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harfbuzz/src/hb-subset.cc

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/*
* Copyright © 2018 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): Garret Rieger, Rod Sheeter, Behdad Esfahbod
*/
#include "hb.hh"
#include "hb-open-type.hh"
#include "hb-subset.hh"
#include "hb-open-file.hh"
#include "hb-ot-cmap-table.hh"
#include "hb-ot-glyf-table.hh"
#include "hb-ot-hdmx-table.hh"
#include "hb-ot-head-table.hh"
#include "hb-ot-hhea-table.hh"
#include "hb-ot-hmtx-table.hh"
#include "hb-ot-maxp-table.hh"
#include "hb-ot-color-sbix-table.hh"
#include "hb-ot-color-colr-table.hh"
#include "hb-ot-color-cpal-table.hh"
#include "hb-ot-os2-table.hh"
#include "hb-ot-post-table.hh"
#include "hb-ot-post-table-v2subset.hh"
#include "hb-ot-cff1-table.hh"
#include "hb-ot-cff2-table.hh"
#include "hb-ot-vorg-table.hh"
#include "hb-ot-name-table.hh"
#include "hb-ot-color-cbdt-table.hh"
#include "hb-ot-layout-gsub-table.hh"
#include "hb-ot-layout-gpos-table.hh"
#include "hb-ot-var-gvar-table.hh"
#include "hb-ot-var-hvar-table.hh"
#include "hb-ot-math-table.hh"
#include "hb-repacker.hh"
using OT::Layout::GSUB::GSUB;
/**
* SECTION:hb-subset
* @title: hb-subset
* @short_description: Subsets font files.
* @include: hb-subset.h
*
* Subsetting reduces the codepoint coverage of font files and removes all data
* that is no longer needed. A subset input describes the desired subset. The input is
* provided along with a font to the subsetting operation. Output is a new font file
* containing only the data specified in the input.
*
* Currently most outline and bitmap tables are supported: glyf, CFF, CFF2, sbix,
* COLR, and CBDT/CBLC. This also includes fonts with variable outlines via OpenType
* variations. Notably EBDT/EBLC and SVG are not supported. Layout subsetting is supported
* only for OpenType Layout tables (GSUB, GPOS, GDEF). Notably subsetting of graphite or AAT tables
* is not yet supported.
*
* Fonts with graphite or AAT tables may still be subsetted but will likely need to use the
* retain glyph ids option and configure the subset to pass through the layout tables untouched.
*/
/*
* The list of tables in the open type spec. Used to check for tables that may need handling
* if we are unable to list the tables in a face.
*/
static hb_tag_t known_tables[] {
HB_TAG ('a', 'v', 'a', 'r'),
HB_OT_TAG_BASE,
HB_OT_TAG_CBDT,
HB_OT_TAG_CBLC,
HB_OT_TAG_cff1,
HB_OT_TAG_cff2,
HB_OT_TAG_cmap,
HB_OT_TAG_COLR,
HB_OT_TAG_CPAL,
HB_TAG ('c', 'v', 'a', 'r'),
HB_TAG ('c', 'v', 't', ' '),
HB_TAG ('D', 'S', 'I', 'G'),
HB_TAG ('E', 'B', 'D', 'T'),
HB_TAG ('E', 'B', 'L', 'C'),
HB_TAG ('E', 'B', 'S', 'C'),
HB_TAG ('f', 'p', 'g', 'm'),
HB_TAG ('f', 'v', 'a', 'r'),
HB_TAG ('g', 'a', 's', 'p'),
HB_OT_TAG_GDEF,
HB_OT_TAG_glyf,
HB_OT_TAG_GPOS,
HB_OT_TAG_GSUB,
HB_OT_TAG_gvar,
HB_OT_TAG_hdmx,
HB_OT_TAG_head,
HB_OT_TAG_hhea,
HB_OT_TAG_hmtx,
HB_OT_TAG_HVAR,
HB_OT_TAG_JSTF,
HB_TAG ('k', 'e', 'r', 'n'),
HB_OT_TAG_loca,
HB_TAG ('L', 'T', 'S', 'H'),
HB_OT_TAG_MATH,
HB_OT_TAG_maxp,
HB_TAG ('M', 'E', 'R', 'G'),
HB_TAG ('m', 'e', 't', 'a'),
HB_TAG ('M', 'V', 'A', 'R'),
HB_TAG ('P', 'C', 'L', 'T'),
HB_OT_TAG_post,
HB_TAG ('p', 'r', 'e', 'p'),
HB_OT_TAG_sbix,
HB_TAG ('S', 'T', 'A', 'T'),
HB_TAG ('S', 'V', 'G', ' '),
HB_TAG ('V', 'D', 'M', 'X'),
HB_OT_TAG_vhea,
HB_OT_TAG_vmtx,
HB_OT_TAG_VORG,
HB_OT_TAG_VVAR,
HB_OT_TAG_name,
HB_OT_TAG_OS2
};
static bool _table_is_empty (const hb_face_t *face, hb_tag_t tag)
{
hb_blob_t* blob = hb_face_reference_table (face, tag);
bool result = (blob == hb_blob_get_empty ());
hb_blob_destroy (blob);
return result;
}
static unsigned int
_get_table_tags (const hb_subset_plan_t* plan,
unsigned int start_offset,
unsigned int *table_count, /* IN/OUT */
hb_tag_t *table_tags /* OUT */)
{
unsigned num_tables = hb_face_get_table_tags (plan->source, 0, nullptr, nullptr);
if (num_tables)
return hb_face_get_table_tags (plan->source, start_offset, table_count, table_tags);
// If face has 0 tables associated with it, assume that it was built from
// hb_face_create_tables and thus is unable to list its tables. Fallback to
// checking each table type we can handle for existence instead.
