From 8d59bf9abb2699c4dc6e07eae339f989f701a065 Mon Sep 17 00:00:00 2001
From: Roy Qu <royqh1979@gmail.com>
Date: Wed, 6 Jul 2022 14:11:32 +0800
Subject: [PATCH] - redesign redo system   - fix: correctly restore editor's
 modified status when undo/redo

---
 NEWS.md                             |   1 +
 RedPandaIDE/qsynedit/SynEdit.cpp    | 187 ++++++++++++----------------
 RedPandaIDE/qsynedit/SynEdit.h      |   4 +-
 RedPandaIDE/qsynedit/TextBuffer.cpp | 147 ++++++++++++++++++----
 RedPandaIDE/qsynedit/TextBuffer.h   |  36 +++++-
 5 files changed, 238 insertions(+), 137 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 93187408..fd815718 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -11,6 +11,7 @@ Red Panda C++ Version 1.1.4
   - fix: undo chains
   - enhancement: prevent group undo when caret position changed
   - fix: undo link break may lose leading spaces
+  - fix: correctly restore editor's modified status when undo/redo
 
 Red Panda C++ Version 1.1.3
 
diff --git a/RedPandaIDE/qsynedit/SynEdit.cpp b/RedPandaIDE/qsynedit/SynEdit.cpp
index b8150286..adab86d1 100644
--- a/RedPandaIDE/qsynedit/SynEdit.cpp
+++ b/RedPandaIDE/qsynedit/SynEdit.cpp
@@ -80,8 +80,8 @@ SynEdit::SynEdit(QWidget *parent) : QAbstractScrollArea(parent),
 
     mUndoList = std::make_shared<SynEditUndoList>();
     mUndoList->connect(mUndoList.get(), &SynEditUndoList::addedUndo, this, &SynEdit::onUndoAdded);
-    mRedoList = std::make_shared<SynEditUndoList>();
-    mRedoList->connect(mRedoList.get(), &SynEditUndoList::addedUndo, this, &SynEdit::onRedoAdded);
+    mRedoList = std::make_shared<SynEditRedoList>();
+//    mRedoList->connect(mRedoList.get(), &SynEditUndoList::addedUndo, this, &SynEdit::onRedoAdded);
 
     mForegroundColor=palette().color(QPalette::Text);
     mBackgroundColor=palette().color(QPalette::Base);
@@ -353,7 +353,7 @@ bool SynEdit::canUndo() const
 
 bool SynEdit::canRedo() const
 {
-    return !mReadOnly && mRedoList->canUndo();
+    return !mReadOnly && mRedoList->canRedo();
 }
 
 int SynEdit::maxScrollWidth() const
@@ -3089,7 +3089,7 @@ void SynEdit::doPasteFromClipboard()
     BufferCoord vEndOfBlock = blockEnd();
     mBlockBegin = vStartOfBlock;
     mBlockEnd = vEndOfBlock;
-    qDebug()<<textToLines(text);
+//    qDebug()<<textToLines(text);
     setSelTextPrimitive(splitStrings(text));
     mUndoList->endBlock();
 }
@@ -3428,7 +3428,7 @@ void SynEdit::updateModifiedStatus()
     bool oldModified = mModified;
     mModified = !mUndoList->initialState();
     setModified(mModified);
-    qDebug()<<mModified<<oldModified;
+//    qDebug()<<mModified<<oldModified;
     if (oldModified!=mModified)
         emit statusChanged(SynStatusChange::scModifyChanged);
 }
@@ -4294,31 +4294,15 @@ void SynEdit::doUndo()
         return;
 
     //Remove Group Break;
-    if (mUndoList->lastChangeReason() ==  SynChangeReason::GroupBreak) {
-        int OldBlockNumber = mRedoList->blockChangeNumber();
-        auto action = finally([&,this]{
-           mRedoList->setBlockChangeNumber(OldBlockNumber);
-        });
+    while (mUndoList->lastChangeReason() ==  SynChangeReason::GroupBreak) {
         PSynEditUndoItem item = mUndoList->popItem();
-        mRedoList->setBlockChangeNumber(item->changeNumber());
-        mRedoList->addGroupBreak();
+        mRedoList->addRedo(item);
     }
 
