Source code
Revision control
Copy as Markdown
Other Tools
/*
* 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-open-file.hh"
#include "hb-subset.hh"
#include "hb-subset-table.hh"
#include "hb-subset-accelerator.hh"
#include "hb-ot-cmap-table.hh"
#include "hb-ot-var-cvar-table.hh"
#include "hb-ot-head-table.hh"
#include "hb-ot-stat-table.hh"
#include "hb-ot-post-table-v2subset.hh"
/**
* 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.
*/
hb_user_data_key_t _hb_subset_accelerator_user_data_key = {};
/*
* 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_TAG('B','A','S','E'),
HB_TAG('C','B','D','T'),
HB_TAG('C','B','L','C'),
HB_TAG('C','F','F',' '),
HB_TAG('C','F','F','2'),
HB_TAG('c','m','a','p'),
HB_TAG('C','O','L','R'),
HB_TAG('C','P','A','L'),
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_TAG('G','D','E','F'),
HB_TAG('g','l','y','f'),
HB_TAG('G','P','O','S'),
HB_TAG('G','S','U','B'),
HB_TAG('g','v','a','r'),
HB_TAG('h','d','m','x'),
HB_TAG('h','e','a','d'),
HB_TAG('h','h','e','a'),
HB_TAG('h','m','t','x'),
HB_TAG('H','V','A','R'),
HB_TAG('J','S','T','F'),
HB_TAG('k','e','r','n'),
HB_TAG('l','o','c','a'),
HB_TAG('L','T','S','H'),
HB_TAG('M','A','T','H'),
HB_TAG('m','a','x','p'),
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_TAG('p','o','s','t'),
HB_TAG('p','r','e','p'),
HB_TAG('s','b','i','x'),
HB_TAG('S','T','A','T'),
HB_TAG('S','V','G',' '),
HB_TAG('V','D','M','X'),
HB_TAG('v','h','e','a'),
HB_TAG('v','m','t','x'),
HB_TAG('V','O','R','G'),
HB_TAG('V','V','A','R'),
HB_TAG('n','a','m','e'),
HB_TAG('O','S','/','2')
};
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 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 (((void) 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 */
return plan->all_axes_pinned || (plan->flags & HB_SUBSET_FLAGS_NO_HINTING);
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_TAG('G','D','E','F'):
case HB_TAG('G','P','O','S'):
case HB_TAG('G','S','U','B'):
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
case HB_TAG('a','v','a','r'):
case HB_TAG('f','v','a','r'):
case HB_TAG('g','v','a','r'):
case HB_TAG('H','V','A','R'):
case HB_TAG('V','V','A','R'):
case HB_TAG('M','V','A','R'):
return plan->all_axes_pinned;
default:
return false;
}
}
static bool
_dependencies_satisfied (hb_subset_plan_t *plan, hb_tag_t tag,
const hb_set_t &subsetted_tags,
const hb_set_t &pending_subset_tags)
{
switch (tag)
{
case HB_TAG('h','m','t','x'):
case HB_TAG('v','m','t','x'):
case HB_TAG('m','a','x','p'):
case HB_TAG('O','S','/','2'):
return !plan->normalized_coords || !pending_subset_tags.has (HB_TAG('g','l','y','f'));
case HB_TAG('G','P','O','S'):
return plan->all_axes_pinned || !pending_subset_tags.has (HB_TAG('G','D','E','F'));
default:
return true;
}
}
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 _hb_subset_table_passthrough (plan, tag);
}
DEBUG_MSG (SUBSET, nullptr, "subset %c%c%c%c", HB_UNTAG (tag));
bool success;
if (_hb_subset_table_layout (plan, buf, tag, &success) ||
_hb_subset_table_var (plan, buf, tag, &success) ||
_hb_subset_table_cff (plan, buf, tag, &success) ||
_hb_subset_table_color (plan, buf, tag, &success) ||
_hb_subset_table_other (plan, buf, tag, &success))
return success;
switch (tag)
{
case HB_TAG('h','e','a','d'):
if (_is_table_present (plan->source, HB_TAG('g','l','y','f')) && !_should_drop_table (plan, HB_TAG('g','l','y','f')))
