src/hb-ot-color-colr-table.hh

/*
 * Copyright © 2018  Ebrahim Byagowi
 * Copyright © 2020  Google, Inc.
 *
 *  This is part of HarfBuzz, a text shaping library.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and its documentation for any purpose, provided that the
 * above copyright notice and the following two paragraphs appear in
 * all copies of this software.
 *
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 * Google Author(s): Calder Kitagawa
 */

#ifndef HB_OT_COLOR_COLR_TABLE_HH
#define HB_OT_COLOR_COLR_TABLE_HH

#include "hb-open-type.hh"
#include "hb-ot-layout-common.hh"

/*
 * COLR -- Color
 * https://docs.microsoft.com/en-us/typography/opentype/spec/colr
 */
#define HB_OT_TAG_COLR HB_TAG('C','O','L','R')


namespace OT {

struct LayerRecord
{
  operator hb_ot_color_layer_t () const { return {glyphId, colorIdx}; }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  public:
  HBGlyphID	glyphId;	/* Glyph ID of layer glyph */
  Index		colorIdx;	/* Index value to use with a
				 * selected color palette.
				 * An index value of 0xFFFF
				 * is a special case indicating
				 * that the text foreground
				 * color (defined by a
				 * higher-level client) should
				 * be used and shall not be
				 * treated as actual index
				 * into CPAL ColorRecord array. */
  public:
  DEFINE_SIZE_STATIC (4);
};

struct BaseGlyphRecord
{
  int cmp (hb_codepoint_t g) const
  { return g < glyphId ? -1 : g > glyphId ? 1 : 0; }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (likely (c->check_struct (this)));
  }

  public:
  HBGlyphID	glyphId;	/* Glyph ID of reference glyph */
  HBUINT16	firstLayerIdx;	/* Index (from beginning of
				 * the Layer Records) to the
				 * layer record. There will be
				 * numLayers consecutive entries
				 * for this base glyph. */
  HBUINT16	numLayers;	/* Number of color layers
				 * associated with this glyph */
  public:
  DEFINE_SIZE_STATIC (6);
};

template <typename T>
struct Variable
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  protected:
  T      value;
  VarIdx varIdx;
  public:
  DEFINE_SIZE_STATIC (4 + T::static_size);
};

template <typename T>
struct NoVariable
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  T      value;
  public:
  DEFINE_SIZE_STATIC (T::static_size);
};

// Color structures

template <template<typename> class Var>
struct ColorIndex
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  HBUINT16	paletteIndex;
  Var<F2DOT14>	alpha;
  public:
  DEFINE_SIZE_STATIC (2 + Var<F2DOT14>::static_size);
};

template <template<typename> class Var>
struct ColorStop
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  Var<F2DOT14>		stopOffset;
  ColorIndex<Var>		color;
  public:
  DEFINE_SIZE_STATIC (Var<F2DOT14>::static_size + ColorIndex<Var>::static_size);
};

struct Extend : HBUINT8
{
  enum {
    EXTEND_PAD     = 0,
    EXTEND_REPEAT  = 1,
    EXTEND_REFLECT = 2,
  };
  public:
  DEFINE_SIZE_STATIC (1);
};

template <template<typename> class Var>
struct ColorLine
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
                  stops.sanitize (c));
  }

  Extend			extend;
  Array16Of<ColorStop<Var>>	stops;
  public:
  DEFINE_SIZE_ARRAY_SIZED (3, stops);
};

// Composition modes

// Compositing modes are taken from https://www.w3.org/TR/compositing-1/
// NOTE: a brief audit of major implementations suggests most support most
// or all of the specified modes.
struct CompositeMode : HBUINT8
{
  enum {
    // Porter-Duff modes
    // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators
    COMPOSITE_CLEAR          =  0,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_clear
    COMPOSITE_SRC            =  1,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_src
    COMPOSITE_DEST           =  2,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_dst
    COMPOSITE_SRC_OVER       =  3,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_srcover
    COMPOSITE_DEST_OVER      =  4,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_dstover
    COMPOSITE_SRC_IN         =  5,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_srcin
    COMPOSITE_DEST_IN        =  6,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_dstin
    COMPOSITE_SRC_OUT        =  7,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_srcout
    COMPOSITE_DEST_OUT       =  8,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_dstout
    COMPOSITE_SRC_ATOP       =  9,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_srcatop
    COMPOSITE_DEST_ATOP      = 10,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_dstatop
    COMPOSITE_XOR            = 11,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_xor
    COMPOSITE_PLUS           = 12,  // https://www.w3.org/TR/compositing-1/#porterduffcompositingoperators_plus
  