     PSynEditUndoItem item = mUndoList->peekItem();
     if (item) {
         size_t oldChangeNumber = item->changeNumber();
-        size_t saveChangeNumber = mRedoList->blockChangeNumber();
-        mRedoList->setBlockChangeNumber(item->changeNumber());
         {
-            auto action = finally([&,this] {
-               mRedoList->setBlockChangeNumber(saveChangeNumber);
-            });
-            //skip group chain breakers
-            if (mUndoList->lastChangeReason()==SynChangeReason::GroupBreak) {
-                while (!mUndoList->isEmpty() && mUndoList->lastChangeReason()==SynChangeReason::GroupBreak) {
-                    doUndoItem();
-                }
-            }
             SynChangeReason  lastChange = mUndoList->lastChangeReason();
             bool keepGoing;
             do {
@@ -4339,6 +4323,8 @@ void SynEdit::doUndo()
             } while (keepGoing);
         }
     }
+    updateModifiedStatus();
+    onChanged();
 }
 
 void SynEdit::doUndoItem()
@@ -4359,43 +4345,47 @@ void SynEdit::doUndoItem()
         mOptions.setFlag(eoScrollPastEol);
         switch(item->changeReason()) {
         case SynChangeReason::Caret:
-            mRedoList->addChange(
+            mRedoList->addRedo(
                         item->changeReason(),
                         caretXY(),
                         caretXY(), QStringList(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             internalSetCaretXY(item->changeStartPos());
             break;
         case SynChangeReason::LeftTop:
             BufferCoord p;
             p.ch = leftChar();
             p.line = topLine();
-            mRedoList->addChange(
+            mRedoList->addRedo(
                         item->changeReason(),
                         p,
                         p, QStringList(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             setLeftChar(item->changeStartPos().ch);
             setTopLine(item->changeStartPos().line);
             break;
         case SynChangeReason::Selection:
-            mRedoList->addChange(
+            mRedoList->addRedo(
                         item->changeReason(),
                         mBlockBegin,
                         mBlockEnd,
                         QStringList(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             setCaretAndSelection(caretXY(), item->changeStartPos(), item->changeEndPos());
             break;
         case SynChangeReason::Insert: {
             QStringList tmpText = getContent(item->changeStartPos(),item->changeEndPos(),item->changeSelMode());
             doDeleteText(item->changeStartPos(),item->changeEndPos(),item->changeSelMode());
-            mRedoList->addChange(
+            mRedoList->addRedo(
                         item->changeReason(),
                         item->changeStartPos(),
                         item->changeEndPos(),
                         tmpText,
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             internalSetCaretXY(item->changeStartPos());
             break;
         }
@@ -4403,23 +4393,25 @@ void SynEdit::doUndoItem()
             setBlockBegin(BufferCoord{item->changeStartPos().ch, item->changeStartPos().line-1});
             setBlockEnd(BufferCoord{item->changeEndPos().ch, item->changeEndPos().line-1});
             doMoveSelDown();
-            mRedoList->addChange(
+            mRedoList->addRedo(
                         item->changeReason(),
                         item->changeStartPos(),
                         item->changeEndPos(),
                         item->changeText(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             break;
         case SynChangeReason::MoveSelectionDown:
             setBlockBegin(BufferCoord{item->changeStartPos().ch, item->changeStartPos().line+1});
             setBlockEnd(BufferCoord{item->changeEndPos().ch, item->changeEndPos().line+1});
             doMoveSelUp();
-            mRedoList->addChange(
+            mRedoList->addRedo(
                         item->changeReason(),
                         item->changeStartPos(),
                         item->changeEndPos(),
                         item->changeText(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             break;
         case SynChangeReason::Delete: {
             // If there's no selection, we have to set
@@ -4431,12 +4423,13 @@ void SynEdit::doUndoItem()
                          item->changeStartPos().line,
                          item->changeEndPos().line);
             internalSetCaretXY(item->changeEndPos());
-            mRedoList->addChange(
+            mRedoList->addRedo(
                         item->changeReason(),
                         item->changeStartPos(),
                         item->changeEndPos(),
                         item->changeText(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             ensureCursorPosVisible();
             break;
         }
@@ -4456,12 +4449,13 @@ void SynEdit::doUndoItem()
                 mDocument->deleteAt(mCaretY);
                 doLinesDeleted(mCaretY, 1);
             }
-            mRedoList->addChange(
+            mRedoList->addRedo(
                         item->changeReason(),
                         item->changeStartPos(),
                         item->changeEndPos(),
                         item->changeText(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             break;
         }
         default:
@@ -4479,51 +4473,38 @@ void SynEdit::doRedo()
     if (!item)
         return;
     size_t oldChangeNumber = item->changeNumber();
-    size_t saveChangeNumber = mUndoList->blockChangeNumber();
-    mUndoList->setBlockChangeNumber(item->changeNumber());
-    {
-        auto action = finally([&,this]{
-            mUndoList->setBlockChangeNumber(saveChangeNumber);
-        });
-        //skip group chain breakers
-        if (mRedoList->lastChangeReason()==SynChangeReason::GroupBreak) {
-            while (!mRedoList->isEmpty() && mRedoList->lastChangeReason()==SynChangeReason::GroupBreak) {
-                doRedoItem();
-            }
-        }
-        SynChangeReason lastChange = mRedoList->lastChangeReason();
-        bool keepGoing;
-        do {
-          doRedoItem();
-          item = mRedoList->peekItem();
-          if (!item)
-              keepGoing = false;
-          else {
-            if (item->changeNumber() == oldChangeNumber)
-                keepGoing = true;
-            else {
-                keepGoing = (mOptions.testFlag(eoGroupUndo) &&
-                (lastChange == item->changeReason()));
-            }
-            oldChangeNumber=item->changeNumber();
-            lastChange = item->changeReason();
-          }
-        } while (keepGoing);
 
