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// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "ui/accessibility/ax_text_utils.h"
#include <algorithm>
#include "base/check_op.h"
#include "base/i18n/break_iterator.h"
#include "base/notreached.h"
#include "base/numerics/safe_conversions.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#include "ui/accessibility/ax_enums.mojom.h"
namespace ui {
namespace {
base::i18n::BreakIterator::BreakType ICUBreakTypeForBoundaryType(
ax::mojom::TextBoundary boundary) {
switch (boundary) {
case ax::mojom::TextBoundary::kCharacter:
return base::i18n::BreakIterator::BREAK_CHARACTER;
case ax::mojom::TextBoundary::kSentenceStart:
return base::i18n::BreakIterator::BREAK_SENTENCE;
case ax::mojom::TextBoundary::kWordStart:
case ax::mojom::TextBoundary::kWordStartOrEnd:
return base::i18n::BreakIterator::BREAK_WORD;
// These are currently unused since line breaking is done via an array of
// line break offsets, and object boundary by finding no boundary within the
// current node.
case ax::mojom::TextBoundary::kObject:
case ax::mojom::TextBoundary::kLineStart:
case ax::mojom::TextBoundary::kParagraphStart:
return base::i18n::BreakIterator::BREAK_NEWLINE;
default:
NOTREACHED() << boundary;
return base::i18n::BreakIterator::BREAK_NEWLINE;
}
}
} // namespace
// line_breaks is a Misnomer. Blink provides the start offsets of each line
// not the line breaks.
// TODO(nektar): Rename line_breaks a11y attribute and variable references.
size_t FindAccessibleTextBoundary(const std::u16string& text,
const std::vector<int>& line_breaks,
ax::mojom::TextBoundary boundary,
size_t start_offset,
ax::mojom::MoveDirection direction,
ax::mojom::TextAffinity affinity) {
DCHECK_NE(boundary, ax::mojom::TextBoundary::kNone);
size_t text_size = text.size();
DCHECK_LE(start_offset, text_size);
DCHECK_NE(direction, ax::mojom::MoveDirection::kNone);
base::i18n::BreakIterator::BreakType break_type =
ICUBreakTypeForBoundaryType(boundary);
base::i18n::BreakIterator break_iter(text, break_type);
if (boundary == ax::mojom::TextBoundary::kCharacter ||
boundary == ax::mojom::TextBoundary::kSentenceStart ||
boundary == ax::mojom::TextBoundary::kWordStart ||
boundary == ax::mojom::TextBoundary::kWordStartOrEnd) {
if (!break_iter.Init())
return start_offset;
}
if (boundary == ax::mojom::TextBoundary::kLineStart) {
if (direction == ax::mojom::MoveDirection::kForward) {
for (int line_break : line_breaks) {
size_t clamped_line_break =
static_cast<size_t>(std::max(0, line_break));
if ((affinity == ax::mojom::TextAffinity::kDownstream &&
clamped_line_break > start_offset) ||
(affinity == ax::mojom::TextAffinity::kUpstream &&
clamped_line_break >= start_offset)) {
return clamped_line_break;
}
}
return text_size;
} else {
for (size_t j = line_breaks.size(); j != 0; --j) {
size_t line_break = line_breaks[j - 1] >= 0 ? line_breaks[j - 1] : 0;
if ((affinity == ax::mojom::TextAffinity::kDownstream &&
line_break <= start_offset) ||
(affinity == ax::mojom::TextAffinity::kUpstream &&
line_break < start_offset)) {
return line_break;
}
}
return 0;
}
}
size_t result = start_offset;
for (;;) {
size_t pos;
if (direction == ax::mojom::MoveDirection::kForward) {
if (result >= text_size)
return text_size;
pos = result;
} else {
if (result == 0)
return 0;
pos = result - 1;
}
switch (boundary) {
case ax::mojom::TextBoundary::kLineStart:
NOTREACHED() << boundary; // This is handled above.
return result;
case ax::mojom::TextBoundary::kCharacter:
if (break_iter.IsGraphemeBoundary(result)) {
// If we are searching forward and we are still at the start offset,
// we need to find the next character.
if (direction == ax::mojom::MoveDirection::kBackward ||
result != start_offset)
return result;
}
break;
case ax::mojom::TextBoundary::kWordStart:
if (break_iter.IsStartOfWord(result)) {
// If we are searching forward and we are still at the start offset,
// we need to find the next word.
