547 lines
17 KiB
C++
547 lines
17 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, 2001, 2002 - 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 characters
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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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* @draft ICU 2.2
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*/
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class LECharMapper /* not : public UObject because this is an interface/mixin class */
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{
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public:
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/**
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* Destructor.
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* @draft ICU 2.4
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*/
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virtual inline ~LECharMapper() {};
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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 character
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*
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* @return the adjusted character
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*
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* @draft ICU 2.2
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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 virtual base class that serves 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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* An instance of an <code>LEFontInstance</code> represents a font at a particular point
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* size. Each instance can represent either a single physical font, or a composite font.
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* A composite font is a collection of physical fonts, each of which contains a subset of
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* the characters contained in the composite font.
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*
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* Note: with the exception of <code>getSubFont</code>, the methods in this class only
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* make sense for a physical font. If you have an <code>LEFontInstance</code> which
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* represents a composite font you should only call the methods below which have
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* an <code>LEGlyphID</code>, an <code>LEUnicode</code> or an <code>LEUnicode32</code>
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* as one of the arguments because these can be used to select a particular subfont.
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*
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* Subclasses which implement composite fonts should supply an implementation of these
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* methods with some default behavior such as returning constant values, or using the
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* values from the first subfont.
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*
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* @draft ICU 2.6
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*/
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class U_LAYOUT_API LEFontInstance : public UObject
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{
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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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* @draft ICU 2.2
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*/
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virtual inline ~LEFontInstance() {};
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/**
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* Get a physical font which can render the given text. For composite fonts,
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* if there is no single physical font which can render all of the text,
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* return a physical font which can render an initial substring of the text,
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* and set the <code>offset</code> parameter to the end of that substring.
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*
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* Internally, the LayoutEngine works with runs of text all in the same
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* font and script, so it is best to call this method with text which is
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* in a single script, passing the script code in as a hint. If you don't
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* know the script of the text, you can use zero, which is the script code
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* for characters used in more than one script.
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*
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* The default implementation of this method is intended for instances of
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* <code>LEFontInstance</code> which represent a physical font. It returns
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* <code>this</code> and indicates that the entire string can be rendered.
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*
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* This method will return a valid <code>LEFontInstance</code> unless you
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* have passed illegal parameters, or an internal error has been encountered.
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* For composite fonts, it may return the warning <code>LE_NO_SUBFONT_WARNING</code>
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* to indicate that the returned font may not be able to render all of
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* the text. Whenever a valid font is returned, the <code>offset</code> parameter
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* will be advanced by at least one.
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*
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* Subclasses which implement composite fonts must override this method.
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* Where it makes sense, they should use the script code as a hint to render
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* characters from the COMMON script in the font which is used for the given
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* script. For example, if the input text is a series of Arabic words separated
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* by spaces, and the script code passed in is <code>arabScriptCode</code> you
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* should return the font used for Arabic characters for all of the input text,
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* including the spaces. If, on the other hand, the input text contains characters
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* which cannot be rendered by the font used for Arabic characters, but which can
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* be rendered by another font, you should return that font for those characters.
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*
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* @param chars - the array of Unicode characters.
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* @param offset - a pointer to the starting offset in the text. On exit this
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* will be set the the limit offset of the text which can be
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* rendered using the returned font.
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* @param limit - the limit offset for the input text.
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* @param script - the script hint.
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* @param success - set to an error code if the arguments are illegal, or no font
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* can be returned for some reason. May also be set to
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* <code>LE_NO_SUBFONT_WARNING</code> if the subfont which
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* was returned cannot render all of the text.
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*
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* @return an <code>LEFontInstance</code> for the sub font which can render the characters, or
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* <code>NULL</code> if there is an error.
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*
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* @see LEScripts.h
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*
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* @draft ICU 2.6
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*/
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virtual const LEFontInstance *getSubFont(const LEUnicode chars[], le_int32 *offset, le_int32 limit, le_int32 script, LEErrorCode &success) const;
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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. Note that in general,
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* it only makes sense to call this method on an <code>LEFontInstance</code>
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* which represents a physical font - i.e. one which has been returned by
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* <code>getSubFont()</code>. This is because each subfont in a composite font
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* will have different tables, and there's no way to know which subfont to access.
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*
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* Subclasses which represent composite fonts should always return <code>NULL</code>.
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*
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* @param tableTag - the four byte table tag. (e.g. 'cmap')
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*
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* @return the address of the table in memory, or <code>NULL</code>
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* if the table doesn't exist.
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*
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* @draft ICU 2.2
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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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* The default implementation of this method will return
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* <code>true</code> if <code>mapCharToGlyph(ch)</code>
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* returns a non-zero value.
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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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* @draft ICU 2.6
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*/
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virtual le_bool canDisplay(LEUnicode32 ch) const;
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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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* @draft ICU 2.2
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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 character 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 character
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* @param count - the number of characters
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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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* @draft ICU 2.6
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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;
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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 character to glyph map. The default implementation of this
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* method calls the mapper, and then calls <code>mapCharToGlyph(mappedCh)</code>.
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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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* @draft ICU 2.6
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*/
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virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper *mapper) const;
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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 character to glyph map. There is no default implementation
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* of this method because it requires information about the platform
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* font implementation.
