372 lines
13 KiB
C++
372 lines
13 KiB
C++
|
|
/*
|
|
* @(#)LayoutEngine.h 1.4 00/03/15
|
|
*
|
|
* (C) Copyright IBM Corp. 1998, 1999, 2000 - All Rights Reserved
|
|
*
|
|
*/
|
|
|
|
#ifndef __LAYOUTENGINE_H
|
|
#define __LAYOUTENGINE_H
|
|
|
|
#include "LETypes.h"
|
|
#include "LEFontInstance.h"
|
|
#include "LEGlyphFilter.h"
|
|
|
|
#include "unicode/utypes.h"
|
|
|
|
#include <string.h>
|
|
|
|
#define ARRAY_COPY(dst, src, count) memcpy(dst, src, (count) * sizeof (src)[0])
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* 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
|
|
{
|
|
protected:
|
|
/**
|
|
* The number of glyphs in the output
|
|
*/
|
|
le_int32 fGlyphCount;
|
|
|
|
/**
|
|
* The output glyph array
|
|
*/
|
|
LEGlyphID *fGlyphs;
|
|
|
|
/**
|
|
* 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;
|
|
|
|
/**
|
|
* 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.
|
|
*/
|
|
float *fPositions;
|
|
|
|
/**
|
|
* The font instance for the text font.
|
|
*
|
|
* @see LEFontInstance
|
|
*/
|
|
LEFontInstance *fFontInstance;
|
|
|
|
/**
|
|
* The script code for the text
|
|
*
|
|
* @see ScriptAndLanguageTags.h for script codes.
|
|
*/
|
|
le_int32 fScriptCode;
|
|
|
|
/**
|
|
* The langauge code for the text
|
|
*
|
|
* @see ScriptAndLanguageTags.h for language codes.
|
|
*/
|
|
le_int32 fLanguageCode;
|
|
|
|
/**
|
|
* 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(LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode);
|
|
|
|
/**
|
|
* This overrides the default no argument constructor to make it
|
|
* difficult for clients to call it. Clients are expected to call
|
|
* layoutEngineFactory.
|
|
*/
|
|
LayoutEngine();
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* @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);
|
|
|
|
/**
|
|
* 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);
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* 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[])
|
|
{
|
|
// default is no adjustments
|
|
};
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
return fFontInstance->getFontTable(tableTag);
|
|
};
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* @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);
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* @see LEGlyphFilter
|
|
*/
|
|
static void adjustMarkGlyphs(const LEGlyphID glyphs[], le_int32 glyphCount, le_bool reverse, LEGlyphFilter *markFilter, float positions[]);
|
|
|
|
public:
|
|
/**
|
|
* 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();
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* @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.
|
|
*/
|
|
le_int32 layoutChars(const LEUnicode chars[], le_int32 offset, le_int32 count, le_int32 max, le_bool rightToLeft, float x, float y);
|
|
|
|
/**
|
|
* 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
|
|
*/
|
|
void getGlyphs(LEGlyphID glyphs[])
|
|
{
|
|
ARRAY_COPY(glyphs, fGlyphs, fGlyphCount);
|
|
};
|
|
|
|
/**
|
|
* 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
|
|
*/
|
|
void getGlyphs(le_uint32 glyphs[], le_uint32 extraBits);
|
|
|
|
/**
|
|
* This method copies the character index array into a caller supplied array.
|
|
* The caller must ensure that the array is large enough to hold all
|
|
* the character indices.
|
|
*
|
|
* @param charIndices - the destiniation character index array
|
|
*/
|
|
void getCharIndices(le_int32 charIndices[])
|
|
{
|
|
ARRAY_COPY(charIndices, fCharIndices, fGlyphCount);
|
|
};
|
|
|
|
/**
|
|
* This method copies the character index array into a caller supplied array.
|
|
* The caller must ensure that the array is large enough to hold all
|
|
* the character indices.
|
|
*
|
|
* @param charIndices - the destiniation character index array
|
|
* @param indexBase - an offset which will be added to each index
|
|
*/
|
|
void getCharIndices(le_int32 charIndices[], le_int32 indexBase);
|
|
|
|
/**
|
|
* This method copies the position array into a caller supplied array.
|
|
* The caller must ensure that the array is large enough to hold all
|
|
* the positions.
|
|
*
|
|
* @param glyphs - the destiniation position array
|
|
*/
|
|
void getGlyphPositions(float positions[])
|
|
{
|
|
ARRAY_COPY(positions, fPositions, fGlyphCount * 2 + 2);
|
|
};
|
|
|
|
/**
|
|
* This method returns the x position of the glyph at the
|
|
* given index.
|
|
*
|
|
* @param glyphIndex - the index of the glyph
|
|
*
|
|
* @return the glyph's x position
|
|
*/
|
|
float getGlyphXPosition(le_int32 glyphIndex)
|
|
{
|
|
return fPositions[glyphIndex * 2];
|
|
};
|
|
|
|
/**
|
|
* 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();
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* @see LEFontInstance
|
|
*/
|
|
static LayoutEngine *layoutEngineFactory(LEFontInstance *fontInstance, le_int32 scriptCode, le_int32 languageCode);
|
|
|
|
};
|
|
|
|
#endif
|
|
|