harfbuzz/src/hb-ot-kern-table.hh

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/*
* Copyright © 2017 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): Behdad Esfahbod
*/
#ifndef HB_OT_KERN_TABLE_HH
#define HB_OT_KERN_TABLE_HH
#include "hb-open-type.hh"
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#include "hb-ot-shape.hh"
#include "hb-ot-layout-gsubgpos.hh"
#include "hb-aat-layout-common.hh"
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template <typename Driver>
struct hb_kern_machine_t
{
hb_kern_machine_t (const Driver &driver_) : driver (driver_) {}
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HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW
inline void kern (hb_font_t *font,
hb_buffer_t *buffer,
hb_mask_t kern_mask,
bool scale = true) const
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{
OT::hb_ot_apply_context_t c (1, font, buffer);
c.set_lookup_mask (kern_mask);
c.set_lookup_props (OT::LookupFlag::IgnoreMarks);
OT::hb_ot_apply_context_t::skipping_iterator_t &skippy_iter = c.iter_input;
skippy_iter.init (&c);
bool horizontal = HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction);
unsigned int count = buffer->len;
hb_glyph_info_t *info = buffer->info;
hb_glyph_position_t *pos = buffer->pos;
for (unsigned int idx = 0; idx < count;)
{
if (!(info[idx].mask & kern_mask))
{
idx++;
continue;
}
skippy_iter.reset (idx, 1);
if (!skippy_iter.next ())
{
idx++;
continue;
}
unsigned int i = idx;
unsigned int j = skippy_iter.idx;
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hb_position_t kern = driver.get_kerning (info[i].codepoint,
info[j].codepoint);
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if (likely (!kern))
goto skip;
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if (horizontal)
{
if (scale)
kern = font->em_scale_x (kern);
hb_position_t kern1 = kern >> 1;
hb_position_t kern2 = kern - kern1;
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pos[i].x_advance += kern1;
pos[j].x_advance += kern2;
pos[j].x_offset += kern2;
}
else
{
if (scale)
kern = font->em_scale_y (kern);
hb_position_t kern1 = kern >> 1;
hb_position_t kern2 = kern - kern1;
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pos[i].y_advance += kern1;
pos[j].y_advance += kern2;
pos[j].y_offset += kern2;
}
buffer->unsafe_to_break (i, j + 1);
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skip:
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idx = skippy_iter.idx;
}
}
const Driver &driver;
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};
/*
* kern -- Kerning
* https://docs.microsoft.com/en-us/typography/opentype/spec/kern
* https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6kern.html
*/
#define HB_OT_TAG_kern HB_TAG('k','e','r','n')
namespace OT {
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struct hb_glyph_pair_t
{
hb_codepoint_t left;
hb_codepoint_t right;
};
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struct KernPair
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{
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inline int get_kerning (void) const
{ return value; }
inline int cmp (const hb_glyph_pair_t &o) const
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{
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int ret = left.cmp (o.left);
if (ret) return ret;
return right.cmp (o.right);
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}
inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
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return_trace (c->check_struct (this));
}
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protected:
GlyphID left;
GlyphID right;
FWORD value;
public:
DEFINE_SIZE_STATIC (6);
};
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template <typename KernSubTableHeader>
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struct KernSubTableFormat0
{
inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
{
hb_glyph_pair_t pair = {left, right};
int i = pairs.bsearch (pair);
if (i == -1)
return 0;
return pairs[i].get_kerning ();
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}
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inline bool apply (AAT::hb_aat_apply_context_t *c) const
{
TRACE_APPLY (this);
if (!c->plan->requested_kerning)
return false;
hb_kern_machine_t<KernSubTableFormat0> machine (*this);
machine.kern (c->font, c->buffer, c->plan->kern_mask);
return_trace (true);
}
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inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
return_trace (pairs.sanitize (c));
}
protected:
KernSubTableHeader header;
