/*

 *

 * (C) Copyright IBM Corp. 1998-2005 - All Rights Reserved

 *

 */

#ifndef __LEFONTINSTANCE_H

#define __LEFONTINSTANCE_H

#include "LETypes.h"

/**

 * \file 

 * \brief C++ API: Layout Engine Font Instance object

 */

U_NAMESPACE_BEGIN

/**

 * Instances of this class are used by <code>LEFontInstance::mapCharsToGlyphs</code> and

 * <code>LEFontInstance::mapCharToGlyph</code> to adjust character codes before the character

 * to glyph mapping process. Examples of this are filtering out control characters

 * and character mirroring - replacing a character which has both a left and a right

 * hand form with the opposite form.

 *

 * @stable ICU 3.2

 */

class LECharMapper /* not : public UObject because this is an interface/mixin class */

{

public:

    /**

     * Destructor.

     * @stable ICU 3.2

     */

    virtual inline ~LECharMapper() {};

    /**

     * This method does the adjustments.

     *

     * @param ch - the input character

     *

     * @return the adjusted character

     *

     * @stable ICU 2.8

     */

    virtual LEUnicode32 mapChar(LEUnicode32 ch) const = 0;

};

/**

 * This is a forward reference to the class which holds the per-glyph

 * storage.

 *

 * @draft ICU 3.0

 */

class LEGlyphStorage;

/**

 * This is a virtual base class that serves as the interface between a LayoutEngine

 * and the platform font environment. It allows a LayoutEngine to access font tables, do

 * character to glyph mapping, and obtain metrics information without knowing any platform

 * specific details. There are also a few utility methods for converting between points,

 * pixels and funits. (font design units)

 *

 * An instance of an <code>LEFontInstance</code> represents a font at a particular point

 * size. Each instance can represent either a single physical font, or a composite font.

 * A composite font is a collection of physical fonts, each of which contains a subset of

 * the characters contained in the composite font.

 *

 * Note: with the exception of <code>getSubFont</code>, the methods in this class only

 * make sense for a physical font. If you have an <code>LEFontInstance</code> which

 * represents a composite font you should only call the methods below which have

 * an <code>LEGlyphID</code>, an <code>LEUnicode</code> or an <code>LEUnicode32</code>

 * as one of the arguments because these can be used to select a particular subfont.

 *

 * Subclasses which implement composite fonts should supply an implementation of these

 * methods with some default behavior such as returning constant values, or using the

 * values from the first subfont.

 *

 * @draft ICU 3.0

 */

class U_LAYOUT_API LEFontInstance : public UObject

{

public:

    /**

     * This virtual destructor is here so that the subclass

     * destructors can be invoked through the base class.

     *

     * @stable ICU 2.8

     */

    virtual inline ~LEFontInstance() {};

    /**

     * Get a physical font which can render the given text. For composite fonts,

     * if there is no single physical font which can render all of the text,

     * return a physical font which can render an initial substring of the text,

     * and set the <code>offset</code> parameter to the end of that substring.

     *

     * Internally, the LayoutEngine works with runs of text all in the same

     * font and script, so it is best to call this method with text which is

     * in a single script, passing the script code in as a hint. If you don't

     * know the script of the text, you can use zero, which is the script code

     * for characters used in more than one script.

     *

     * The default implementation of this method is intended for instances of

     * <code>LEFontInstance</code> which represent a physical font. It returns

     * <code>this</code> and indicates that the entire string can be rendered.

     *

     * This method will return a valid <code>LEFontInstance</code> unless you

     * have passed illegal parameters, or an internal error has been encountered. 

     * For composite fonts, it may return the warning <code>LE_NO_SUBFONT_WARNING</code>

     * to indicate that the returned font may not be able to render all of

     * the text. Whenever a valid font is returned, the <code>offset</code> parameter

     * will be advanced by at least one.

     *

     * Subclasses which implement composite fonts must override this method.

     * Where it makes sense, they should use the script code as a hint to render

     * characters from the COMMON script in the font which is used for the given

     * script. For example, if the input text is a series of Arabic words separated

     * by spaces, and the script code passed in is <code>arabScriptCode</code> you

     * should return the font used for Arabic characters for all of the input text,

     * including the spaces. If, on the other hand, the input text contains characters

     * which cannot be rendered by the font used for Arabic characters, but which can

     * be rendered by another font, you should return that font for those characters.

     *

     * @param chars   - the array of Unicode characters.

     * @param offset  - a pointer to the starting offset in the text. On exit this

     *                  will be set the the limit offset of the text which can be

     *                  rendered using the returned font.

     * @param limit   - the limit offset for the input text.

     * @param script  - the script hint.

     * @param success - set to an error code if the arguments are illegal, or no font

     *                  can be returned for some reason. May also be set to

     *                  <code>LE_NO_SUBFONT_WARNING</code> if the subfont which

     *                  was returned cannot render all of the text.

     *

     * @return an <code>LEFontInstance</code> for the sub font which can render the characters, or

     *         <code>NULL</code> if there is an error.

