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