    // Blend modes
    // https://www.w3.org/TR/compositing-1/#blending
    COMPOSITE_SCREEN         = 13,  // https://www.w3.org/TR/compositing-1/#blendingscreen
    COMPOSITE_OVERLAY        = 14,  // https://www.w3.org/TR/compositing-1/#blendingoverlay
    COMPOSITE_DARKEN         = 15,  // https://www.w3.org/TR/compositing-1/#blendingdarken
    COMPOSITE_LIGHTEN        = 16,  // https://www.w3.org/TR/compositing-1/#blendinglighten
    COMPOSITE_COLOR_DODGE    = 17,  // https://www.w3.org/TR/compositing-1/#blendingcolordodge
    COMPOSITE_COLOR_BURN     = 18,  // https://www.w3.org/TR/compositing-1/#blendingcolorburn
    COMPOSITE_HARD_LIGHT     = 19,  // https://www.w3.org/TR/compositing-1/#blendinghardlight
    COMPOSITE_SOFT_LIGHT     = 20,  // https://www.w3.org/TR/compositing-1/#blendingsoftlight
    COMPOSITE_DIFFERENCE     = 21,  // https://www.w3.org/TR/compositing-1/#blendingdifference
    COMPOSITE_EXCLUSION      = 22,  // https://www.w3.org/TR/compositing-1/#blendingexclusion
    COMPOSITE_MULTIPLY       = 23,  // https://www.w3.org/TR/compositing-1/#blendingmultiply
  
    // Modes that, uniquely, do not operate on components
    // https://www.w3.org/TR/compositing-1/#blendingnonseparable
    COMPOSITE_HSL_HUE        = 24,  // https://www.w3.org/TR/compositing-1/#blendinghue
    COMPOSITE_HSL_SATURATION = 25,  // https://www.w3.org/TR/compositing-1/#blendingsaturation
    COMPOSITE_HSL_COLOR      = 26,  // https://www.w3.org/TR/compositing-1/#blendingcolor
    COMPOSITE_HSL_LUMINOSITY = 27,  // https://www.w3.org/TR/compositing-1/#blendingluminosity
  };
  public:
  DEFINE_SIZE_STATIC (1);
};

template <template<typename> class Var>
struct Affine2x3
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  Var<HBFixed> xx;
  Var<HBFixed> yx;
  Var<HBFixed> xy;
  Var<HBFixed> yy;
  Var<HBFixed> dx;
  Var<HBFixed> dy;
  public:
  DEFINE_SIZE_STATIC (6 * Var<HBFixed>::static_size);
};

struct PaintColrLayers
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  HBUINT8	format; /* format = 1 */
  HBUINT8	numLayers;
  HBUINT32	firstLayerIndex;  /* index into COLRv1::layersV1 */
  public:
  DEFINE_SIZE_STATIC (6);
};

template <template<typename> class Var>
struct PaintSolid
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  HBUINT8		format; /* format = 2(noVar) or 3(Var)*/
  ColorIndex<Var>	color;
  public:
  DEFINE_SIZE_STATIC (1 + ColorIndex<Var>::static_size);
};

template <template<typename> class Var>
struct PaintLinearGradient
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && colorLine.sanitize (c, this));
  }

  HBUINT8			format; /* format = 4(noVar) or 5 (Var) */
  Offset24To<ColorLine<Var>>	colorLine; /* Offset (from beginning of PaintLinearGradient
                                            * table) to ColorLine subtable. */
  Var<FWORD>			x0;
  Var<FWORD>			y0;
  Var<FWORD>			x1;
  Var<FWORD>			y1;
  Var<FWORD>			x2;
  Var<FWORD>			y2;
  public:
  DEFINE_SIZE_STATIC (4 + 6 * Var<FWORD>::static_size);
};

template <template<typename> class Var>
struct PaintRadialGradient
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && colorLine.sanitize (c, this));
  }

