harfbuzz/src/hb-subset.cc

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/*
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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.
*
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* Google Author(s): Garret Rieger, Rod Sheeter, Behdad Esfahbod
*/
#include "hb.hh"
#include "hb-open-type.hh"
#include "hb-subset.hh"
#include "hb-subset-glyf.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"
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#include "hb-ot-hhea-table.hh"
#include "hb-ot-hmtx-table.hh"
#include "hb-ot-maxp-table.hh"
#include "hb-ot-os2-table.hh"
#include "hb-ot-post-table.hh"
#include "hb-ot-layout-gsub-table.hh"
#include "hb-ot-layout-gpos-table.hh"
static unsigned int
_plan_estimate_subset_table_size (hb_subset_plan_t *plan,
unsigned int table_len)
{
unsigned int src_glyphs = plan->source->get_num_glyphs ();
unsigned int dst_glyphs = plan->glyphset->get_population ();
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if (unlikely (!src_glyphs))
return 512 + table_len;
return 512 + (unsigned int) (table_len * sqrt ((double) dst_glyphs / src_glyphs));
}
template<typename TableType>
static bool
_subset2 (hb_subset_plan_t *plan)
{
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;
hb_bool_t result = false;
if (source_blob->data)
{
hb_vector_t<char> buf;
unsigned int buf_size = _plan_estimate_subset_table_size (plan, source_blob->length);
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);
return false;
}
retry:
hb_serialize_context_t serializer (buf, buf_size);
hb_subset_context_t c (plan, &serializer);
result = table->subset (&c);
if (serializer.ran_out_of_room)
{
buf_size += (buf_size >> 1) + 32;
DEBUG_MSG(SUBSET, nullptr, "OT::%c%c%c%c ran out of room; reallocating to %u bytes.", HB_UNTAG(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(tag), buf_size);
return false;
}
goto retry;
}
if (result)
{
hb_blob_t *dest_blob = serializer.copy_blob ();
DEBUG_MSG(SUBSET, nullptr, "OT::%c%c%c%c final subset table size: %u bytes.", HB_UNTAG(tag), dest_blob->length);
result = c.plan->add_table (tag, dest_blob);
hb_blob_destroy (dest_blob);
}
else
{
DEBUG_MSG(SUBSET, nullptr, "OT::%c%c%c%c::subset table subsetted to empty.", HB_UNTAG(tag));
result = true;
}
}
else
DEBUG_MSG(SUBSET, nullptr, "OT::%c%c%c%c::subset sanitize failed on source table.", HB_UNTAG(tag));
hb_blob_destroy (source_blob);
DEBUG_MSG(SUBSET, nullptr, "OT::%c%c%c%c::subset %s", HB_UNTAG(tag), result ? "success" : "FAILED!");
return result;
}
template<typename TableType>
static bool
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_subset (hb_subset_plan_t *plan)
{
hb_blob_t *source_blob = hb_sanitize_context_t ().reference_table<TableType> (plan->source);
const TableType *table = source_blob->as<TableType> ();
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hb_tag_t tag = TableType::tableTag;
hb_bool_t result = false;
if (source_blob->data)
result = table->subset (plan);
else
DEBUG_MSG(SUBSET, nullptr, "OT::%c%c%c%c::subset sanitize failed on source table.", HB_UNTAG(tag));
hb_blob_destroy (source_blob);
DEBUG_MSG(SUBSET, nullptr, "OT::%c%c%c%c::subset %s", HB_UNTAG(tag), result ? "success" : "FAILED!");
return result;
}
static bool
_subset_table (hb_subset_plan_t *plan,
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hb_tag_t tag)
{
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DEBUG_MSG(SUBSET, nullptr, "begin subset %c%c%c%c", HB_UNTAG(tag));
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bool result = true;
switch (tag) {
case HB_OT_TAG_glyf:
result = _subset<const OT::glyf> (plan);
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break;
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case HB_OT_TAG_hdmx:
result = _subset<const OT::hdmx> (plan);
break;
case HB_OT_TAG_head:
// TODO that won't work well if there is no glyf
DEBUG_MSG(SUBSET, nullptr, "skip head, handled by glyf");
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result = true;
break;
case HB_OT_TAG_hhea:
DEBUG_MSG(SUBSET, nullptr, "skip hhea handled by hmtx");
return true;
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case HB_OT_TAG_hmtx:
result = _subset<const OT::hmtx> (plan);
