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 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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/*
 *
 * (C) Copyright IBM Corp. 1998-2005 - All Rights Reserved
 *
 */

#ifndef __LAYOUTENGINE_H
#define __LAYOUTENGINE_H

#include "LETypes.h"

#include <string.h>

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
{
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;

    /**
     * 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
     *
     * @see LEFontInstance
     * @see ScriptAndLanguageTags.h
     *
     * @internal
     */
    LayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode,
        le_int32 languageCode, le_int32 typoFlags);

    /**
     * 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 32 bit versions of the computeGlyphs and
     * positionGlyphs methods.(It doesn't * call the
     * adjustGlyphPositions method because that doesn't apply for
     * default * processing.) 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.
     */
    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);
};

#endif