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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_FALLBACK_ITERATOR_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_FALLBACK_ITERATOR_H_
#include "third_party/blink/renderer/platform/fonts/font_data_for_range_set.h"
#include "third_party/blink/renderer/platform/fonts/font_fallback_priority.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_vector.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/hash_set.h"
#include "third_party/blink/renderer/platform/wtf/ref_counted.h"
#include "third_party/blink/renderer/platform/wtf/text/wtf_uchar.h"
namespace blink {
class FontDescription;
class FontFallbackList;
class SimpleFontData;
class PLATFORM_EXPORT FontFallbackIterator {
STACK_ALLOCATED();
public:
using HintCharList = Vector<UChar32, 16>;
FontFallbackIterator(const FontDescription&,
FontFallbackList*,
FontFallbackPriority);
FontFallbackIterator(FontFallbackIterator&&) = default;
FontFallbackIterator(const FontFallbackIterator&) = delete;
FontFallbackIterator& operator=(const FontFallbackIterator&) = delete;
bool operator==(const FontFallbackIterator& other) const;
bool operator!=(const FontFallbackIterator& other) const {
return !(*this == other);
}
bool HasNext() const { return fallback_stage_ != kOutOfLuck; }
// Returns whether the next call to Next() needs a full hint list, or whether
// a single character is sufficient. Intended to serve as an optimization in
// HarfBuzzShaper to avoid spending too much time and resources collecting a
// full hint character list. Returns true when the next font in line is a
// segmented font, i.e. one that requires the hint list to work out which
// unicode range segment should be used.
bool NeedsHintList() const;
// Some system fallback APIs (Windows, Android) require a character, or a
// portion of the string to be passed. On Mac and Linux, we get a list of
// fonts without passing in characters.
FontDataForRangeSet* Next(const HintCharList& hint_list);
void Reset();
private:
bool RangeSetContributesForHint(const HintCharList& hint_list,
const FontDataForRangeSet*);
bool AlreadyLoadingRangeForHintChar(UChar32 hint_char);
void WillUseRange(const AtomicString& family, const FontDataForRangeSet&);
FontDataForRangeSet* UniqueOrNext(FontDataForRangeSet* candidate,
const HintCharList& hint_list);
const SimpleFontData* FallbackPriorityFont(UChar32 hint);
const SimpleFontData* UniqueSystemFontForHintList(
const HintCharList& hint_list);
const FontDescription& font_description_;
FontFallbackList* font_fallback_list_;
int current_font_data_index_;
unsigned segmented_face_index_;
enum FallbackStage {
kFallbackPriorityFonts,
kFontGroupFonts,
kSegmentedFace,
kPreferencesFonts,
kSystemFonts,
kFirstCandidateForNotdefGlyph,
kOutOfLuck
};
FallbackStage fallback_stage_;
HashSet<UChar32> previously_asked_for_hint_;
// FontFallbackIterator is meant for single use by HarfBuzzShaper,
// traversing through the fonts for shaping only once. We must not return
// duplicate FontDataForRangeSet objects from the Next() iteration function
// as returning a duplicate value causes a shaping run that won't return any
// results. The exception is that if all fonts fail, we return the first
// candidate to be used for rendering the .notdef glyph, and set HasNext() to
// false.
HashSet<uint32_t> unique_font_data_for_range_sets_returned_;
FontDataForRangeSet* first_candidate_ = nullptr;
HeapVector<Member<FontDataForRangeSet>> tracked_loading_range_sets_;
FontFallbackPriority font_fallback_priority_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_FALLBACK_ITERATOR_H_
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