--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/fontservices/textshaperplugin/IcuSource/layout/LayoutEngine.h Tue Feb 02 02:02:46 2010 +0200
@@ -0,0 +1,494 @@
+
+/*
+ *
+ * (C) Copyright IBM Corp. 1998-2005 - All Rights Reserved
+ *
+ */
+
+#ifndef __LAYOUTENGINE_H
+#define __LAYOUTENGINE_H
+
+#include "LETypes.h"
+
+/**
+ * \file
+ * \brief C++ API: Virtual base class for complex text layout.
+ */
+
+U_NAMESPACE_BEGIN
+
+class LEFontInstance;
+class LEGlyphFilter;
+class LEGlyphStorage;
+
+/**
+ * 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
+ *
+ * @stable ICU 2.8
+ */
+class U_LAYOUT_API LayoutEngine : public UObject {
+protected:
+ /**
+ * The object which holds the glyph storage
+ *
+ * @internal
+ */
+ LEGlyphStorage *fGlyphStorage;
+
+ /**
+ * 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;
+
+ /**
+ * The typographic control flags
+ *
+ * @internal
+ */
+ le_int32 fTypoFlags;
+
+ /**
+ * The glyph ID of Malayalam RA for RAKAR
+ *
+ * @internal
+ */
+ LEGlyphID fGidOfRA;
+
+ /**
+ * 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 languageCode - the language for the text
+ * @param typoFlags - the typographic control flags for the text. Set bit 1 if kerning
+ * is desired, set bit 2 if ligature formation is desired. Others are reserved.
+ *
+ * @see LEFontInstance
+ * @see ScriptAndLanguageTags.h
+ *
+ * @internal
+ */
+ LayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, le_int32 typoFlags);
+
+ /**
+ * Returns true if the constructor failed, leaving the object in an
+ * inconsistent state.
+ *
+ * @internal
+ */
+ le_bool isBogus();
+
+ /**
+ * 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 any required pre-processing to the input characters. It
+ * may generate output characters that differ from the input charcters due to
+ * insertions, deletions, or reorderings. In such cases, it will also generate an
+ * output character index array reflecting these changes.
+ *
+ * Subclasses must override this method.
+ *
+ * Input parameters:
+ * @param chars - the input character context
+ * @param offset - the index 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 characters are in a right to left directional run
+ * @param outChars - the output character array, if different from the input
+ * @param glyphStorage - the object that holds the per-glyph storage. The character index array may be set.
+ * @param success - set to an error code if the operation fails
+ *
+ * @return the output character count (input character count if no change)
+ *
+ * @internal
+ */
+ virtual le_int32 characterProcessing(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft,
+ LEUnicode *&outChars, LEGlyphStorage &glyphStorage, LEErrorCode &success);
+
+ /**
+ * 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
+ * @param glyphStorage - the object which holds the per-glyph storage. The glyph and char indices arrays
+ * will be set.
+ *
+ * Output parameters:
+ * @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, LEGlyphStorage &glyphStorage, 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 glyphStorage - the object which holds the per-glyph storage. The glyph position array will be set.
+ * @param x - the starting X position
+ * @param y - the starting Y position
+ * @param success - set to an error code if the operation fails
+ *
+ * @internal
+ */
+ virtual void positionGlyphs(LEGlyphStorage &glyphStorage, float x, float y, 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 - <code>TRUE</code> if the glyphs in the glyph array have been reordered
+ * @param glyphStorage - the object which holds the per-glyph storage. The glyph positions will be
+ * adjusted as needed.
+ * @param success - output parameter set to an error code if the operation fails
+ *
+ * @internal
+ */
+ virtual void adjustGlyphPositions(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, LEGlyphStorage &glyphStorage, LEErrorCode &success);
+
+ /**
+ * 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 <code>TRUE</code>, the output will be in reverse order
+ * @param mirror - if <code>TRUE</code>, do character mirroring
+ * @param glyphStorage - the object which holds the per-glyph storage. The glyph and char
+ * indices arrays will be filled in.
+ * @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, LEGlyphStorage &glyphStorage, 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 glyphStorage - the object containing the per-glyph storage. The positions array will be modified.
+ * @param markFilter - used to identify mark glyphs
+ * @param success - output parameter set to an error code if the operation fails
+ *
+ * @see LEGlyphFilter
+ *
+ * @internal
+ */
+ static void adjustMarkGlyphs(LEGlyphStorage &glyphStorage, LEGlyphFilter *markFilter, 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.
+ * This method uses the input characters to identify marks. This is required in
+ * cases where the font does not contain enough information to identify them based
+ * on the glyph IDs.
+ *
+ * @param chars - the array of input characters
+ * @param charCount - the number of input characers
+ * @param glyphStorage - the object containing the per-glyph storage. The positions array will be modified.
+ * @param reverse - <code>TRUE</code> if the glyph array has been reordered
+ * @param markFilter - used to identify mark glyphs
+ * @param success - output parameter set to an error code if the operation fails
+ *
+ * @see LEGlyphFilter
+ *
+ * @internal
+ */
+ static void adjustMarkGlyphs(const LEUnicode chars[], le_int32 charCount, le_bool reverse, LEGlyphStorage &glyphStorage, LEGlyphFilter *markFilter, 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.
+ *
+ * @stable ICU 2.8
+ */
+ 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.
+ *
+ * @stable ICU 2.8
+ */
+ 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
+ *
+ * @stable ICU 2.8
+ */
+ le_int32 getGlyphCount() const;
+
+ /**
+ * 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
+ *
+ * @stable ICU 2.8
+ */
+ 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
+ *
+ * @stable ICU 2.8
+ */
+ 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
+ *
+ * @stable ICU 2.8
+ */
+ 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
+ *
+ * @stable ICU 2.8
+ */
+ 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 positions - the destiniation position array
+ * @param success - set to an error code if the operation fails
+ *
+ * @stable ICU 2.8
+ */
+ 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
+ *
+ * @stable ICU 2.8
+ */
+ 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)
+ *
+ * @stable ICU 2.8
+ */
+ 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 languageCode - 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
+ *
+ * @stable ICU 2.8
+ */
+ static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, LEErrorCode &success);
+
+ /**
+ * Override of existing call that provides flags to control typography.
+ * @draft ICU 3.4
+ */
+ static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, le_int32 typo_flags, LEErrorCode &success);
+
+ /**
+ * ICU "poor man's RTTI", returns a UClassID for the actual class.
+ *
+ * @stable ICU 2.8
+ */
+ virtual UClassID getDynamicClassID() const;
+
+ /**
+ * ICU "poor man's RTTI", returns a UClassID for this class.
+ *
+ * @stable ICU 2.8
+ */
+ static UClassID getStaticClassID();
+
+};
+
+U_NAMESPACE_END
+#endif
+