harfbuzz: check in harfbuzz-ng, add gyp define to use it

third_party/harfbuzz-ng/src/hb-ot-layout-gpos-private.hh

+/*
+ * Copyright (C) 2007,2008,2009,2010  Red Hat, Inc.
+ * Copyright (C) 2010  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.
+ *
+ * Red Hat Author(s): Behdad Esfahbod
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#ifndef HB_OT_LAYOUT_GPOS_PRIVATE_HH
+#define HB_OT_LAYOUT_GPOS_PRIVATE_HH
+
+#include "hb-ot-layout-gsubgpos-private.hh"
+
+HB_BEGIN_DECLS
+
+
+/* buffer var allocations */
+#define attach_lookback() var.u16[0] /* number of glyphs to go back to attach this glyph to its base */
+#define cursive_chain() var.i16[1] /* character to which this connects, may be positive or negative */
+
+
+/* Shared Tables: ValueRecord, Anchor Table, and MarkArray */
+
+typedef USHORT Value;
+
+typedef Value ValueRecord[VAR];
+
+struct ValueFormat : USHORT
+{
+  enum
+  {
+    xPlacement  = 0x0001,       /* Includes horizontal adjustment for placement */
+    yPlacement  = 0x0002,       /* Includes vertical adjustment for placement */
+    xAdvance    = 0x0004,       /* Includes horizontal adjustment for advance */
+    yAdvance    = 0x0008,       /* Includes vertical adjustment for advance */
+    xPlaDevice  = 0x0010,       /* Includes horizontal Device table for placement */
+    yPlaDevice  = 0x0020,       /* Includes vertical Device table for placement */
+    xAdvDevice  = 0x0040,       /* Includes horizontal Device table for advance */
+    yAdvDevice  = 0x0080,       /* Includes vertical Device table for advance */
+    ignored     = 0x0F00,       /* Was used in TrueType Open for MM fonts */
+    reserved    = 0xF000,       /* For future use */
+
+    devices     = 0x00F0        /* Mask for having any Device table */
+  };
+
+/* All fields are options.  Only those available advance the value pointer. */
+#if 0
+  SHORT         xPlacement;             /* Horizontal adjustment for
+                                         * placement--in design units */
+  SHORT         yPlacement;             /* Vertical adjustment for
+                                         * placement--in design units */
+  SHORT         xAdvance;               /* Horizontal adjustment for
+                                         * advance--in design units (only used
+                                         * for horizontal writing) */
+  SHORT         yAdvance;               /* Vertical adjustment for advance--in
+                                         * design units (only used for vertical
+                                         * writing) */
+  Offset        xPlaDevice;             /* Offset to Device table for
+                                         * horizontal placement--measured from
+                                         * beginning of PosTable (may be NULL) */
+  Offset        yPlaDevice;             /* Offset to Device table for vertical
+                                         * placement--measured from beginning
+                                         * of PosTable (may be NULL) */
+  Offset        xAdvDevice;             /* Offset to Device table for
+                                         * horizontal advance--measured from
+                                         * beginning of PosTable (may be NULL) */
+  Offset        yAdvDevice;             /* Offset to Device table for vertical
+                                         * advance--measured from beginning of
+                                         * PosTable (may be NULL) */
+#endif
+
+  inline unsigned int get_len (void) const
+  { return _hb_popcount32 ((unsigned int) *this); }
+  inline unsigned int get_size (void) const
+  { return get_len () * Value::static_size; }
+
+  void apply_value (hb_ot_layout_context_t *layout,
+                    const void             *base,
+                    const Value            *values,
+                    hb_glyph_position_t    &glyph_pos) const
+  {
+    unsigned int x_ppem, y_ppem;
+    unsigned int format = *this;
+
+    if (!format) return;
+
+    /* design units -> fractional pixel */
+    if (format & xPlacement) glyph_pos.x_offset  += layout->scale_x (get_short (values++));
+    if (format & yPlacement) glyph_pos.y_offset  += layout->scale_y (get_short (values++));
+    if (format & xAdvance)   glyph_pos.x_advance += layout->scale_x (get_short (values++));
+    if (format & yAdvance)   glyph_pos.y_advance += layout->scale_y (get_short (values++));
+
+    if (!has_device ()) return;
+
+    x_ppem = layout->font->x_ppem;
+    y_ppem = layout->font->y_ppem;
+
+    if (!x_ppem && !y_ppem) return;
+
+    /* pixel -> fractional pixel */
+    if (format & xPlaDevice) {
+      if (x_ppem) glyph_pos.x_offset  += (base + get_device (values++)).get_x_delta (layout); else values++;
+    }
+    if (format & yPlaDevice) {
+      if (y_ppem) glyph_pos.y_offset  += (base + get_device (values++)).get_y_delta (layout); else values++;
+    }
+    if (format & xAdvDevice) {
+      if (x_ppem) glyph_pos.x_advance += (base + get_device (values++)).get_x_delta (layout); else values++;
+    }
+    if (format & yAdvDevice) {
+      if (y_ppem) glyph_pos.y_advance += (base + get_device (values++)).get_y_delta (layout); else values++;
+    }
+  }
+
+  private:
+  inline bool sanitize_value_devices (hb_sanitize_context_t *c, void *base, Value *values) {
+    unsigned int format = *this;
+
+    if (format & xPlacement) values++;
+    if (format & yPlacement) values++;
+    if (format & xAdvance)   values++;
+    if (format & yAdvance)   values++;
+
+    if ((format & xPlaDevice) && !get_device (values++).sanitize (c, base)) return false;
+    if ((format & yPlaDevice) && !get_device (values++).sanitize (c, base)) return false;
+    if ((format & xAdvDevice) && !get_device (values++).sanitize (c, base)) return false;
+    if ((format & yAdvDevice) && !get_device (values++).sanitize (c, base)) return false;
+
+    return true;
+  }
+
+  static inline OffsetTo<Device>& get_device (Value* value)
+  { return *CastP<OffsetTo<Device> > (value); }
+  static inline const OffsetTo<Device>& get_device (const Value* value)
+  { return *CastP<OffsetTo<Device> > (value); }
+
+  static inline const SHORT& get_short (const Value* value)
+  { return *CastP<SHORT> (value); }
+
+  public:
+
+  inline bool has_device (void) const {
