path: root/Build/source/texk/web2c/xetexdir/XeTeXOTMath.cpp

/****************************************************************************\
 Part of the XeTeX typesetting system
 Copyright (c) 1994-2008 by SIL International
 Copyright (c) 2009 by Jonathan Kew
 Copyright (c) 2012 by Khaled Hosny

 SIL Author(s): Jonathan Kew

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#include <assert.h>

#include "XeTeXOTMath.h"

#include "XeTeX_ext.h"
#include "XeTeXLayoutInterface.h"
#include "XeTeXFontInst.h"
#include "XeTeXswap.h"

typedef void*	voidptr;

extern "C" {
	extern voidptr*	fontlayoutengine;
	extern integer*	fontarea;
	extern integer*	fontsize;
}

static int32_t getCoverage(const Coverage* coverage, GlyphID g)
{
	if (SWAP(coverage->format) == 1) {
		const CoverageFormat1 *table = (const CoverageFormat1 *) coverage;
		for (int i = 0; i < SWAP(table->glyphCount); i++) {
			if (SWAP(table->glyphArray[i]) == g)
				return i;
		}
	} else if (SWAP(coverage->format) == 2) {
		const CoverageFormat2 *table = (const CoverageFormat2 *) coverage;
		for (int i = 0; i < SWAP(table->rangeCount); i++) {
			if (SWAP(table->rangeArray[i].start) <= g && SWAP(table->rangeArray[i].end) >= g)
				return SWAP(table->rangeArray[i].startCoverageIndex) + (g - SWAP(table->rangeArray[i].start));
		}
	}

	return -1;
}

static SInt16 getMathConstant(XeTeXFontInst* fontInst, mathConstantIndex whichConstant)
{
	const char* table = (const char*)fontInst->getFontTable(kMATH);
	if (table == NULL)
		return 0;

	const UInt16* constants = (const UInt16*)(table + SWAP(((const MathTableHeader*)table)->mathConstants));

	if (whichConstant < firstMathValueRecord) {
		/* it's a simple 16-bit value */
		return SWAP(constants[whichConstant]);
	}
	else if (whichConstant <= lastMathValueRecord) {
		const MathValueRecord* valueRecords = (const MathValueRecord*)
			((char*)constants + firstMathValueRecord * sizeof(UInt16) - firstMathValueRecord * sizeof(MathValueRecord));
		return SWAP(valueRecords[whichConstant].value);
	}
	else if (whichConstant <= lastMathConstant) {
		return SWAP(constants[whichConstant + (lastMathValueRecord - firstMathValueRecord + 1)]);
	}
	else
		return 0; /* or abort, with "internal error" or something */
}

int
get_ot_math_constant(int f, int n)
{
	int	rval = 0;

	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
		rval = getMathConstant(font, (mathConstantIndex)n);
		/* scale according to font size, except the ones that are percentages */
		if (n > scriptScriptPercentScaleDown && n < radicalDegreeBottomRaisePercent)
			rval = D2Fix(font->unitsToPoints(rval));
	}
	return rval;
}

/* fontdimen IDs for math symbols font (family 2) */
#define math_x_height	5
#define math_quad		6
#define num1			8	/* numerator shift-up in display styles */
#define num2			9	/* numerator shift-up in non-display, non-\.{\\atop} */
#define num3			10	/* numerator shift-up in non-display \.{\\atop} */
#define denom1			11	/* denominator shift-down in display styles */
#define denom2			12	/* denominator shift-down in non-display styles */
#define sup1			13	/* superscript shift-up in uncramped display style */
#define sup2			14	/* superscript shift-up in uncramped non-display */
#define sup3			15	/* superscript shift-up in cramped styles */
#define sub1			16	/* subscript shift-down if superscript is absent */
#define sub2			17	/* subscript shift-down if superscript is present */
#define sup_drop		18	/* superscript baseline below top of large box */
#define sub_drop		19	/* subscript baseline below bottom of large box */
#define delim1			20	/* size of \.{\\atopwithdelims} delimiters */
#define delim2			21	/* size of \.{\\atopwithdelims} delimiters in non-displays */
#define axis_height		22	/* height of fraction lines above the baseline */

const mathConstantIndex TeX_sym_to_OT_map[] = {
	unknown,
	unknown,
	unknown,
	unknown,
	unknown,
	accentBaseHeight, // x-height
	unknown, // quad
	unknown,
	fractionNumeratorDisplayStyleShiftUp,
	fractionNumeratorShiftUp,
	stackTopShiftUp,
	fractionDenominatorDisplayStyleShiftDown,
	fractionDenominatorShiftDown,
	superscriptShiftUp, // ??
	superscriptShiftUp, // ??
	superscriptShiftUpCramped,
	subscriptShiftDown, // ??
	subscriptShiftDown, // ??
	superscriptBaselineDropMax, // ??
	subscriptBaselineDropMin, // ??
	delimitedSubFormulaMinHeight,
	unknown, // using quad instead for now
	axisHeight
};