auto it =
hb_concat (
+ hb_array (known_tables)
| hb_filter ([&] (hb_tag_t tag) {
return !_table_is_empty (plan->source, tag) && !plan->no_subset_tables->has (tag);
})
| hb_map ([] (hb_tag_t tag) -> hb_tag_t { return tag; }),
plan->no_subset_tables->iter ()
| hb_filter([&] (hb_tag_t tag) {
return !_table_is_empty (plan->source, tag);
}));
it += start_offset;
unsigned num_written = 0;
while (bool (it) && num_written < *table_count)
table_tags[num_written++] = *it++;
*table_count = num_written;
return num_written;
}
static unsigned
_plan_estimate_subset_table_size (hb_subset_plan_t *plan,
unsigned table_len,
bool same_size)
{
unsigned src_glyphs = plan->source->get_num_glyphs ();
unsigned dst_glyphs = plan->glyphset ()->get_population ();
if (unlikely (!src_glyphs) || same_size)
return 512 + table_len;
return 512 + (unsigned) (table_len * sqrt ((double) dst_glyphs / src_glyphs));
}
/*
* Repack the serialization buffer if any offset overflows exist.
*/
static hb_blob_t*
_repack (hb_tag_t tag, const hb_serialize_context_t& c)
{
if (tag != HB_OT_TAG_GPOS
&& tag != HB_OT_TAG_GSUB)
{
// Check for overflow in a non-handled table.
return c.successful () ? c.copy_blob () : nullptr;
}
if (!c.offset_overflow ())
return c.copy_blob ();
hb_blob_t* result = hb_resolve_overflows (c.object_graph (), tag);
if (unlikely (!result))
{
DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c offset overflow resolution failed.",
HB_UNTAG (tag));
return nullptr;
}
return result;
}
template<typename TableType>
static
bool
_try_subset (const TableType *table,
hb_vector_t<char>* buf,
hb_subset_context_t* c /* OUT */)
{
c->serializer->start_serialize<TableType> ();
if (c->serializer->in_error ()) return false;
bool needed = table->subset (c);
if (!c->serializer->ran_out_of_room ())
{
c->serializer->end_serialize ();
return needed;
}
unsigned buf_size = buf->allocated;
buf_size = buf_size * 2 + 16;
DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c ran out of room; reallocating to %u bytes.",
HB_UNTAG (c->table_tag), buf_size);
if (unlikely (!buf->alloc (buf_size)))
{
DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c failed to reallocate %u bytes.",
HB_UNTAG (c->table_tag), buf_size);
return needed;
}
c->serializer->reset (buf->arrayZ, buf->allocated);
return _try_subset (table, buf, c);
}
template<typename TableType>
static bool
_subset (hb_subset_plan_t *plan, hb_vector_t<char> &buf)
{
hb_blob_t *source_blob = hb_sanitize_context_t ().reference_table<TableType> (plan->source);
const TableType *table = source_blob->as<TableType> ();
hb_tag_t tag = TableType::tableTag;
if (!source_blob->data)
{
DEBUG_MSG (SUBSET, nullptr,
"OT::%c%c%c%c::subset sanitize failed on source table.", HB_UNTAG (tag));
hb_blob_destroy (source_blob);
return false;
}
/* Tables that we want to allocate same space as the source table. For GSUB/GPOS it's
