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

/****************************************************************************\
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 Copyright (c) 2009 by Jonathan Kew
 Copyright (c) 2012-2015 by Khaled Hosny

 SIL Author(s): Jonathan Kew

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#include <w2c/config.h>

#include <assert.h>
#include <algorithm>

#include "XeTeXOTMath.h"

#include "XeTeX_web.h"
#include "XeTeXLayoutInterface.h"
#include "XeTeXFontInst.h"

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

    if (fontarea[f] == OTGR_FONT_FLAG) {
        XeTeXFontInst*  font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
        hb_font_t* hbFont = font->getHbFont();
        rval = hb_ot_math_get_constant(hbFont, constant);
        /* scale according to font size, except the ones that are percentages */
        switch (constant) {
            case HB_OT_MATH_CONSTANT_SCRIPT_PERCENT_SCALE_DOWN:
            case HB_OT_MATH_CONSTANT_SCRIPT_SCRIPT_PERCENT_SCALE_DOWN:
            case HB_OT_MATH_CONSTANT_RADICAL_DEGREE_BOTTOM_RAISE_PERCENT:
                break;
            default:
                rval = D2Fix(font->unitsToPoints(rval));
                break;
        }
    }
    return rval;
}

#define unknown ((hb_ot_math_constant_t)-1)

/* 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 hb_ot_math_constant_t TeX_sym_to_OT_map[] = {
    unknown,
    unknown,
    unknown,
    unknown,
    unknown,
    HB_OT_MATH_CONSTANT_ACCENT_BASE_HEIGHT, // x-height
    unknown, // quad
    unknown,
    HB_OT_MATH_CONSTANT_FRACTION_NUMERATOR_DISPLAY_STYLE_SHIFT_UP,
    HB_OT_MATH_CONSTANT_FRACTION_NUMERATOR_SHIFT_UP,
    HB_OT_MATH_CONSTANT_STACK_TOP_SHIFT_UP,
    HB_OT_MATH_CONSTANT_FRACTION_DENOMINATOR_DISPLAY_STYLE_SHIFT_DOWN,
    HB_OT_MATH_CONSTANT_FRACTION_DENOMINATOR_SHIFT_DOWN,
    HB_OT_MATH_CONSTANT_SUPERSCRIPT_SHIFT_UP, // ??
    HB_OT_MATH_CONSTANT_SUPERSCRIPT_SHIFT_UP, // ??
    HB_OT_MATH_CONSTANT_SUPERSCRIPT_SHIFT_UP_CRAMPED,
    HB_OT_MATH_CONSTANT_SUBSCRIPT_SHIFT_DOWN, // ??
    HB_OT_MATH_CONSTANT_SUBSCRIPT_SHIFT_DOWN, // ??
    HB_OT_MATH_CONSTANT_SUPERSCRIPT_BASELINE_DROP_MAX, // ??
    HB_OT_MATH_CONSTANT_SUBSCRIPT_BASELINE_DROP_MIN, // ??
    HB_OT_MATH_CONSTANT_DELIMITED_SUB_FORMULA_MIN_HEIGHT,
    unknown, // using quad instead for now
    HB_OT_MATH_CONSTANT_AXIS_HEIGHT
};

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

    if (n == math_quad) {
        rval = fontsize[f];
    }
    else if (n == delim2) { // XXX not sure what OT parameter we should use here;
                            // for now we use 1.5em, clamped to delim1 height
        rval = std::min<int>(1.5 * fontsize[f], get_native_mathsy_param(f, delim1));
    }
    else {
        if (n < sizeof(TeX_sym_to_OT_map) / sizeof(hb_ot_math_constant_t)) {
            hb_ot_math_constant_t 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 hb_ot_math_constant_t TeX_ext_to_OT_map[] = {
    unknown,
    unknown,
    unknown,
    unknown,
    unknown,
    HB_OT_MATH_CONSTANT_ACCENT_BASE_HEIGHT, // x-height
    unknown, // quad
    unknown,
    HB_OT_MATH_CONSTANT_FRACTION_RULE_THICKNESS, // default_rule_thickness
    HB_OT_MATH_CONSTANT_UPPER_LIMIT_GAP_MIN, // big_op_spacing1
    HB_OT_MATH_CONSTANT_LOWER_LIMIT_GAP_MIN, // big_op_spacing2
    HB_OT_MATH_CONSTANT_UPPER_LIMIT_BASELINE_RISE_MIN, // big_op_spacing3
    HB_OT_MATH_CONSTANT_LOWER_LIMIT_BASELINE_DROP_MIN, // big_op_spacing4
    HB_OT_MATH_CONSTANT_STACK_GAP_MIN // 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(hb_ot_math_constant_t)) {
            hb_ot_math_constant_t 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)
{
    hb_codepoint_t rval = g;
    *adv = -1;