int
get_native_mathsy_param(int f, int n)
{
	int	rval = 0;

	if (n == math_quad || n == delim2)
		rval = fontsize[f];
	else {
		if (n < sizeof(TeX_sym_to_OT_map) / sizeof(mathConstantIndex)) {
			mathConstantIndex ot_index = TeX_sym_to_OT_map[n];
			if (ot_index != unknown)
				rval = get_ot_math_constant(f, (int)ot_index);
		}
	}
//	fprintf(stderr, " math_sy(%d, %d) returns %.3f\n", f, n, Fix2D(rval));
	
	return rval;
}

/* fontdimen IDs for math extension font (family 3) */
#define default_rule_thickness	8	/* thickness of \.{\\over} bars */
#define big_op_spacing1			9	/* minimum clearance above a displayed op */
#define big_op_spacing2			10	/* minimum clearance below a displayed op */
#define big_op_spacing3			11	/* minimum baselineskip above displayed op */
#define big_op_spacing4			12	/* minimum baselineskip below displayed op */
#define big_op_spacing5			13	/* padding above and below displayed limits */

const mathConstantIndex TeX_ext_to_OT_map[] = {
	unknown,
	unknown,
	unknown,
	unknown,
	unknown,
	accentBaseHeight, // x-height
	unknown, // quad
	unknown,
	fractionRuleThickness, // default_rule_thickness
	upperLimitGapMin, // big_op_spacing1
	lowerLimitGapMin, // big_op_spacing2
	upperLimitBaselineRiseMin, // big_op_spacing3
	lowerLimitBaselineDropMin, // big_op_spacing4
	stackGapMin // big_op_spacing5
};

int
get_native_mathex_param(int f, int n)
{
	int	rval = 0;

	if (n == math_quad)
		rval = fontsize[f];
	else {
		if (n < sizeof(TeX_ext_to_OT_map) / sizeof(mathConstantIndex)) {
			mathConstantIndex ot_index = TeX_ext_to_OT_map[n];
			if (ot_index != unknown)
				rval = get_ot_math_constant(f, (int)ot_index);
		}
	}
//	fprintf(stderr, " math_ex(%d, %d) returns %.3f\n", f, n, Fix2D(rval));
	
	return rval;
}

int
get_ot_math_variant(int f, int g, int v, integer* adv, int horiz)
{
	int	rval = g;
	*adv = -1;
	
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);

		const char* table = (const char*)font->getFontTable(kMATH);
		if (table == NULL)
			return rval;

		uint16_t	offset = SWAP(((const MathTableHeader*)table)->mathVariants);
		if (offset == 0)
			return rval;
		const MathVariants* variants = (const MathVariants*)(table + offset);

		offset = horiz ? SWAP(variants->horizGlyphCoverage) : SWAP(variants->vertGlyphCoverage);
		if (offset == 0)
			return rval;
		const Coverage* coverage = (const Coverage*)(((const char*)variants) + offset);

		int32_t	index = getCoverage(coverage, g);
		if (index >= 0) {
			if (horiz)
				index += SWAP(variants->vertGlyphCount);
			const MathGlyphConstruction*	construction = (const MathGlyphConstruction*)(((const char*)variants)
															+ SWAP(variants->vertGlyphConstruction[index]));
			if (v < SWAP(construction->variantCount)) {
				rval = SWAP(construction->mathGlyphVariantRecord[v].variantGlyph);
				*adv = D2Fix(font->unitsToPoints(SWAP(construction->mathGlyphVariantRecord[v].advanceMeasurement)));
			}
		}
	}
	
	return rval;
}

void*
get_ot_assembly_ptr(int f, int g, int horiz)
{
	void*	rval = NULL;
	
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);

		const char* table = (const char*)font->getFontTable(kMATH);
		if (table == NULL)
			return rval;

		uint16_t	offset = SWAP(((const MathTableHeader*)table)->mathVariants);
		if (offset == 0)
			return rval;
		const MathVariants* variants = (const MathVariants*)(table + offset);

		offset = horiz ? SWAP(variants->horizGlyphCoverage) : SWAP(variants->vertGlyphCoverage);
		if (offset == 0)
			return rval;
		const Coverage* coverage = (const Coverage*)(((const char*)variants) + offset);

		int32_t	index = getCoverage(coverage, g);
		if (index >= 0) {
			if (horiz)
				index += SWAP(variants->vertGlyphCount);
			const MathGlyphConstruction*	construction = (const MathGlyphConstruction*)(((const char*)variants)
															+ SWAP(variants->vertGlyphConstruction[index]));
			offset = SWAP(construction->glyphAssembly);
			if (offset != 0)
				rval = (void*)(((const char*)construction) + offset);
		}
	}
	
	return rval;
}

int
get_ot_math_ital_corr(int f, int g)
{
	int	rval = 0;
	
