Source code
Revision control
Copy as Markdown
Other Tools
/* -*- 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
#include "TextUpdater.h"
#include "CacheConstants.h"
#include "DocAccessible-inl.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);
}