* because those are expensive to subset, so giving them more room is fine. */
bool same_size_table = TableType::tableTag == HB_OT_TAG_GSUB ||
TableType::tableTag == HB_OT_TAG_GPOS ||
TableType::tableTag == HB_OT_TAG_name;
unsigned buf_size = _plan_estimate_subset_table_size (plan, source_blob->length, same_size_table);
DEBUG_MSG (SUBSET, nullptr,
"OT::%c%c%c%c initial estimated table size: %u bytes.", HB_UNTAG (tag), buf_size);
if (unlikely (!buf.alloc (buf_size)))
{
DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c failed to allocate %u bytes.", HB_UNTAG (tag), buf_size);
hb_blob_destroy (source_blob);
return false;
}
bool needed = false;
hb_serialize_context_t serializer (buf.arrayZ, buf.allocated);
{
hb_subset_context_t c (source_blob, plan, &serializer, tag);
needed = _try_subset (table, &buf, &c);
}
hb_blob_destroy (source_blob);
if (serializer.in_error () && !serializer.only_offset_overflow ())
{
DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c::subset FAILED!", HB_UNTAG (tag));
return false;
}
if (!needed)
{
DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c::subset table subsetted to empty.", HB_UNTAG (tag));
return true;
}
bool result = false;
hb_blob_t *dest_blob = _repack (tag, serializer);
if (dest_blob)
{
DEBUG_MSG (SUBSET, nullptr,
"OT::%c%c%c%c final subset table size: %u bytes.",
HB_UNTAG (tag), dest_blob->length);
result = plan->add_table (tag, dest_blob);
hb_blob_destroy (dest_blob);
}
DEBUG_MSG (SUBSET, nullptr, "OT::%c%c%c%c::subset %s",
HB_UNTAG (tag), result ? "success" : "FAILED!");
return result;
}
static bool
_is_table_present (hb_face_t *source, hb_tag_t tag)
{
if (!hb_face_get_table_tags (source, 0, nullptr, nullptr)) {
// If face has 0 tables associated with it, assume that it was built from
// hb_face_create_tables and thus is unable to list its tables. Fallback to
// checking if the blob associated with tag is empty.
return !_table_is_empty (source, tag);
}
hb_tag_t table_tags[32];
unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);
while ((hb_face_get_table_tags (source, offset, &num_tables, table_tags), num_tables))
{
for (unsigned i = 0; i < num_tables; ++i)
if (table_tags[i] == tag)
return true;
offset += num_tables;
}
return false;
}
static bool
_should_drop_table (hb_subset_plan_t *plan, hb_tag_t tag)
{
if (plan->drop_tables->has (tag))
return true;
switch (tag)
{
case HB_TAG ('c','v','a','r'): /* hint table, fallthrough */
case HB_TAG ('c','v','t',' '): /* hint table, fallthrough */
case HB_TAG ('f','p','g','m'): /* hint table, fallthrough */
case HB_TAG ('p','r','e','p'): /* hint table, fallthrough */
case HB_TAG ('h','d','m','x'): /* hint table, fallthrough */
case HB_TAG ('V','D','M','X'): /* hint table, fallthrough */
return plan->flags & HB_SUBSET_FLAGS_NO_HINTING;
#ifdef HB_NO_SUBSET_LAYOUT
// Drop Layout Tables if requested.