+    unsigned int format = *this;
+    return (format & devices) != 0;
+  }
+
+  inline bool sanitize_value (hb_sanitize_context_t *c, void *base, Value *values) {
+    TRACE_SANITIZE ();
+    return c->check_range (values, get_size ())
+        && (!has_device () || sanitize_value_devices (c, base, values));
+  }
+
+  inline bool sanitize_values (hb_sanitize_context_t *c, void *base, Value *values, unsigned int count) {
+    TRACE_SANITIZE ();
+    unsigned int len = get_len ();
+
+    if (!c->check_array (values, get_size (), count)) return false;
+
+    if (!has_device ()) return true;
+
+    for (unsigned int i = 0; i < count; i++) {
+      if (!sanitize_value_devices (c, base, values))
+        return false;
+      values += len;
+    }
+
+    return true;
+  }
+
+  /* Just sanitize referenced Device tables.  Doesn't check the values themselves. */
+  inline bool sanitize_values_stride_unsafe (hb_sanitize_context_t *c, void *base, Value *values, unsigned int count, unsigned int stride) {
+    TRACE_SANITIZE ();
+
+    if (!has_device ()) return true;
+
+    for (unsigned int i = 0; i < count; i++) {
+      if (!sanitize_value_devices (c, base, values))
+        return false;
+      values += stride;
+    }
+
+    return true;
+  }
+};
+
+
+struct AnchorFormat1
+{
+  friend struct Anchor;
+
+  private:
+  inline void get_anchor (hb_ot_layout_context_t *layout, hb_codepoint_t glyph_id HB_UNUSED,
+                          hb_position_t *x, hb_position_t *y) const
+  {
+      *x = layout->scale_x (xCoordinate);
+      *y = layout->scale_y (yCoordinate);
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 1 */
+  SHORT         xCoordinate;            /* Horizontal value--in design units */
+  SHORT         yCoordinate;            /* Vertical value--in design units */
+  public:
+  DEFINE_SIZE_STATIC (6);
+};
+
+struct AnchorFormat2
+{
+  friend struct Anchor;
+
+  private:
+  inline void get_anchor (hb_ot_layout_context_t *layout, hb_codepoint_t glyph_id,
+                          hb_position_t *x, hb_position_t *y) const
+  {
+      unsigned int x_ppem = layout->font->x_ppem;
+      unsigned int y_ppem = layout->font->y_ppem;
+      hb_position_t cx, cy;
+      hb_bool_t ret = false;
+
+      if (x_ppem || y_ppem)
+        ret = hb_font_get_contour_point (layout->font, layout->face, anchorPoint, glyph_id, &cx, &cy);
+      *x = x_ppem && ret ? cx : layout->scale_x (xCoordinate);
+      *y = y_ppem && ret ? cy : layout->scale_y (yCoordinate);
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 2 */
+  SHORT         xCoordinate;            /* Horizontal value--in design units */
+  SHORT         yCoordinate;            /* Vertical value--in design units */
+  USHORT        anchorPoint;            /* Index to glyph contour point */
+  public:
+  DEFINE_SIZE_STATIC (8);
+};
+
+struct AnchorFormat3
+{
+  friend struct Anchor;
+
+  private:
+  inline void get_anchor (hb_ot_layout_context_t *layout, hb_codepoint_t glyph_id HB_UNUSED,
+                          hb_position_t *x, hb_position_t *y) const
+  {
+      *x = layout->scale_x (xCoordinate);
+      *y = layout->scale_y (yCoordinate);
+
+      /* pixel -> fractional pixel */
+      if (layout->font->x_ppem)
+        *x += (this+xDeviceTable).get_x_delta (layout);
+      if (layout->font->y_ppem)
+        *y += (this+yDeviceTable).get_x_delta (layout);
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this)
+        && xDeviceTable.sanitize (c, this)
+        && yDeviceTable.sanitize (c, this);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 3 */
+  SHORT         xCoordinate;            /* Horizontal value--in design units */
+  SHORT         yCoordinate;            /* Vertical value--in design units */
+  OffsetTo<Device>
+                xDeviceTable;           /* Offset to Device table for X
+                                         * coordinate-- from beginning of
+                                         * Anchor table (may be NULL) */
+  OffsetTo<Device>
+                yDeviceTable;           /* Offset to Device table for Y
+                                         * coordinate-- from beginning of
+                                         * Anchor table (may be NULL) */
+  public:
+  DEFINE_SIZE_STATIC (10);
+};
+
+struct Anchor
+{
+  inline void get_anchor (hb_ot_layout_context_t *layout, hb_codepoint_t glyph_id,
+                          hb_position_t *x, hb_position_t *y) const
+  {
+    *x = *y = 0;
+    switch (u.format) {
+    case 1: u.format1.get_anchor (layout, glyph_id, x, y); return;
+    case 2: u.format2.get_anchor (layout, glyph_id, x, y); return;
+    case 3: u.format3.get_anchor (layout, glyph_id, x, y); return;
+    default:                                                return;
+    }
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (!u.format.sanitize (c)) return false;
+    switch (u.format) {
+    case 1: return u.format1.sanitize (c);
+    case 2: return u.format2.sanitize (c);
+    case 3: return u.format3.sanitize (c);
+    default:return true;
+    }
+  }
+
+  private:
+  union {
+  USHORT                format;         /* Format identifier */
+  AnchorFormat1         format1;
+  AnchorFormat2         format2;
+  AnchorFormat3         format3;
+  } u;
+  public:
+  DEFINE_SIZE_UNION (2, format);
+};
+
+
+struct AnchorMatrix
+{
+  inline const Anchor& get_anchor (unsigned int row, unsigned int col, unsigned int cols) const {
+    if (unlikely (row >= rows || col >= cols)) return Null(Anchor);
+    return this+matrix[row * cols + col];
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c, unsigned int cols) {
+    TRACE_SANITIZE ();
+    if (!c->check_struct (this)) return false;
+    if (unlikely (rows > 0 && cols >= ((unsigned int) -1) / rows)) return false;
+    unsigned int count = rows * cols;
+    if (!c->check_array (matrix, matrix[0].static_size, count)) return false;
+    for (unsigned int i = 0; i < count; i++)
+      if (!matrix[i].sanitize (c, this)) return false;
+    return true;
+  }
+
+  USHORT        rows;                   /* Number of rows */
+  private:
+  OffsetTo<Anchor>
+                matrix[VAR];            /* Matrix of offsets to Anchor tables--
+                                         * from beginning of AnchorMatrix table */
+  public:
+  DEFINE_SIZE_ARRAY (2, matrix);
