scuffed-code/icu4c/source/layout/LayoutEngine.h

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/*
* %W% %W%
*
* (C) Copyright IBM Corp. 1998, 1999, 2000, 2001 - All Rights Reserved
*
*/
#ifndef __LAYOUTENGINE_H
#define __LAYOUTENGINE_H
#ifndef __LETYPES_H
#include "LETypes.h"
#endif
#include <string.h>
U_NAMESPACE_BEGIN
class LEFontInstance;
class LEGlyphFilter;
/**
* This is a virtual base class used to do complex text layout. The text must all
* be in a single font, script, and language. An instance of a LayoutEngine can be
* created by calling the layoutEngineFactory method. Fonts are identified by
* instances of the LEFontInstance class. Script and language codes are identified
* by integer codes, which are defined in ScriptAndLanuageTags.h.
*
* Note that this class is not public API. It is declared public so that it can be
* exported from the library that it is a part of.
*
* The input to the layout process is an array of characters in logical order,
* and a starting X, Y position for the text. The output is an array of glyph indices,
* an array of character indices for the glyphs, and an array of glyph positions.
* These arrays are protected members of LayoutEngine which can be retreived by a
* public method. The reset method can be called to free these arrays so that the
* LayoutEngine can be reused.
*
* The layout process is done in three steps. There is a protected virtual method
* for each step. These methods have a default implementation which only does
* character to glyph mapping and default positioning using the glyph's advance
* widths. Subclasses can override these methods for more advanced layout.
* There is a public method which invokes the steps in the correct order.
*
* The steps are:
*
* 1) Glyph processing - character to glyph mapping and any other glyph processing
* such as ligature substitution and contextual forms.
*
* 2) Glyph positioning - position the glyphs based on their advance widths.
*
* 3) Glyph position adjustments - adjustment of glyph positions for kerning,
* accent placement, etc.
*
* NOTE: in all methods below, output parameters are references to pointers so
* the method can allocate and free the storage as needed. All storage allocated
* in this way is owned by the object which created it, and will be freed when it
* is no longer needed, or when the object's destructor is invoked.
*
* @see LEFontInstance
* @see ScriptAndLanguageTags.h
*/
class U_LAYOUT_API LayoutEngine : public UObject {
protected:
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/**
* The number of glyphs in the output
*/
le_int32 fGlyphCount;
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/**
* The output glyph array
*/
LEGlyphID *fGlyphs;
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/**
* The character index array. One entry for each output glyph, giving the index
* in the input character array of the character which corresponds to this glyph.
*/
le_int32 *fCharIndices;
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/**
* The glyph position array. There are two entries for each glyph giving the
* X and Y positions of the glyph. Thus, for glyph i, the X position is at index
* 2i, and the Y position is at index 2i + 1. There are also two entries for the
* X and Y position of the advance of the last glyph.
*/
float *fPositions;
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/**
* The font instance for the text font.
*
* @see LEFontInstance
*/
const LEFontInstance *fFontInstance;
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/**
* The script code for the text
*
* @see ScriptAndLanguageTags.h for script codes.
*/
le_int32 fScriptCode;
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/**
* The langauge code for the text
*
* @see ScriptAndLanguageTags.h for language codes.
*/
le_int32 fLanguageCode;
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/**
* This constructs an instance for a given font, script and language. Subclass constructors
* must call this constructor.
*
* @param fontInstance - the font for the text
* @param scriptCode - the script for the text
* @param langaugeCode - the language for the text
*
* @see LEFontInstance
* @see ScriptAndLanguageTags.h
*/
LayoutEngine(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode);
/**
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* This overrides the default no argument constructor to make it
* difficult for clients to call it. Clients are expected to call
* layoutEngineFactory.
*/
LayoutEngine();
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/**
* This method does the glyph processing. It converts an array of characters
* into an array of glyph indices and character indices. The characters to be
* processed are passed in a surrounding context. The context is specified as
* a starting address and a maximum character count. An offset and a count are
* used to specify the characters to be processed.
*
* The default implementation of this method only does character to glyph mapping.
* Subclasses needing more elaborate glyph processing must override this method.
*
* Input parameters:
* @param chars - the character context
* @param offset - the offset of the first character to process
* @param count - the number of characters to process
* @param max - the number of characters in the context.
* @param rightToLeft - true if the text is in a right to left directional run
*
* Output parameters:
* @param glyphs - the glyph index array
* @param charIndices - the character index array
* @param success - set to an error code if the operation fails
*
* @return the number of glyphs in the glyph index array
*/
virtual le_int32 computeGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, LEGlyphID *&glyphs, le_int32 *&charIndices, LEErrorCode &success);
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/**
* This method does basic glyph positioning. The default implementation positions
* the glyphs based on their advance widths. This is sufficient for most uses. It
* is not expected that many subclasses will override this method.
