michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "TextUpdater.h"
michael@0: 
michael@0: #include "Accessible-inl.h"
michael@0: #include "DocAccessible-inl.h"
michael@0: #include "TextLeafAccessible.h"
michael@0: #include <algorithm>
michael@0: 
michael@0: using namespace mozilla::a11y;
michael@0: 
michael@0: void
michael@0: TextUpdater::Run(DocAccessible* aDocument, TextLeafAccessible* aTextLeaf,
michael@0:                  const nsAString& aNewText)
michael@0: {
michael@0:   NS_ASSERTION(aTextLeaf, "No text leaf accessible?");
michael@0: 
michael@0:   const nsString& oldText = aTextLeaf->Text();
michael@0:   uint32_t oldLen = oldText.Length(), newLen = aNewText.Length();
michael@0:   uint32_t minLen = std::min(oldLen, newLen);
michael@0: 
michael@0:   // Skip coinciding begin substrings.
michael@0:   uint32_t skipStart = 0;
michael@0:   for (; skipStart < minLen; skipStart++) {
michael@0:     if (aNewText[skipStart] != oldText[skipStart])
michael@0:       break;
michael@0:   }
michael@0: 
michael@0:   // The text was changed. Do update.
michael@0:   if (skipStart != minLen || oldLen != newLen) {
michael@0:     TextUpdater updater(aDocument, aTextLeaf);
michael@0:     updater.DoUpdate(aNewText, oldText, skipStart);
michael@0:   }
michael@0: }
michael@0: 
michael@0: void
michael@0: TextUpdater::DoUpdate(const nsAString& aNewText, const nsAString& aOldText,
michael@0:                       uint32_t aSkipStart)
michael@0: {
michael@0:   Accessible* parent = mTextLeaf->Parent();
michael@0:   if (!parent)
michael@0:     return;
michael@0: 
michael@0:   mHyperText = parent->AsHyperText();
michael@0:   if (!mHyperText) {
michael@0:     NS_ERROR("Text leaf parent is not hypertext!");
michael@0:     return;
michael@0:   }
michael@0: 
michael@0:   // Get the text leaf accessible offset and invalidate cached offsets after it.
michael@0:   mTextOffset = mHyperText->GetChildOffset(mTextLeaf, true);
michael@0:   NS_ASSERTION(mTextOffset != -1,
michael@0:                "Text leaf hasn't offset within hyper text!");
michael@0: 
michael@0:   uint32_t oldLen = aOldText.Length(), newLen = aNewText.Length();
michael@0:   uint32_t minLen = std::min(oldLen, newLen);
michael@0: 
michael@0:   // Trim coinciding substrings from the end.
michael@0:   uint32_t skipEnd = 0;
michael@0:   while (minLen - skipEnd > aSkipStart &&
michael@0:          aNewText[newLen - skipEnd - 1] == aOldText[oldLen - skipEnd - 1]) {
michael@0:     skipEnd++;
michael@0:   }
michael@0: 
michael@0:   uint32_t strLen1 = oldLen - aSkipStart - skipEnd;
michael@0:   uint32_t strLen2 = newLen - aSkipStart - skipEnd;
michael@0: 
michael@0:   const nsAString& str1 = Substring(aOldText, aSkipStart, strLen1);
michael@0:   const nsAString& str2 = Substring(aNewText, aSkipStart, strLen2);
michael@0: 
michael@0:   // Increase offset of the text leaf on skipped characters amount.
michael@0:   mTextOffset += aSkipStart;
michael@0: 
michael@0:   // It could be single insertion or removal or the case of long strings. Do not
michael@0:   // calculate the difference between long strings and prefer to fire pair of
michael@0:   // insert/remove events as the old string was replaced on the new one.
michael@0:   if (strLen1 == 0 || strLen2 == 0 ||
michael@0:       strLen1 > kMaxStrLen || strLen2 > kMaxStrLen) {
michael@0:     if (strLen1 > 0) {
michael@0:       // Fire text change event for removal.
michael@0:       nsRefPtr<AccEvent> textRemoveEvent =
michael@0:         new AccTextChangeEvent(mHyperText, mTextOffset, str1, false);
michael@0:       mDocument->FireDelayedEvent(textRemoveEvent);
michael@0:     }
michael@0: 
michael@0:     if (strLen2 > 0) {
michael@0:       // Fire text change event for insertion.
michael@0:       nsRefPtr<AccEvent> textInsertEvent =
michael@0:         new AccTextChangeEvent(mHyperText, mTextOffset, str2, true);
michael@0:       mDocument->FireDelayedEvent(textInsertEvent);
michael@0:     }
michael@0: 
michael@0:     mDocument->MaybeNotifyOfValueChange(mHyperText);
michael@0: 
michael@0:     // Update the text.
michael@0:     mTextLeaf->SetText(aNewText);
michael@0:     return;
michael@0:   }
michael@0: 
michael@0:   // Otherwise find the difference between strings and fire events.