  HBUINT8			format; /* format = 6(noVar) or 7 (Var) */
  Offset24To<ColorLine<Var>>	colorLine; /* Offset (from beginning of PaintRadialGradient
                                            * table) to ColorLine subtable. */
  Var<FWORD>			x0;
  Var<FWORD>			y0;
  Var<UFWORD>			radius0;
  Var<FWORD>			x1;
  Var<FWORD>			y1;
  Var<UFWORD>			radius1;
  public:
  DEFINE_SIZE_STATIC (4 + 6 * Var<FWORD>::static_size);
};

template <template<typename> class Var>
struct PaintSweepGradient
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && colorLine.sanitize (c, this));
  }

  HBUINT8			format; /* format = 8(noVar) or 9 (Var) */
  Offset24To<ColorLine<Var>>	colorLine; /* Offset (from beginning of PaintSweepGradient
                                            * table) to ColorLine subtable. */
  Var<FWORD>			centerX;
  Var<FWORD>			centerY;
  Var<HBFixed>			startAngle;
  Var<HBFixed>			endAngle;
  public:
  DEFINE_SIZE_STATIC (2 * Var<FWORD>::static_size + 2 * Var<HBFixed>::static_size);
};

struct Paint;
// Paint a non-COLR glyph, filled as indicated by paint.
struct PaintGlyph
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && paint.sanitize (c, this));
  }

  HBUINT8		format; /* format = 10 */
  Offset24To<Paint>	paint;  /* Offset (from beginning of PaintGlyph table) to Paint subtable. */
  HBUINT16		gid;
  public:
  DEFINE_SIZE_STATIC (6);
};

struct PaintColrGlyph
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this));
  }

  HBUINT8	format; /* format = 11 */
  HBUINT16	gid;
  public:
  DEFINE_SIZE_STATIC (3);
};

template <template<typename> class Var>
struct PaintTransform
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && src.sanitize (c, this));
  }

  HBUINT8		format; /* format = 12(noVar) or 13 (Var) */
  Offset24To<Paint>	src; /* Offset (from beginning of PaintTransform table) to Paint subtable. */
  Affine2x3<Var>	transform;
  public:
  DEFINE_SIZE_STATIC (4 + Affine2x3<Var>::static_size);
};

template <template<typename> class Var>
struct PaintTranslate
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && src.sanitize (c, this));
  }

  HBUINT8		format; /* format = 14(noVar) or 15 (Var) */
  Offset24To<Paint>	src; /* Offset (from beginning of PaintTranslate table) to Paint subtable. */
  Var<HBFixed>		dx;
  Var<HBFixed>		dy;
  public:
  DEFINE_SIZE_STATIC (4 + Var<HBFixed>::static_size);
};

template <template<typename> class Var>
struct PaintRotate
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && src.sanitize (c, this));
  }

  HBUINT8		format; /* format = 16 (noVar) or 17(Var) */
  Offset24To<Paint>	src; /* Offset (from beginning of PaintRotate table) to Paint subtable. */
  Var<HBFixed>		angle;
  Var<HBFixed>		centerX;
  Var<HBFixed>		centerY;
  public:
  DEFINE_SIZE_STATIC (4 + 3 * Var<HBFixed>::static_size);
};

template <template<typename> class Var>
struct PaintSkew
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) && src.sanitize (c, this));
  }

  HBUINT8		format; /* format = 18(noVar) or 19 (Var) */
  Offset24To<Paint>	src; /* Offset (from beginning of PaintSkew table) to Paint subtable. */
  Var<HBFixed>		xSkewAngle;
  Var<HBFixed>		ySkewAngle;
  Var<HBFixed>		centerX;
  Var<HBFixed>		centerY;
  public:
  DEFINE_SIZE_STATIC (4 + 4 * Var<HBFixed>::static_size);
};

struct PaintComposite
{
  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
                  src.sanitize (c, this) &&
                  backdrop.sanitize (c, this));
  }