*
* Input parameters:
* @param glyphs - the input glyph array
* @param glyphCount - the number of glyphs in the glyph array
* @param x - the starting X position
* @param y - the starting Y position
*
* Output parameters:
* @param positions - the output X and Y positions (two entries per glyph)
*/
virtual void positionGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, float x, float y, float *&positions, LEErrorCode &success);
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/**
* This method does positioning adjustments like accent positioning and
* kerning. The default implementation does nothing. Subclasses needing
* position adjustments must override this method.
*
* Note that this method has both characters and glyphs as input so that
* it can use the character codes to determine glyph types if that information
* isn't directly available. (e.g. Some Arabic OpenType fonts don't have a GDEF
* table)
*
* @param chars - the input character context
* @param offset - the offset of the first character to process
* @param count - the number of characters to process
* @param reverse - true if the glyphs in the glyph array have been reordered
* @param glyphs - the input glyph array
* @param glyphCount - the number of glyphs
* @param positions - the position array, will be updated as needed
* @param success - output parameter set to an error code if the operation fails
*
* Note: the positions are passed as a plain array because this method should
* not need to reallocate them.
*/
virtual void adjustGlyphPositions(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, LEGlyphID glyphs[], le_int32 glyphCount, float positions[], LEErrorCode &success)
{
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if (LE_FAILURE(success)) {
return;
}
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if (chars == NULL || glyphs == NULL || positions == NULL || offset < 0 || count < 0) {
success = LE_ILLEGAL_ARGUMENT_ERROR;
return;
}
// default is no adjustments
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return;
};
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/**
* This method gets a table from the font associated with
* the text. The default implementation gets the table from
* the font instance. Subclasses which need to get the tables
* some other way must override this method.
*
* @param tableTag - the four byte table tag.
*
* @return the address of the table.
*/
virtual const void *getFontTable(LETag tableTag) const;
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/**
* This method does character to glyph mapping. The default implementation
* uses the font instance to do the mapping. It will allocate the glyph and
* character index arrays if they're not already allocated. If it allocates the
* character index array, it will fill it it.
*
* This method supports right to left
* text with the ability to store the glyphs in reverse order, and by supporting
* character mirroring, which will replace a character which has a left and right
* form, such as parens, with the opposite form before mapping it to a glyph index.
*
* Input parameters:
* @param chars - the input character context
* @param offset - the offset of the first character to be mapped
* @param count - the number of characters to be mapped
* @param reverse - if true, the output will be in reverse order
* @param mirror - if true, do character mirroring
*
* Output parameters:
* @param glyphs - the glyph array
* @param charIndices - the character index array
* @param success - set to an error code if the operation fails
*
* @see LEFontInstance
*/
virtual void mapCharsToGlyphs(const LEUnicode chars[], le_int32 offset, le_int32 count, le_bool reverse, le_bool mirror, LEGlyphID *&glyphs, le_int32 *&charIndices, LEErrorCode &success);
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/**
* This is a convenience method that forces the advance width of mark
* glyphs to be zero, which is required for proper selection and highlighting.
*
* @param glyphs - the glyph array
* @param glyphCount - the number of glyphs
* @param reverse - true if the glyph array has been reordered
* @param markFilter - used to identify mark glyphs
* @param positions - the glyph position array - updated as required
* @param success - output parameter set to an error code if the operation fails
*
* @see LEGlyphFilter
*/
static void adjustMarkGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, le_bool reverse, LEGlyphFilter *markFilter, float positions[], LEErrorCode &success);
public:
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/**
* The destructor. It will free any storage allocated for the
* glyph, character index and position arrays by calling the reset
* method. It is declared virtual so that it will be invoked by the
* subclass destructors.
*/
virtual ~LayoutEngine();
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/**
* This method will invoke the layout steps in their correct order by calling
* the computeGlyphs, positionGlyphs and adjustGlyphPosition methods.. It will
* compute the glyph, character index and position arrays.
*
* @param chars - the input character context
* @param offset - the offset of the first character to process
* @param count - the number of characters to process
* @param max - the number of characters in the input context
* @param rightToLeft - true if the characers are in a right to left directional run
* @param x - the initial X position
* @param y - the initial Y position
* @param success - output parameter set to an error code if the operation fails
*
* @return the number of glyphs in the glyph array
*
* Note; the glyph, character index and position array can be accessed
* using the getter method below.
*/
virtual le_int32 layoutChars(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, float x, float y, LEErrorCode &success);
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/**
* This method returns the number of glyphs in the glyph array. Note
* that the number of glyphs will be greater than or equal to the number
* of characters used to create the LayoutEngine.
*
* @return the number of glyphs in the glyph array
*/
le_int32 getGlyphCount() const
{
return fGlyphCount;
};
/**
* This method copies the glyph array into a caller supplied array.