     *

     * @see LEScripts.h

     *

     * @stable ICU 3.2

     */

    virtual const LEFontInstance *getSubFont(const LEUnicode chars[], le_int32 *offset, le_int32 limit, le_int32 script, LEErrorCode &success) const;

    //

    // Font file access

    //

    /**

     * This method reads a table from the font. Note that in general,

     * it only makes sense to call this method on an <code>LEFontInstance</code>

     * which represents a physical font - i.e. one which has been returned by

     * <code>getSubFont()</code>. This is because each subfont in a composite font

     * will have different tables, and there's no way to know which subfont to access.

     *

     * Subclasses which represent composite fonts should always return <code>NULL</code>.

     *

     * @param tableTag - the four byte table tag. (e.g. 'cmap') 

     *

     * @return the address of the table in memory, or <code>NULL</code>

     *         if the table doesn't exist.

     *

     * @stable ICU 2.8

     */

    virtual const void *getFontTable(LETag tableTag) const = 0;

    /**

     * This method is used to determine if the font can

     * render the given character. This can usually be done

     * by looking the character up in the font's character

     * to glyph mapping.

     *

     * The default implementation of this method will return

     * <code>TRUE</code> if <code>mapCharToGlyph(ch)</code>

     * returns a non-zero value.

     *

     * @param ch - the character to be tested

     *

     * @return <code>TRUE</code> if the font can render ch.

     *

     * @stable ICU 3.2

     */

    virtual inline le_bool canDisplay(LEUnicode32 ch) const;

    /**

     * This method returns the number of design units in

     * the font's EM square.

     *

     * @return the number of design units pre EM.

     *

     * @stable ICU 2.8

     */

    virtual le_int32 getUnitsPerEM() const = 0;

    /**

     * This method maps an array of character codes to an array of glyph

     * indices, using the font's character to glyph map.

     *

     * The default implementation iterates over all of the characters and calls

     * <code>mapCharToGlyph(ch, mapper)</code> on each one. It also handles surrogate

     * characters, storing the glyph ID for the high surrogate, and a deleted glyph (0xFFFF)

     * for the low surrogate.

     *

     * Most sublcasses will not need to implement this method.

     *

     * @param chars - the character array

     * @param offset - the index of the first character

     * @param count - the number of characters

     * @param reverse - if <code>TRUE</code>, store the glyph indices in reverse order.

     * @param mapper - the character mapper.

     * @param glyphStorage - the object which contains the output glyph array

     *

     * @see LECharMapper

     *

     * @draft ICU 3.0

     */

    virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, LEGlyphStorage &glyphStorage) const;

    /**

     * This method maps a single character to a glyph index, using the

     * font's character to glyph map. The default implementation of this

     * method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.

     *

     * @param ch - the character

     * @param mapper - the character mapper

     *

     * @return the glyph index

     *

     * @see LECharMapper

     *

     * @stable ICU 3.2

     */

    virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const;

    /**

     * This method maps a single character to a glyph index, using the

     * font's character to glyph map. There is no default implementation

     * of this method because it requires information about the platform

     * font implementation.

     *

     * @param ch - the character

     *

     * @return the glyph index

     *

     * @stable ICU 3.2

     */

    virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) const = 0;

    //

    // Metrics

    //

    /**

     * This method gets the X and Y advance of a particular glyph, in pixels.

     *

     * @param glyph - the glyph index

     * @param advance - the X and Y pixel values will be stored here

     *

     * @stable ICU 3.2

     */

    virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance) const = 0;

    /**

     * This method gets the hinted X and Y pixel coordinates of a particular

     * point in the outline of the given glyph.

     *

     * @param glyph - the glyph index

     * @param pointNumber - the number of the point

     * @param point - the point's X and Y pixel values will be stored here

     *

     * @return <code>TRUE</code> if the point coordinates could be stored.

     *

     * @stable ICU 2.8

     */

    virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber, LEPoint &point) const = 0;

    /**

     * This method returns the width of the font's EM square

     * in pixels.

     *

     * @return the pixel width of the EM square

     *

     * @stable ICU 2.8

     */

    virtual float getXPixelsPerEm() const = 0;

    /**

     * This method returns the height of the font's EM square

     * in pixels.

     *

     * @return the pixel height of the EM square

     *

     * @stable ICU 2.8

     */

    virtual float getYPixelsPerEm() const = 0;

    /**

     * This method converts font design units in the

     * X direction to points.

     *

     * @param xUnits - design units in the X direction

     *

     * @return points in the X direction

     *

     * @stable ICU 3.2

     */

    virtual inline float xUnitsToPoints(float xUnits) const;

    /**

     * This method converts font design units in the

     * Y direction to points.

     *

     * @param yUnits - design units in the Y direction

     *

     * @return points in the Y direction

     *

     * @stable ICU 3.2

     */

    virtual inline float yUnitsToPoints(float yUnits) const;

    /**

     * This method converts font design units to points.

     *

     * @param units - X and Y design units

     * @param points - set to X and Y points

     *

     * @stable ICU 3.2

     */

    virtual inline void unitsToPoints(LEPoint &units, LEPoint &points) const;

    /**

     * This method converts pixels in the

     * X direction to font design units.