+};
+
+
+struct MarkRecord
+{
+  friend struct MarkArray;
+
+  inline bool sanitize (hb_sanitize_context_t *c, void *base) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this)
+        && markAnchor.sanitize (c, base);
+  }
+
+  private:
+  USHORT        klass;                  /* Class defined for this mark */
+  OffsetTo<Anchor>
+                markAnchor;             /* Offset to Anchor table--from
+                                         * beginning of MarkArray table */
+  public:
+  DEFINE_SIZE_STATIC (4);
+};
+
+struct MarkArray : ArrayOf<MarkRecord>  /* Array of MarkRecords--in Coverage order */
+{
+  inline bool apply (hb_apply_context_t *c,
+                     unsigned int mark_index, unsigned int glyph_index,
+                     const AnchorMatrix &anchors, unsigned int class_count,
+                     unsigned int glyph_pos) const
+  {
+    TRACE_APPLY ();
+    const MarkRecord &record = ArrayOf<MarkRecord>::operator[](mark_index);
+    unsigned int mark_class = record.klass;
+
+    const Anchor& mark_anchor = this + record.markAnchor;
+    const Anchor& glyph_anchor = anchors.get_anchor (glyph_index, mark_class, class_count);
+
+    hb_position_t mark_x, mark_y, base_x, base_y;
+
+    mark_anchor.get_anchor (c->layout, c->buffer->info[c->buffer->i].codepoint, &mark_x, &mark_y);
+    glyph_anchor.get_anchor (c->layout, c->buffer->info[glyph_pos].codepoint, &base_x, &base_y);
+
+    hb_glyph_position_t &o = c->buffer->pos[c->buffer->i];
+    o.x_offset = base_x - mark_x;
+    o.y_offset = base_y - mark_y;
+    o.attach_lookback() = c->buffer->i - glyph_pos;
+
+    c->buffer->i++;
+    return true;
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return ArrayOf<MarkRecord>::sanitize (c, this);
+  }
+};
+
+
+/* Lookups */
+
+struct SinglePosFormat1
+{
+  friend struct SinglePos;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    unsigned int index = (this+coverage) (c->buffer->info[c->buffer->i].codepoint);
+    if (likely (index == NOT_COVERED))
+      return false;
+
+    valueFormat.apply_value (c->layout, this, values, c->buffer->pos[c->buffer->i]);
+
+    c->buffer->i++;
+    return true;
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this)
+        && coverage.sanitize (c, this)
+        && valueFormat.sanitize_value (c, this, values);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 1 */
+  OffsetTo<Coverage>
+                coverage;               /* Offset to Coverage table--from
+                                         * beginning of subtable */
+  ValueFormat   valueFormat;            /* Defines the types of data in the
+                                         * ValueRecord */
+  ValueRecord   values;                 /* Defines positioning
+                                         * value(s)--applied to all glyphs in
+                                         * the Coverage table */
+  public:
+  DEFINE_SIZE_ARRAY (6, values);
+};
+
+struct SinglePosFormat2
+{
+  friend struct SinglePos;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    unsigned int index = (this+coverage) (c->buffer->info[c->buffer->i].codepoint);
+    if (likely (index == NOT_COVERED))
+      return false;
+
+    if (likely (index >= valueCount))
+      return false;
+
+    valueFormat.apply_value (c->layout, this,
+                             &values[index * valueFormat.get_len ()],
+                             c->buffer->pos[c->buffer->i]);
+
+    c->buffer->i++;
+    return true;
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this)
+        && coverage.sanitize (c, this)
+        && valueFormat.sanitize_values (c, this, values, valueCount);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 2 */
+  OffsetTo<Coverage>
+                coverage;               /* Offset to Coverage table--from
+                                         * beginning of subtable */
+  ValueFormat   valueFormat;            /* Defines the types of data in the
+                                         * ValueRecord */
+  USHORT        valueCount;             /* Number of ValueRecords */
+  ValueRecord   values;                 /* Array of ValueRecords--positioning
+                                         * values applied to glyphs */
+  public:
+  DEFINE_SIZE_ARRAY (8, values);
+};
+
+struct SinglePos
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    switch (u.format) {
+    case 1: return u.format1.apply (c);
+    case 2: return u.format2.apply (c);
+    default:return false;
+    }
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (!u.format.sanitize (c)) return false;
+    switch (u.format) {
+    case 1: return u.format1.sanitize (c);
+    case 2: return u.format2.sanitize (c);
+    default:return true;
+    }
+  }
+
+  private:
+  union {
+  USHORT                format;         /* Format identifier */
+  SinglePosFormat1      format1;
+  SinglePosFormat2      format2;
+  } u;
+};
+
+
+struct PairValueRecord
+{
+  friend struct PairSet;
+
+  private:
+  GlyphID       secondGlyph;            /* GlyphID of second glyph in the
+                                         * pair--first glyph is listed in the
+                                         * Coverage table */
+  ValueRecord   values;                 /* Positioning data for the first glyph
+                                         * followed by for second glyph */
+  public:
+  DEFINE_SIZE_ARRAY (2, values);
+};
+
+struct PairSet
+{
+  friend struct PairPosFormat1;
+
+  inline bool apply (hb_apply_context_t *c,
+                     const ValueFormat *valueFormats,
+                     unsigned int pos) const
+  {
+    TRACE_APPLY ();
+    unsigned int len1 = valueFormats[0].get_len ();
+    unsigned int len2 = valueFormats[1].get_len ();
+    unsigned int record_size = USHORT::static_size * (1 + len1 + len2);
+
+    unsigned int count = len;
+    const PairValueRecord *record = CastP<PairValueRecord> (array);
+    for (unsigned int i = 0; i < count; i++)
+    {
+      if (c->buffer->info[pos].codepoint == record->secondGlyph)
+      {
+        valueFormats[0].apply_value (c->layout, this, &record->values[0], c->buffer->pos[c->buffer->i]);
+        valueFormats[1].apply_value (c->layout, this, &record->values[len1], c->buffer->pos[pos]);
+        if (len2)
+          pos++;
+        c->buffer->i = pos;
+        return true;