+    //skip group chain breakers
+    while (mRedoList->lastChangeReason()==SynChangeReason::GroupBreak) {
+        PSynEditUndoItem item = mRedoList->popItem();
+        mUndoList->restoreChange(item);
     }
-    //Remove Group Break
-    if (mRedoList->lastChangeReason() == SynChangeReason::GroupBreak) {
-        int OldBlockNumber = mUndoList->blockChangeNumber();
-        item = mRedoList->popItem();
-        {
-            auto action2=finally([&,this]{
-                mUndoList->setBlockChangeNumber(OldBlockNumber);
-            });
-            mUndoList->setBlockChangeNumber(item->changeNumber());
-            mUndoList->addGroupBreak();
+    SynChangeReason lastChange = mRedoList->lastChangeReason();
+    bool keepGoing;
+    do {
+      doRedoItem();
+      item = mRedoList->peekItem();
+      if (!item)
+          keepGoing = false;
+      else {
+        if (item->changeNumber() == oldChangeNumber)
+            keepGoing = true;
+        else {
+            keepGoing = (mOptions.testFlag(eoGroupUndo) &&
+            (lastChange == item->changeReason()));
         }
-        updateModifiedStatus();
+        oldChangeNumber=item->changeNumber();
+        lastChange = item->changeReason();
+      }
+    } while (keepGoing);
+
+    //restore Group Break
+    while (mRedoList->lastChangeReason()==SynChangeReason::GroupBreak) {
+        PSynEditUndoItem item = mRedoList->popItem();
+        mUndoList->restoreChange(item);
     }
+    updateModifiedStatus();
+    onChanged();
 }
 
