/* * %W% %W% * * (C) Copyright IBM Corp. 1998-2003 - All Rights Reserved * */ #ifndef __LAYOUTENGINE_H #define __LAYOUTENGINE_H #ifndef __LETYPES_H #include "LETypes.h" #endif #include <string.h> U_NAMESPACE_BEGIN class LEFontInstance; class LEGlyphFilter; /** * This is a virtual base class used to do complex text layout. The text must all * be in a single font, script, and language. An instance of a LayoutEngine can be * created by calling the layoutEngineFactory method. Fonts are identified by * instances of the LEFontInstance class. Script and language codes are identified * by integer codes, which are defined in ScriptAndLanuageTags.h. * * Note that this class is not public API. It is declared public so that it can be * exported from the library that it is a part of. * * The input to the layout process is an array of characters in logical order, * and a starting X, Y position for the text. The output is an array of glyph indices, * an array of character indices for the glyphs, and an array of glyph positions. * These arrays are protected members of LayoutEngine which can be retreived by a * public method. The reset method can be called to free these arrays so that the * LayoutEngine can be reused. * * The layout process is done in three steps. There is a protected virtual method * for each step. These methods have a default implementation which only does * character to glyph mapping and default positioning using the glyph's advance * widths. Subclasses can override these methods for more advanced layout. * There is a public method which invokes the steps in the correct order. * * The steps are: * * 1) Glyph processing - character to glyph mapping and any other glyph processing * such as ligature substitution and contextual forms. * * 2) Glyph positioning - position the glyphs based on their advance widths. * * 3) Glyph position adjustments - adjustment of glyph positions for kerning, * accent placement, etc. * * NOTE: in all methods below, output parameters are references to pointers so * the method can allocate and free the storage as needed. All storage allocated * in this way is owned by the object which created it, and will be freed when it * is no longer needed, or when the object's destructor is invoked. * * @see LEFontInstance * @see ScriptAndLanguageTags.h * * @draft ICU 2.2 */ class U_LAYOUT_API LayoutEngine : public UObject { protected: /** * The number of glyphs in the output * * @internal */ le_int32 fGlyphCount; /** * The output glyph array * * @internal */ LEGlyphID *fGlyphs; /** * The character index array. One entry for each output glyph, giving the index * in the input character array of the character which corresponds to this glyph. * * @internal */ le_int32 *fCharIndices; /** * The glyph position array. There are two entries for each glyph giving the * X and Y positions of the glyph. Thus, for glyph i, the X position is at index * 2i, and the Y position is at index 2i + 1. There are also two entries for the * X and Y position of the advance of the last glyph. * * @internal */ float *fPositions; /** * The font instance for the text font. * * @see LEFontInstance * * @internal */ const LEFontInstance *fFontInstance; /** * The script code for the text * * @see ScriptAndLanguageTags.h for script codes. * * @internal */ le_int32 fScriptCode; /** * The langauge code for the text * * @see ScriptAndLanguageTags.h for language codes. * * @internal */ le_int32 fLanguageCode; /** * This constructs an instance for a given font, script and language. Subclass constructors * must call this constructor. * * @param fontInstance - the font for the text * @param scriptCode - the script for the text * @param langaugeCode - the language for the text * * @see LEFontInstance * @see ScriptAndLanguageTags.h * * @internal */ LayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode); /** * This overrides the default no argument constructor to make it * difficult for clients to call it. Clients are expected to call * layoutEngineFactory. * * @internal */ LayoutEngine(); /** * This method does the glyph processing. It converts an array of characters * into an array of glyph indices and character indices. The characters to be * processed are passed in a surrounding context. The context is specified as * a starting address and a maximum character count. An offset and a count are * used to specify the characters to be processed. * * The default implementation of this method only does character to glyph mapping. * Subclasses needing more elaborate glyph processing must override this method. * * Input parameters: * @param chars - the character context * @param offset - the offset of the first character to process * @param count - the number of characters to process * @param max - the number of characters in the context. * @param rightToLeft - true if the text is in a right to left directional run * * Output parameters: * @param glyphs - the glyph index array * @param charIndices - the character index array * @param success - set to an error code if the operation fails * * @return the number of glyphs in