+      }
+      record = &StructAtOffset<PairValueRecord> (record, record_size);
+    }
+
+    return false;
+  }
+
+  struct sanitize_closure_t {
+    void *base;
+    ValueFormat *valueFormats;
+    unsigned int len1; /* valueFormats[0].get_len() */
+    unsigned int stride; /* 1 + len1 + len2 */
+  };
+
+  inline bool sanitize (hb_sanitize_context_t *c, const sanitize_closure_t *closure) {
+    TRACE_SANITIZE ();
+    if (!(c->check_struct (this)
+       && c->check_array (array, USHORT::static_size * closure->stride, len))) return false;
+
+    unsigned int count = len;
+    PairValueRecord *record = CastP<PairValueRecord> (array);
+    return closure->valueFormats[0].sanitize_values_stride_unsafe (c, closure->base, &record->values[0], count, closure->stride)
+        && closure->valueFormats[1].sanitize_values_stride_unsafe (c, closure->base, &record->values[closure->len1], count, closure->stride);
+  }
+
+  private:
+  USHORT        len;                    /* Number of PairValueRecords */
+  USHORT        array[VAR];             /* Array of PairValueRecords--ordered
+                                         * by GlyphID of the second glyph */
+  public:
+  DEFINE_SIZE_ARRAY (2, array);
+};
+
+struct PairPosFormat1
+{
+  friend struct PairPos;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    unsigned int end = MIN (c->buffer->len, c->buffer->i + c->context_length);
+    if (unlikely (c->buffer->i + 2 > end))
+      return false;
+
+    unsigned int index = (this+coverage) (c->buffer->info[c->buffer->i].codepoint);
+    if (likely (index == NOT_COVERED))
+      return false;
+
+    unsigned int j = c->buffer->i + 1;
+    while (_hb_ot_layout_skip_mark (c->layout->face, &c->buffer->info[j], c->lookup_props, NULL))
+    {
+      if (unlikely (j == end))
+        return false;
+      j++;
+    }
+
+    return (this+pairSet[index]).apply (c, &valueFormat1, j);
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+
+    unsigned int len1 = valueFormat1.get_len ();
+    unsigned int len2 = valueFormat2.get_len ();
+    PairSet::sanitize_closure_t closure = {
+      this,
+      &valueFormat1,
+      len1,
+      1 + len1 + len2
+    };
+
+    return c->check_struct (this)
+        && coverage.sanitize (c, this)
+        && pairSet.sanitize (c, this, &closure);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 1 */
+  OffsetTo<Coverage>
+                coverage;               /* Offset to Coverage table--from
+                                         * beginning of subtable */
+  ValueFormat   valueFormat1;           /* Defines the types of data in
+                                         * ValueRecord1--for the first glyph
+                                         * in the pair--may be zero (0) */
+  ValueFormat   valueFormat2;           /* Defines the types of data in
+                                         * ValueRecord2--for the second glyph
+                                         * in the pair--may be zero (0) */
+  OffsetArrayOf<PairSet>
+                pairSet;                /* Array of PairSet tables
+                                         * ordered by Coverage Index */
+  public:
+  DEFINE_SIZE_ARRAY (10, pairSet);
+};
+
+struct PairPosFormat2
+{
+  friend struct PairPos;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    unsigned int end = MIN (c->buffer->len, c->buffer->i + c->context_length);
+    if (unlikely (c->buffer->i + 2 > end))
+      return false;
+
+    unsigned int index = (this+coverage) (c->buffer->info[c->buffer->i].codepoint);
+    if (likely (index == NOT_COVERED))
+      return false;
+
+    unsigned int j = c->buffer->i + 1;
+    while (_hb_ot_layout_skip_mark (c->layout->face, &c->buffer->info[j], c->lookup_props, NULL))
+    {
+      if (unlikely (j == end))
+        return false;
+      j++;
+    }
+
+    unsigned int len1 = valueFormat1.get_len ();
+    unsigned int len2 = valueFormat2.get_len ();
+    unsigned int record_len = len1 + len2;
+
+    unsigned int klass1 = (this+classDef1) (c->buffer->info[c->buffer->i].codepoint);
+    unsigned int klass2 = (this+classDef2) (c->buffer->info[j].codepoint);
+    if (unlikely (klass1 >= class1Count || klass2 >= class2Count))
+      return false;
+
+    const Value *v = &values[record_len * (klass1 * class2Count + klass2)];
+    valueFormat1.apply_value (c->layout, this, v, c->buffer->pos[c->buffer->i]);
+    valueFormat2.apply_value (c->layout, this, v + len1, c->buffer->pos[j]);
+
+    if (len2)
+      j++;
+    c->buffer->i = j;
+
+    return true;
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (!(c->check_struct (this)
+       && coverage.sanitize (c, this)
+       && classDef1.sanitize (c, this)
+       && classDef2.sanitize (c, this))) return false;
+
+    unsigned int len1 = valueFormat1.get_len ();
+    unsigned int len2 = valueFormat2.get_len ();
+    unsigned int stride = len1 + len2;
+    unsigned int record_size = valueFormat1.get_size () + valueFormat2.get_size ();
+    unsigned int count = (unsigned int) class1Count * (unsigned int) class2Count;
+    return c->check_array (values, record_size, count) &&
+           valueFormat1.sanitize_values_stride_unsafe (c, this, &values[0], count, stride) &&
+           valueFormat2.sanitize_values_stride_unsafe (c, this, &values[len1], count, stride);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 2 */
+  OffsetTo<Coverage>
+                coverage;               /* Offset to Coverage table--from
+                                         * beginning of subtable */
+  ValueFormat   valueFormat1;           /* ValueRecord definition--for the
+                                         * first glyph of the pair--may be zero
+                                         * (0) */
+  ValueFormat   valueFormat2;           /* ValueRecord definition--for the
+                                         * second glyph of the pair--may be
+                                         * zero (0) */
+  OffsetTo<ClassDef>
+                classDef1;              /* Offset to ClassDef table--from
+                                         * beginning of PairPos subtable--for
+                                         * the first glyph of the pair */
+  OffsetTo<ClassDef>
+                classDef2;              /* Offset to ClassDef table--from
