source/layout/LEFontInstance.h - external/github.com/unicode-org/icu - Git at Google


 /*
  * @(#)LEFontInstance.h 1.3 00/03/15
  *
  * (C) Copyright IBM Corp. 1998-2003 - All Rights Reserved
  *
  */

 #ifndef __LEFONTINSTANCE_H
 #define __LEFONTINSTANCE_H

 #include "LETypes.h"

 U_NAMESPACE_BEGIN

 /**
  * Instances of this class are used by LEFontInstance::mapCharsToGlyphs and
  * LEFontInstance::mapCharToGlyph 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.
  *
  * @draft ICU 2.2
  */
 class LECharMapper /* not : public UObject because this is an interface/mixin class */
 {
 public:
     /**
      * Destructor.
      * @draft ICU 2.4
      */
     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 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 2.6
  */
 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
      *
      * @draft ICU 2.6
      */
     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 TRUE if the font can render ch.
      *
      * @draft ICU 2.6
      */
     virtual 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.
      *
      * @param chars - the character array
      * @param offset - the index of the first character
      * @param count - the number of characters
      * @param reverse - if TRUE, store the glyph indices in reverse order.
      * @param mapper - the character mapper.
      * @param glyphs - the output glyph array
      *
      * @see LECharMapper
      *
      * @draft ICU 2.6
      */
     virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, LEGlyphID glyphs[]) 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
      *
      * @draft ICU 2.6
      */
     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
      *
      * @draft ICU 2.6
      */
     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
      *
      * @draft ICU 2.2
      */
     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 TRUE 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
      *
      * @draft ICU 2.6
      */
     virtual 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
      *
      * @draft ICU 2.6
      */
     virtual 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
      *
      * @draft ICU 2.6
      */
     virtual 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
      *
      * @draft ICU 2.6
      */
     virtual 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
      *
      * @draft ICU 2.6
      */
     virtual 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
      *
      * @draft ICU 2.6
      */
     virtual 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
      *
      * @draft ICU 2.6
      */
     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
      *
      * @draft ICU 2.6
      */
     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
      *
      * @draft ICU 2.6
      */
     virtual 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 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 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.
      *
      * @draft ICU 2.6
      */
     virtual le_int32 getAscent() const = 0;

     /**
      * Get the font's descent.
      *
      * @return the font's descent, in points. This value
      * will always be positive.
      *
      * @draft ICU 2.6
      */
     virtual le_int32 getDescent() const = 0;

     /**
      * Get the font's leading.
      *
      * @return the font's leading, in points. This value
      * will always be positive.
      *
      * @draft ICU 2.6
      */
     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.
      *
      * @draft ICU 2.6
      */
     virtual le_int32 getLineHeight() const;

     /**
      * ICU "poor man's RTTI", returns a UClassID for the actual class.
      *
      * @draft ICU 2.6
      */
     virtual inline UClassID getDynamicClassID() const { return getStaticClassID(); }

     /**
      * ICU "poor man's RTTI", returns a UClassID for this class.
      *
      * @draft ICU 2.6
      */
     static inline UClassID getStaticClassID() { return (UClassID)&fgClassID; }

 private:

     /**
      * The address of this static class variable serves as this class's ID
      * for ICU "poor man's RTTI".
      */
     static const char fgClassID;
 };

 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);
     units.fY = yPixelsToUnits(pixels.fY);
 }

 inline void LEFontInstance::transformFunits(float xFunits, float yFunits, LEPoint &pixels) const
 {
     pixels.fX = xUnitsToPoints(xFunits) * getScaleFactorX();
     pixels.fY = yUnitsToPoints(yFunits) * getScaleFactorY();
 }

 inline float LEFontInstance::fixedToFloat(le_int32 fixed)
 {
     return (float) (fixed / 65536.0);
 }

 inline le_int32 LEFontInstance::floatToFixed(float theFloat)
 {
     return (le_int32) (theFloat * 65536.0);
 }

 inline le_int32 LEFontInstance::getLineHeight() const
 {
     return getAscent() + getDescent() + getLeading();
 }

