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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/354829279): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "ui/gfx/font_fallback_skia_impl.h"
#include <set>
#include <string>
#include <string_view>
#include "skia/ext/font_utils.h"
#include "third_party/icu/source/common/unicode/normalizer2.h"
#include "third_party/icu/source/common/unicode/uchar.h"
#include "third_party/icu/source/common/unicode/utf16.h"
#include "third_party/skia/include/core/SkFontMgr.h"
#include "third_party/skia/include/core/SkTypeface.h"
namespace gfx {
namespace {
// Returns true when the codepoint has an unicode decomposition and store
// the decomposed string into |output|.
bool UnicodeDecomposeCodepoint(UChar32 codepoint, icu::UnicodeString* output) {
static const icu::Normalizer2* normalizer = nullptr;
UErrorCode error = U_ZERO_ERROR;
if (!normalizer) {
normalizer = icu::Normalizer2::getNFDInstance(error);
if (U_FAILURE(error))
return false;
DCHECK(normalizer);
}
return normalizer->getDecomposition(codepoint, *output);
}
// Extracts every codepoint and its decomposed codepoints from unicode
// decomposition. Inserts in |codepoints| the set of codepoints in |text|.
void RetrieveCodepointsAndDecomposedCodepoints(std::u16string_view text,
std::set<UChar32>* codepoints) {
size_t offset = 0;
while (offset < text.length()) {
UChar32 codepoint;
U16_NEXT(text.data(), offset, text.length(), codepoint);
if (codepoints->insert(codepoint).second) {
// For each codepoint, add the decomposed codepoints.
icu::UnicodeString decomposed_text;
if (UnicodeDecomposeCodepoint(codepoint, &decomposed_text)) {
for (int i = 0; i < decomposed_text.length(); ++i) {
codepoints->insert(decomposed_text[i]);
}
}
}
}
}
// Returns the amount of codepoint in |text| without a glyph representation in
// |typeface|. A codepoint is present if there is a corresponding glyph in
// typeface, or if there are glyphs for each of its decomposed codepoints.
size_t ComputeMissingGlyphsForGivenTypeface(std::u16string_view text,
sk_sp<SkTypeface> typeface) {
// Validate that every character has a known glyph in the font.
size_t missing_glyphs = 0;
size_t i = 0;
while (i < text.length()) {
UChar32 codepoint;
U16_NEXT(text.data(), i, text.length(), codepoint);
// The glyph is present in the font.
if (typeface->unicharToGlyph(codepoint) != 0)
continue;
// Do not count missing codepoints when they are ignorable as they will be
// ignored by the shaping engine.
if (u_hasBinaryProperty(codepoint, UCHAR_DEFAULT_IGNORABLE_CODE_POINT))
continue;
// No glyph is present in the font for the codepoint. Try the decomposed
// codepoints instead.
icu::UnicodeString decomposed_text;
if (UnicodeDecomposeCodepoint(codepoint, &decomposed_text) &&
!decomposed_text.isEmpty()) {
// Check that every decomposed codepoint is in the font.
bool every_codepoint_found = true;
for (int offset = 0; offset < decomposed_text.length(); ++offset) {
if (typeface->unicharToGlyph(decomposed_text[offset]) == 0) {
every_codepoint_found = false;
break;
}
}
// The decomposed codepoints can be mapped to glyphs by the font.
if (every_codepoint_found)
continue;
}
// The current glyphs can't be find.
++missing_glyphs;
}
return missing_glyphs;
}
} // namespace
sk_sp<SkTypeface> GetSkiaFallbackTypeface(const Font& template_font,
const std::string& locale,
std::u16string_view text) {
if (text.empty())
return nullptr;
sk_sp<SkFontMgr> font_mgr(skia::DefaultFontMgr());
const char* bcp47_locales[] = {locale.c_str()};
int num_locales = locale.empty() ? 0 : 1;
const char** locales = locale.empty() ? nullptr : bcp47_locales;
const int font_weight = (template_font.GetWeight() == Font::Weight::INVALID)
? static_cast<int>(Font::Weight::NORMAL)
: static_cast<int>(template_font.GetWeight());
const bool italic = (template_font.GetStyle() & Font::ITALIC) != 0;
SkFontStyle skia_style(
font_weight, SkFontStyle::kNormal_Width,
italic ? SkFontStyle::kItalic_Slant : SkFontStyle::kUpright_Slant);
std::set<SkTypefaceID> tested_typeface;
sk_sp<SkTypeface> fallback_typeface;
size_t fewest_missing_glyphs = text.length() + 1;
// Retrieve the set of codepoints (or unicode decomposed codepoints) from
// the input text.
std::set<UChar32> codepoints;
RetrieveCodepointsAndDecomposedCodepoints(text, &codepoints);
// Determine which fallback font is given the fewer missing glyphs.
for (UChar32 codepoint : codepoints) {
sk_sp<SkTypeface> typeface(font_mgr->matchFamilyStyleCharacter(
template_font.GetFontName().c_str(), skia_style, locales, num_locales,
codepoint));
// If the typeface is not found or was already tested, skip it.
if (!typeface || !tested_typeface.insert(typeface->uniqueID()).second)
continue;
// Validate that every codepoint has a known glyph in the font.
size_t missing_glyphs =
ComputeMissingGlyphsForGivenTypeface(text, typeface);
if (missing_glyphs < fewest_missing_glyphs) {
fewest_missing_glyphs = missing_glyphs;
fallback_typeface = typeface;
}
// The font is a valid fallback font for the given text.
if (missing_glyphs == 0)
break;
}
return fallback_typeface;
}
} // namespace gfx
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