break;
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case HB_OT_TAG_vhea:
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DEBUG_MSG(SUBSET, nullptr, "skip vhea handled by vmtx");
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return true;
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case HB_OT_TAG_vmtx:
result = _subset<const OT::vmtx> (plan);
break;
case HB_OT_TAG_maxp:
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result = _subset<const OT::maxp> (plan);
break;
case HB_OT_TAG_loca:
DEBUG_MSG(SUBSET, nullptr, "skip loca handled by glyf");
return true;
case HB_OT_TAG_cmap:
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result = _subset<const OT::cmap> (plan);
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break;
case HB_OT_TAG_os2:
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result = _subset<const OT::os2> (plan);
break;
case HB_OT_TAG_post:
result = _subset<const OT::post> (plan);
break;
case HB_OT_TAG_GSUB:
result = _subset2<const OT::GSUB> (plan);
break;
case HB_OT_TAG_GPOS:
result = _subset2<const OT::GPOS> (plan);
break;
default:
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hb_blob_t *source_table = hb_face_reference_table(plan->source, tag);
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if (likely (source_table))
result = plan->add_table(tag, source_table);
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else
result = false;
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hb_blob_destroy (source_table);
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break;
}
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DEBUG_MSG(SUBSET, nullptr, "subset %c%c%c%c %s", HB_UNTAG(tag), result ? "ok" : "FAILED");
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return result;
}
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static bool
_should_drop_table(hb_subset_plan_t *plan, hb_tag_t tag)
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{
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->drop_hints;
// Drop Layout Tables if requested.
case HB_TAG ('G', 'D', 'E', 'F'): /* temporary */
case HB_TAG ('G', 'P', 'O', 'S'): /* temporary */
case HB_TAG ('G', 'S', 'U', 'B'): /* temporary */
return plan->drop_layout;
// Drop these tables below by default, list pulled
// from fontTools:
case HB_TAG ('B', 'A', 'S', 'E'):
case HB_TAG ('J', 'S', 'T', 'F'):
case HB_TAG ('D', 'S', 'I', 'G'):
case HB_TAG ('E', 'B', 'D', 'T'):
case HB_TAG ('E', 'B', 'L', 'C'):
case HB_TAG ('E', 'B', 'S', 'C'):
case HB_TAG ('S', 'V', 'G', ' '):
case HB_TAG ('P', 'C', 'L', 'T'):
case HB_TAG ('L', 'T', 'S', 'H'):
// Graphite tables:
case HB_TAG ('F', 'e', 'a', 't'):
case HB_TAG ('G', 'l', 'a', 't'):
case HB_TAG ('G', 'l', 'o', 'c'):
case HB_TAG ('S', 'i', 'l', 'f'):
case HB_TAG ('S', 'i', 'l', 'l'):
// Colour
case HB_TAG ('s', 'b', 'i', 'x'):
return true;
default:
return false;
}
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}
/**
* hb_subset:
* @source: font face data to be subset.
* @input: input to use for the subsetting.
*
* Subsets a font according to provided input.
**/
hb_face_t *
hb_subset (hb_face_t *source,
hb_subset_input_t *input)
{
if (unlikely (!input || !source)) return hb_face_get_empty();
hb_subset_plan_t *plan = hb_subset_plan_create (source, input);
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hb_tag_t table_tags[32];
unsigned int offset = 0, count;
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bool success = true;
do {
count = ARRAY_LENGTH (table_tags);
hb_face_get_table_tags (source, offset, &count, table_tags);
for (unsigned int i = 0; i < count; i++)
{
hb_tag_t tag = table_tags[i];
if (_should_drop_table(plan, tag))
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{
DEBUG_MSG(SUBSET, nullptr, "drop %c%c%c%c", HB_UNTAG(tag));
continue;
}
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success = success && _subset_table (plan, tag);
}
offset += count;
} while (success && count == ARRAY_LENGTH (table_tags));
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hb_face_t *result = success ? hb_face_reference(plan->dest) : hb_face_get_empty();
hb_subset_plan_destroy (plan);
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return result;
}