| /* |
| * Copyright (C) 2006 The Android Open Source Project |
| * |
| * 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. |
| */ |
| |
| #ifndef SkFontHost_DEFINED |
| #define SkFontHost_DEFINED |
| |
| #include "SkScalerContext.h" |
| #include "SkTypeface.h" |
| |
| class SkDescriptor; |
| class SkStream; |
| class SkWStream; |
| |
| typedef uint32_t SkFontID; |
| typedef uint32_t SkFontTableTag; |
| |
| /** \class SkFontHost |
| |
| This class is ported to each environment. It is responsible for bridging |
| the gap between the (sort of) abstract class SkTypeface and the |
| platform-specific implementation that provides access to font files. |
| |
| One basic task is for each create (subclass of) SkTypeface, the FontHost is |
| resonsible for assigning a uniqueID. The ID should be unique for the |
| underlying font file/data, not unique per typeface instance. Thus it is |
| possible/common to request a typeface for the same font more than once |
| (e.g. asking for the same font by name several times). The FontHost may |
| return seperate typeface instances in that case, or it may choose to use a |
| cache and return the same instance (but calling typeface->ref(), since the |
| caller is always responsible for calling unref() on each instance that is |
| returned). Either way, the fontID for those instance(s) will be the same. |
| In addition, the fontID should never be set to 0. That value is used as a |
| sentinel to indicate no-font-id. |
| |
| The major aspects are: |
| 1) Given either a name/style, return a subclass of SkTypeface that |
| references the closest matching font available on the host system. |
| 2) Given the data for a font (either in a stream or a file name), return |
| a typeface that allows access to that data. |
| 3) Each typeface instance carries a 32bit ID for its corresponding font. |
| SkFontHost turns that ID into a stream to access the font's data. |
| 4) Given a font ID, return a subclass of SkScalerContext, which connects a |
| font scaler (e.g. freetype or other) to the font's data. |
| 5) Utilites to manage the font cache (budgeting) and gamma correction |
| */ |
| class SkFontHost { |
| public: |
| /** Return a new, closest matching typeface given either an existing family |
| (specified by a typeface in that family) or by a familyName, and a |
| requested style. |
| 1) If familyFace is null, use famillyName. |
| 2) If famillyName is null, use familyFace. |
| 3) If both are null, return the default font that best matches style |
| */ |
| static SkTypeface* CreateTypeface(const SkTypeface* familyFace, |
| const char famillyName[], |
| SkTypeface::Style style); |
| |
| /** Return a new typeface given the data buffer. If the data does not |
| represent a valid font, returns null. |
| |
| If a typeface instance is returned, the caller is responsible for |
| calling unref() on the typeface when they are finished with it. |
| |
| The returned typeface may or may not have called ref() on the stream |
| parameter. If the typeface has not called ref(), then it may have made |
| a copy of the releveant data. In either case, the caller is still |
| responsible for its refcnt ownership of the stream. |
| */ |
| static SkTypeface* CreateTypefaceFromStream(SkStream*); |
| |
| /** Return a new typeface from the specified file path. If the file does not |
| represent a valid font, this returns null. If a typeface is returned, |
| the caller is responsible for calling unref() when it is no longer used. |
| */ |
| static SkTypeface* CreateTypefaceFromFile(const char path[]); |
| |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /** Returns true if the specified unique ID matches an existing font. |
| Returning false is similar to calling OpenStream with an invalid ID, |
| which will return NULL in that case. |
| */ |
| static bool ValidFontID(SkFontID uniqueID); |
| |
| /** Return a new stream to read the font data, or null if the uniqueID does |
| not match an existing typeface. .The caller must call stream->unref() |
| when it is finished reading the data. |
| */ |
| static SkStream* OpenStream(SkFontID uniqueID); |
| |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /** Write a unique identifier to the stream, so that the same typeface can |
| be retrieved with Deserialize(). |
| */ |
| static void Serialize(const SkTypeface*, SkWStream*); |
| |
| /** Given a stream created by Serialize(), return a new typeface (like |
| CreateTypeface) or return NULL if no match is found. |