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);

		const char* table = (const char*)font->getFontTable(kMATH);
		if (table == NULL)
			return rval;

		uint16_t	offset = SWAP(((const MathTableHeader*)table)->mathGlyphInfo);
		if (offset == 0)
			return rval;
		const MathGlyphInfo* glyphInfo = (const MathGlyphInfo*)(table + offset);

		offset = SWAP(glyphInfo->mathItalicsCorrectionInfo);
		if (offset == 0)
			return rval;
		const MathItalicsCorrectionInfo* italCorrInfo = (const MathItalicsCorrectionInfo*)(((const char*)glyphInfo) + offset);

		offset = SWAP(italCorrInfo->coverage);
		if (offset == 0)
			return rval;
		const Coverage* coverage = (const Coverage*)(((const char*)italCorrInfo) + offset);

		int32_t	index = getCoverage(coverage, g);
		if (index >= 0 && index < SWAP(italCorrInfo->italicsCorrectionCount))
			rval = D2Fix(font->unitsToPoints(SWAP(italCorrInfo->italicsCorrection[index].value)));
	}
	
	return rval;
}

int
get_ot_math_accent_pos(int f, int g)
{
	int	rval = 0x7fffffffUL;
	
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);

		const char* table = (const char*)font->getFontTable(kMATH);
		if (table == NULL)
			return rval;

		uint16_t	offset = SWAP(((const MathTableHeader*)table)->mathGlyphInfo);
		if (offset == 0)
			return rval;
		const MathGlyphInfo* glyphInfo = (const MathGlyphInfo*)(table + offset);

		offset = SWAP(glyphInfo->mathTopAccentAttachment);
		if (offset == 0)
			return rval;
		const MathTopAccentAttachment* accentAttachment = (const MathTopAccentAttachment*)(((const char*)glyphInfo) + offset);

		offset = SWAP(accentAttachment->coverage);
		if (offset == 0)
			return rval;
		const Coverage* coverage = (const Coverage*)(((const char*)accentAttachment) + offset);

		int32_t	index = getCoverage(coverage, g);
		if (index >= 0 && index < SWAP(accentAttachment->topAccentAttachmentCount)) {
			rval = (int16_t)SWAP(accentAttachment->topAccentAttachment[index].value);
			rval = D2Fix(font->unitsToPoints(rval));
		}
	}
	
	return rval;
}

int
ot_min_connector_overlap(int f)
{
	int	rval = 0;
	
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);

		const char* table = (const char*)font->getFontTable(kMATH);
		if (table == NULL)
			return rval;

		uint16_t	offset = SWAP(((const MathTableHeader*)table)->mathVariants);
		if (offset == 0)
			return rval;
		const MathVariants* variants = (const MathVariants*)(table + offset);

		rval = D2Fix(font->unitsToPoints(SWAP(variants->minConnectorOverlap)));
	}

	return rval;
}

typedef enum {
	topRight,
	topLeft,
	bottomRight,
	bottomLeft,
} MathKernSide;

static int
getMathKernAt(int f, int g, MathKernSide side, int height)
{
	int rval = 0;
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst* font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);

		const char* table = (const char*)font->getFontTable(kMATH);
		if (table == NULL)
			return rval;

		uint16_t	offset = SWAP(((const MathTableHeader*)table)->mathGlyphInfo);
		if (offset == 0)
			return rval;

		const MathGlyphInfo* glyphInfo = (const MathGlyphInfo*)(table + offset);

		offset = SWAP(glyphInfo->mathKernInfo);
		if (offset == 0)
			return rval;

		const MathKernInfo* mathKernInfo = (const MathKernInfo*)(((const char*)glyphInfo) + offset);

		offset = SWAP(mathKernInfo->coverage);
		if (offset == 0)
			return rval;

		const Coverage* coverage = (const Coverage*)(((const char*)mathKernInfo) + offset);

		int32_t index = getCoverage(coverage, g);
		if (index >= 0 && index < SWAP(mathKernInfo->kernInfoCount)) {
			if (side == topRight)
				offset = SWAP(mathKernInfo->kernInfo[index].topRight);
			else if (side == bottomRight)
				offset = SWAP(mathKernInfo->kernInfo[index].bottomRight);
			else if (side == topLeft)
				offset = SWAP(mathKernInfo->kernInfo[index].topLeft);
			else if (side == bottomLeft)
				offset = SWAP(mathKernInfo->kernInfo[index].bottomLeft);
			else
				assert(0); // we should not reach here

			if (offset == 0)
				return rval;

			const MathKernTable* kernTable = (const MathKernTable*)(((const char*)mathKernInfo) + offset);

			uint16_t count = SWAP(kernTable->heightCount);