    if (fontarea[f] == OTGR_FONT_FLAG) {
        XeTeXFontInst*  font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
        hb_font_t* hbFont = font->getHbFont();
        hb_ot_math_glyph_variant_t variant[1];
        unsigned int count = 1;
        hb_ot_math_get_glyph_variants(hbFont, g, horiz ? HB_DIRECTION_RTL : HB_DIRECTION_TTB, v, &count, variant);
        if (count > 0) {
            rval = variant->glyph;
            *adv = D2Fix(font->unitsToPoints(variant->advance));
        }
    }

    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]);
        hb_font_t* hbFont = font->getHbFont();

        unsigned int count = hb_ot_math_get_glyph_assembly(hbFont, g, horiz ? HB_DIRECTION_RTL : HB_DIRECTION_TTB, 0, NULL, NULL, NULL);
        if (count > 0) {
            GlyphAssembly* a = (GlyphAssembly*) xmalloc(sizeof(GlyphAssembly));
            a->count = count;
            a->parts = (hb_ot_math_glyph_part_t*) xmalloc(count * sizeof(hb_ot_math_glyph_part_t));
            hb_ot_math_get_glyph_assembly(hbFont, g, horiz ? HB_DIRECTION_RTL : HB_DIRECTION_TTB, 0, &a->count, a->parts, NULL);
            rval = (void*) a;
        }
    }

    return rval;
}

void
free_ot_assembly(GlyphAssembly* a)
{
    if (!a)
        return;
    free (a->parts);
    free (a);
}

int
get_ot_math_ital_corr(int f, int g)
{
    hb_position_t rval = 0;

    if (fontarea[f] == OTGR_FONT_FLAG) {
        XeTeXFontInst*  font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
        hb_font_t* hbFont = font->getHbFont();
        rval = hb_ot_math_get_glyph_italics_correction(hbFont, g);
        rval = D2Fix(font->unitsToPoints(rval));
    }

    return rval;
}

int
get_ot_math_accent_pos(int f, int g)
{
    hb_position_t rval = 0x7fffffffUL;

    if (fontarea[f] == OTGR_FONT_FLAG) {
        XeTeXFontInst*  font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
        hb_font_t* hbFont = font->getHbFont();
        rval = hb_ot_math_get_glyph_top_accent_attachment(hbFont, g);
        rval = D2Fix(font->unitsToPoints(rval));
    }

    return rval;
}

int
ot_min_connector_overlap(int f)
{
    hb_position_t rval = 0;

    if (fontarea[f] == OTGR_FONT_FLAG) {
        XeTeXFontInst*  font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
        hb_font_t* hbFont = font->getHbFont();
        rval = hb_ot_math_get_min_connector_overlap(hbFont, HB_DIRECTION_RTL);
        rval = D2Fix(font->unitsToPoints(rval));
    }

    return rval;
}

static int
getMathKernAt(int f, int g, int height, hb_ot_math_kern_t side)
{
    hb_position_t rval = 0;

    if (fontarea[f] == OTGR_FONT_FLAG) {
        XeTeXFontInst* font = (XeTeXFontInst*)getFont((XeTeXLayoutEngine)fontlayoutengine[f]);
        hb_font_t* hbFont = font->getHbFont();
        rval = hb_ot_math_get_glyph_kerning(hbFont, g, side, height);
    }

    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,    // Base font and glyph number
                 int sf, int sg,   // Sub/superscript font and glyph number
                 int cmd,          // sup_cmd or sub_cmd
                 int shift_scaled  // TeX scaled points
                 )
{
  int rval = 0;

  // Cf. https://docs.microsoft.com/en-us/typography/opentype/spec/math#mathkerninfo-table

  if (fontarea[f] == OTGR_FONT_FLAG && fontarea[sf] == OTGR_FONT_FLAG) {
    XeTeXFontInst* font  = (XeTeXFontInst*) getFont((XeTeXLayoutEngine)fontlayoutengine[f]);

    XeTeXFontInst* sfont = (XeTeXFontInst*) getFont((XeTeXLayoutEngine)fontlayoutengine[sf]);

    // Do calculations in glyph units.