| */ |
| static SkTypeface* Deserialize(SkStream*); |
| |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /** Return a subclass of SkScalarContext |
| */ |
| static SkScalerContext* CreateScalerContext(const SkDescriptor* desc); |
| |
| /** Given a "current" fontID, return the next logical fontID to use |
| when searching fonts for a given unicode value. Typically the caller |
| will query a given font, and if a unicode value is not supported, they |
| will call this, and if 0 is not returned, will search that font, and so |
| on. This process must be finite, and when the fonthost sees a |
| font with no logical successor, it must return 0. |
| */ |
| static uint32_t NextLogicalFont(SkFontID fontID); |
| |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /** Return the number of tables in the font |
| */ |
| static int CountTables(SkFontID); |
| |
| /** Copy into tags[] (allocated by the caller) the list of table tags in |
| the font, and return the number. This will be the same as CountTables() |
| or 0 if an error occured. |
| */ |
| static int GetTableTags(SkFontID, SkFontTableTag[]); |
| |
| /** Given a table tag, return the size of its contents, or 0 if not present |
| */ |
| static size_t GetTableSize(SkFontID, SkFontTableTag); |
| |
| /** Copy the contents of a table into data (allocated by the caller). Note |
| that the contents of the table will be in their native endian order |
| (which for most truetype tables is big endian). If the table tag is |
| not found, or there is an error copying the data, then 0 is returned. |
| If this happens, it is possible that some or all of the memory pointed |
| to by data may have been written to, even though an error has occured. |
| |
| @param fontID the font to copy the table from |
| @param tag The table tag whose contents are to be copied |
| @param offset The offset in bytes into the table's contents where the |
| copy should start from. |
| @param length The number of bytes, starting at offset, of table data |
| to copy. |
| @param data storage address where the table contents are copied to |
| @return the number of bytes actually copied into data. If offset+length |
| exceeds the table's size, then only the bytes up to the table's |
| size are actually copied, and this is the value returned. If |
| offset > the table's size, or tag is not a valid table, |
| then 0 is returned. |
| */ |
| static size_t GetTableData(SkFontID fontID, SkFontTableTag tag, |
| size_t offset, size_t length, void* data); |
| |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /** Return the number of bytes (approx) that should be purged from the font |
| cache. The input parameter is the cache's estimate of how much as been |
| allocated by the cache so far. |
| To purge (basically) everything, return the input parameter. |
| To purge nothing, return 0 |
| */ |
| static size_t ShouldPurgeFontCache(size_t sizeAllocatedSoFar); |
| |
| /** Return SkScalerContext gamma flag, or 0, based on the paint that will be |
| used to draw something with antialiasing. |
| */ |
| static int ComputeGammaFlag(const SkPaint& paint); |
| |
| /** Return NULL or a pointer to 256 bytes for the black (table[0]) and |
| white (table[1]) gamma tables. |
| */ |
| static void GetGammaTables(const uint8_t* tables[2]); |
| |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /** LCDs either have their color elements arranged horizontally or |
| vertically. When rendering subpixel glyphs we need to know which way |
| round they are. |
| |
| Note, if you change this after startup, you'll need to flush the glyph |
| cache because it'll have the wrong type of masks cached. |
| */ |
| enum LCDOrientation { |
| kHorizontal_LCDOrientation = 0, //!< this is the default |
| kVertical_LCDOrientation = 1, |
| }; |
| |
| static void SetSubpixelOrientation(LCDOrientation orientation); |
| static LCDOrientation GetSubpixelOrientation(); |
| |
| /** LCD color elements can vary in order. For subpixel text we need to know |
| the order which the LCDs uses so that the color fringes are in the |
| correct place. |
| |
| Note, if you change this after startup, you'll need to flush the glyph |
| cache because it'll have the wrong type of masks cached. |
| */ |
| enum LCDOrder { |
| kRGB_LCDOrder = 0, //!< this is the default |
| kBGR_LCDOrder = 1, |
| }; |
| |
| static void SetSubpixelOrder(LCDOrder order); |
| static LCDOrder GetSubpixelOrder(); |
| }; |
| |
| #endif |
| |