  HBUINT8		format; /* format = 20 */
  Offset24To<Paint>	src; /* Offset (from beginning of PaintComposite table) to source Paint subtable. */
  CompositeMode		mode;   /* If mode is unrecognized use COMPOSITE_CLEAR */
  Offset24To<Paint>	backdrop; /* Offset (from beginning of PaintComposite table) to backdrop Paint subtable. */
  public:
  DEFINE_SIZE_STATIC (8);
};

struct Paint
{
  template <typename context_t, typename ...Ts>
  typename context_t::return_t dispatch (context_t *c, Ts&&... ds) const
  {
    TRACE_DISPATCH (this, u.format);
    if (unlikely (!c->may_dispatch (this, &u.format))) return_trace (c->no_dispatch_return_value ());
    switch (u.format) {
    case 1: return_trace (c->dispatch (u.paintformat1, hb_forward<Ts> (ds)...));
    case 2: return_trace (c->dispatch (u.paintformat2, hb_forward<Ts> (ds)...));
    case 3: return_trace (c->dispatch (u.paintformat3, hb_forward<Ts> (ds)...));
    case 4: return_trace (c->dispatch (u.paintformat4, hb_forward<Ts> (ds)...));
    case 5: return_trace (c->dispatch (u.paintformat5, hb_forward<Ts> (ds)...));
    case 6: return_trace (c->dispatch (u.paintformat6, hb_forward<Ts> (ds)...));
    case 7: return_trace (c->dispatch (u.paintformat7, hb_forward<Ts> (ds)...));
    case 8: return_trace (c->dispatch (u.paintformat8, hb_forward<Ts> (ds)...));
    case 9: return_trace (c->dispatch (u.paintformat9, hb_forward<Ts> (ds)...));
    case 10: return_trace (c->dispatch (u.paintformat10, hb_forward<Ts> (ds)...));
    case 11: return_trace (c->dispatch (u.paintformat11, hb_forward<Ts> (ds)...));
    case 12: return_trace (c->dispatch (u.paintformat12, hb_forward<Ts> (ds)...));
    case 13: return_trace (c->dispatch (u.paintformat13, hb_forward<Ts> (ds)...));
    case 14: return_trace (c->dispatch (u.paintformat14, hb_forward<Ts> (ds)...));
    case 15: return_trace (c->dispatch (u.paintformat15, hb_forward<Ts> (ds)...));
    case 16: return_trace (c->dispatch (u.paintformat16, hb_forward<Ts> (ds)...));
    case 17: return_trace (c->dispatch (u.paintformat17, hb_forward<Ts> (ds)...));
    case 18: return_trace (c->dispatch (u.paintformat18, hb_forward<Ts> (ds)...));
    case 19: return_trace (c->dispatch (u.paintformat19, hb_forward<Ts> (ds)...));
    case 20: return_trace (c->dispatch (u.paintformat20, hb_forward<Ts> (ds)...));
    default:return_trace (c->default_return_value ());
    }
  }

  protected:
  union {
  HBUINT8				format;
  PaintColrLayers			paintformat1;
  PaintSolid<NoVariable>		paintformat2;
  PaintSolid<Variable>			paintformat3;
  PaintLinearGradient<NoVariable>	paintformat4;
  PaintLinearGradient<Variable>		paintformat5;
  PaintRadialGradient<NoVariable>	paintformat6;
  PaintRadialGradient<Variable>		paintformat7;
  PaintSweepGradient<NoVariable>	paintformat8;
  PaintSweepGradient<Variable>		paintformat9;
  PaintGlyph				paintformat10;
  PaintColrGlyph			paintformat11;
  PaintTransform<NoVariable>		paintformat12;
  PaintTransform<Variable>		paintformat13;
  PaintTranslate<NoVariable>		paintformat14;
  PaintTranslate<Variable>		paintformat15;
  PaintRotate<NoVariable>		paintformat16;
  PaintRotate<Variable>			paintformat17;
  PaintSkew<NoVariable>			paintformat18;
  PaintSkew<Variable>			paintformat19;
  PaintComposite			paintformat20;
  } u;
};

struct BaseGlyphV1Record
{
  int cmp (hb_codepoint_t g) const
  { return g < glyphId ? -1 : g > glyphId ? 1 : 0; }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (likely (c->check_struct (this) && paint.sanitize (c, this)));
  }