 U_NAMESPACE_END
 #endif

	/*
	* @(#)LEFontInstance.h 1.3 00/03/15
	*
	* (C) Copyright IBM Corp. 1998-2003 - All Rights Reserved
	*
	*/

	#ifndef __LEFONTINSTANCE_H
	#define __LEFONTINSTANCE_H

	#include "LETypes.h"

	U_NAMESPACE_BEGIN

	/**
	* Instances of this class are used by LEFontInstance::mapCharsToGlyphs and
	* LEFontInstance::mapCharToGlyph 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.
	*
	* @draft ICU 2.2
	*/
	class LECharMapper /* not : public UObject because this is an interface/mixin class */
	{
	public:
	/**
	* Destructor.
	* @draft ICU 2.4
	*/
	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 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 2.6
	*/
	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
	*
	* @draft ICU 2.6
	*/
	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 TRUE if the font can render ch.
	*
	* @draft ICU 2.6
	*/
	virtual 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.
	*
	* @param chars - the character array
	* @param offset - the index of the first character
	* @param count - the number of characters
	* @param reverse - if TRUE, store the glyph indices in reverse order.
	* @param mapper - the character mapper.
	* @param glyphs - the output glyph array
	*
	* @see LECharMapper
	*
	* @draft ICU 2.6
	*/
	virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, LEGlyphID glyphs[]) 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
	*
	* @draft ICU 2.6
	*/
	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
	*
	* @draft ICU 2.6
	*/
	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
	*
	* @draft ICU 2.2
	*/
	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 TRUE 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
	*
	* @draft ICU 2.6
	*/
	virtual 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
	*
	* @draft ICU 2.6
	*/
	virtual 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
	*
	* @draft ICU 2.6
	*/
	virtual 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
	*
	* @draft ICU 2.6
	*/
	virtual 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
	*
	* @draft ICU 2.6
	*/
	virtual 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
	*
	* @draft ICU 2.6
	*/
	virtual 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
	*
	* @draft ICU 2.6
	*/
	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
	*
	* @draft ICU 2.6
	*/
	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
	*
	* @draft ICU 2.6
	*/
	virtual 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 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 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.
	*
	* @draft ICU 2.6
	*/
	virtual le_int32 getAscent() const = 0;

	/**
	* Get the font's descent.
	*
	* @return the font's descent, in points. This value
	* will always be positive.
	*
	* @draft ICU 2.6
	*/
	virtual le_int32 getDescent() const = 0;

	/**
	* Get the font's leading.
	*
	* @return the font's leading, in points. This value
	* will always be positive.
	*
	* @draft ICU 2.6
	*/
	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.
	*
	* @draft ICU 2.6
	*/
	virtual le_int32 getLineHeight() const;

	/**
	* ICU "poor man's RTTI", returns a UClassID for the actual class.
	*
	* @draft ICU 2.6
	*/
	virtual inline UClassID getDynamicClassID() const { return getStaticClassID(); }

	/**
	* ICU "poor man's RTTI", returns a UClassID for this class.
	*
	* @draft ICU 2.6
	*/
	static inline UClassID getStaticClassID() { return (UClassID)&fgClassID; }

	private:

	/**
	* The address of this static class variable serves as this class's ID
	* for ICU "poor man's RTTI".
	*/
	static const char fgClassID;
	};

	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);
	units.fY = yPixelsToUnits(pixels.fY);
	}

	inline void LEFontInstance::transformFunits(float xFunits, float yFunits, LEPoint &pixels) const
	{
	pixels.fX = xUnitsToPoints(xFunits) * getScaleFactorX();
	pixels.fY = yUnitsToPoints(yFunits) * getScaleFactorY();
	}

	inline float LEFontInstance::fixedToFloat(le_int32 fixed)
	{
	return (float) (fixed / 65536.0);
	}

	inline le_int32 LEFontInstance::floatToFixed(float theFloat)
	{
	return (le_int32) (theFloat * 65536.0);
	}

	inline le_int32 LEFontInstance::getLineHeight() const
	{
	return getAscent() + getDescent() + getLeading();
	}

	U_NAMESPACE_END
	#endif