[wxWidgets.git] / src / stc / scintilla / src / CellBuffer.cxx

// Scintilla source code edit control
/** @file CellBuffer.cxx
 ** Manages a buffer of cells.
 **/
// Copyright 1998-2001 by Neil Hodgson <neilh@scintilla.org>
// The License.txt file describes the conditions under which this software may be distributed.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>

#include "Platform.h"

#include "Scintilla.h"
#include "SVector.h"
#include "CellBuffer.h"

MarkerHandleSet::MarkerHandleSet() {
        root = 0;
}

MarkerHandleSet::~MarkerHandleSet() {
        MarkerHandleNumber *mhn = root;
        while (mhn) {
                MarkerHandleNumber *mhnToFree = mhn;
                mhn = mhn->next;
                delete mhnToFree;
        }
        root = 0;
}

int MarkerHandleSet::Length() {
        int c = 0;
        MarkerHandleNumber *mhn = root;
        while (mhn) {
                c++;
                mhn = mhn->next;
        }
        return c;
}

int MarkerHandleSet::NumberFromHandle(int handle) {
        MarkerHandleNumber *mhn = root;
        while (mhn) {
                if (mhn->handle == handle) {
                        return mhn->number;
                }
                mhn = mhn->next;
        }
        return - 1;
}

int MarkerHandleSet::MarkValue() {
        unsigned int m = 0;
        MarkerHandleNumber *mhn = root;
        while (mhn) {
                m |= (1 << mhn->number);
                mhn = mhn->next;
        }
        return m;
}

bool MarkerHandleSet::Contains(int handle) {
        MarkerHandleNumber *mhn = root;
        while (mhn) {
                if (mhn->handle == handle) {
                        return true;
                }
                mhn = mhn->next;
        }
        return false;
}

bool MarkerHandleSet::InsertHandle(int handle, int markerNum) {
        MarkerHandleNumber *mhn = new MarkerHandleNumber;
        if (!mhn)
                return false;
        mhn->handle = handle;
        mhn->number = markerNum;
        mhn->next = root;
        root = mhn;
        return true;
}

void MarkerHandleSet::RemoveHandle(int handle) {
        MarkerHandleNumber **pmhn = &root;
        while (*pmhn) {
                MarkerHandleNumber *mhn = *pmhn;
                if (mhn->handle == handle) {
                        *pmhn = mhn->next;
                        delete mhn;
                        return ;
                }
                pmhn = &((*pmhn)->next);
        }
}

void MarkerHandleSet::RemoveNumber(int markerNum) {
        MarkerHandleNumber **pmhn = &root;
        while (*pmhn) {
                MarkerHandleNumber *mhn = *pmhn;
                if (mhn->number == markerNum) {
                        *pmhn = mhn->next;
                        delete mhn;
                        return ;
                }
                pmhn = &((*pmhn)->next);
        }
}

void MarkerHandleSet::CombineWith(MarkerHandleSet *other) {
        MarkerHandleNumber **pmhn = &root;
        while (*pmhn) {
                pmhn = &((*pmhn)->next);
        }
        *pmhn = other->root;
        other->root = 0;
}

LineVector::LineVector() {
        linesData = 0;
        lines = 0;
        size = 0;
        levels = 0;
        sizeLevels = 0;
        handleCurrent = 1;

        Init();
}

LineVector::~LineVector() {
        for (int line = 0; line < lines; line++) {
                delete linesData[line].handleSet;
                linesData[line].handleSet = 0;
        }
        delete []linesData;
        linesData = 0;
        delete []levels;
        levels = 0;
}

void LineVector::Init() {
        for (int line = 0; line < lines; line++) {
                delete linesData[line].handleSet;
                linesData[line].handleSet = 0;
        }
        delete []linesData;
        linesData = new LineData[static_cast<int>(growSize)];
        size = growSize;
        lines = 1;
        delete []levels;
        levels = 0;
        sizeLevels = 0;
}

void LineVector::Expand(int sizeNew) {
        LineData *linesDataNew = new LineData[sizeNew];
        if (linesDataNew) {
                for (int i = 0; i < size; i++)
                        linesDataNew[i] = linesData[i];
                // Do not delete handleSets here as they are transferred to new linesData
                delete []linesData;
                linesData = linesDataNew;
                size = sizeNew;
        } else {
                Platform::DebugPrintf("No memory available\n");
                // TODO: Blow up
        }