BinSearchArrayOf<KernPair> pairs; /* Array of kerning pairs. */
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public:
DEFINE_SIZE_ARRAY (KernSubTableHeader::static_size + 8, pairs);
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};
template <typename KernSubTableHeader>
struct KernSubTableFormat1
{
typedef void EntryData;
struct driver_context_t
{
static const bool in_place = true;
enum Flags
{
Push = 0x8000, /* If set, push this glyph on the kerning stack. */
DontAdvance = 0x4000, /* If set, don't advance to the next glyph
* before going to the new state. */
Offset = 0x3FFF, /* Byte offset from beginning of subtable to the
* value table for the glyphs on the kerning stack. */
};
inline driver_context_t (const KernSubTableFormat1 *table_,
AAT::hb_aat_apply_context_t *c_) :
c (c_),
table (table_),
/* Apparently the offset kernAction is from the beginning of the state-machine,
* similar to offsets in morx table, NOT from beginning of this table, like
* other subtables in kerx. Discovered via testing. */
kernAction (&table->machine + table->kernAction),
depth (0) {}
inline bool is_actionable (AAT::StateTableDriver<AAT::MortTypes, EntryData> *driver HB_UNUSED,
const AAT::Entry<EntryData> *entry)
{
return entry->flags & Offset;
}
inline bool transition (AAT::StateTableDriver<AAT::MortTypes, EntryData> *driver,
const AAT::Entry<EntryData> *entry)
{
hb_buffer_t *buffer = driver->buffer;
unsigned int flags = entry->flags;
if (flags & Push)
{
if (likely (depth < ARRAY_LENGTH (stack)))
stack[depth++] = buffer->idx;
else
depth = 0; /* Probably not what CoreText does, but better? */
}
if (entry->flags & Offset)
{
unsigned int kernIndex = AAT::MortTypes::offsetToIndex (entry->flags & Offset, &table->machine, kernAction.arrayZ);
const FWORD *actions = &kernAction[kernIndex];
if (!c->sanitizer.check_array (actions, depth))
{
depth = 0;
return false;
}
hb_mask_t kern_mask = c->plan->kern_mask;
for (unsigned int i = 0; i < depth; i++)
{
/* Apparently, when spec says "Each pops one glyph from the kerning stack
* and applies the kerning value to it.", it doesn't mean it in that order.
* The deepest item in the stack corresponds to the first item in the action
* list. Discovered by testing. */
unsigned int idx = stack[i];
int v = *actions++;
if (idx < buffer->len && buffer->info[idx].mask & kern_mask)
{
if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
{
buffer->pos[idx].x_advance += c->font->em_scale_x (v);
if (HB_DIRECTION_IS_BACKWARD (buffer->props.direction))
buffer->pos[idx].x_offset += c->font->em_scale_x (v);
}
else
{
buffer->pos[idx].y_advance += c->font->em_scale_y (v);
if (HB_DIRECTION_IS_BACKWARD (buffer->props.direction))
buffer->pos[idx].y_offset += c->font->em_scale_y (v);
}
}
}
depth = 0;
}
return true;
}
private:
AAT::hb_aat_apply_context_t *c;
const KernSubTableFormat1 *table;
const UnsizedArrayOf<FWORD> &kernAction;
unsigned int stack[8];
unsigned int depth;
};
inline bool apply (AAT::hb_aat_apply_context_t *c) const
{
TRACE_APPLY (this);
if (!c->plan->requested_kerning)
return false;
driver_context_t dc (this, c);
AAT::StateTableDriver<AAT::MortTypes, EntryData> driver (machine, c->buffer, c->font->face);
driver.drive (&dc);
return_trace (true);
}
inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
/* The rest of array sanitizations are done at run-time. */
return_trace (likely (c->check_struct (this) &&
machine.sanitize (c)));
}
protected:
KernSubTableHeader header;
AAT::StateTable<AAT::MortTypes, EntryData> machine;
OffsetTo<UnsizedArrayOf<FWORD>, HBUINT16, false> kernAction;
public:
DEFINE_SIZE_STATIC (KernSubTableHeader::static_size + 10);
};
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struct KernClassTable
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{
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inline unsigned int get_class (hb_codepoint_t g) const { return classes[g - firstGlyph]; }
inline bool sanitize (hb_sanitize_context_t *c) const
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{
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TRACE_SANITIZE (this);
return_trace (c->check_struct (this) &&
classes.sanitize (c));
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}
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protected:
HBUINT16 firstGlyph; /* First glyph in class range. */
ArrayOf<HBUINT16> classes; /* Glyph classes. */
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public:
DEFINE_SIZE_ARRAY (4, classes);
};
template <typename KernSubTableHeader>
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struct KernSubTableFormat2
{
inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right,