case HB_OT_TAG_GDEF:
case HB_OT_TAG_GPOS:
case HB_OT_TAG_GSUB:
case HB_TAG ('m','o','r','x'):
case HB_TAG ('m','o','r','t'):
case HB_TAG ('k','e','r','x'):
case HB_TAG ('k','e','r','n'):
return true;
#endif
default:
return false;
}
}
static bool
_passthrough (hb_subset_plan_t *plan, hb_tag_t tag)
{
hb_blob_t *source_table = hb_face_reference_table (plan->source, tag);
bool result = plan->add_table (tag, source_table);
hb_blob_destroy (source_table);
return result;
}
static bool
_subset_table (hb_subset_plan_t *plan,
hb_vector_t<char> &buf,
hb_tag_t tag)
{
if (plan->no_subset_tables->has (tag)) {
return _passthrough (plan, tag);
}
DEBUG_MSG (SUBSET, nullptr, "subset %c%c%c%c", HB_UNTAG (tag));
switch (tag)
{
case HB_OT_TAG_glyf: return _subset<const OT::glyf> (plan, buf);
case HB_OT_TAG_hdmx: return _subset<const OT::hdmx> (plan, buf);
case HB_OT_TAG_name: return _subset<const OT::name> (plan, buf);
case HB_OT_TAG_head:
if (_is_table_present (plan->source, HB_OT_TAG_glyf) && !_should_drop_table (plan, HB_OT_TAG_glyf))
return true; /* skip head, handled by glyf */
return _subset<const OT::head> (plan, buf);
case HB_OT_TAG_hhea: return true; /* skip hhea, handled by hmtx */
case HB_OT_TAG_hmtx: return _subset<const OT::hmtx> (plan, buf);
case HB_OT_TAG_vhea: return true; /* skip vhea, handled by vmtx */
case HB_OT_TAG_vmtx: return _subset<const OT::vmtx> (plan, buf);
case HB_OT_TAG_maxp: return _subset<const OT::maxp> (plan, buf);
case HB_OT_TAG_sbix: return _subset<const OT::sbix> (plan, buf);
case HB_OT_TAG_loca: return true; /* skip loca, handled by glyf */
case HB_OT_TAG_cmap: return _subset<const OT::cmap> (plan, buf);
case HB_OT_TAG_OS2 : return _subset<const OT::OS2 > (plan, buf);
case HB_OT_TAG_post: return _subset<const OT::post> (plan, buf);
case HB_OT_TAG_COLR: return _subset<const OT::COLR> (plan, buf);
case HB_OT_TAG_CPAL: return _subset<const OT::CPAL> (plan, buf);
case HB_OT_TAG_CBLC: return _subset<const OT::CBLC> (plan, buf);
case HB_OT_TAG_CBDT: return true; /* skip CBDT, handled by CBLC */
case HB_OT_TAG_MATH: return _subset<const OT::MATH> (plan, buf);
#ifndef HB_NO_SUBSET_CFF
case HB_OT_TAG_cff1: return _subset<const OT::cff1> (plan, buf);
case HB_OT_TAG_cff2: return _subset<const OT::cff2> (plan, buf);
case HB_OT_TAG_VORG: return _subset<const OT::VORG> (plan, buf);
#endif
#ifndef HB_NO_SUBSET_LAYOUT
case HB_OT_TAG_GDEF: return _subset<const OT::GDEF> (plan, buf);
case HB_OT_TAG_GSUB: return _subset<const GSUB> (plan, buf);
case HB_OT_TAG_GPOS: return _subset<const OT::GPOS> (plan, buf);
case HB_OT_TAG_gvar: return _subset<const OT::gvar> (plan, buf);
case HB_OT_TAG_HVAR: return _subset<const OT::HVAR> (plan, buf);
case HB_OT_TAG_VVAR: return _subset<const OT::VVAR> (plan, buf);
#endif
default:
if (plan->flags & HB_SUBSET_FLAGS_PASSTHROUGH_UNRECOGNIZED)
return _passthrough (plan, tag);
// Drop table
return true;
}
}
/**
* hb_subset_or_fail:
* @source: font face data to be subset.
* @input: input to use for the subsetting.
*
* Subsets a font according to provided input. Returns nullptr
* if the subset operation fails.
*
* Since: 2.9.0
**/
hb_face_t *
hb_subset_or_fail (hb_face_t *source, const hb_subset_input_t *input)
{
if (unlikely (!input || !source)) return hb_face_get_empty ();
hb_subset_plan_t *plan = hb_subset_plan_create_or_fail (source, input);
if (unlikely (!plan)) {
return nullptr;
}
hb_face_t * result = hb_subset_plan_execute_or_fail (plan);
hb_subset_plan_destroy (plan);
return result;
}
/**
* hb_subset_plan_execute_or_fail:
* @plan: a subsetting plan.
*
* Executes the provided subsetting @plan.
*
* Return value:
* on success returns a reference to generated font subset. If the subsetting operation fails
* returns nullptr.
*
* Since: 4.0.0
**/
hb_face_t *
hb_subset_plan_execute_or_fail (hb_subset_plan_t *plan)
{
if (unlikely (!plan || plan->in_error ())) {
return nullptr;
}
hb_set_t tags_set;
bool success = true;
hb_tag_t table_tags[32];
unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);
hb_vector_t<char> buf;
buf.alloc (4096 - 16);
while ((_get_table_tags (plan, offset, &num_tables, table_tags), num_tables))
{
for (unsigned i = 0; i < num_tables; ++i)
{
hb_tag_t tag = table_tags[i];
if (_should_drop_table (plan, tag) && !tags_set.has (tag)) continue;
tags_set.add (tag);
success = _subset_table (plan, buf, tag);
if (unlikely (!success)) goto end;
}
offset += num_tables;
}
end:
return success ? hb_face_reference (plan->dest) : nullptr;
}
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