 void SynEdit::doRedoItem()
@@ -4545,33 +4526,36 @@ void SynEdit::doRedoItem()
         });
         switch(item->changeReason()) {
         case SynChangeReason::Caret:
-            mUndoList->addChange(
+            mUndoList->restoreChange(
                         item->changeReason(),
                         caretXY(),
                         caretXY(),
                         QStringList(),
-                        mActiveSelectionMode);
+                        mActiveSelectionMode,
+                        item->changeNumber());
             internalSetCaretXY(item->changeStartPos());
             break;
         case SynChangeReason::LeftTop:
             BufferCoord p;
             p.ch = leftChar();
             p.line = topLine();
-            mUndoList->addChange(
+            mUndoList->restoreChange(
                         item->changeReason(),
                         p,
                         p, QStringList(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             setLeftChar(item->changeStartPos().ch);
             setTopLine(item->changeStartPos().line);
             break;
         case SynChangeReason::Selection:
-            mUndoList->addChange(
+            mUndoList->restoreChange(
                         item->changeReason(),
                         mBlockBegin,
                         mBlockEnd,
                         QStringList(),
-                        mActiveSelectionMode);
+                        mActiveSelectionMode,
+                        item->changeNumber());
             setCaretAndSelection(
                         caretXY(),
                         item->changeStartPos(),
@@ -4581,23 +4565,25 @@ void SynEdit::doRedoItem()
             setBlockBegin(BufferCoord{item->changeStartPos().ch, item->changeStartPos().line});
             setBlockEnd(BufferCoord{item->changeEndPos().ch, item->changeEndPos().line});
             doMoveSelUp();
-            mUndoList->addChange(
+            mUndoList->restoreChange(
                         item->changeReason(),
                         item->changeStartPos(),
                         item->changeEndPos(),
                         item->changeText(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             break;
         case SynChangeReason::MoveSelectionDown:
             setBlockBegin(BufferCoord{item->changeStartPos().ch, item->changeStartPos().line});
             setBlockEnd(BufferCoord{item->changeEndPos().ch, item->changeEndPos().line});
             doMoveSelDown();
-            mUndoList->addChange(
+            mUndoList->restoreChange(
                         item->changeReason(),
                         item->changeStartPos(),
                         item->changeEndPos(),
                         item->changeText(),
-                        item->changeSelMode());
+                        item->changeSelMode(),
+                        item->changeNumber());
             break;
         case SynChangeReason::Insert:
             setCaretAndSelection(
@@ -4608,25 +4594,26 @@ void SynEdit::doRedoItem()
                          item->changeStartPos().line,
                          item->changeEndPos().line);
             internalSetCaretXY(item->changeEndPos());
-            mUndoList->addChange(item->changeReason(),
+            mUndoList->restoreChange(item->changeReason(),
                                  item->changeStartPos(),
                                  item->changeEndPos(),
                                  QStringList(),
-                                 item->changeSelMode());
+                                 item->changeSelMode(),
+                                 item->changeNumber());
             break;
         case SynChangeReason::Delete: {
             doDeleteText(item->changeStartPos(),item->changeEndPos(),item->changeSelMode());
-            mUndoList->addChange(item->changeReason(), item->changeStartPos(),
+            mUndoList->restoreChange(item->changeReason(), item->changeStartPos(),
                                  item->changeEndPos(),item->changeText(),
-                                 item->changeSelMode());
+                                 item->changeSelMode(),item->changeNumber());
             internalSetCaretXY(item->changeStartPos());
             break;
         };
         case SynChangeReason::LineBreak: {
             BufferCoord CaretPt = item->changeStartPos();
-            mUndoList->addChange(item->changeReason(), item->changeStartPos(),
+            mUndoList->restoreChange(item->changeReason(), item->changeStartPos(),
                                  item->changeEndPos(),item->changeText(),
-                                 item->changeSelMode());
+                                 item->changeSelMode(),item->changeNumber());
             setCaretAndSelection(CaretPt, CaretPt, CaretPt);
             commandProcessor(SynEditorCommand::ecLineBreak);
             break;
@@ -6591,8 +6578,6 @@ int SynEdit::charWidth() const
 void SynEdit::setUndoLimit(int size)
 {
     mUndoList->setMaxUndoActions(size);
-
-    mRedoList->setMaxUndoActions(size);
 }
 
 int SynEdit::charsInWindow() const
@@ -6909,12 +6894,6 @@ void SynEdit::setTopLine(int Value)
     }
 }
 