DCHECK_NE(direction, ax::mojom::MoveDirection::kNone);
if (direction == ax::mojom::MoveDirection::kBackward ||
result != start_offset)
return result;
}
break;
case ax::mojom::TextBoundary::kWordStartOrEnd:
if (break_iter.IsStartOfWord(result)) {
// If we are searching forward and we are still at the start offset,
// we need to find the next word.
DCHECK_NE(direction, ax::mojom::MoveDirection::kNone);
if (direction == ax::mojom::MoveDirection::kBackward ||
result != start_offset)
return result;
} else if (break_iter.IsEndOfWord(result)) {
// If we are searching backward and we are still at the end offset, we
// need to find the previous word.
DCHECK_NE(direction, ax::mojom::MoveDirection::kNone);
if (direction == ax::mojom::MoveDirection::kForward ||
result != start_offset)
return result;
}
break;
case ax::mojom::TextBoundary::kSentenceStart:
if (break_iter.IsSentenceBoundary(result)) {
// If we are searching forward and we are still at the start offset,
// we need to find the next sentence.
if (direction == ax::mojom::MoveDirection::kBackward ||
result != start_offset) {
// ICU sometimes returns sentence boundaries in the whitespace
// between sentences. For the purposes of accessibility, we want to
// include all whitespace at the end of a sentence. We move the
// boundary past the last whitespace offset. This works the same for
// backwards and forwards searches.
while (result < text_size &&
base::IsUnicodeWhitespace(text[result]))
result++;
return result;
}
}
break;
case ax::mojom::TextBoundary::kParagraphStart:
if (text[pos] == '\n')
return result;
break;
default:
break;
}
if (direction == ax::mojom::MoveDirection::kForward) {
result++;
} else {
result--;
}
}
}
std::vector<int> GetWordStartOffsets(const std::u16string& text) {
std::vector<int> word_starts;
base::i18n::BreakIterator iter(text, base::i18n::BreakIterator::BREAK_WORD);
if (!iter.Init())
return word_starts;
// iter.Advance() returns false if we've run past end of the text.
while (iter.Advance()) {
if (!iter.IsWord())
continue;
word_starts.push_back(
base::checked_cast<int>(iter.prev()) /* start index */);
}
return word_starts;
}
std::vector<int> GetWordEndOffsets(const std::u16string& text) {
std::vector<int> word_ends;
base::i18n::BreakIterator iter(text, base::i18n::BreakIterator::BREAK_WORD);
if (!iter.Init())
return word_ends;
// iter.Advance() returns false if we've run past end of the text.
while (iter.Advance()) {
if (!iter.IsWord())
continue;
word_ends.push_back(base::checked_cast<int>(iter.pos()) /* end index */);
}
return word_ends;
}
std::vector<int> GetSentenceStartOffsets(const std::u16string& text) {
std::vector<int> sentence_starts;
base::i18n::BreakIterator iter(text,
base::i18n::BreakIterator::BREAK_SENTENCE);
if (!iter.Init())
return sentence_starts;
// iter.Advance() returns false if we've run past end of the text.
while (iter.Advance()) {
sentence_starts.push_back(
base::checked_cast<int>(iter.prev()) /* start index */);
}
return sentence_starts;
}
std::vector<int> GetSentenceEndOffsets(const std::u16string& text) {
std::vector<int> sentence_ends;
base::i18n::BreakIterator iter(text,
base::i18n::BreakIterator::BREAK_SENTENCE);
if (!iter.Init())
return sentence_ends;
// iter.Advance() returns false if we've run past end of the text.
while (iter.Advance()) {
sentence_ends.push_back(
base::checked_cast<int>(iter.pos()) /* end index */);
}
return sentence_ends;
}
} // namespace ui
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