Spade
Mini Shell
/*
*
* (C) Copyright IBM Corp. 1998-2012 - All Rights Reserved
*
*/
#ifndef __LEFONTINSTANCE_H
#define __LEFONTINSTANCE_H
#include "LETypes.h"
/**
* \file
* \brief C++ API: Layout Engine Font Instance object
*/
U_NAMESPACE_BEGIN
/**
* Instances of this class are used by
<code>LEFontInstance::mapCharsToGlyphs</code> and
* <code>LEFontInstance::mapCharToGlyph</code> to adjust
character codes before the character
* to glyph mapping process. Examples of this are filtering out control
characters
* and character mirroring - replacing a character which has both a left
and a right
* hand form with the opposite form.
*
* @stable ICU 3.2
*/
class LECharMapper /* not : public UObject because this is an
interface/mixin class */
{
public:
/**
* Destructor.
* @stable ICU 3.2
*/
virtual ~LECharMapper();
/**
* This method does the adjustments.
*
* @param ch - the input character
*
* @return the adjusted character
*
* @stable ICU 2.8
*/
virtual LEUnicode32 mapChar(LEUnicode32 ch) const = 0;
};
/**
* This is a forward reference to the class which holds the per-glyph
* storage.
*
* @stable ICU 3.0
*/
class LEGlyphStorage;
/**
* This is a virtual base class that serves as the interface between a
LayoutEngine
* and the platform font environment. It allows a LayoutEngine to access
font tables, do
* character to glyph mapping, and obtain metrics information without
knowing any platform
* specific details. There are also a few utility methods for converting
between points,
* pixels and funits. (font design units)
*
* An instance of an <code>LEFontInstance</code> represents a
font at a particular point
* size. Each instance can represent either a single physical font, or a
composite font.
* A composite font is a collection of physical fonts, each of which
contains a subset of
* the characters contained in the composite font.
*
* Note: with the exception of <code>getSubFont</code>, the
methods in this class only
* make sense for a physical font. If you have an
<code>LEFontInstance</code> which
* represents a composite font you should only call the methods below which
have
* an <code>LEGlyphID</code>, an
<code>LEUnicode</code> or an
<code>LEUnicode32</code>
* as one of the arguments because these can be used to select a particular
subfont.
*
* Subclasses which implement composite fonts should supply an
implementation of these
* methods with some default behavior such as returning constant values, or
using the
* values from the first subfont.
*
* @stable ICU 3.0
*/
class U_LAYOUT_API LEFontInstance : public UObject
{
public:
/**
* This virtual destructor is here so that the subclass
* destructors can be invoked through the base class.
*
* @stable ICU 2.8
*/
virtual ~LEFontInstance();
/**
* Get a physical font which can render the given text. For composite
fonts,
* if there is no single physical font which can render all of the
text,
* return a physical font which can render an initial substring of the
text,
* and set the <code>offset</code> parameter to the end of
that substring.
*
* Internally, the LayoutEngine works with runs of text all in the same
* font and script, so it is best to call this method with text which
is
* in a single script, passing the script code in as a hint. If you
don't
* know the script of the text, you can use zero, which is the script
code
* for characters used in more than one script.
*
* The default implementation of this method is intended for instances
of
* <code>LEFontInstance</code> which represent a physical
font. It returns
* <code>this</code> and indicates that the entire string
can be rendered.
*
* This method will return a valid
<code>LEFontInstance</code> unless you
* have passed illegal parameters, or an internal error has been
encountered.
* For composite fonts, it may return the warning
<code>LE_NO_SUBFONT_WARNING</code>
* to indicate that the returned font may not be able to render all of
* the text. Whenever a valid font is returned, the
<code>offset</code> parameter
* will be advanced by at least one.
*
* Subclasses which implement composite fonts must override this
method.
* Where it makes sense, they should use the script code as a hint to
render
* characters from the COMMON script in the font which is used for the
given
* script. For example, if the input text is a series of Arabic words
separated
* by spaces, and the script code passed in is
<code>arabScriptCode</code> you
* should return the font used for Arabic characters for all of the
input text,
* including the spaces. If, on the other hand, the input text contains
characters
* which cannot be rendered by the font used for Arabic characters, but
which can
* be rendered by another font, you should return that font for those
characters.
*
* @param chars - the array of Unicode characters.
* @param offset - a pointer to the starting offset in the text. On
exit this
* will be set the the limit offset of the text which
can be
* rendered using the returned font.
* @param limit - the limit offset for the input text.
* @param script - the script hint.
* @param success - set to an error code if the arguments are illegal,
or no font
* can be returned for some reason. May also be set to
* <code>LE_NO_SUBFONT_WARNING</code> if
the subfont which
* was returned cannot render all of the text.
*
* @return an <code>LEFontInstance</code> for the sub font
which can render the characters, or
* <code>NULL</code> if there is an error.