the glyph index array * * @internal */ virtual le_int32 computeGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, LEGlyphID *&glyphs, le_int32 *&charIndices, LEErrorCode &success); /** * This method does basic glyph positioning. The default implementation positions * the glyphs based on their advance widths. This is sufficient for most uses. It * is not expected that many subclasses will override this method. * * Input parameters: * @param glyphs - the input glyph array * @param glyphCount - the number of glyphs in the glyph array * @param x - the starting X position * @param y - the starting Y position * * Output parameters: * @param positions - the output X and Y positions (two entries per glyph) * * @internal */ virtual void positionGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, float x, float y, float *&positions, LEErrorCode &success); /** * This method does positioning adjustments like accent positioning and * kerning. The default implementation does nothing. Subclasses needing * position adjustments must override this method. * * Note that this method has both characters and glyphs as input so that * it can use the character codes to determine glyph types if that information * isn't directly available. (e.g. Some Arabic OpenType fonts don't have a GDEF * table) * * @param chars - the input character context * @param offset - the offset of the first character to process * @param count - the number of characters to process * @param reverse - true if the glyphs in the glyph array have been reordered * @param glyphs - the input glyph array * @param glyphCount - the number of glyphs * @param positions - the position array, will be updated as needed * @param success - output parameter set to an error code if the operation fails * * Note: the positions are passed as a plain array because this method should * not need to reallocate them. * * @internal */ virtual void adjustGlyphPositions(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool /*reverse*/, LEGlyphID glyphs[], le_int32 glyphCount, float positions[], LEErrorCode &success) { if (LE_FAILURE(success)) { return; } if (chars == NULL || glyphs == NULL || positions == NULL || offset < 0 || count < 0 || glyphCount < 0) { success = LE_ILLEGAL_ARGUMENT_ERROR; return; } // default is no adjustments return; }; /** * This method gets a table from the font associated with * the text. The default implementation gets the table from * the font instance. Subclasses which need to get the tables * some other way must override this method. * * @param tableTag - the four byte table tag. * * @return the address of the table. * * @internal */ virtual const void *getFontTable(LETag tableTag) const; /** * This method does character to glyph mapping. The default implementation * uses the font instance to do the mapping. It will allocate the glyph and * character index arrays if they're not already allocated. If it allocates the * character index array, it will fill it it. * * This method supports right to left * text with the ability to store the glyphs in reverse order, and by supporting * character mirroring, which will replace a character which has a left and right * form, such as parens, with the opposite form before mapping it to a glyph index. * * Input parameters: * @param chars - the input character context * @param offset - the offset of the first character to be mapped * @param count - the number of characters to be mapped * @param reverse - if true, the output will be in reverse order * @param mirror - if true, do character mirroring * * Output parameters: * @param glyphs - the glyph array * @param charIndices - the character index array * @param success - set to an error code if the operation fails * * @see LEFontInstance * * @internal */ virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, le_bool mirror, LEGlyphID *&glyphs, le_int32 *&charIndices, LEErrorCode &success); /** * This is a convenience method that forces the advance width of mark * glyphs to be zero, which is required for proper selection and highlighting. * * @param glyphs - the glyph array * @param glyphCount - the number of glyphs * @param reverse - true if the glyph array has been reordered * @param markFilter - used to identify mark glyphs * @param positions - the glyph position array - updated as required * @param success - output parameter set to an error code if the operation fails * * @see LEGlyphFilter * * @internal */ static void adjustMarkGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, le_bool reverse, LEGlyphFilter *markFilter, float positions[], LEErrorCode &success); public: /** * The destructor. It will free any storage allocated for the * glyph, character index and position arrays by calling the reset * method. It is declared virtual so that it will be invoked by the * subclass destructors. * * @draft ICU 2.2 */ virtual ~LayoutEngine(); /** * This method will invoke the layout steps in their correct order by calling * the computeGlyphs, positionGlyphs and adjustGlyphPosition methods.. It will * compute the glyph, character index and position