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120 lines
3.6 KiB
C++
120 lines
3.6 KiB
C++
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/i18n/bidi_line_iterator.h"
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#include "base/logging.h"
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namespace base {
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namespace i18n {
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namespace {
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UBiDiLevel GetParagraphLevelForDirection(TextDirection direction) {
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switch (direction) {
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case UNKNOWN_DIRECTION:
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return UBIDI_DEFAULT_LTR;
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break;
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case RIGHT_TO_LEFT:
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return 1; // Highest RTL level.
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break;
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case LEFT_TO_RIGHT:
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return 0; // Highest LTR level.
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break;
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default:
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NOTREACHED();
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return 0;
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}
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}
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// Overrides the default bidi class for a given character, for the custom
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// "AS_URL" behavior. Returns U_BIDI_CLASS_DEFAULT to defer to the default ICU
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// behavior.
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//
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// Matches the C callback interface of ICU's UBiDiClassCallback type (which is
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// why there is an unused argument).
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UCharDirection GetURLBiDiClassCallback(const void* /*unused*/, UChar32 c) {
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// Note: Use a switch statement instead of strchr() to avoid iterating over a
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// string for each character (the switch allows for much better compiler
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// optimization).
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switch (c) {
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// The set of characters that delimit URL components (separating the scheme,
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// username, password, domain labels, host, path segments, query
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// names/values and fragment).
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case '#':
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case '&':
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case '.':
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case '/':
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case ':':
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case '=':
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case '?':
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case '@':
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// Treat all of these characters as strong LTR, which effectively
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// surrounds all of the text components of a URL (e.g., the domain labels
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// and path segments) in a left-to-right embedding. This ensures that the
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// URL components read from left to right, regardless of any RTL
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// characters. (Within each component, RTL sequences are rendered from
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// right to left as expected.)
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return U_LEFT_TO_RIGHT;
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default:
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return U_BIDI_CLASS_DEFAULT;
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}
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}
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} // namespace
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BiDiLineIterator::BiDiLineIterator() : bidi_(nullptr) {}
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BiDiLineIterator::~BiDiLineIterator() {
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if (bidi_) {
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ubidi_close(bidi_);
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bidi_ = nullptr;
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}
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}
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bool BiDiLineIterator::Open(const string16& text,
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TextDirection direction,
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CustomBehavior behavior) {
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DCHECK(!bidi_);
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UErrorCode error = U_ZERO_ERROR;
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bidi_ = ubidi_openSized(static_cast<int>(text.length()), 0, &error);
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if (U_FAILURE(error))
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return false;
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if (behavior == CustomBehavior::AS_URL) {
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ubidi_setClassCallback(bidi_, GetURLBiDiClassCallback, nullptr, nullptr,
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nullptr, &error);
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if (U_FAILURE(error))
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return false;
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}
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ubidi_setPara(bidi_, text.data(), static_cast<int>(text.length()),
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GetParagraphLevelForDirection(direction), nullptr, &error);
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return (U_SUCCESS(error));
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}
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int BiDiLineIterator::CountRuns() const {
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DCHECK(bidi_ != nullptr);
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UErrorCode error = U_ZERO_ERROR;
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const int runs = ubidi_countRuns(bidi_, &error);
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return U_SUCCESS(error) ? runs : 0;
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}
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UBiDiDirection BiDiLineIterator::GetVisualRun(int index,
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int* start,
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int* length) const {
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DCHECK(bidi_ != nullptr);
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return ubidi_getVisualRun(bidi_, index, start, length);
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}
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void BiDiLineIterator::GetLogicalRun(int start,
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int* end,
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UBiDiLevel* level) const {
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DCHECK(bidi_ != nullptr);
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ubidi_getLogicalRun(bidi_, start, end, level);
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}
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} // namespace i18n
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} // namespace base
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