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*
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* @param ch - the character
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*
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* @return the glyph index
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*
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* @draft ICU 2.6
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*/
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virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) 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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* @draft ICU 2.2
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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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* @draft ICU 2.2
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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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* @draft ICU 2.2
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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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* @draft ICU 2.2
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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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* @draft ICU 2.6
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*/
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virtual float xUnitsToPoints(float xUnits) const;
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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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* @draft ICU 2.6
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*/
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virtual float yUnitsToPoints(float yUnits) const;
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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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* @draft ICU 2.6
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*/
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virtual void unitsToPoints(LEPoint &units, LEPoint &points) const;
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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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* @draft ICU 2.6
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*/
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virtual float xPixelsToUnits(float xPixels) const;
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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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* @draft ICU 2.6
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*/
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virtual float yPixelsToUnits(float yPixels) const;
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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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* @draft ICU 2.6
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*/
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virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units) const;
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/**
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* Get the X scale factor from the font's transform. The default
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* implementation of <code>transformFunits()</code> will call this method.
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*
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* @return the X scale factor.
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*
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*
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* @see transformFunits
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*
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* @draft ICU 2.6
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*/
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virtual float getScaleFactorX() const = 0;
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/**
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* Get the Y scale factor from the font's transform. The default
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* implementation of <code>transformFunits()</code> will call this method.
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*
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* @return the Yscale factor.
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*
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* @see transformFunits
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*
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* @draft ICU 2.6
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*/
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virtual float getScaleFactorY() 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. The default
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* implementation of this method calls <code>getScaleFactorX()</code>
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* and <code>getScaleFactorY()</code>.
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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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* @see getScaleFactorX
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* @see getScaleFactorY
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*
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* @draft ICU 2.6
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*/
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virtual void transformFunits(float xFunits, float yFunits, LEPoint &pixels) const;
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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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* @draft ICU 2.2
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*/
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static float fixedToFloat(le_int32 fixed);
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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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* @draft ICU 2.2
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*/
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static le_int32 floatToFixed(float theFloat);
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//
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// These methods won't ever be called by the LayoutEngine,
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// but are useful for clients of <code>LEFontInstance</code> who
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// need to render text.
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//
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/**
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* Get the font's ascent.
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*
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* @return the font's ascent, in points. This value
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* will always be positive.
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*
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* @draft ICU 2.6
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*/
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virtual le_int32 getAscent() const = 0;
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/**
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* Get the font's descent.
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*
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* @return the font's descent, in points. This value
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* will always be positive.
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*
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* @draft ICU 2.6
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*/
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virtual le_int32 getDescent() const = 0;
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/**
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* Get the font's leading.
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*
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* @return the font's leading, in points. This value
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* will always be positive.
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*
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* @draft ICU 2.6
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*/
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virtual le_int32 getLeading() const = 0;
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/**
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* Get the line height required to display text in
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* this font. The default implementation of this method
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* returns the sum of the ascent, descent, and leading.
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*
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* @return the line height, in points. This vaule will
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* always be positive.
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*
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* @draft ICU 2.6
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*/
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virtual le_int32 getLineHeight() const;
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/**
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* ICU "poor man's RTTI", returns a UClassID for the actual class.
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*
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* @draft ICU 2.6
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*/
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virtual inline UClassID getDynamicClassID() const { return getStaticClassID(); }
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/**
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* ICU "poor man's RTTI", returns a UClassID for this class.
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*
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* @draft ICU 2.6
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*/
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static inline UClassID getStaticClassID() { return (UClassID)&fgClassID; }
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private:
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/**
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* The address of this static class variable serves as this class's ID
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* for ICU "poor man's RTTI".
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*/
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static const char fgClassID;
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};
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inline le_bool LEFontInstance::canDisplay(LEUnicode32 ch) const
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{
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return mapCharToGlyph(ch) != 0;
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}
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inline float LEFontInstance::xUnitsToPoints(float xUnits) const
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{
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return (xUnits * getXPixelsPerEm()) / (float) getUnitsPerEM();
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}
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inline float LEFontInstance::yUnitsToPoints(float yUnits) const
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{
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return (yUnits * getYPixelsPerEm()) / (float) getUnitsPerEM();
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}
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inline void LEFontInstance::unitsToPoints(LEPoint &units, LEPoint &points) const
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{
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points.fX = xUnitsToPoints(units.fX);
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points.fY = yUnitsToPoints(units.fY);
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}
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inline float LEFontInstance::xPixelsToUnits(float xPixels) const
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{
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return (xPixels * getUnitsPerEM()) / (float) getXPixelsPerEm();
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}
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inline float LEFontInstance::yPixelsToUnits(float yPixels) const
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{
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return (yPixels * getUnitsPerEM()) / (float) getYPixelsPerEm();
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}
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inline void LEFontInstance::pixelsToUnits(LEPoint &pixels, LEPoint &units) const
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{
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units.fX = xPixelsToUnits(pixels.fX);
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units.fY = yPixelsToUnits(pixels.fY);
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}
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inline void LEFontInstance::transformFunits(float xFunits, float yFunits, LEPoint &pixels) const
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{
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pixels.fX = xUnitsToPoints(xFunits) * getScaleFactorX();
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pixels.fY = yUnitsToPoints(yFunits) * getScaleFactorY();
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}
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inline float LEFontInstance::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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inline le_int32 LEFontInstance::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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inline le_int32 LEFontInstance::getLineHeight() const
|
|
{
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|
return getAscent() + getDescent() + getLeading();
|
|
}
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U_NAMESPACE_END
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#endif
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