michael@0:   // Note: we can skip initial and final coinciding characters since they don't
michael@0:   // affect the Levenshtein distance.
michael@0: 
michael@0:   // Compute the flat structured matrix need to compute the difference.
michael@0:   uint32_t len1 = strLen1 + 1, len2 = strLen2 + 1;
michael@0:   uint32_t* entries = new uint32_t[len1 * len2];
michael@0: 
michael@0:   for (uint32_t colIdx = 0; colIdx < len1; colIdx++)
michael@0:     entries[colIdx] = colIdx;
michael@0: 
michael@0:   uint32_t* row = entries;
michael@0:   for (uint32_t rowIdx = 1; rowIdx < len2; rowIdx++) {
michael@0:     uint32_t* prevRow = row;
michael@0:     row += len1;
michael@0:     row[0] = rowIdx;
michael@0:     for (uint32_t colIdx = 1; colIdx < len1; colIdx++) {
michael@0:       if (str1[colIdx - 1] != str2[rowIdx - 1]) {
michael@0:         uint32_t left = row[colIdx - 1];
michael@0:         uint32_t up = prevRow[colIdx];
michael@0:         uint32_t upleft = prevRow[colIdx - 1];
michael@0:         row[colIdx] = std::min(upleft, std::min(left, up)) + 1;
michael@0:       } else {
michael@0:         row[colIdx] = prevRow[colIdx - 1];
michael@0:       }
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   // Compute events based on the difference.
michael@0:   nsTArray<nsRefPtr<AccEvent> > events;
michael@0:   ComputeTextChangeEvents(str1, str2, entries, events);
michael@0: 
michael@0:   delete [] entries;
michael@0: 
michael@0:   // Fire events.
michael@0:   for (int32_t idx = events.Length() - 1; idx >= 0; idx--)
michael@0:     mDocument->FireDelayedEvent(events[idx]);
michael@0: 
michael@0:   mDocument->MaybeNotifyOfValueChange(mHyperText);
michael@0: 
michael@0:   // Update the text.
michael@0:   mTextLeaf->SetText(aNewText);
michael@0: }
michael@0: 
michael@0: void
michael@0: TextUpdater::ComputeTextChangeEvents(const nsAString& aStr1,
michael@0:                                      const nsAString& aStr2,
michael@0:                                      uint32_t* aEntries,
michael@0:                                      nsTArray<nsRefPtr<AccEvent> >& aEvents)
michael@0: {
michael@0:   int32_t colIdx = aStr1.Length(), rowIdx = aStr2.Length();
michael@0: 
michael@0:   // Point at which strings last matched.
michael@0:   int32_t colEnd = colIdx;
michael@0:   int32_t rowEnd = rowIdx;
michael@0: 
michael@0:   int32_t colLen = colEnd + 1;
michael@0:   uint32_t* row = aEntries + rowIdx * colLen;
michael@0:   uint32_t dist = row[colIdx]; // current Levenshtein distance
michael@0:   while (rowIdx && colIdx) { // stop when we can't move diagonally
michael@0:     if (aStr1[colIdx - 1] == aStr2[rowIdx - 1]) { // match
michael@0:       if (rowIdx < rowEnd) { // deal with any pending insertion
michael@0:         FireInsertEvent(Substring(aStr2, rowIdx, rowEnd - rowIdx),
michael@0:                         rowIdx, aEvents);
michael@0:       }
michael@0:       if (colIdx < colEnd) { // deal with any pending deletion
michael@0:         FireDeleteEvent(Substring(aStr1, colIdx, colEnd - colIdx),
michael@0:                         rowIdx, aEvents);
michael@0:       }
michael@0: 
michael@0:       colEnd = --colIdx; // reset the match point
michael@0:       rowEnd = --rowIdx;
michael@0:       row -= colLen;
michael@0:       continue;
michael@0:     }
michael@0:     --dist;
michael@0:     if (dist == row[colIdx - 1 - colLen]) { // substitution
michael@0:       --colIdx;
michael@0:       --rowIdx;
michael@0:       row -= colLen;
michael@0:       continue;
michael@0:     }
michael@0:     if (dist == row[colIdx - colLen]) { // insertion
michael@0:       --rowIdx;
michael@0:       row -= colLen;
michael@0:       continue;
michael@0:     }
michael@0:     if (dist == row[colIdx - 1]) { // deletion
michael@0:       --colIdx;
michael@0:       continue;
michael@0:     }
michael@0:     NS_NOTREACHED("huh?");
michael@0:     return;
michael@0:   }
michael@0: 
michael@0:   if (rowEnd)
michael@0:     FireInsertEvent(Substring(aStr2, 0, rowEnd), 0, aEvents);
michael@0:   if (colEnd)
michael@0:     FireDeleteEvent(Substring(aStr1, 0, colEnd), 0, aEvents);
michael@0: }