCDOrientation = 0, //!< this is the default 264 kVertical_LCDOrientation = 1, 265 }; 266 267 static void SetSubpixelOrientation(LCDOrientation orientation); 268 static LCDOrientation GetSubpixelOrientation(); 269 270 /** LCD color elements can vary in order. For subpixel text we need to know 271 the order which the LCDs uses so that the color fringes are in the 272 correct place. 273 274 Note, if you change this after startup, you'll need to flush the glyph 275 cache because it'll have the wrong type of masks cached. 276 277 kNONE_LCDOrder means that the subpixel elements are not spatially 278 separated in any usable fashion. 279 */ 280 enum LCDOrder { 281 kRGB_LCDOrder = 0, //!< this is the default 282 kBGR_LCDOrder = 1, 283 kNONE_LCDOrder = 2, 284 }; 285 286 static void SetSubpixelOrder(LCDOrder order); 287 static LCDOrder GetSubpixelOrder(); 288 289 #ifdef ANDROID 290 /////////////////////////////////////////////////////////////////////////// 291 292 /** 293 * Return the number of font units per em. 294 * 295 * @param fontID the font to query. 296 * @return the number of font units per em or 0 on error. 297 */ 298 static uint32_t GetUnitsPerEm(SkFontID fontID); 299 #endif 300 }; 301 302 #endif 303 304