+                                         * beginning of PairPos subtable--for
+                                         * the second glyph of the pair */
+  USHORT        class1Count;            /* Number of classes in ClassDef1
+                                         * table--includes Class0 */
+  USHORT        class2Count;            /* Number of classes in ClassDef2
+                                         * table--includes Class0 */
+  ValueRecord   values;                 /* Matrix of value pairs:
+                                         * class1-major, class2-minor,
+                                         * Each entry has value1 and value2 */
+  public:
+  DEFINE_SIZE_ARRAY (16, values);
+};
+
+struct PairPos
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    switch (u.format) {
+    case 1: return u.format1.apply (c);
+    case 2: return u.format2.apply (c);
+    default:return false;
+    }
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (!u.format.sanitize (c)) return false;
+    switch (u.format) {
+    case 1: return u.format1.sanitize (c);
+    case 2: return u.format2.sanitize (c);
+    default:return true;
+    }
+  }
+
+  private:
+  union {
+  USHORT                format;         /* Format identifier */
+  PairPosFormat1        format1;
+  PairPosFormat2        format2;
+  } u;
+};
+
+
+struct EntryExitRecord
+{
+  friend struct CursivePosFormat1;
+
+  inline bool sanitize (hb_sanitize_context_t *c, void *base) {
+    TRACE_SANITIZE ();
+    return entryAnchor.sanitize (c, base)
+        && exitAnchor.sanitize (c, base);
+  }
+
+  private:
+  OffsetTo<Anchor>
+                entryAnchor;            /* Offset to EntryAnchor table--from
+                                         * beginning of CursivePos
+                                         * subtable--may be NULL */
+  OffsetTo<Anchor>
+                exitAnchor;             /* Offset to ExitAnchor table--from
+                                         * beginning of CursivePos
+                                         * subtable--may be NULL */
+  public:
+  DEFINE_SIZE_STATIC (4);
+};
+
+struct CursivePosFormat1
+{
+  friend struct CursivePos;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+
+    /* We don't handle mark glyphs here. */
+    if (c->property & HB_OT_LAYOUT_GLYPH_CLASS_MARK)
+      return false;
+
+    unsigned int end = MIN (c->buffer->len, c->buffer->i + c->context_length);
+    if (unlikely (c->buffer->i + 2 > end))
+      return false;
+
+    const EntryExitRecord &this_record = entryExitRecord[(this+coverage) (c->buffer->info[c->buffer->i].codepoint)];
+    if (!this_record.exitAnchor)
+      return false;
+
+    unsigned int j = c->buffer->i + 1;
+    while (_hb_ot_layout_skip_mark (c->layout->face, &c->buffer->info[j], c->lookup_props, NULL))
+    {
+      if (unlikely (j == end))
+        return false;
+      j++;
+    }
+
+    const EntryExitRecord &next_record = entryExitRecord[(this+coverage) (c->buffer->info[j].codepoint)];
+    if (!next_record.entryAnchor)
+      return false;
+
+    unsigned int i = c->buffer->i;
+
+    hb_position_t entry_x, entry_y, exit_x, exit_y;
+    (this+this_record.exitAnchor).get_anchor (c->layout, c->buffer->info[i].codepoint, &exit_x, &exit_y);
+    (this+next_record.entryAnchor).get_anchor (c->layout, c->buffer->info[j].codepoint, &entry_x, &entry_y);
+
+    hb_direction_t direction = c->buffer->props.direction;
+
+    /* Align the exit anchor of the left/top glyph with the entry anchor of the right/bottom glyph
+     * by adjusting advance of the left/top glyph. */
+    if (HB_DIRECTION_IS_BACKWARD (direction))
+    {
+      if (likely (HB_DIRECTION_IS_HORIZONTAL (direction)))
+        c->buffer->pos[j].x_advance = c->buffer->pos[j].x_offset + entry_x - exit_x;
+      else
+        c->buffer->pos[j].y_advance = c->buffer->pos[j].y_offset + entry_y - exit_y;
+    }
+    else
+    {
+      if (likely (HB_DIRECTION_IS_HORIZONTAL (direction)))
+        c->buffer->pos[i].x_advance = c->buffer->pos[i].x_offset + exit_x - entry_x;
+      else
+        c->buffer->pos[i].y_advance = c->buffer->pos[i].y_offset + exit_y - entry_y;
+    }
+
+    if  (c->lookup_props & LookupFlag::RightToLeft)
+    {
+      c->buffer->pos[i].cursive_chain() = j - i;
+      if (likely (HB_DIRECTION_IS_HORIZONTAL (direction)))
+        c->buffer->pos[i].y_offset = entry_y - exit_y;
+      else
+        c->buffer->pos[i].x_offset = entry_x - exit_x;
+    }
+    else
+    {
+      c->buffer->pos[j].cursive_chain() = i - j;
+      if (likely (HB_DIRECTION_IS_HORIZONTAL (direction)))
+        c->buffer->pos[j].y_offset = exit_y - entry_y;
+      else
+        c->buffer->pos[j].x_offset = exit_x - entry_x;
+    }
+
+    c->buffer->i = j;
+    return true;
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return coverage.sanitize (c, this)
+        && entryExitRecord.sanitize (c, this);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 1 */
+  OffsetTo<Coverage>
+                coverage;               /* Offset to Coverage table--from
+                                         * beginning of subtable */
+  ArrayOf<EntryExitRecord>
+                entryExitRecord;        /* Array of EntryExit records--in
+                                         * Coverage Index order */
+  public:
+  DEFINE_SIZE_ARRAY (6, entryExitRecord);
+};
+
+struct CursivePos
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    switch (u.format) {
+    case 1: return u.format1.apply (c);
+    default:return false;
+    }
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (!u.format.sanitize (c)) return false;
+    switch (u.format) {
+    case 1: return u.format1.sanitize (c);
+    default:return true;
+    }
+  }
+
+  private:
+  union {
+  USHORT                format;         /* Format identifier */
+  CursivePosFormat1     format1;
+  } u;
+};
+
+
+typedef AnchorMatrix BaseArray;         /* base-major--
+                                         * in order of BaseCoverage Index--,
+                                         * mark-minor--
+                                         * ordered by class--zero-based. */
+
+struct MarkBasePosFormat1
+{
+  friend struct MarkBasePos;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    unsigned int mark_index = (this+markCoverage) (c->buffer->info[c->buffer->i].codepoint);