*
* @see LEScripts.h
*
* @stable ICU 3.2
*/
virtual const LEFontInstance *getSubFont(const LEUnicode chars[],
le_int32 *offset, le_int32 limit, le_int32 script, LEErrorCode
&success) const;
//
// Font file access
//
/**
* This method reads a table from the font. Note that in general,
* it only makes sense to call this method on an
<code>LEFontInstance</code>
* which represents a physical font - i.e. one which has been returned
by
* <code>getSubFont()</code>. This is because each subfont
in a composite font
* will have different tables, and there's no way to know which
subfont to access.
*
* Subclasses which represent composite fonts should always return
<code>NULL</code>.
*
* @param tableTag - the four byte table tag. (e.g. 'cmap')
*
* @return the address of the table in memory, or
<code>NULL</code>
* if the table doesn't exist.
*
* @stable ICU 2.8
*/
virtual const void *getFontTable(LETag tableTag) const = 0;
/**
* This method 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>.
*
* This version sets a length, for range checking.
*
* @param tableTag - the four byte table tag. (e.g. 'cmap')
* @param length - ignored on entry, on exit will be the length of the
table if known, or -1 if unknown.
* @return the address of the table in memory, or
<code>NULL</code>
* if the table doesn't exist.
* @internal
*/
virtual const void* getFontTable(LETag tableTag, size_t &length)
const { length=-1; return getFontTable(tableTag); } /* -1 = unknown length
*/
/**
* This method is used to determine if the font can
* render the given character. This can usually be done
* by looking the character up in the font's character
* to glyph mapping.
*
* The default implementation of this method will return
* <code>TRUE</code> if
<code>mapCharToGlyph(ch)</code>
* returns a non-zero value.
*
* @param ch - the character to be tested
*
* @return <code>TRUE</code> if the font can render ch.
*
* @stable ICU 3.2
*/
virtual le_bool canDisplay(LEUnicode32 ch) const;
/**
* This method returns the number of design units in
* the font's EM square.
*
* @return the number of design units pre EM.
*
* @stable ICU 2.8
*/
virtual le_int32 getUnitsPerEM() const = 0;
/**
* This method maps an array of character codes to an array of glyph
* indices, using the font's character to glyph map.
*
* The default implementation iterates over all of the characters and
calls
* <code>mapCharToGlyph(ch, mapper)</code> on each one. It
also handles surrogate
* characters, storing the glyph ID for the high surrogate, and a
deleted glyph (0xFFFF)
* for the low surrogate.
*
* Most sublcasses will not need to implement this method.
*
* @param chars - the character array
* @param offset - the index of the first character
* @param count - the number of characters
* @param reverse - if <code>TRUE</code>, store the glyph
indices in reverse order.
* @param mapper - the character mapper.
* @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ
characters should map to a glyph w/ no contours.
* @param glyphStorage - the object which contains the output glyph
array
*
* @see LECharMapper
*
* @stable ICU 3.6
*/
virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset,
le_int32 count, le_bool reverse, const LECharMapper *mapper, le_bool
filterZeroWidth, LEGlyphStorage &glyphStorage) const;
/**
* This method maps a single character to a glyph index, using the
* font's character to glyph map. The default implementation of
this
* method calls the mapper, and then calls
<code>mapCharToGlyph(mappedCh)</code>.
*
* @param ch - the character
* @param mapper - the character mapper
* @param filterZeroWidth - <code>TRUE</code> if ZWJ / ZWNJ
characters should map to a glyph w/ no contours.
*
* @return the glyph index
*
* @see LECharMapper
*
* @stable ICU 3.6
*/
virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper
*mapper, le_bool filterZeroWidth) const;
/**
* This method maps a single character to a glyph index, using the
* font's character to glyph map. The default implementation of
this
* method calls the mapper, and then calls
<code>mapCharToGlyph(mappedCh)</code>.
*
* @param ch - the character
* @param mapper - the character mapper
*
* @return the glyph index
*
* @see LECharMapper
*
* @stable ICU 3.2
*/
virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch, const LECharMapper
*mapper) const;
/**
* This method maps a single character to a glyph index, using the
* font's character to glyph map. There is no default
implementation
* of this method because it requires information about the platform
* font implementation.
*
* @param ch - the character
*
* @return the glyph index
*
* @stable ICU 3.2
*/
virtual LEGlyphID mapCharToGlyph(LEUnicode32 ch) const = 0;
//
// Metrics
//
/**
* This method gets the X and Y advance of a particular glyph, in
pixels.
*
* @param glyph - the glyph index
* @param advance - the X and Y pixel values will be stored here
*
* @stable ICU 3.2
*/
virtual void getGlyphAdvance(LEGlyphID glyph, LEPoint &advance)
const = 0;
/**
* This method gets the hinted X and Y pixel coordinates of a
particular
* point in the outline of the given glyph.
*
* @param glyph - the glyph index
* @param pointNumber - the number of the point
* @param point - the point's X and Y pixel values will be stored
here
*
* @return <code>TRUE</code> if the point coordinates could
be stored.
*
* @stable ICU 2.8
*/
virtual le_bool getGlyphPoint(LEGlyphID glyph, le_int32 pointNumber,
LEPoint &point) const = 0;
/**
* This method returns the width of the font's EM square
* in pixels.