-void SynEdit::onRedoAdded()
-{
-    updateModifiedStatus();
-    onChanged();
-}
-
 void SynEdit::onGutterChanged()
 {
     if (mGutter.showLineNumbers() && mGutter.autoSize())
diff --git a/RedPandaIDE/qsynedit/SynEdit.h b/RedPandaIDE/qsynedit/SynEdit.h
index 5cc23748..1e871e84 100644
--- a/RedPandaIDE/qsynedit/SynEdit.h
+++ b/RedPandaIDE/qsynedit/SynEdit.h
@@ -633,7 +633,7 @@ private slots:
     void onLinesDeleted(int index, int count);
     void onLinesInserted(int index, int count);
     void onLinesPutted(int index, int count);
-    void onRedoAdded();
+    //void onRedoAdded();
     void onScrollTimeout();
     void onDraggingScrollTimeout();
     void onUndoAdded();
@@ -687,7 +687,7 @@ private:
     bool mCaretUseTextColor;
     QColor mActiveLineColor;
     PSynEditUndoList mUndoList;
-    PSynEditUndoList mRedoList;
+    PSynEditRedoList mRedoList;
     QPoint mMouseDownPos;
     bool mHideSelection;
     int mMouseWheelAccumulator;
diff --git a/RedPandaIDE/qsynedit/TextBuffer.cpp b/RedPandaIDE/qsynedit/TextBuffer.cpp
index 4ffe95f4..4503feca 100644
--- a/RedPandaIDE/qsynedit/TextBuffer.cpp
+++ b/RedPandaIDE/qsynedit/TextBuffer.cpp
@@ -840,16 +840,17 @@ SynEditUndoList::SynEditUndoList():QObject()
     mInsideRedo = false;
 
     mBlockChangeNumber=0;
-    mBlockLockCount=0;
+    mBlockLock=0;
     mFullUndoImposible=false;
     mBlockCount=0;
     mLastPoppedItemChangeNumber=0;
     mInitialChangeNumber = 0;
+    mLastRestoredItemChangeNumber=0;
 }
 
-void SynEditUndoList::addChange(SynChangeReason AReason, const BufferCoord &AStart,
-                                const BufferCoord &AEnd, const QStringList& ChangeText,
-                                SynSelectionMode SelMode)
+void SynEditUndoList::addChange(SynChangeReason reason, const BufferCoord &startPos,
+                                const BufferCoord &endPos, const QStringList& changeText,
+                                SynSelectionMode selMode)
 {
     int changeNumber;
     if (inBlock()) {
@@ -857,15 +858,41 @@ void SynEditUndoList::addChange(SynChangeReason AReason, const BufferCoord &ASta
     } else {
         changeNumber = getNextChangeNumber();
     }
+    PSynEditUndoItem  newItem = std::make_shared<SynEditUndoItem>(
+                reason,
+                selMode,startPos,endPos,changeText,
+                changeNumber);
+//    qDebug()<<"add change"<<changeNumber<<(int)reason;
+    mItems.append(newItem);
+    ensureMaxEntries();
+    if (reason!=SynChangeReason::GroupBreak && !inBlock()) {
+        mBlockCount++;
+//        qDebug()<<"add"<<mBlockCount;
+        emit addedUndo();
+    }
+}
+
+void SynEditUndoList::restoreChange(SynChangeReason AReason, const BufferCoord &AStart, const BufferCoord &AEnd, const QStringList &ChangeText, SynSelectionMode SelMode, size_t changeNumber)
+{
     PSynEditUndoItem  newItem = std::make_shared<SynEditUndoItem>(AReason,
                                                                   SelMode,AStart,AEnd,ChangeText,
                                                                   changeNumber);
-    mItems.append(newItem);
+    restoreChange(newItem);
+}
+
+void SynEditUndoList::restoreChange(PSynEditUndoItem item)
+{
+    size_t changeNumber = item->changeNumber();
+    mItems.append(item);
     ensureMaxEntries();
-    if (AReason!=SynChangeReason::GroupBreak && !inBlock()) {
+    if (changeNumber>mNextChangeNumber)
+        mNextChangeNumber=changeNumber;
+    if (changeNumber!=mLastRestoredItemChangeNumber) {
+//        qDebug()<<"restore"<<mBlockCount;
         mBlockCount++;
         emit addedUndo();
     }
+    mLastRestoredItemChangeNumber=changeNumber;
 }
 
 void SynEditUndoList::addGroupBreak()
@@ -880,8 +907,11 @@ void SynEditUndoList::addGroupBreak()
 