+    if (likely (mark_index == NOT_COVERED))
+      return false;
+
+    /* now we search backwards for a non-mark glyph */
+    unsigned int property;
+    unsigned int j = c->buffer->i;
+    do
+    {
+      if (unlikely (!j))
+        return false;
+      j--;
+    } while (_hb_ot_layout_skip_mark (c->layout->face, &c->buffer->info[j], LookupFlag::IgnoreMarks, &property));
+
+    /* The following assertion is too strong, so we've disabled it. */
+    if (!(property & HB_OT_LAYOUT_GLYPH_CLASS_BASE_GLYPH))
+    {/*return false;*/}
+
+    unsigned int base_index = (this+baseCoverage) (c->buffer->info[j].codepoint);
+    if (base_index == NOT_COVERED)
+      return false;
+
+    return (this+markArray).apply (c, mark_index, base_index, this+baseArray, classCount, j);
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this)
+        && markCoverage.sanitize (c, this)
+        && baseCoverage.sanitize (c, this)
+        && markArray.sanitize (c, this)
+        && baseArray.sanitize (c, this, (unsigned int) classCount);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 1 */
+  OffsetTo<Coverage>
+                markCoverage;           /* Offset to MarkCoverage table--from
+                                         * beginning of MarkBasePos subtable */
+  OffsetTo<Coverage>
+                baseCoverage;           /* Offset to BaseCoverage table--from
+                                         * beginning of MarkBasePos subtable */
+  USHORT        classCount;             /* Number of classes defined for marks */
+  OffsetTo<MarkArray>
+                markArray;              /* Offset to MarkArray table--from
+                                         * beginning of MarkBasePos subtable */
+  OffsetTo<BaseArray>
+                baseArray;              /* Offset to BaseArray table--from
+                                         * beginning of MarkBasePos subtable */
+  public:
+  DEFINE_SIZE_STATIC (12);
+};
+
+struct MarkBasePos
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    switch (u.format) {
+    case 1: return u.format1.apply (c);
+    default:return false;
+    }
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (!u.format.sanitize (c)) return false;
+    switch (u.format) {
+    case 1: return u.format1.sanitize (c);
+    default:return true;
+    }
+  }
+
+  private:
+  union {
+  USHORT                format;         /* Format identifier */
+  MarkBasePosFormat1    format1;
+  } u;
+};
+
+
+typedef AnchorMatrix LigatureAttach;    /* component-major--
+                                         * in order of writing direction--,
+                                         * mark-minor--
+                                         * ordered by class--zero-based. */
+
+typedef OffsetListOf<LigatureAttach> LigatureArray;
+                                        /* Array of LigatureAttach
+                                         * tables ordered by
+                                         * LigatureCoverage Index */
+
+struct MarkLigPosFormat1
+{
+  friend struct MarkLigPos;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    unsigned int mark_index = (this+markCoverage) (c->buffer->info[c->buffer->i].codepoint);
+    if (likely (mark_index == NOT_COVERED))
+      return false;
+
+    /* now we search backwards for a non-mark glyph */
+    unsigned int property;
+    unsigned int j = c->buffer->i;
+    do
+    {
+      if (unlikely (!j))
+        return false;
+      j--;
+    } while (_hb_ot_layout_skip_mark (c->layout->face, &c->buffer->info[j], LookupFlag::IgnoreMarks, &property));
+
+    /* The following assertion is too strong, so we've disabled it. */
+    if (!(property & HB_OT_LAYOUT_GLYPH_CLASS_LIGATURE))
+    {/*return false;*/}
+
+    unsigned int lig_index = (this+ligatureCoverage) (c->buffer->info[j].codepoint);
+    if (lig_index == NOT_COVERED)
+      return false;
+
+    const LigatureArray& lig_array = this+ligatureArray;
+    const LigatureAttach& lig_attach = lig_array[lig_index];
+
+    /* Find component to attach to */
+    unsigned int comp_count = lig_attach.rows;
+    if (unlikely (!comp_count))
+      return false;
+    unsigned int comp_index;
+    /* We must now check whether the ligature ID of the current mark glyph
+     * is identical to the ligature ID of the found ligature.  If yes, we
+     * can directly use the component index.  If not, we attach the mark
+     * glyph to the last component of the ligature. */
+    if (c->buffer->info[j].lig_id() && c->buffer->info[j].lig_id() == c->buffer->info[c->buffer->i].lig_id() && c->buffer->info[c->buffer->i].lig_comp())
+    {
+      comp_index = c->buffer->info[c->buffer->i].lig_comp() - 1;
+      if (comp_index >= comp_count)
+        comp_index = comp_count - 1;
+    }
+    else
+      comp_index = comp_count - 1;
+
+    return (this+markArray).apply (c, mark_index, comp_index, lig_attach, classCount, j);
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this)
+        && markCoverage.sanitize (c, this)
+        && ligatureCoverage.sanitize (c, this)
+        && markArray.sanitize (c, this)
+        && ligatureArray.sanitize (c, this, (unsigned int) classCount);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 1 */
+  OffsetTo<Coverage>
+                markCoverage;           /* Offset to Mark Coverage table--from
+                                         * beginning of MarkLigPos subtable */
+  OffsetTo<Coverage>
+                ligatureCoverage;       /* Offset to Ligature Coverage
+                                         * table--from beginning of MarkLigPos
+                                         * subtable */
+  USHORT        classCount;             /* Number of defined mark classes */
+  OffsetTo<MarkArray>
+                markArray;              /* Offset to MarkArray table--from
+                                         * beginning of MarkLigPos subtable */
+  OffsetTo<LigatureArray>
+                ligatureArray;          /* Offset to LigatureArray table--from
+                                         * beginning of MarkLigPos subtable */
+  public:
+  DEFINE_SIZE_STATIC (12);
+};
+
+struct MarkLigPos
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    switch (u.format) {
+    case 1: return u.format1.apply (c);
+    default:return false;
+    }
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (!u.format.sanitize (c)) return false;