* The caller must ensure that the array is large enough to hold all
* the glyphs.
*
* @param glyphs - the destiniation glyph array
* @param success - set to an error code if the operation fails
*/
void getGlyphs(LEGlyphID glyphs[], LEErrorCode &success) const
{
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if (LE_FAILURE(success)) {
return;
}
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if (glyphs == NULL) {
success = LE_ILLEGAL_ARGUMENT_ERROR;
return;
}
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if (fGlyphs == NULL) {
success = LE_NO_LAYOUT_ERROR;
}
LE_ARRAY_COPY(glyphs, fGlyphs, fGlyphCount);
};
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/**
* This method copies the glyph array into a caller supplied array,
* ORing in extra bits. (This functionality is needed by the JDK,
* which uses 32 bits pre glyph idex, with the high 16 bits encoding
* the composite font slot number)
*
* @param glyphs - the destination (32 bit) glyph array
* @param extraBits - this value will be ORed with each glyph index
* @param success - set to an error code if the operation fails
*/
virtual void getGlyphs(le_uint32 glyphs[], le_uint32 extraBits, LEErrorCode &success) const;
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/**
* This method copies the character index array into a caller supplied array.
* The caller must ensure that the array is large enough to hold a
* character index for each glyph.
*
* @param charIndices - the destiniation character index array
* @param success - set to an error code if the operation fails
*/
void getCharIndices(le_int32 charIndices[], LEErrorCode &success) const
{
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if LE_FAILURE(success) {
return;
}
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if (charIndices == NULL) {
success = LE_ILLEGAL_ARGUMENT_ERROR;
return;
}
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if (fCharIndices == NULL) {
success = LE_NO_LAYOUT_ERROR;
return;
}
LE_ARRAY_COPY(charIndices, fCharIndices, fGlyphCount);
};
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/**
* This method copies the character index array into a caller supplied array.
* The caller must ensure that the array is large enough to hold a
* character index for each glyph.
*
* @param charIndices - the destiniation character index array
* @param indexBase - an offset which will be added to each index
* @param success - set to an error code if the operation fails
*/
void getCharIndices(le_int32 charIndices[], le_int32 indexBase, LEErrorCode &success) const;
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/**
* This method copies the position array into a caller supplied array.
* The caller must ensure that the array is large enough to hold an
* X and Y position for each glyph, plus an extra X and Y for the
* advance of the last glyph.
*
* @param glyphs - the destiniation position array
* @param success - set to an error code if the operation fails
*/
void getGlyphPositions(float positions[], LEErrorCode &success) const
{
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if LE_FAILURE(success) {
return;
}
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if (positions == NULL) {
success = LE_ILLEGAL_ARGUMENT_ERROR;
return;
}
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if (fPositions == NULL) {
success = LE_NO_LAYOUT_ERROR;
return;
}
LE_ARRAY_COPY(positions, fPositions, fGlyphCount * 2 + 2);
};
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/**
* This method returns the X and Y position of the glyph at
* the given index.
*
* Input parameters:
* @param glyphIndex - the index of the glyph
*
* Output parameters:
* @param x - the glyph's X position
* @param y - the glyph's Y position
* @param success - set to an error code if the operation fails
*
*/
void getGlyphPosition(le_int32 glyphIndex, float &x, float &y, LEErrorCode &success) const
{
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if (LE_FAILURE(success)) {
return;
}
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if (glyphIndex > fGlyphCount) {
success = LE_INDEX_OUT_OF_BOUNDS_ERROR;
return;
}
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if (fPositions == NULL) {
success = LE_NO_LAYOUT_ERROR;
return;
}
x = fPositions[glyphIndex * 2];
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y = fPositions[glyphIndex * 2 + 1];
};
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/**
* This method frees the glyph, character index and position arrays
* so that the LayoutEngine can be reused to layout a different
* characer array. (This method is also called by the destructor)
*/
virtual void reset();
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/**
* This method returns a LayoutEngine capable of laying out text
* in the given font, script and langauge. Note that the LayoutEngine
* returned may be a subclass of LayoutEngine.
*
* @param fontInstance - the font of the text
* @param scriptCode - the script of the text
* @param langaugeCode - the language of the text
* @param success - output parameter set to an error code if the operation fails
*
* @return a LayoutEngine which can layout text in the given font.
*
* @see LEFontInstance
*/
static LayoutEngine *layoutEngineFactory(const LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode, LEErrorCode &success);
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/**
* ICU "poor man's RTTI", returns a UClassID for the actual class.
*
* @draft ICU 2.2
*/
virtual inline UClassID getDynamicClassID() const { return getStaticClassID(); }
/**
* ICU "poor man's RTTI", returns a UClassID for this class.
*
* @draft ICU 2.2
*/
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;
};
U_NAMESPACE_END
#endif