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-rw-r--r--accessible/base/TextUpdater.cpp217
1 files changed, 217 insertions, 0 deletions
diff --git a/accessible/base/TextUpdater.cpp b/accessible/base/TextUpdater.cpp
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+++ b/accessible/base/TextUpdater.cpp
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "TextUpdater.h"
+
+#include "LocalAccessible-inl.h"
+#include "CacheConstants.h"
+#include "DocAccessible-inl.h"
+#include "nsAccessibilityService.h"
+#include "TextLeafAccessible.h"
+#include <algorithm>
+
+using namespace mozilla::a11y;
+
+void TextUpdater::Run(DocAccessible* aDocument, TextLeafAccessible* aTextLeaf,
+ const nsAString& aNewText) {
+ NS_ASSERTION(aTextLeaf, "No text leaf accessible?");
+
+ const nsString& oldText = aTextLeaf->Text();
+ uint32_t oldLen = oldText.Length(), newLen = aNewText.Length();
+ uint32_t minLen = std::min(oldLen, newLen);
+
+ // Skip coinciding begin substrings.
+ uint32_t skipStart = 0;
+ for (; skipStart < minLen; skipStart++) {
+ if (aNewText[skipStart] != oldText[skipStart]) break;
+ }
+
+ // The text was changed. Do update.
+ if (skipStart != minLen || oldLen != newLen) {
+ TextUpdater updater(aDocument, aTextLeaf);
+ updater.DoUpdate(aNewText, oldText, skipStart);
+ aDocument->QueueCacheUpdate(aTextLeaf, CacheDomain::Text);
+ }
+}
+
+void TextUpdater::DoUpdate(const nsAString& aNewText, const nsAString& aOldText,
+ uint32_t aSkipStart) {
+ LocalAccessible* parent = mTextLeaf->LocalParent();
+ if (!parent) return;
+
+ mHyperText = parent->AsHyperText();
+ if (!mHyperText) {
+ MOZ_ASSERT_UNREACHABLE("Text leaf parent is not hypertext!");
+ return;
+ }
+
+ // Get the text leaf accessible offset and invalidate cached offsets after it.
+ mTextOffset = mHyperText->GetChildOffset(mTextLeaf, true);
+ NS_ASSERTION(mTextOffset != -1, "Text leaf hasn't offset within hyper text!");
+
+ // Don't bother diffing if the hypertext isn't editable. Diffing non-editable
+ // text can lead to weird screen reader results with live regions, e.g.,
+ // changing "text" to "testing" might read the diff "s ing" when we'd really
+ // just like to hear "testing."
+ if (!mHyperText->IsEditable()) {
+ // Fire text change event for removal.
+ RefPtr<AccEvent> textRemoveEvent =
+ new AccTextChangeEvent(mHyperText, mTextOffset, aOldText, false);
+ mDocument->FireDelayedEvent(textRemoveEvent);
+
+ // Fire text change event for insertion if there's text to insert.
+ if (!aNewText.IsEmpty()) {
+ RefPtr<AccEvent> textInsertEvent =
+ new AccTextChangeEvent(mHyperText, mTextOffset, aNewText, true);
+ mDocument->FireDelayedEvent(textInsertEvent);
+ }
+
+ mDocument->MaybeNotifyOfValueChange(mHyperText);
+
+ // Update the text.
+ mTextLeaf->SetText(aNewText);
+ return;
+ }
+
+ uint32_t oldLen = aOldText.Length(), newLen = aNewText.Length();
+ uint32_t minLen = std::min(oldLen, newLen);
+
+ // Trim coinciding substrings from the end.
+ uint32_t skipEnd = 0;
+ while (minLen - skipEnd > aSkipStart &&
+ aNewText[newLen - skipEnd - 1] == aOldText[oldLen - skipEnd - 1]) {
+ skipEnd++;
+ }
+
+ uint32_t strLen1 = oldLen - aSkipStart - skipEnd;
+ uint32_t strLen2 = newLen - aSkipStart - skipEnd;
+
+ const nsAString& str1 = Substring(aOldText, aSkipStart, strLen1);
+ const nsAString& str2 = Substring(aNewText, aSkipStart, strLen2);
+
+ // Increase offset of the text leaf on skipped characters amount.
+ mTextOffset += aSkipStart;
+
+ // It could be single insertion or removal or the case of long strings. Do not
+ // calculate the difference between long strings and prefer to fire pair of
+ // insert/remove events as the old string was replaced on the new one.
+ if (strLen1 == 0 || strLen2 == 0 || strLen1 > kMaxStrLen ||
+ strLen2 > kMaxStrLen) {
+ if (strLen1 > 0) {
+ // Fire text change event for removal.