+    switch (u.format) {
+    case 1: return u.format1.sanitize (c);
+    default:return true;
+    }
+  }
+
+  private:
+  union {
+  USHORT                format;         /* Format identifier */
+  MarkLigPosFormat1     format1;
+  } u;
+};
+
+
+typedef AnchorMatrix Mark2Array;        /* mark2-major--
+                                         * in order of Mark2Coverage Index--,
+                                         * mark1-minor--
+                                         * ordered by class--zero-based. */
+
+struct MarkMarkPosFormat1
+{
+  friend struct MarkMarkPos;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    unsigned int mark1_index = (this+mark1Coverage) (c->buffer->info[c->buffer->i].codepoint);
+    if (likely (mark1_index == NOT_COVERED))
+      return false;
+
+    /* now we search backwards for a suitable mark glyph until a non-mark glyph */
+    unsigned int property;
+    unsigned int j = c->buffer->i;
+    do
+    {
+      if (unlikely (!j))
+        return false;
+      j--;
+    } while (_hb_ot_layout_skip_mark (c->layout->face, &c->buffer->info[j], c->lookup_props, &property));
+
+    if (!(property & HB_OT_LAYOUT_GLYPH_CLASS_MARK))
+      return false;
+
+    /* Two marks match only if they belong to the same base, or same component
+     * of the same ligature.  That is, the component numbers must match, and
+     * if those are non-zero, the ligid number should also match. */
+    if ((c->buffer->info[j].lig_comp() != c->buffer->info[c->buffer->i].lig_comp()) ||
+        (c->buffer->info[j].lig_comp() && c->buffer->info[j].lig_id() != c->buffer->info[c->buffer->i].lig_id()))
+      return false;
+
+    unsigned int mark2_index = (this+mark2Coverage) (c->buffer->info[j].codepoint);
+    if (mark2_index == NOT_COVERED)
+      return false;
+
+    return (this+mark1Array).apply (c, mark1_index, mark2_index, this+mark2Array, classCount, j);
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    return c->check_struct (this)
+        && mark1Coverage.sanitize (c, this)
+        && mark2Coverage.sanitize (c, this)
+        && mark1Array.sanitize (c, this)
+        && mark2Array.sanitize (c, this, (unsigned int) classCount);
+  }
+
+  private:
+  USHORT        format;                 /* Format identifier--format = 1 */
+  OffsetTo<Coverage>
+                mark1Coverage;          /* Offset to Combining Mark1 Coverage
+                                         * table--from beginning of MarkMarkPos
+                                         * subtable */
+  OffsetTo<Coverage>
+                mark2Coverage;          /* Offset to Combining Mark2 Coverage
+                                         * table--from beginning of MarkMarkPos
+                                         * subtable */
+  USHORT        classCount;             /* Number of defined mark classes */
+  OffsetTo<MarkArray>
+                mark1Array;             /* Offset to Mark1Array table--from
+                                         * beginning of MarkMarkPos subtable */
+  OffsetTo<Mark2Array>
+                mark2Array;             /* Offset to Mark2Array table--from
+                                         * beginning of MarkMarkPos subtable */
+  public:
+  DEFINE_SIZE_STATIC (12);
+};
+
+struct MarkMarkPos
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    switch (u.format) {
+    case 1: return u.format1.apply (c);
+    default:return false;
+    }
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (!u.format.sanitize (c)) return false;
+    switch (u.format) {
+    case 1: return u.format1.sanitize (c);
+    default:return true;
+    }
+  }
+
+  private:
+  union {
+  USHORT                format;         /* Format identifier */
+  MarkMarkPosFormat1    format1;
+  } u;
+};
+
+
+HB_BEGIN_DECLS
+static inline bool position_lookup (hb_apply_context_t *c, unsigned int lookup_index);
+HB_END_DECLS
+
+struct ContextPos : Context
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    return Context::apply (c, position_lookup);
+  }
+};
+
+struct ChainContextPos : ChainContext
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline bool apply (hb_apply_context_t *c) const
+  {
+    TRACE_APPLY ();
+    return ChainContext::apply (c, position_lookup);
+  }
+};
+
+
+struct ExtensionPos : Extension
+{
+  friend struct PosLookupSubTable;
+
+  private:
+  inline const struct PosLookupSubTable& get_subtable (void) const
+  {
+    unsigned int offset = get_offset ();
+    if (unlikely (!offset)) return Null(PosLookupSubTable);
+    return StructAtOffset<PosLookupSubTable> (this, offset);
+  }
+
+  inline bool apply (hb_apply_context_t *c) const;
+
+  inline bool sanitize (hb_sanitize_context_t *c);
+};
+
+
+
+/*
+ * PosLookup
+ */
+
+
+struct PosLookupSubTable
+{
+  friend struct PosLookup;
+
+  enum {
+    Single              = 1,
+    Pair                = 2,
+    Cursive             = 3,
+    MarkBase            = 4,
+    MarkLig             = 5,
+    MarkMark            = 6,
+    Context             = 7,
+    ChainContext        = 8,
+    Extension           = 9
+  };
+
+  inline bool apply (hb_apply_context_t *c, unsigned int lookup_type) const
+  {
+    TRACE_APPLY ();
+    switch (lookup_type) {
+    case Single:                return u.single.apply (c);
+    case Pair:                  return u.pair.apply (c);
+    case Cursive:               return u.cursive.apply (c);
+    case MarkBase:              return u.markBase.apply (c);
+    case MarkLig:               return u.markLig.apply (c);
+    case MarkMark:              return u.markMark.apply (c);
+    case Context:               return u.c.apply (c);
+    case ChainContext:          return u.chainContext.apply (c);
+    case Extension:             return u.extension.apply (c);
+    default:return false;
+    }
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c, unsigned int lookup_type) {
+    TRACE_SANITIZE ();
+    switch (lookup_type) {
+    case Single:                return u.single.sanitize (c);
+    case Pair:                  return u.pair.sanitize (c);
+    case Cursive:               return u.cursive.sanitize (c);
+    case MarkBase:              return u.markBase.sanitize (c);
+    case MarkLig:               return u.markLig.sanitize (c);
+    case MarkMark:              return u.markMark.sanitize (c);
