/*

 *

 * (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