			// XXX: the following makes no sense WRT my understanding of the
			// spec! it is just how things worked for me.
			if (count == 0)
				rval = SWAP(kernTable->kern[-1].value);
			else if (height < SWAP(kernTable->height[0].value))
				rval = SWAP(kernTable->kern[1].value);
			else if (height > SWAP(kernTable->height[count].value))
				rval = SWAP(kernTable->kern[count+1].value);
			else {
				for (int i = 0; i < count; i++) {
					if (height > SWAP(kernTable->height[i].value)) {
						rval = SWAP(kernTable->kern[i+1].value);
						break;
					}
				}
			}

			//fprintf(stderr, "   kern: %f %f\n", font->unitsToPoints(height), font->unitsToPoints(rval));
		}
	}

	return rval;
}

static float
glyph_height(int f, int g)
{
	float rval = 0.0;

	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXLayoutEngine engine = (XeTeXLayoutEngine)fontlayoutengine[f];
		getGlyphHeightDepth(engine, g, &rval, NULL);
	}

	return rval;
}

static float
glyph_depth(int f, int g)
{
	float rval = 0.0;

	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXLayoutEngine engine = (XeTeXLayoutEngine)fontlayoutengine[f];
		getGlyphHeightDepth(engine, g, NULL, &rval);
	}

	return rval;
}

// keep in sync with xetex.web
#define sup_cmd 0
#define sub_cmd 1

int
get_ot_math_kern(int f, int g, int sf, int sg, int cmd, int shift)
{
	int rval = 0;

	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst* font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
		int kern = 0, skern = 0;
		float corr_height_top = 0.0, corr_height_bot = 0.0;

		shift = Fix2D(shift);

		if (cmd == sup_cmd) { // superscript
			corr_height_top =  font->pointsToUnits(glyph_height(f, g));
			corr_height_bot = -font->pointsToUnits(glyph_depth(sf, sg) + shift);

			kern = getMathKernAt(f, g, topRight, corr_height_top);
			skern = getMathKernAt(sf, sg, bottomLeft, corr_height_top);
			rval = kern + skern;

			kern = getMathKernAt(f, g, topRight, corr_height_bot);
			skern = getMathKernAt(sf, sg, bottomLeft, corr_height_bot);
			if ((kern + skern) < rval)
				rval = kern + skern;

		} else if (cmd == sub_cmd) { // subscript
			corr_height_top =  font->pointsToUnits(glyph_height(sf, sg) - shift);
			corr_height_bot = -font->pointsToUnits(glyph_depth(f, g));

			kern = getMathKernAt(f, g, bottomRight, corr_height_top);
			skern = getMathKernAt(sf, sg, topLeft, corr_height_top);
			rval = kern + skern;

			kern = getMathKernAt(f, g, bottomRight, corr_height_bot);
			skern = getMathKernAt(sf, sg, topLeft, corr_height_bot);
			if ((kern + skern) < rval)
				rval = kern + skern;

		} else {
			assert(0); // we should not reach here
		}

		rval = D2Fix(font->unitsToPoints(rval));
	}

	return rval;
}

int
ot_part_count(const GlyphAssembly* a)
{
	return SWAP(a->partCount);
}

int
ot_part_glyph(const GlyphAssembly* a, int i)
{
	return SWAP(a->partRecords[i].glyph);
}

int
ot_part_is_extender(const GlyphAssembly* a, int i)
{
	return (SWAP(a->partRecords[i].partFlags) & fExtender) != 0;
}

int
ot_part_start_connector(int f, const GlyphAssembly* a, int i)
{
	int	rval = 0;
	
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
		rval = D2Fix(font->unitsToPoints(SWAP(a->partRecords[i].startConnectorLength)));
	}
	
	return rval;
}

int
ot_part_end_connector(int f, const GlyphAssembly* a, int i)
{
	int	rval = 0;
	
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
		rval = D2Fix(font->unitsToPoints(SWAP(a->partRecords[i].endConnectorLength)));
	}
	
	return rval;
}

int
ot_part_full_advance(int f, const GlyphAssembly* a, int i)
{
	int	rval = 0;
	
	if (fontarea[f] == OTGR_FONT_FLAG) {
		XeTeXFontInst*	font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
		rval = D2Fix(font->unitsToPoints(SWAP(a->partRecords[i].fullAdvance)));
	}
	
	return rval;
}