 void SynEditUndoList::beginBlock()
 {
-    mBlockLockCount++;
-    mBlockChangeNumber = getNextChangeNumber();
+//    qDebug()<<"begin block";
+    if (mBlockLock==0)
+        mBlockChangeNumber = getNextChangeNumber();
+    mBlockLock++;
+
 }
 
 void SynEditUndoList::clear()
@@ -890,19 +920,22 @@ void SynEditUndoList::clear()
     mFullUndoImposible = false;
     mInitialChangeNumber=0;
     mLastPoppedItemChangeNumber=0;
+    mLastRestoredItemChangeNumber=0;
     mBlockCount=0;
-    mBlockLockCount=0;
+    mBlockLock=0;
 }
 
 void SynEditUndoList::endBlock()
 {
-    if (mBlockLockCount > 0) {
-        mBlockLockCount--;
-        if (mBlockLockCount == 0)  {
+//    qDebug()<<"end block";
+    if (mBlockLock > 0) {
+        mBlockLock--;
+        if (mBlockLock == 0)  {
             size_t iBlockID = mBlockChangeNumber;
             mBlockChangeNumber = 0;
             if (mItems.count() > 0 && peekItem()->changeNumber() == iBlockID) {
                 mBlockCount++;
+//                qDebug()<<"end block"<<mBlockCount;
                 emit addedUndo();
             }
         }
@@ -911,7 +944,7 @@ void SynEditUndoList::endBlock()
 
 bool SynEditUndoList::inBlock()
 {
-    return mBlockLockCount>0;
+    return mBlockLock>0;
 }
 
 unsigned int SynEditUndoList::getNextChangeNumber()
@@ -946,10 +979,12 @@ PSynEditUndoItem SynEditUndoList::popItem()
         return PSynEditUndoItem();
     else {
         PSynEditUndoItem item = mItems.last();
-        if (mLastPoppedItemChangeNumber!=item->changeNumber()) {
+//        qDebug()<<"popped"<<item->changeNumber()<<item->changeText()<<(int)item->changeReason()<<mLastPoppedItemChangeNumber;
+        if (mLastPoppedItemChangeNumber!=item->changeNumber() && item->changeReason()!=SynChangeReason::GroupBreak) {
             mBlockCount--;
+//            qDebug()<<"pop"<<mBlockCount;
             if (mBlockCount<0) {
-                qDebug()<<"block count calculation error";
+//                qDebug()<<"block count calculation error";
                 mBlockCount=0;
             }
         }
@@ -999,16 +1034,6 @@ void SynEditUndoList::setInitialState()
         mInitialChangeNumber = peekItem()->changeNumber();
 }
 