+ RefPtr<AccEvent> textRemoveEvent =
+ new AccTextChangeEvent(mHyperText, mTextOffset, str1, false);
+ mDocument->FireDelayedEvent(textRemoveEvent);
+ }
+
+ if (strLen2 > 0) {
+ // Fire text change event for insertion.
+ RefPtr<AccEvent> textInsertEvent =
+ new AccTextChangeEvent(mHyperText, mTextOffset, str2, true);
+ mDocument->FireDelayedEvent(textInsertEvent);
+ }
+
+ mDocument->MaybeNotifyOfValueChange(mHyperText);
+
+ // Update the text.
+ mTextLeaf->SetText(aNewText);
+ return;
+ }
+
+ // Otherwise find the difference between strings and fire events.
+ // Note: we can skip initial and final coinciding characters since they don't
+ // affect the Levenshtein distance.
+
+ // Compute the flat structured matrix need to compute the difference.
+ uint32_t len1 = strLen1 + 1, len2 = strLen2 + 1;
+ uint32_t* entries = new uint32_t[len1 * len2];
+
+ for (uint32_t colIdx = 0; colIdx < len1; colIdx++) entries[colIdx] = colIdx;
+
+ uint32_t* row = entries;
+ for (uint32_t rowIdx = 1; rowIdx < len2; rowIdx++) {
+ uint32_t* prevRow = row;
+ row += len1;
+ row[0] = rowIdx;
+ for (uint32_t colIdx = 1; colIdx < len1; colIdx++) {
+ if (str1[colIdx - 1] != str2[rowIdx - 1]) {
+ uint32_t left = row[colIdx - 1];
+ uint32_t up = prevRow[colIdx];
+ uint32_t upleft = prevRow[colIdx - 1];
+ row[colIdx] = std::min(upleft, std::min(left, up)) + 1;
+ } else {
+ row[colIdx] = prevRow[colIdx - 1];
+ }
+ }
+ }
+
+ // Compute events based on the difference.
+ nsTArray<RefPtr<AccEvent> > events;
+ ComputeTextChangeEvents(str1, str2, entries, events);
+
+ delete[] entries;
+
+ // Fire events.
+ for (int32_t idx = events.Length() - 1; idx >= 0; idx--) {
+ mDocument->FireDelayedEvent(events[idx]);
+ }
+
+ mDocument->MaybeNotifyOfValueChange(mHyperText);
+
+ // Update the text.
+ mTextLeaf->SetText(aNewText);
+}
+
+void TextUpdater::ComputeTextChangeEvents(
+ const nsAString& aStr1, const nsAString& aStr2, uint32_t* aEntries,
+ nsTArray<RefPtr<AccEvent> >& aEvents) {
+ int32_t colIdx = aStr1.Length(), rowIdx = aStr2.Length();
+
+ // Point at which strings last matched.
+ int32_t colEnd = colIdx;
+ int32_t rowEnd = rowIdx;
+
+ int32_t colLen = colEnd + 1;
+ uint32_t* row = aEntries + rowIdx * colLen;
+ uint32_t dist = row[colIdx]; // current Levenshtein distance
+ while (rowIdx && colIdx) { // stop when we can't move diagonally
+ if (aStr1[colIdx - 1] == aStr2[rowIdx - 1]) { // match
+ if (rowIdx < rowEnd) { // deal with any pending insertion
+ FireInsertEvent(Substring(aStr2, rowIdx, rowEnd - rowIdx), rowIdx,
+ aEvents);
+ }
+ if (colIdx < colEnd) { // deal with any pending deletion
+ FireDeleteEvent(Substring(aStr1, colIdx, colEnd - colIdx), rowIdx,
+ aEvents);
+ }
+
+ colEnd = --colIdx; // reset the match point
+ rowEnd = --rowIdx;
+ row -= colLen;
+ continue;
+ }
+ --dist;
+ if (dist == row[colIdx - 1 - colLen]) { // substitution
+ --colIdx;
+ --rowIdx;
+ row -= colLen;
+ continue;
+ }
+ if (dist == row[colIdx - colLen]) { // insertion
+ --rowIdx;
+ row -= colLen;
+ continue;
+ }
+ if (dist == row[colIdx - 1]) { // deletion
+ --colIdx;
+ continue;
+ }
+ MOZ_ASSERT_UNREACHABLE("huh?");
+ return;
+ }
+
+ if (rowEnd) FireInsertEvent(Substring(aStr2, 0, rowEnd), 0, aEvents);
+ if (colEnd) FireDeleteEvent(Substring(aStr1, 0, colEnd), 0, aEvents);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-02 20:02:35 +0000