/*
* (C) Copyright IBM Corp. and others 1998-2013 - All Rights Reserved
* (C) Copyright Google, Inc. 2012-2013 - All Rights Reserved
*/
#ifndef __LAYOUTENGINE_H
#define __LAYOUTENGINE_H
#include "LETypes.h"
struct hb_font_t;
struct hb_buffer_t;
U_NAMESPACE_BEGIN
class LEFontInstance;
class LEGlyphStorage;
/**
* This is a 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.
*
* @see LEFontInstance
* @see ScriptAndLanguageTags.h
*
* @stable ICU 2.8
*/
class U_LAYOUT_API LayoutEngine : public UObject {
public:
#ifndef U_HIDE_INTERNAL_API
/** @internal Flag to request kerning. */
static const le_int32 kTypoFlagKern;
/** @internal Flag to request ligatures. */
static const le_int32 kTypoFlagLiga;
#endif /* U_HIDE_INTERNAL_API */
private:
hb_font_t *fHbFont;
hb_buffer_t *fHbBuffer;
LEGlyphStorage *fGlyphStorage;
le_int32 fTypoFlags;
#ifndef U_HIDE_INTERNAL_API
/**
* 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 (a bitfield). Use kTypoFlagKern
* if kerning is desired, kTypoFlagLiga if ligature formation is desired. Others are reserved.
* @param success - set to an error code if the operation fails
*
* @see LEFontInstance
* @see ScriptAndLanguageTags.h
*
* @internal
*/
LayoutEngine(const LEFontInstance *fontInstance,
le_int32 scriptCode,
le_int32 languageCode,
le_int32 typoFlags,
LEErrorCode &success);
#endif /* U_HIDE_INTERNAL_API */
// Do not enclose the protected default constructor with #ifndef U_HIDE_INTERNAL_API
// or else the compiler will create a public default constructor.
/**
* This overrides the default no argument constructor to make it
* difficult for clients to call it. Clients are expected to call
* layoutEngineFactory.
*
* @internal
*/
LayoutEngine();
public:
/**
* The destructor. It will free any storage allocated for the
* glyph, character index and position arrays by calling the reset
* method.
*
* @stable ICU 2.8
*/
~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 methods below.
*
* Note: If you call this method more than once, you must call the reset()
* method first to free the glyph, character index and position arrays
* allocated by the previous call.
*
* @stable ICU 2.8
*/
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
*/
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
*/
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.
* @stable 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