*
* @return the pixel width of the EM square
*
* @stable ICU 2.8
*/
virtual float getXPixelsPerEm() const = 0;
/**
* This method returns the height of the font's EM square
* in pixels.
*
* @return the pixel height of the EM square
*
* @stable ICU 2.8
*/
virtual float getYPixelsPerEm() const = 0;
/**
* This method converts font design units in the
* X direction to points.
*
* @param xUnits - design units in the X direction
*
* @return points in the X direction
*
* @stable ICU 3.2
*/
virtual float xUnitsToPoints(float xUnits) const;
/**
* This method converts font design units in the
* Y direction to points.
*
* @param yUnits - design units in the Y direction
*
* @return points in the Y direction
*
* @stable ICU 3.2
*/
virtual float yUnitsToPoints(float yUnits) const;
/**
* This method converts font design units to points.
*
* @param units - X and Y design units
* @param points - set to X and Y points
*
* @stable ICU 3.2
*/
virtual void unitsToPoints(LEPoint &units, LEPoint &points)
const;
/**
* This method converts pixels in the
* X direction to font design units.
*
* @param xPixels - pixels in the X direction
*
* @return font design units in the X direction
*
* @stable ICU 3.2
*/
virtual float xPixelsToUnits(float xPixels) const;
/**
* This method converts pixels in the
* Y direction to font design units.
*
* @param yPixels - pixels in the Y direction
*
* @return font design units in the Y direction
*
* @stable ICU 3.2
*/
virtual float yPixelsToUnits(float yPixels) const;
/**
* This method converts pixels to font design units.
*
* @param pixels - X and Y pixel
* @param units - set to X and Y font design units
*
* @stable ICU 3.2
*/
virtual void pixelsToUnits(LEPoint &pixels, LEPoint &units)
const;
/**
* Get the X scale factor from the font's transform. The default
* implementation of <code>transformFunits()</code> will
call this method.
*
* @return the X scale factor.
*
*
* @see transformFunits
*
* @stable ICU 3.2
*/
virtual float getScaleFactorX() const = 0;
/**
* Get the Y scale factor from the font's transform. The default
* implementation of <code>transformFunits()</code> will
call this method.
*
* @return the Yscale factor.
*
* @see transformFunits
*
* @stable ICU 3.2
*/
virtual float getScaleFactorY() const = 0;
/**
* This method transforms an X, Y point in font design units to a
* pixel coordinate, applying the font's transform. The default
* implementation of this method calls
<code>getScaleFactorX()</code>
* and <code>getScaleFactorY()</code>.
*
* @param xFunits - the X coordinate in font design units
* @param yFunits - the Y coordinate in font design units
* @param pixels - the tranformed co-ordinate in pixels
*
* @see getScaleFactorX
* @see getScaleFactorY
*
* @stable ICU 3.2
*/
virtual void transformFunits(float xFunits, float yFunits, LEPoint
&pixels) const;
/**
* This is a convenience method used to convert
* values in a 16.16 fixed point format to floating point.
*
* @param fixed - the fixed point value
*
* @return the floating point value
*
* @stable ICU 2.8
*/
static inline float fixedToFloat(le_int32 fixed);
/**
* This is a convenience method used to convert
* floating point values to 16.16 fixed point format.
*
* @param theFloat - the floating point value
*
* @return the fixed point value
*
* @stable ICU 2.8
*/
static inline le_int32 floatToFixed(float theFloat);
//
// These methods won't ever be called by the LayoutEngine,
// but are useful for clients of
<code>LEFontInstance</code> who
// need to render text.
//
/**
* Get the font's ascent.
*
* @return the font's ascent, in points. This value
* will always be positive.
*
* @stable ICU 3.2
*/
virtual le_int32 getAscent() const = 0;
/**
* Get the font's descent.
*
* @return the font's descent, in points. This value
* will always be positive.
*
* @stable ICU 3.2
*/
virtual le_int32 getDescent() const = 0;
/**
* Get the font's leading.
*
* @return the font's leading, in points. This value
* will always be positive.
*
* @stable ICU 3.2
*/
virtual le_int32 getLeading() const = 0;
/**
* Get the line height required to display text in
* this font. The default implementation of this method
* returns the sum of the ascent, descent, and leading.
*
* @return the line height, in points. This vaule will
* always be positive.
*
* @stable ICU 3.2
*/
virtual le_int32 getLineHeight() const;
/**
* ICU "poor man's RTTI", returns a UClassID for the
actual class.
*
* @stable ICU 3.2
*/
virtual UClassID getDynamicClassID() const;
/**
* ICU "poor man's RTTI", returns a UClassID for this
class.
*
* @stable ICU 3.2
*/
static UClassID getStaticClassID();
};
inline float LEFontInstance::fixedToFloat(le_int32 fixed)
{
return (float) (fixed / 65536.0);
}
inline le_int32 LEFontInstance::floatToFixed(float theFloat)
{
return (le_int32) (theFloat * 65536.0);
}
U_NAMESPACE_END
#endif