     *

     * @param xPixels - pixels in the X direction

     *

     * @return font design units in the X direction

     *

     * @stable ICU 3.2

     */

    virtual inline float xPixelsToUnits(float xPixels) const;

    /**

     * This method converts pixels in the

     * Y direction to font design units.

     *

     * @param yPixels - pixels in the Y direction

     *

     * @return font design units in the Y direction

     *

     * @stable ICU 3.2

     */

    virtual inline float yPixelsToUnits(float yPixels) const;

    /**

     * This method converts pixels to font design units.

     *

     * @param pixels - X and Y pixel

     * @param units - set to X and Y font design units

     *

     * @stable ICU 3.2

     */

    virtual inline void pixelsToUnits(LEPoint &pixels, LEPoint &units) const;

    /**

     * Get the X scale factor from the font's transform. The default

     * implementation of <code>transformFunits()</code> will call this method.

     *

     * @return the X scale factor.

     *

     *

     * @see transformFunits

     *

     * @stable ICU 3.2

     */

    virtual float getScaleFactorX() const = 0;

    /**

     * Get the Y scale factor from the font's transform. The default

     * implementation of <code>transformFunits()</code> will call this method.

     *

     * @return the Yscale factor.

     *

     * @see transformFunits

     *

     * @stable ICU 3.2

     */

    virtual float getScaleFactorY() const = 0;

    /**

     * This method transforms an X, Y point in font design units to a

     * pixel coordinate, applying the font's transform. The default

     * implementation of this method calls <code>getScaleFactorX()</code>

     * and <code>getScaleFactorY()</code>.

     *

     * @param xFunits - the X coordinate in font design units

     * @param yFunits - the Y coordinate in font design units

     * @param pixels - the tranformed co-ordinate in pixels

     *

     * @see getScaleFactorX

     * @see getScaleFactorY

     *

     * @stable ICU 3.2

     */

    virtual inline void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const;

    /**

     * This is a convenience method used to convert

     * values in a 16.16 fixed point format to floating point.

     *

     * @param fixed - the fixed point value

     *

     * @return the floating point value

     *

     * @stable ICU 2.8

     */

    static inline float fixedToFloat(le_int32 fixed);

    /**

     * This is a convenience method used to convert

     * floating point values to 16.16 fixed point format.

     *

     * @param theFloat - the floating point value

     *

     * @return the fixed point value

     *

     * @stable ICU 2.8

     */

    static inline le_int32 floatToFixed(float theFloat);

    //

    // These methods won't ever be called by the LayoutEngine,

    // but are useful for clients of <code>LEFontInstance</code> who

    // need to render text.

    //

    /**

     * Get the font's ascent.

     *

     * @return the font's ascent, in points. This value

     * will always be positive.

     *

     * @stable ICU 3.2

     */

    virtual le_int32 getAscent() const = 0;

    /**

     * Get the font's descent.

     *

     * @return the font's descent, in points. This value

     * will always be positive.

     *

     * @stable ICU 3.2

     */

    virtual le_int32 getDescent() const = 0;

    /**

     * Get the font's leading.

     *

     * @return the font's leading, in points. This value

     * will always be positive.

     *

     * @stable ICU 3.2

     */

    virtual le_int32 getLeading() const = 0;

    /**

     * Get the line height required to display text in

     * this font. The default implementation of this method

     * returns the sum of the ascent, descent, and leading.

     *

     * @return the line height, in points. This vaule will

     * always be positive.

     *

     * @stable ICU 3.2

     */

    virtual le_int32 getLineHeight() const;

    /**

     * ICU "poor man's RTTI", returns a UClassID for the actual class.

     *

     * @stable ICU 3.2

     */

    virtual UClassID getDynamicClassID() const;

    /**

     * ICU "poor man's RTTI", returns a UClassID for this class.

     *

     * @stable ICU 3.2

     */

    static UClassID getStaticClassID();

};

inline le_bool LEFontInstance::canDisplay(LEUnicode32 ch) const

{

    return LE_GET_GLYPH(mapCharToGlyph(ch)) != 0;

}

inline float LEFontInstance::xUnitsToPoints(float xUnits) const

{

    return (xUnits * getXPixelsPerEm()) / (float) getUnitsPerEM();

}

inline float LEFontInstance::yUnitsToPoints(float yUnits) const

{

    return (yUnits * getYPixelsPerEm()) / (float) getUnitsPerEM();

}

inline void LEFontInstance::unitsToPoints(LEPoint &units, LEPoint &points) const

{

    points.fX = xUnitsToPoints(units.fX);

    points.fY = yUnitsToPoints(units.fY);

}

inline float LEFontInstance::xPixelsToUnits(float xPixels) const

{

    return (xPixels * getUnitsPerEM()) / (float) getXPixelsPerEm();

}

inline float LEFontInstance::yPixelsToUnits(float yPixels) const

{

    return (yPixels * getUnitsPerEM()) / (float) getYPixelsPerEm();

}

inline void LEFontInstance::pixelsToUnits(LEPoint &pixels, LEPoint &units) const

{

    units.fX = xPixelsToUnits(pixels.fX);