  public:
  HBGlyphID		glyphId;    /* Glyph ID of reference glyph */
  Offset32To<Paint>	paint;      /* Offset (from beginning of BaseGlyphV1Record) to Paint,
                                     * Typically PaintColrLayers */
  public:
  DEFINE_SIZE_STATIC (6);
};

typedef SortedArray32Of<BaseGlyphV1Record> BaseGlyphV1List;

struct LayerV1List : Array32OfOffset32To<Paint>
{
  const Paint& get_paint (unsigned i) const
  { return this+(*this)[i]; }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (Array32OfOffset32To<Paint>::sanitize (c, this));
  }
};

struct COLR
{
  static constexpr hb_tag_t tableTag = HB_OT_TAG_COLR;

  bool has_data () const { return numBaseGlyphs; }

  unsigned int get_glyph_layers (hb_codepoint_t       glyph,
				 unsigned int         start_offset,
				 unsigned int        *count, /* IN/OUT.  May be NULL. */
				 hb_ot_color_layer_t *layers /* OUT.     May be NULL. */) const
  {
    const BaseGlyphRecord &record = (this+baseGlyphsZ).bsearch (numBaseGlyphs, glyph);

    hb_array_t<const LayerRecord> all_layers = (this+layersZ).as_array (numLayers);
    hb_array_t<const LayerRecord> glyph_layers = all_layers.sub_array (record.firstLayerIdx,
								       record.numLayers);
    if (count)
    {
      + glyph_layers.sub_array (start_offset, count)
      | hb_sink (hb_array (layers, *count))
      ;
    }
    return glyph_layers.length;
  }

  struct accelerator_t
  {
    accelerator_t () {}
    ~accelerator_t () { fini (); }

    void init (hb_face_t *face)
    { colr = hb_sanitize_context_t ().reference_table<COLR> (face); }

    void fini () { this->colr.destroy (); }

    bool is_valid () { return colr.get_blob ()->length; }

    void closure_glyphs (hb_codepoint_t glyph,
			 hb_set_t *related_ids /* OUT */) const
    { colr->closure_glyphs (glyph, related_ids); }

    private:
    hb_blob_ptr_t<COLR> colr;
  };

  void closure_glyphs (hb_codepoint_t glyph,
		       hb_set_t *related_ids /* OUT */) const
  {
    const BaseGlyphRecord *record = get_base_glyph_record (glyph);
    if (!record) return;

    auto glyph_layers = (this+layersZ).as_array (numLayers).sub_array (record->firstLayerIdx,
								       record->numLayers);
    if (!glyph_layers.length) return;
    related_ids->add_array (&glyph_layers[0].glyphId, glyph_layers.length, LayerRecord::min_size);
  }

  bool sanitize (hb_sanitize_context_t *c) const
  {
    TRACE_SANITIZE (this);
    return_trace (c->check_struct (this) &&
                  (this+baseGlyphsZ).sanitize (c, numBaseGlyphs) &&
                  (this+layersZ).sanitize (c, numLayers) &&
                  (version == 0 || (version == 1 &&
                                    baseGlyphsV1List.sanitize (c, this) &&
                                    layersV1.sanitize (c, this) &&
                                    varStore.sanitize (c, this))));
  }

  template<typename BaseIterator, typename LayerIterator,
	   hb_requires (hb_is_iterator (BaseIterator)),
	   hb_requires (hb_is_iterator (LayerIterator))>
  bool serialize (hb_serialize_context_t *c,
		  unsigned version,
		  BaseIterator base_it,
		  LayerIterator layer_it)
  {
    TRACE_SERIALIZE (this);
    if (unlikely (base_it.len () != layer_it.len ()))
      return_trace (false);

    if (unlikely (!c->extend_min (this))) return_trace (false);
    this->version = version;
    numLayers = 0;
    numBaseGlyphs = base_it.len ();
    baseGlyphsZ = COLR::min_size;
    layersZ = COLR::min_size + numBaseGlyphs * BaseGlyphRecord::min_size;

    for (const hb_item_type<BaseIterator> _ : + base_it.iter ())
    {
      auto* record = c->embed (_);
      if (unlikely (!record)) return_trace (false);
      record->firstLayerIdx = numLayers;
      numLayers += record->numLayers;
    }