AAT::hb_aat_apply_context_t *c) const
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{
/* This subtable is disabled. It's not cleaer to me *exactly* where the offests are
* based from. I *think* they should be based from beginning of kern subtable wrapper,
* *NOT* "this". Since we know of no fonts that use this subtable, we are disabling
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* it. Someday fix it and re-enable. */
return 0;
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unsigned int l = (this+leftClassTable).get_class (left);
unsigned int r = (this+rightClassTable).get_class (right);
unsigned int offset = l + r;
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const FWORD *v = &StructAtOffset<FWORD> (&(this+array), offset);
#if 0
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if (unlikely ((const char *) v < (const char *) &array ||
(const char *) v > (const char *) end - 2))
#endif
return 0;
return *v;
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}
inline bool apply (AAT::hb_aat_apply_context_t *c) const
{
TRACE_APPLY (this);
if (!c->plan->requested_kerning)
return false;
accelerator_t accel (*this, c);
hb_kern_machine_t<accelerator_t> machine (accel);
machine.kern (c->font, c->buffer, c->plan->kern_mask);
return_trace (true);
}
struct accelerator_t
{
const KernSubTableFormat2 &table;
AAT::hb_aat_apply_context_t *c;
inline accelerator_t (const KernSubTableFormat2 &table_,
AAT::hb_aat_apply_context_t *c_) :
table (table_), c (c_) {}
inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
{ return table.get_kerning (left, right, c); }
};
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inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
return_trace (true); /* Disabled. See above. */
return_trace (c->check_struct (this) &&
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leftClassTable.sanitize (c, this) &&
rightClassTable.sanitize (c, this) &&
array.sanitize (c, this));
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}
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protected:
KernSubTableHeader header;
HBUINT16 rowWidth; /* The width, in bytes, of a row in the table. */
OffsetTo<KernClassTable> leftClassTable; /* Offset from beginning of this subtable to
* left-hand class table. */
OffsetTo<KernClassTable> rightClassTable;/* Offset from beginning of this subtable to
* right-hand class table. */
OffsetTo<FWORD> array; /* Offset from beginning of this subtable to
* the start of the kerning array. */
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public:
DEFINE_SIZE_MIN (KernSubTableHeader::static_size + 8);
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};
template <typename KernSubTableHeader>
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struct KernSubTableFormat3
{
inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
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{
hb_array_t<const FWORD> kernValue = kernValueZ.as_array (kernValueCount);
hb_array_t<const HBUINT8> leftClass = StructAfter<const UnsizedArrayOf<HBUINT8> > (kernValue).as_array (glyphCount);
hb_array_t<const HBUINT8> rightClass = StructAfter<const UnsizedArrayOf<HBUINT8> > (leftClass).as_array (glyphCount);
hb_array_t<const HBUINT8> kernIndex = StructAfter<const UnsizedArrayOf<HBUINT8> > (rightClass).as_array (leftClassCount * rightClassCount);
unsigned int leftC = leftClass[left];
unsigned int rightC = rightClass[right];
if (unlikely (leftC >= leftClassCount || rightC >= rightClassCount))
return 0;
unsigned int i = leftC * rightClassCount + rightC;
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return kernValue[kernIndex[i]];
}
inline bool apply (AAT::hb_aat_apply_context_t *c) const
{
TRACE_APPLY (this);
if (!c->plan->requested_kerning)
return false;
hb_kern_machine_t<KernSubTableFormat3> machine (*this);
machine.kern (c->font, c->buffer, c->plan->kern_mask);
return_trace (true);
}
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inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
return_trace (c->check_struct (this) &&
c->check_range (kernValueZ,
kernValueCount * sizeof (FWORD) +
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glyphCount * 2 +
leftClassCount * rightClassCount));
}
protected:
KernSubTableHeader header;
HBUINT16 glyphCount; /* The number of glyphs in this font. */
HBUINT8 kernValueCount; /* The number of kerning values. */
HBUINT8 leftClassCount; /* The number of left-hand classes. */
HBUINT8 rightClassCount;/* The number of right-hand classes. */
HBUINT8 flags; /* Set to zero (reserved for future use). */
UnsizedArrayOf<FWORD> kernValueZ; /* The kerning values.