}

void LineVector::ExpandLevels(int sizeNew) {
        if (sizeNew == -1)
                sizeNew = size;
        int *levelsNew = new int[sizeNew];
        if (levelsNew) {
                int i = 0;
                for (; i < sizeLevels; i++)
                        levelsNew[i] = levels[i];
                for (; i < sizeNew; i++)
                        levelsNew[i] = SC_FOLDLEVELBASE;
                delete []levels;
                levels = levelsNew;
                sizeLevels = sizeNew;
        } else {
                Platform::DebugPrintf("No memory available\n");
                // TODO: Blow up
        }

}

void LineVector::ClearLevels() {
        delete []levels;
        levels = 0;
        sizeLevels = 0;
}

void LineVector::InsertValue(int pos, int value) {
        //Platform::DebugPrintf("InsertValue[%d] = %d\n", pos, value);
        if ((lines + 2) >= size) {
                Expand(size + growSize);
                if (levels) {
                        ExpandLevels(size + growSize);
                }
        }
        lines++;
        for (int i = lines; i > pos; i--) {
                linesData[i] = linesData[i - 1];
        }
        linesData[pos].startPosition = value;
        linesData[pos].handleSet = 0;
        if (levels) {
                for (int j = lines; j > pos; j--) {
                        levels[j] = levels[j - 1];
                }
                if (pos == 0) {
                        levels[pos] = SC_FOLDLEVELBASE;
                } else if (pos == (lines - 1)) {        // Last line will not be a folder
                        levels[pos] = SC_FOLDLEVELBASE;
                } else {
                        levels[pos] = levels[pos - 1];
                }
        }
}

void LineVector::SetValue(int pos, int value) {
        //Platform::DebugPrintf("SetValue[%d] = %d\n", pos, value);
        if ((pos + 2) >= size) {
                //Platform::DebugPrintf("Resize %d %d\n", size,pos);
                Expand(pos + growSize);
                //Platform::DebugPrintf("end Resize %d %d\n", size,pos);
                lines = pos;
                if (levels) {
                        ExpandLevels(pos + growSize);
                }
        }
        linesData[pos].startPosition = value;
}

void LineVector::Remove(int pos) {
        //Platform::DebugPrintf("Remove %d\n", pos);
        // Retain the markers from the deleted line by oring them into the previous line
        if (pos > 0) {
                MergeMarkers(pos - 1);
        }
        for (int i = pos; i < lines; i++) {
                linesData[i] = linesData[i + 1];
        }
        if (levels) {
                // Level information merges back onto previous line
                int posAbove = pos - 1;
                if (posAbove < 0)
                        posAbove = 0;
                for (int j = posAbove; j < lines; j++) {
                        levels[j] = levels[j + 1];
                }
        }
        lines--;
}

int LineVector::LineFromPosition(int pos) {
        //Platform::DebugPrintf("LineFromPostion %d lines=%d end = %d\n", pos, lines, linesData[lines].startPosition);
        if (lines == 0)
                return 0;
        //Platform::DebugPrintf("LineFromPosition %d\n", pos);
        if (pos >= linesData[lines].startPosition)
                return lines - 1;
        int lower = 0;
        int upper = lines;
        do {
                int middle = (upper + lower + 1) / 2;   // Round high
                if (pos < linesData[middle].startPosition) {
                        upper = middle - 1;
                } else {
                        lower = middle;
                }
        } while (lower < upper);
        //Platform::DebugPrintf("LineFromPostion %d %d %d\n", pos, lower, linesData[lower].startPosition, linesData[lower > 1 ? lower - 1 : 0].startPosition);
        return lower;
}