+    case Context:               return u.c.sanitize (c);
+    case ChainContext:          return u.chainContext.sanitize (c);
+    case Extension:             return u.extension.sanitize (c);
+    default:return true;
+    }
+  }
+
+  private:
+  union {
+  USHORT                sub_format;
+  SinglePos             single;
+  PairPos               pair;
+  CursivePos            cursive;
+  MarkBasePos           markBase;
+  MarkLigPos            markLig;
+  MarkMarkPos           markMark;
+  ContextPos            c;
+  ChainContextPos       chainContext;
+  ExtensionPos          extension;
+  } u;
+  public:
+  DEFINE_SIZE_UNION (2, sub_format);
+};
+
+
+struct PosLookup : Lookup
+{
+  inline const PosLookupSubTable& get_subtable (unsigned int i) const
+  { return this+CastR<OffsetArrayOf<PosLookupSubTable> > (subTable)[i]; }
+
+  inline bool apply_once (hb_ot_layout_context_t *layout,
+                          hb_buffer_t *buffer,
+                          hb_mask_t lookup_mask,
+                          unsigned int context_length,
+                          unsigned int nesting_level_left) const
+  {
+    unsigned int lookup_type = get_type ();
+    hb_apply_context_t c[1] = {{0}};
+
+    c->layout = layout;
+    c->buffer = buffer;
+    c->lookup_mask = lookup_mask;
+    c->context_length = context_length;
+    c->nesting_level_left = nesting_level_left;
+    c->lookup_props = get_props ();
+
+    if (!_hb_ot_layout_check_glyph_property (c->layout->face, &c->buffer->info[c->buffer->i], c->lookup_props, &c->property))
+      return false;
+
+    for (unsigned int i = 0; i < get_subtable_count (); i++)
+      if (get_subtable (i).apply (c, lookup_type))
+        return true;
+
+    return false;
+  }
+
+   inline bool apply_string (hb_ot_layout_context_t *layout,
+                             hb_buffer_t *buffer,
+                             hb_mask_t    mask) const
+  {
+    bool ret = false;
+
+    if (unlikely (!buffer->len))
+      return false;
+
+    buffer->i = 0;
+    while (buffer->i < buffer->len)
+    {
+      if ((buffer->info[buffer->i].mask & mask) &&
+          apply_once (layout, buffer, mask, NO_CONTEXT, MAX_NESTING_LEVEL))
+        ret = true;
+      else
+        buffer->i++;
+    }
+
+    return ret;
+  }
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (unlikely (!Lookup::sanitize (c))) return false;
+    OffsetArrayOf<PosLookupSubTable> &list = CastR<OffsetArrayOf<PosLookupSubTable> > (subTable);
+    return list.sanitize (c, this, get_type ());
+  }
+};
+
+typedef OffsetListOf<PosLookup> PosLookupList;
+
+/*
+ * GPOS
+ */
+
+struct GPOS : GSUBGPOS
+{
+  static const hb_tag_t Tag     = HB_OT_TAG_GPOS;
+
+  inline const PosLookup& get_lookup (unsigned int i) const
+  { return CastR<PosLookup> (GSUBGPOS::get_lookup (i)); }
+
+  inline bool position_lookup (hb_ot_layout_context_t *layout,
+                               hb_buffer_t  *buffer,
+                               unsigned int  lookup_index,
+                               hb_mask_t     mask) const
+  { return get_lookup (lookup_index).apply_string (layout, buffer, mask); }
+
+  static inline void position_finish (hb_buffer_t *buffer);
+
+  inline bool sanitize (hb_sanitize_context_t *c) {
+    TRACE_SANITIZE ();
+    if (unlikely (!GSUBGPOS::sanitize (c))) return false;
+    OffsetTo<PosLookupList> &list = CastR<OffsetTo<PosLookupList> > (lookupList);
+    return list.sanitize (c, this);
+  }
+  public:
+  DEFINE_SIZE_STATIC (10);
+};
+
+void
+GPOS::position_finish (hb_buffer_t *buffer)
+{
+  unsigned int i, j;
+  unsigned int len = hb_buffer_get_length (buffer);
+  hb_glyph_position_t *pos = hb_buffer_get_glyph_positions (buffer);
+  hb_direction_t direction = buffer->props.direction;
+
+  /* Handle cursive connections:
+   * First handle all chain-back connections, then handle all chain-forward connections. */
+  if (likely (HB_DIRECTION_IS_HORIZONTAL (direction)))
+  {
+    for (j = 0; j < len; j++) {
+      if (pos[j].cursive_chain() < 0)
+        pos[j].y_offset += pos[j + pos[j].cursive_chain()].y_offset;
+    }
+    for (i = len; i > 0; i--) {
+      j = i - 1;
+      if (pos[j].cursive_chain() > 0)
+        pos[j].y_offset += pos[j + pos[j].cursive_chain()].y_offset;
+    }
+  }
+  else
+  {
+    for (j = 0; j < len; j++) {
+      if (pos[j].cursive_chain() < 0)
+        pos[j].x_offset += pos[j + pos[j].cursive_chain()].x_offset;
+    }
+    for (i = len; i > 0; i--) {
+      j = i - 1;
+      if (pos[j].cursive_chain() > 0)
+        pos[j].x_offset += pos[j + pos[j].cursive_chain()].x_offset;
+    }
+  }
+
+
+  /* Handle attachments */
+  for (i = 0; i < len; i++)
+    if (pos[i].attach_lookback())
+    {
+      unsigned int back = i - pos[i].attach_lookback();
+      pos[i].x_offset += pos[back].x_offset;
+      pos[i].y_offset += pos[back].y_offset;
+
+      if (HB_DIRECTION_IS_BACKWARD (buffer->props.direction))
+        for (j = back + 1; j < i + 1; j++) {
+          pos[i].x_offset += pos[j].x_advance;
+          pos[i].y_offset += pos[j].y_advance;
+        }
+      else
+        for (j = back; j < i; j++) {
+          pos[i].x_offset -= pos[j].x_advance;
+          pos[i].y_offset -= pos[j].y_advance;
+        }
+    }
+}
+
+
+/* Out-of-class implementation for methods recursing */
+
+inline bool ExtensionPos::apply (hb_apply_context_t *c) const
+{
+  TRACE_APPLY ();
+  return get_subtable ().apply (c, get_type ());
+}
+
+inline bool ExtensionPos::sanitize (hb_sanitize_context_t *c)
+{
+  TRACE_SANITIZE ();
+  if (unlikely (!Extension::sanitize (c))) return false;
+  unsigned int offset = get_offset ();
+  if (unlikely (!offset)) return true;
+  return StructAtOffset<PosLookupSubTable> (this, offset).sanitize (c, get_type ());
+}
+
+static inline bool position_lookup (hb_apply_context_t *c, unsigned int lookup_index)
+{
+  const GPOS &gpos = *(c->layout->face->ot_layout->gpos);
+  const PosLookup &l = gpos.get_lookup (lookup_index);
+
+  if (unlikely (c->nesting_level_left == 0))
+    return false;
+
+  if (unlikely (c->context_length < 1))
+    return false;
+
+  return l.apply_once (c->layout, c->buffer, c->lookup_mask, c->context_length, c->nesting_level_left - 1);
+}
+
+
+#undef attach_lookback
+#undef cursive_chain
+
+
+HB_END_DECLS
+
+#endif /* HB_OT_LAYOUT_GPOS_PRIVATE_HH */