* Length kernValueCount. */
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#if 0
UnsizedArrayOf<HBUINT8>leftClass; /* The left-hand classes.
* Length glyphCount. */
UnsizedArrayOf<HBUINT8>rightClass; /* The right-hand classes.
* Length glyphCount. */
UnsizedArrayOf<HBUINT8>kernIndex; /* The indices into the kernValue array.
* Length leftClassCount * rightClassCount */
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#endif
public:
DEFINE_SIZE_ARRAY (KernSubTableHeader::static_size + 6, kernValueZ);
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};
template <typename KernSubTableHeader>
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struct KernSubTable
{
inline unsigned int get_size (void) const { return u.header.length; }
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inline unsigned int get_type (void) const { return u.header.format; }
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inline bool is_crossStream (void) const
{ return u.header.coverage & u.header.CrossStream; }
inline bool is_variation (void) const
{ return u.header.coverage & u.header.Variation; }
inline bool is_horizontal (void) const
{ return (u.header.coverage & u.header.Direction) == u.header.DirectionHorizontal; }
inline bool is_override (void) const
{ return bool (u.header.coverage & u.header.Override); }
inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
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{
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switch (get_type ()) {
/* This method hooks up to hb_font_t's get_h_kerning. Only support Format0. */
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case 0: return u.format0.get_kerning (left, right);
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default:return 0;
}
}
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template <typename context_t>
inline typename context_t::return_t dispatch (context_t *c) const
{
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unsigned int subtable_type = get_type ();
TRACE_DISPATCH (this, subtable_type);
switch (subtable_type) {
case 0: return_trace (c->dispatch (u.format0));
case 1: return_trace (c->dispatch (u.format1));
case 2: return_trace (c->dispatch (u.format2));
case 3: return_trace (c->dispatch (u.format3));
default: return_trace (c->default_return_value ());
}
}
inline bool sanitize (hb_sanitize_context_t *c) const
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{
TRACE_SANITIZE (this);
if (unlikely (!u.header.sanitize (c) ||
u.header.length < u.header.min_size ||
!c->check_range (this, u.header.length))) return_trace (false);
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return_trace (dispatch (c));
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}
protected:
union {
KernSubTableHeader header;
KernSubTableFormat0<KernSubTableHeader> format0;
KernSubTableFormat1<KernSubTableHeader> format1;
KernSubTableFormat2<KernSubTableHeader> format2;
KernSubTableFormat3<KernSubTableHeader> format3;
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} u;
public:
DEFINE_SIZE_MIN (0);
};
template <typename T>
struct KernTable
{
/* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
inline const T* thiz (void) const { return static_cast<const T *> (this); }
inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right) const
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{
typedef KernSubTable<typename T::SubTableHeader> SubTable;
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int v = 0;
const SubTable *st = CastP<SubTable> (&thiz()->dataZ);
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unsigned int count = thiz()->nTables;
for (unsigned int i = 0; i < count; i++)
{
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if (!st->is_variation () || !st->is_crossStream () || !st->is_horizontal ())
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continue;
if (st->is_override ())
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v = 0;
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v += st->get_kerning (left, right);
st = &StructAfter<SubTable> (*st);
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}
return v;
}
inline void apply (AAT::hb_aat_apply_context_t *c) const
{
typedef KernSubTable<typename T::SubTableHeader> SubTable;
c->set_lookup_index (0);
const SubTable *st = CastP<SubTable> (&thiz()->dataZ);
unsigned int count = thiz()->nTables;
/* If there's an override subtable, skip subtables before that. */
unsigned int last_override = 0;
for (unsigned int i = 0; i < count; i++)
{
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if (!st->is_variation () && !st->is_crossStream () &&
st->is_override ())
last_override = i;
st = &StructAfter<SubTable> (*st);
}
st = CastP<SubTable> (&thiz()->dataZ);
for (unsigned int i = 0; i < count; i++)
{