return true; /* skip head, handled by glyf */
return _hb_subset_table<const OT::head> (plan, buf);
case HB_TAG('S','T','A','T'):
if (!plan->user_axes_location.is_empty ()) return _hb_subset_table<const OT::STAT> (plan, buf);
else return _hb_subset_table_passthrough (plan, tag);
case HB_TAG('c','v','t',' '):
#ifndef HB_NO_VAR
if (_is_table_present (plan->source, HB_TAG('c','v','a','r')) &&
plan->normalized_coords && !plan->pinned_at_default)
{
auto &cvar = *plan->source->table.cvar;
return OT::cvar::add_cvt_and_apply_deltas (plan, cvar.get_tuple_var_data (), &cvar);
}
#endif
return _hb_subset_table_passthrough (plan, tag);
}
if (plan->flags & HB_SUBSET_FLAGS_PASSTHROUGH_UNRECOGNIZED)
return _hb_subset_table_passthrough (plan, tag);
// Drop table
return true;
}
static void _attach_accelerator_data (hb_subset_plan_t* plan,
hb_face_t* face /* IN/OUT */)
{
if (!plan->inprogress_accelerator) return;
// Transfer the accelerator from the plan to us.
hb_subset_accelerator_t* accel = plan->inprogress_accelerator;
plan->inprogress_accelerator = nullptr;
if (accel->in_error ())
{
hb_subset_accelerator_t::destroy (accel);
return;
}
// Populate caches that need access to the final tables.
hb_blob_ptr_t<OT::cmap> cmap_ptr (hb_sanitize_context_t ().reference_table<OT::cmap> (face));
accel->cmap_cache = OT::cmap::create_filled_cache (cmap_ptr);
accel->destroy_cmap_cache = OT::SubtableUnicodesCache::destroy;
if (!hb_face_set_user_data(face,
hb_subset_accelerator_t::user_data_key(),
accel,
hb_subset_accelerator_t::destroy,
true))
hb_subset_accelerator_t::destroy (accel);
}
/**
* 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 or the face has no glyphs.
*
* 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 nullptr;
if (unlikely (!source->get_num_glyphs ()))
{
DEBUG_MSG (SUBSET, nullptr, "No glyphs in source font.");
return nullptr;
}
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_tag_t table_tags[32];
unsigned offset = 0, num_tables = ARRAY_LENGTH (table_tags);
hb_set_t subsetted_tags, pending_subset_tags;
while (((void) _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)) continue;
pending_subset_tags.add (tag);
}
offset += num_tables;
}
bool success = true;
{
// Grouping to deallocate buf before calling hb_face_reference (plan->dest).
hb_vector_t<char> buf;
buf.alloc (8192 - 16);
while (!pending_subset_tags.is_empty ())
{
if (subsetted_tags.in_error ()
|| pending_subset_tags.in_error ()) {
success = false;
goto end;
}
bool made_changes = false;
for (hb_tag_t tag : pending_subset_tags)
{
if (!_dependencies_satisfied (plan, tag,
subsetted_tags,
pending_subset_tags))
{
// delayed subsetting for some tables since they might have dependency on other tables
// in some cases: e.g: during instantiating glyf tables, hmetrics/vmetrics are updated
// and saved in subset plan, hmtx/vmtx subsetting need to use these updated metrics values
continue;
}
pending_subset_tags.del (tag);
subsetted_tags.add (tag);
made_changes = true;
success = _subset_table (plan, buf, tag);
if (unlikely (!success)) goto end;
}
if (!made_changes)
{
DEBUG_MSG (SUBSET, nullptr, "Table dependencies unable to be satisfied. Subset failed.");
success = false;
goto end;
}
}
}
if (success && plan->attach_accelerator_data) {
_attach_accelerator_data (plan, plan->dest);
}
end:
return success ? hb_face_reference (plan->dest) : nullptr;
}