265 lines
7.9 KiB
C++
265 lines
7.9 KiB
C++
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/*
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* @(#)LEFontInstance.h 1.3 00/03/15
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*
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* (C) Copyright IBM Corp. 1998, 1999, 2000 - All Rights Reserved
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*
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*/
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#ifndef __LEFONTINSTANCE_H
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#define __LEFONTINSTANCE_H
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#include "LETypes.h"
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U_NAMESPACE_BEGIN
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/**
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* Instances of this class are used by LEFontInstance::mapCharsToGlyphs and
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* LEFontInstance::mapCharToGlyph to adjust character codes before the character
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* to glyph mapping process. Examples of this are filtering out control charcters
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* and character mirroring - replacing a character which has both a left and a right
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* hand form with the opposite form.
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*/
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class LECharMapper /* not : public UObject because this is an interface/mixin class */ {
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public:
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/**
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* This method does the adjustments.
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*
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* @param ch - the input charcter
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*
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* @return the adjusted character
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*/
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virtual LEUnicode32 mapChar(LEUnicode32 ch) const = 0;
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};
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/**
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* This is a pure virtual base class that servers as the interface between a LayoutEngine
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* and the platform font environment. It allows a LayoutEngine to access font tables, do
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* character to glyph mapping, and obtain metrics information without knowing any platform
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* specific details. There are also a few utility methods for converting between points,
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* pixels and funits. (font design units)
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*
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* Each instance of an LEFontInstance represents a renerable instance of a font. (i.e. a
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* single font at a particular point size, with a particular transform)
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*/
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class LEFontInstance /* not : public UObject because this is an interface/mixin class */ {
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public:
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/**
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* This virtual destructor is here so that the subclass
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* destructors can be invoked through the base class.
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*/
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virtual ~LEFontInstance() { };
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//
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// Font file access
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//
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/**
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* This method reads a table from the font.
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*
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* @param tableTag - the four byte table tag
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*
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* @return the address of the table in memory
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*/
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virtual const void *getFontTable(LETag tableTag) const = 0;
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/**
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* This method is used to determine if the font can
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* render the given character. This can usually be done
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* by looking the character up in the font's character
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* to glyph mapping.
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*
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* @param ch - the character to be tested
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*
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* @return true if the font can render ch.
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*/
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virtual le_bool canDisplay(LEUnicode32 ch) const = 0;
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/**
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* This method returns the number of design units in
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* the font's EM square.
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*
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* @return the number of design units pre EM.
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*/
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virtual le_int32 getUnitsPerEM() const = 0;
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/**
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* This method maps an array of charcter codes to an array of glyph
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* indices, using the font's character to glyph map.
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*
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* @param chars - the character array
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* @param offset - the index of the first charcter
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* @param count - the number of charcters
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* @param reverse - if true, store the glyph indices in reverse order.
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* @param mapper - the character mapper.
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* @param glyphs - the output glyph array
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*
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* @see LECharMapper
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*/
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virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, const LECharMapper *mapper, LEGlyphID glyphs[]) const = 0;
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/**
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* This method maps a single character to a glyph index, using the
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* font's charcter to glyph map.
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*
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* @param ch - the character
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* @param mapper - the character mapper
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*
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* @return the glyph index
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*
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* @see LECharMapper
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*/
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virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const = 0;
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/**
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* This method gets a name from the font. (e.g. the family name) The encoding
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* of the name is specified by the platform, the script, and the language.
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*
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* @param platformID - the platform id
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* @param scriptID - the script id
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* @param langaugeID - the language id
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* @param name - the destination character array (can be null)
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*
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* @return the number of characters in the name
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*/
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virtual le_int32 getName(le_uint16 platformID, le_uint16 scriptID, le_uint16 languageID, le_uint16 nameID, LEUnicode *name) const = 0;
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//
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// Metrics
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//
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/**
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* This method gets the X and Y advance of a particular glyph, in pixels.
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*
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* @param glyph - the glyph index
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* @param advance - the X and Y pixel values will be stored here
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*/
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virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance) const = 0;
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/**
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* This method gets the hinted X and Y pixel coordinates of a particular
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* point in the outline of the given glyph.
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*
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* @param glyph - the glyph index
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* @param pointNumber - the number of the point
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* @param point - the point's X and Y pixel values will be stored here
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*
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* @return true if the point coordinates could be stored.
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*/
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virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber, LEPoint &point) const = 0;
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/**
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* This method returns the width of the font's EM square
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* in pixels.
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*
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* @return the pixel width of the EM square
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*/
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virtual float getXPixelsPerEm() const = 0;
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/**
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* This method returns the height of the font's EM square
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* in pixels.
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*
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* @return the pixel height of the EM square
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*/
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virtual float getYPixelsPerEm() const = 0;
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/**
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* This method converts font design units in the
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* X direction to points.
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*
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* @param xUnits - design units in the X direction
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*
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* @return points in the X direction
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*/
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virtual float xUnitsToPoints(float xUnits) const = 0;
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/**
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* This method converts font design units in the
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* Y direction to points.
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*
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* @param yUnits - design units in the Y direction
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*
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* @return points in the Y direction
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*/
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virtual float yUnitsToPoints(float yUunits) const = 0;
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/**
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* This method converts font design units to points.
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*
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* @param units - X and Y design units
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* @param points - set to X and Y points
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*/
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virtual void unitsToPoints(LEPoint &units, LEPoint &points) const = 0;
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/**
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* This method converts pixels in the
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* X direction to font design units.
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*
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* @param xPixels - pixels in the X direction
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*
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* @return font design units in the X direction
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*/
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virtual float xPixelsToUnits(float xPixels) const = 0;
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/**
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* This method converts pixels in the
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* Y direction to font design units.
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*
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* @param yPixels - pixels in the Y direction
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*
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* @return font design units in the Y direction
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*/
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virtual float yPixelsToUnits(float yPixels) const = 0;
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/**
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* This method converts pixels to font design units.
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*
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* @param pixels - X and Y pixel
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* @param units - set to X and Y font design units
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*/
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virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units) const = 0;
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/**
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* This method transforms an X, Y point in font design units to a
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* pixel coordinate, applying the font's transform.
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*
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* @param xFunits - the X coordinate in font design units
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* @param yFunits - the Y coordinate in font design units
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* @param pixels - the tranformed co-ordinate in pixels
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*/
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virtual void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const = 0;
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/**
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* This is a convenience method used to convert
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* values in a 16.16 fixed point format to floating point.
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*
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* @param fixed - the fixed point value
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*
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* @return the floating point value
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*/
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static float fixedToFloat(le_int32 fixed)
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{
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return (float) (fixed / 65536.0);
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};
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/**
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* This is a convenience method used to convert
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* floating point values to 16.16 fixed point format.
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*
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* @param theFloat - the floating point value
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*
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* @return the fixed point value
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*/
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static le_int32 floatToFixed(float theFloat)
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{
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return (le_int32) (theFloat * 65536.0);
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};
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};
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U_NAMESPACE_END
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#endif
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