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if (st->is_variation () || st->is_crossStream ())
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goto skip;
if (HB_DIRECTION_IS_HORIZONTAL (c->buffer->props.direction) != st->is_horizontal ())
goto skip;
if (i < last_override)
goto skip;
if (!c->buffer->message (c->font, "start kern subtable %d", c->lookup_index))
goto skip;
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c->sanitizer.set_object (*st);
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st->dispatch (c);
(void) c->buffer->message (c->font, "end kern subtable %d", c->lookup_index);
skip:
st = &StructAfter<SubTable> (*st);
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c->set_lookup_index (c->lookup_index + 1);
}
}
inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
if (unlikely (!c->check_struct (thiz()) ||
thiz()->version != T::VERSION))
return_trace (false);
typedef KernSubTable<typename T::SubTableHeader> SubTable;
const SubTable *st = CastP<SubTable> (&thiz()->dataZ);
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unsigned int count = thiz()->nTables;
for (unsigned int i = 0; i < count; i++)
{
if (unlikely (!st->sanitize (c)))
return_trace (false);
st = &StructAfter<SubTable> (*st);
}
return_trace (true);
}
};
struct KernOT : KernTable<KernOT>
{
friend struct KernTable<KernOT>;
static const uint16_t VERSION = 0x0000u;
struct SubTableHeader
{
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enum Coverage
{
Direction = 0x01u,
Minimum = 0x02u,
CrossStream = 0x04u,
Override = 0x08u,
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Variation = 0x00u, /* Not supported. */
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DirectionHorizontal= 0x01u
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};
inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
return_trace (c->check_struct (this));
}
public:
HBUINT16 versionZ; /* Unused. */
HBUINT16 length; /* Length of the subtable (including this header). */
HBUINT8 format; /* Subtable format. */
HBUINT8 coverage; /* Coverage bits. */
public:
DEFINE_SIZE_STATIC (6);
};
protected:
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HBUINT16 version; /* Version--0x0000u */
HBUINT16 nTables; /* Number of subtables in the kerning table. */
UnsizedArrayOf<HBUINT8> dataZ;
public:
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DEFINE_SIZE_ARRAY (4, dataZ);
};
struct KernAAT : KernTable<KernAAT>
{
friend struct KernTable<KernAAT>;
static const uint32_t VERSION = 0x00010000u;
struct SubTableHeader
{
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enum Coverage
{
Direction = 0x80u,
CrossStream = 0x40u,
Variation = 0x20u,
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Override = 0x00u, /* Not supported. */
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DirectionHorizontal= 0x00u
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};
inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
return_trace (c->check_struct (this));
}
public:
HBUINT32 length; /* Length of the subtable (including this header). */
HBUINT8 coverage; /* Coverage bits. */
HBUINT8 format; /* Subtable format. */
HBUINT16 tupleIndex; /* The tuple index (used for variations fonts).
* This value specifies which tuple this subtable covers. */
public:
DEFINE_SIZE_STATIC (8);
};
protected:
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HBUINT32 version; /* Version--0x00010000u */
HBUINT32 nTables; /* Number of subtables in the kerning table. */
UnsizedArrayOf<HBUINT8> dataZ;
public:
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DEFINE_SIZE_ARRAY (8, dataZ);
};
struct kern
{
static const hb_tag_t tableTag = HB_OT_TAG_kern;
inline bool has_data (void) const
{ return u.version32 != 0; }
inline int get_h_kerning (hb_codepoint_t left, hb_codepoint_t right) const
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{
switch (u.major) {
case 0: return u.ot.get_h_kerning (left, right);
case 1: return u.aat.get_h_kerning (left, right);
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default:return 0;
}
}
inline void apply (AAT::hb_aat_apply_context_t *c) const
{
/* TODO Switch to dispatch(). */
switch (u.major) {
case 0: u.ot.apply (c); return;
case 1: u.aat.apply (c); return;
default: return;
}
}
inline bool sanitize (hb_sanitize_context_t *c) const
{
TRACE_SANITIZE (this);
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if (!u.version32.sanitize (c)) return_trace (false);
switch (u.major) {
case 0: return_trace (u.ot.sanitize (c));
case 1: return_trace (u.aat.sanitize (c));
default:return_trace (true);
}
}
protected:
union {
HBUINT32 version32;
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HBUINT16 major;
KernOT ot;
KernAAT aat;
} u;
public:
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DEFINE_SIZE_UNION (4, version32);
};
} /* namespace OT */
#endif /* HB_OT_KERN_TABLE_HH */