    for (const hb_item_type<LayerIterator>& _ : + layer_it.iter ())
      _.as_array ().copy (c);

    return_trace (true);
  }

  const BaseGlyphRecord* get_base_glyph_record (hb_codepoint_t gid) const
  {
    if ((unsigned int) gid == 0) // Ignore notdef.
      return nullptr;
    const BaseGlyphRecord* record = &(this+baseGlyphsZ).bsearch (numBaseGlyphs, (unsigned int) gid);
    if ((record && (hb_codepoint_t) record->glyphId != gid))
      record = nullptr;
    return record;
  }

  bool subset (hb_subset_context_t *c) const
  {
    TRACE_SUBSET (this);

    const hb_map_t &reverse_glyph_map = *c->plan->reverse_glyph_map;

    auto base_it =
    + hb_range (c->plan->num_output_glyphs ())
    | hb_map_retains_sorting ([&](hb_codepoint_t new_gid)
			      {
				hb_codepoint_t old_gid = reverse_glyph_map.get (new_gid);

				const BaseGlyphRecord* old_record = get_base_glyph_record (old_gid);
				if (unlikely (!old_record))
				  return hb_pair_t<bool, BaseGlyphRecord> (false, Null (BaseGlyphRecord));

				BaseGlyphRecord new_record = {};
				new_record.glyphId = new_gid;
				new_record.numLayers = old_record->numLayers;
				return hb_pair_t<bool, BaseGlyphRecord> (true, new_record);
			      })
    | hb_filter (hb_first)
    | hb_map_retains_sorting (hb_second)
    ;

    auto layer_it =
    + hb_range (c->plan->num_output_glyphs ())
    | hb_map (reverse_glyph_map)
    | hb_map_retains_sorting ([&](hb_codepoint_t old_gid)
			      {
				const BaseGlyphRecord* old_record = get_base_glyph_record (old_gid);
				hb_vector_t<LayerRecord> out_layers;

				if (unlikely (!old_record ||
					      old_record->firstLayerIdx >= numLayers ||
					      old_record->firstLayerIdx + old_record->numLayers > numLayers))
				  return hb_pair_t<bool, hb_vector_t<LayerRecord>> (false, out_layers);

				auto layers = (this+layersZ).as_array (numLayers).sub_array (old_record->firstLayerIdx,
											     old_record->numLayers);
				out_layers.resize (layers.length);
				for (unsigned int i = 0; i < layers.length; i++) {
				  out_layers[i] = layers[i];
				  hb_codepoint_t new_gid = 0;
				  if (unlikely (!c->plan->new_gid_for_old_gid (out_layers[i].glyphId, &new_gid)))
				    return hb_pair_t<bool, hb_vector_t<LayerRecord>> (false, out_layers);
				  out_layers[i].glyphId = new_gid;
				}

				return hb_pair_t<bool, hb_vector_t<LayerRecord>> (true, out_layers);
			      })
    | hb_filter (hb_first)
    | hb_map_retains_sorting (hb_second)
    ;

    if (unlikely (!base_it || !layer_it || base_it.len () != layer_it.len ()))
      return_trace (false);

    COLR *colr_prime = c->serializer->start_embed<COLR> ();
    return_trace (colr_prime->serialize (c->serializer, version, base_it, layer_it));
  }

  protected:
  HBUINT16	version;	/* Table version number (starts at 0). */
  HBUINT16	numBaseGlyphs;	/* Number of Base Glyph Records. */
  NNOffset32To<SortedUnsizedArrayOf<BaseGlyphRecord>>
		baseGlyphsZ;	/* Offset to Base Glyph records. */
  NNOffset32To<UnsizedArrayOf<LayerRecord>>
		layersZ;	/* Offset to Layer Records. */
  HBUINT16	numLayers;	/* Number of Layer Records. */
  // Version-1 additions
  Offset32To<BaseGlyphV1List>		baseGlyphsV1List;
  Offset32To<LayerV1List>		layersV1;
  Offset32To<VariationStore>		varStore;
  public:
  DEFINE_SIZE_MIN (14);
};

} /* namespace OT */


#endif /* HB_OT_COLOR_COLR_TABLE_HH */