    // The next four lines could be streamlined by having
    // glyph_height() and glyph_depth() return the metrics in glyph
    // units, but that would require tweaking getGlyphHeightDepth(),
    // which is used elsewhere.

    int g_height = font->pointsToUnits(glyph_height(f, g));
    int g_depth  = font->pointsToUnits(glyph_depth(f, g));

    int sg_height = sfont->pointsToUnits(glyph_height(sf, sg));
    int sg_depth  = sfont->pointsToUnits(glyph_depth(sf, sg));

    // Convert the shift amount to base glyph units.
    int shift = font->pointsToUnits(Fix2D(shift_scaled));

    // Multiply sub/superscript glyph units by scale_factor to make
    // them commensurate with base glyph units.

    float f_size  = font->getPointSize();
    float sf_size = sfont->getPointSize();

    assert(f_size != 0.0);

    float scale_factor = sf_size / f_size;

    if (cmd == sup_cmd) { // superscript
      // (1) Calculate the kern at the bottom of the superscript-glyph
      // bounding box.

      // In base glyph units, the bottom of the superscript is at a
      // distance of (shift - scale_factor * sg_depth) above the
      // baseline.

      int kern = getMathKernAt(f, g, shift - scale_factor * sg_depth,
                               HB_OT_MATH_KERN_TOP_RIGHT);

      // In superscript glyph units, the bottom of the superscript is
      // a distance of sg_depth below the baseline.

      int skern = getMathKernAt(sf, sg, -sg_depth,
                                HB_OT_MATH_KERN_BOTTOM_LEFT);

      int top_kern = kern + scale_factor * skern;

      // (2) Calculate the kern at the top of the base-glyph bounding
      // box.

      // In base glyph units, the top of the base glyph is a distance
      // of g_height above the baseline.

      kern = getMathKernAt(f, g, g_height, HB_OT_MATH_KERN_TOP_RIGHT);

      // In superscript glyph units, the top of the base glyph is a
      // distance of (g_height - shift)/scale_factor above the
      // baseline.

      skern = getMathKernAt(sf, sg, (g_height - shift) / scale_factor,
                            HB_OT_MATH_KERN_BOTTOM_LEFT);

      int bot_kern = kern + scale_factor * skern;

      // (3) The spec says "Take the minimum of these two sums," but
      // surely we want the kern that results in the greater
      // separation between the base and the superscript?  That
      // corresponds to the maximum.  (In the case where both kerns
      // are negative, this is the same as the kern with the minimum
      // *absolute* value, which is presumably what the spec means.)

      rval = (top_kern > bot_kern) ? top_kern : bot_kern;
    } else if (cmd == sub_cmd) { // subscript
      // (1) Calculate the kern at the top of the subscript-glyph
      // bounding box.

      // In base glyph units,, the top of the subscript is at a height
      // of scale_factor * sg_height - shift.

      int kern = getMathKernAt(f, g, scale_factor * sg_height - shift,
                               HB_OT_MATH_KERN_BOTTOM_RIGHT);

      // In subscript glyph units, the top of the subscript-glyph
      // bounding box is sg_height above the baseline.

      int skern = getMathKernAt(sf, sg, sg_height,
                                HB_OT_MATH_KERN_TOP_LEFT);

      int top_kern = kern + scale_factor * skern;

      // (2) Calculate the kern at the bottom of the base-glyph
      // bounding box.

      // In base glyph units, the bottom of the base-glyph is at
      // g_depth below the baseline:

      kern = getMathKernAt(f, g, -g_depth,
                           HB_OT_MATH_KERN_BOTTOM_RIGHT);

      // In subscript glyph units, the bottom of the base glyph is at
      // a height of shift - g_depth above the baseline, translated
      // into subscript glyph units.

      skern = getMathKernAt(sf, sg, (shift - g_depth) / scale_factor,
                            HB_OT_MATH_KERN_TOP_LEFT);

      int bot_kern = kern + scale_factor * skern;

      // (3) See above.

      rval = (top_kern > bot_kern) ? top_kern : bot_kern;
    } else {
      assert(0); // we should not reach here
    }

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

  return rval;
}

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

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

int
ot_part_is_extender(const GlyphAssembly* a, int i)
{
    return (a->parts[i].flags & HB_MATH_GLYPH_PART_FLAG_EXTENDER) != 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(a->parts[i].start_connector_length));
    }

    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(a->parts[i].end_connector_length));
    }

    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(a->parts[i].full_advance));
    }

    return rval;
}