1 // Copyright 2018 Google LLC.
2 // Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
3
4 #include "src/pdf/SkPDFSubsetFont.h"
5
6 #if defined(SK_PDF_USE_HARFBUZZ_SUBSET)
7
8 #include "include/core/SkStream.h"
9 #include "include/core/SkTypeface.h"
10 #include "include/private/base/SkAssert.h"
11 #include "include/private/base/SkMalloc.h"
12 #include "include/private/base/SkTemplates.h"
13 #include "include/private/base/SkTo.h"
14 #include "src/pdf/SkPDFGlyphUse.h"
15
16 #include "hb.h" // NO_G3_REWRITE
17 #include "hb-subset.h" // NO_G3_REWRITE
18
19 #include <cstddef>
20 #include <memory>
21 #include <utility>
22
23 namespace {
24
25 using HBBlob = std::unique_ptr<hb_blob_t, SkFunctionObject<hb_blob_destroy>>;
26 using HBFace = std::unique_ptr<hb_face_t, SkFunctionObject<hb_face_destroy>>;
27 using HBSubsetInput = std::unique_ptr<hb_subset_input_t, SkFunctionObject<hb_subset_input_destroy>>;
28 using HBSet = std::unique_ptr<hb_set_t, SkFunctionObject<hb_set_destroy>>;
29
stream_to_blob(std::unique_ptr<SkStreamAsset> asset)30 HBBlob stream_to_blob(std::unique_ptr<SkStreamAsset> asset) {
31 size_t size = asset->getLength();
32 HBBlob blob;
33 if (const void* base = asset->getMemoryBase()) {
34 blob.reset(hb_blob_create(const_cast<char*>(static_cast<const char*>(base)), SkToUInt(size),
35 HB_MEMORY_MODE_READONLY, asset.release(),
36 [](void* p) { delete (SkStreamAsset*)p; }));
37 } else {
38 void* ptr = size ? sk_malloc_throw(size) : nullptr;
39 asset->read(ptr, size);
40 blob.reset(hb_blob_create((char*)ptr, SkToUInt(size),
41 HB_MEMORY_MODE_READONLY, ptr, sk_free));
42 }
43 SkASSERT(blob);
44 hb_blob_make_immutable(blob.get());
45 return blob;
46 }
47
to_data(HBBlob blob)48 sk_sp<SkData> to_data(HBBlob blob) {
49 if (!blob) {
50 return nullptr;
51 }
52 unsigned int length;
53 const char* data = hb_blob_get_data(blob.get(), &length);
54 if (!data || !length) {
55 return nullptr;
56 }
57 return SkData::MakeWithProc(data, SkToSizeT(length),
58 [](const void*, void* ctx) { hb_blob_destroy((hb_blob_t*)ctx); },
59 blob.release());
60 }
61
make_subset(hb_subset_input_t * input,hb_face_t * face,bool retainZeroGlyph)62 HBFace make_subset(hb_subset_input_t* input, hb_face_t* face, bool retainZeroGlyph) {
63 // TODO: When possible, check if a font is 'tricky' with FT_IS_TRICKY.
64 // If it isn't known if a font is 'tricky', retain the hints.
65 unsigned int flags = HB_SUBSET_FLAGS_RETAIN_GIDS;
66 if (retainZeroGlyph) {
67 flags |= HB_SUBSET_FLAGS_NOTDEF_OUTLINE;
68 }
69 hb_subset_input_set_flags(input, flags);
70 return HBFace(hb_subset_or_fail(face, input));
71 }
72
subset_harfbuzz(const SkTypeface & typeface,const SkPDFGlyphUse & glyphUsage)73 sk_sp<SkData> subset_harfbuzz(const SkTypeface& typeface, const SkPDFGlyphUse& glyphUsage) {
74 int index = 0;
75 std::unique_ptr<SkStreamAsset> typefaceAsset = typeface.openStream(&index);
76 HBFace face;
77 HBBlob blob(stream_to_blob(std::move(typefaceAsset)));
78 // hb_face_create always succeeds. Check that the format is minimally recognized first.
79 // See https://github.com/harfbuzz/harfbuzz/issues/248
80 unsigned int num_hb_faces = hb_face_count(blob.get());
81 if (0 < num_hb_faces && (unsigned)index < num_hb_faces) {
82 face.reset(hb_face_create(blob.get(), (unsigned)index));
83 // Check the number of glyphs as a basic sanitization step.
84 if (face && hb_face_get_glyph_count(face.get()) == 0) {
85 face.reset();
86 }
87 }
88
89 HBSubsetInput input(hb_subset_input_create_or_fail());
90 SkASSERT(input);
91 if (!face || !input) {
92 return nullptr;
93 }
94 hb_set_t* glyphs = hb_subset_input_glyph_set(input.get());
95 glyphUsage.getSetValues([&glyphs](unsigned gid) { hb_set_add(glyphs, gid);});
96
97 HBFace subset = make_subset(input.get(), face.get(), glyphUsage.has(0));
98 if (!subset) {
99 return nullptr;
100 }
101
102 HBBlob result(hb_face_reference_blob(subset.get()));
103 return to_data(std::move(result));
104 }
105
106 } // namespace
107
SkPDFSubsetFont(const SkTypeface & typeface,const SkPDFGlyphUse & glyphUsage)108 sk_sp<SkData> SkPDFSubsetFont(const SkTypeface& typeface, const SkPDFGlyphUse& glyphUsage) {
109 return subset_harfbuzz(typeface, glyphUsage);
110 }
111
112 #else
113
SkPDFSubsetFont(const SkTypeface &,const SkPDFGlyphUse &)114 sk_sp<SkData> SkPDFSubsetFont(const SkTypeface&, const SkPDFGlyphUse&) {
115 return nullptr;
116 }
117
118 #endif // defined(SK_PDF_USE_HARFBUZZ_SUBSET)
119