arrays. * * @param chars - the input character context * @param offset - the offset of the first character to process * @param count - the number of characters to process * @param max - the number of characters in the input context * @param rightToLeft - true if the characers are in a right to left directional run * @param x - the initial X position * @param y - the initial Y position * @param success - output parameter set to an error code if the operation fails * * @return the number of glyphs in the glyph array * * Note; the glyph, character index and position array can be accessed * using the getter method below. * * @draft ICU 2.2 */ virtual le_int32 layoutChars(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, float x, float y, LEErrorCode &success); /** * This method returns the number of glyphs in the glyph array. Note * that the number of glyphs will be greater than or equal to the number * of characters used to create the LayoutEngine. * * @return the number of glyphs in the glyph array * * @draft ICU 2.2 */ le_int32 getGlyphCount() const { return fGlyphCount; }; /** * This method copies the glyph array into a caller supplied array. * The caller must ensure that the array is large enough to hold all * the glyphs. * * @param glyphs - the destiniation glyph array * @param success - set to an error code if the operation fails * * @draft ICU 2.2 */ void getGlyphs(LEGlyphID glyphs[], LEErrorCode &success) const; /** * This method copies the glyph array into a caller supplied array, * ORing in extra bits. (This functionality is needed by the JDK, * which uses 32 bits pre glyph idex, with the high 16 bits encoding * the composite font slot number) * * @param glyphs - the destination (32 bit) glyph array * @param extraBits - this value will be ORed with each glyph index * @param success - set to an error code if the operation fails * * @draft ICU 2.2 */ virtual void getGlyphs(le_uint32 glyphs[], le_uint32 extraBits, LEErrorCode &success) const; /** * This method copies the character index array into a caller supplied array. * The caller must ensure that the array is large enough to hold a * character index for each glyph. * * @param charIndices - the destiniation character index array * @param success - set to an error code if the operation fails * * @draft ICU 2.2 */ void getCharIndices(le_int32 charIndices[], LEErrorCode &success) const; /** * This method copies the character index array into a caller supplied array. * The caller must ensure that the array is large enough to hold a * character index for each glyph. * * @param charIndices - the destiniation character index array * @param indexBase - an offset which will be added to each index * @param success - set to an error code if the operation fails * * @draft ICU 2.2 */ void getCharIndices(le_int32 charIndices[], le_int32 indexBase, LEErrorCode &success) const; /** * This method copies the position array into a caller supplied array. * The caller must ensure that the array is large enough to hold an * X and Y position for each glyph, plus an extra X and Y for the * advance of the last glyph. * * @param glyphs - the destiniation position array * @param success - set to an error code if the operation fails * * @draft ICU 2.2 */ void getGlyphPositions(float positions[], LEErrorCode &success) const; /** * This method returns the X and Y position of the glyph at * the given index. * * Input parameters: * @param glyphIndex - the index of the glyph * * Output parameters: * @param x - the glyph's X position * @param y - the glyph's Y position * @param success - set to an error code if the operation fails * * @draft ICU 2.2 */ void getGlyphPosition(le_int32 glyphIndex, float &x, float &y, LEErrorCode &success) const; /** * This method frees the glyph, character index and position arrays * so that the LayoutEngine can be reused to layout a different * characer array. (This method is also called by the destructor) * * @draft ICU 2.2 */ virtual void reset(); /** * This method returns a LayoutEngine capable of laying out text * in the given font, script and langauge. Note that the LayoutEngine * returned may be a subclass of LayoutEngine. * * @param fontInstance - the font of the text * @param scriptCode - the script of the text * @param langaugeCode - the language of the text * @param success - output parameter set to an error code if the operation fails * * @return a LayoutEngine which can layout text in the given font. * * @see LEFontInstance * * @draft ICU 2.2 */ static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, LEErrorCode &success); /** * ICU "poor man's RTTI", returns a UClassID for the actual class. * * @draft ICU 2.2 */ virtual inline UClassID getDynamicClassID() const { return getStaticClassID(); } /** * ICU "poor man's RTTI", returns a UClassID for this class. * * @draft ICU 2.2 */ static inline UClassID getStaticClassID() { return (UClassID)&fgClassID; } private: /** * The address of this static class variable serves as this class's ID * for ICU "poor man's RTTI". */ static const char fgClassID; }; U_NAMESPACE_END #endif