-int SynEditUndoList::blockChangeNumber() const
-{
-    return mBlockChangeNumber;
-}
-
-void SynEditUndoList::setBlockChangeNumber(int blockChangeNumber)
-{
-    mBlockChangeNumber = blockChangeNumber;
-}
-
 bool SynEditUndoList::insideRedo() const
 {
     return mInsideRedo;
@@ -1030,10 +1055,12 @@ void SynEditUndoList::ensureMaxEntries()
         mFullUndoImposible = true;
         while (mBlockCount > mMaxUndoActions && !mItems.isEmpty()) {
             //remove all undo item in block
-            size_t changeNumber = mItems.front()->changeNumber();
+            PSynEditUndoItem item = mItems.front();
+            size_t changeNumber = item->changeNumber();
             while (mItems.count()>0 && mItems.front()->changeNumber() == changeNumber)
                 mItems.removeFirst();
-            mBlockCount--;
+            if (item->changeReason()!=SynChangeReason::GroupBreak)
+                mBlockCount--;
       }
     }
 }
@@ -1079,3 +1106,69 @@ SynChangeReason SynEditUndoItem::changeReason() const
 {
     return mChangeReason;
 }
+
+SynEditRedoList::SynEditRedoList()
+{
+
+}
+
+void SynEditRedoList::addRedo(SynChangeReason AReason, const BufferCoord &AStart, const BufferCoord &AEnd, const QStringList &ChangeText, SynSelectionMode SelMode, size_t changeNumber)
+{
+    PSynEditUndoItem  newItem = std::make_shared<SynEditUndoItem>(
+                AReason,
+                SelMode,AStart,AEnd,ChangeText,
+                changeNumber);
+    mItems.append(newItem);
+}
+
+void SynEditRedoList::addRedo(PSynEditUndoItem item)
+{
+    mItems.append(item);
+}
+
+void SynEditRedoList::clear()
+{
+    mItems.clear();
+}
+
+SynChangeReason SynEditRedoList::lastChangeReason()
+{
+    if (mItems.count() == 0)
+        return SynChangeReason::Nothing;
+    else
+        return mItems.last()->changeReason();
+}
+
+bool SynEditRedoList::isEmpty()
+{
+    return mItems.isEmpty();
+}
+
+PSynEditUndoItem SynEditRedoList::peekItem()
+{
+    if (mItems.count() == 0)
+        return PSynEditUndoItem();
+    else
+        return mItems.last();
+}
+
+PSynEditUndoItem SynEditRedoList::popItem()
+{
+    if (mItems.count() == 0)
+        return PSynEditUndoItem();
+    else {
+        PSynEditUndoItem item = mItems.last();
+        mItems.removeLast();
+        return item;
+    }
+}
+
+bool SynEditRedoList::canRedo()
+{
+    return mItems.count()>0;
+}
+
+int SynEditRedoList::itemCount()
+{
+    return mItems.count();
+}
diff --git a/RedPandaIDE/qsynedit/TextBuffer.h b/RedPandaIDE/qsynedit/TextBuffer.h
index 06a98c5f..4eee01f6 100644
--- a/RedPandaIDE/qsynedit/TextBuffer.h
+++ b/RedPandaIDE/qsynedit/TextBuffer.h
@@ -196,6 +196,7 @@ public:
     QStringList changeText() const;
     size_t changeNumber() const;
 };
+
 using PSynEditUndoItem = std::shared_ptr<SynEditUndoItem>;
 
 class SynEditUndoList : public QObject {
@@ -206,6 +207,11 @@ public:
     void addChange(SynChangeReason AReason, const BufferCoord& AStart, const BufferCoord& AEnd,
       const QStringList& ChangeText, SynSelectionMode SelMode);
 
+    void restoreChange(SynChangeReason AReason, const BufferCoord& AStart, const BufferCoord& AEnd,
+                       const QStringList& ChangeText, SynSelectionMode SelMode, size_t changeNumber);
+
+    void restoreChange(PSynEditUndoItem item);
+
     void addGroupBreak();
     void beginBlock();
     void endBlock();
@@ -224,9 +230,6 @@ public:
     bool initialState();
     void setInitialState();
 
-    int blockChangeNumber() const;
-    void setBlockChangeNumber(int blockChangeNumber);
-
     bool insideRedo() const;
     void setInsideRedo(bool insideRedo);
 
@@ -240,9 +243,10 @@ protected:
     unsigned int getNextChangeNumber();
 protected:
     size_t mBlockChangeNumber;
-    int mBlockLockCount;
+    int mBlockLock;
     int mBlockCount; // count of action blocks;
     size_t mLastPoppedItemChangeNumber;
+    size_t mLastRestoredItemChangeNumber;
     bool mFullUndoImposible;
     QVector<PSynEditUndoItem> mItems;
     int mMaxUndoActions;
@@ -251,6 +255,30 @@ protected:
     bool mInsideRedo;
 };
 
+class SynEditRedoList : public QObject {
+    Q_OBJECT
+public:
+    explicit SynEditRedoList();
+
+    void addRedo(SynChangeReason AReason, const BufferCoord& AStart, const BufferCoord& AEnd,
+                 const QStringList& ChangeText, SynSelectionMode SelMode, size_t changeNumber);
+    void addRedo(PSynEditUndoItem item);
+
+    void clear();
+    SynChangeReason lastChangeReason();
+    bool isEmpty();
+    PSynEditUndoItem peekItem();
+    PSynEditUndoItem popItem();
+
+    bool canRedo();
+    int itemCount();
+
+protected:
+    QVector<PSynEditUndoItem> mItems;
+};
+
+
 using PSynEditUndoList = std::shared_ptr<SynEditUndoList>;
+using PSynEditRedoList = std::shared_ptr<SynEditRedoList>;
 
 #endif // SYNEDITSTRINGLIST_H