int LineVector::AddMark(int line, int markerNum) {
        handleCurrent++;
        if (!linesData[line].handleSet) {
                // Need new structure to hold marker handle
                linesData[line].handleSet = new MarkerHandleSet;
                if (!linesData[line].handleSet)
                        return - 1;
        }
        linesData[line].handleSet->InsertHandle(handleCurrent, markerNum);

        return handleCurrent;
}

void LineVector::MergeMarkers(int pos) {
        if (linesData[pos + 1].handleSet != NULL) {
                if (linesData[pos].handleSet == NULL )
                        linesData[pos].handleSet = new MarkerHandleSet;
                linesData[pos].handleSet->CombineWith(linesData[pos + 1].handleSet);
                delete linesData[pos + 1].handleSet;
                linesData[pos + 1].handleSet = NULL;
        }
}

void LineVector::DeleteMark(int line, int markerNum) {
        if (linesData[line].handleSet) {
                if (markerNum == -1) {
                        delete linesData[line].handleSet;
                        linesData[line].handleSet = 0;
                } else {
                        linesData[line].handleSet->RemoveNumber(markerNum);
                        if (linesData[line].handleSet->Length() == 0) {
                                delete linesData[line].handleSet;
                                linesData[line].handleSet = 0;
                        }
                }
        }
}

void LineVector::DeleteMarkFromHandle(int markerHandle) {
        int line = LineFromHandle(markerHandle);
        if (line >= 0) {
                linesData[line].handleSet->RemoveHandle(markerHandle);
                if (linesData[line].handleSet->Length() == 0) {
                        delete linesData[line].handleSet;
                        linesData[line].handleSet = 0;
                }
        }
}

int LineVector::LineFromHandle(int markerHandle) {
        for (int line = 0; line < lines; line++) {
                if (linesData[line].handleSet) {
                        if (linesData[line].handleSet->Contains(markerHandle)) {
                                return line;
                        }
                }
        }
        return - 1;
}

Action::Action() {
        at = startAction;
        position = 0;
        data = 0;
        lenData = 0;
}

Action::~Action() {
        Destroy();
}

void Action::Create(actionType at_, int position_, char *data_, int lenData_, bool mayCoalesce_) {
        delete []data;
        position = position_;
        at = at_;
        data = data_;
        lenData = lenData_;
        mayCoalesce = mayCoalesce_;
}

void Action::Destroy() {
        delete []data;
        data = 0;
}

void Action::Grab(Action *source) {
        delete []data;

        position = source->position;
        at = source->at;
        data = source->data;
        lenData = source->lenData;
        mayCoalesce = source->mayCoalesce;

        // Ownership of source data transferred to this
        source->position = 0;
        source->at = startAction;
        source->data = 0;
        source->lenData = 0;
        source->mayCoalesce = true;
}

// The undo history stores a sequence of user operations that represent the user's view of the
// commands executed on the text.
// Each user operation contains a sequence of text insertion and text deletion actions.
// All the user operations are stored in a list of individual actions with 'start' actions used
// as delimiters between user operations.
// Initially there is one start action in the history.
// As each action is performed, it is recorded in the history. The action may either become
// part of the current user operation or may start a new user operation. If it is to be part of the
// current operation, then it overwrites the current last action. If it is to be part of a new
// operation, it is appended after the current last action.
// After writing the new action, a new start action is appended at the end of the history.
// The decision of whether to start a new user operation is based upon two factors. If a
// compound operation has been explicitly started by calling BeginUndoAction and no matching
// EndUndoAction (these calls nest) has been called, then the action is coalesced into the current
// operation. If there is no outstanding BeginUndoAction call then a new operation is started
// unless it looks as if the new action is caused by the user typing or deleting a stream of text.
// Sequences that look like typing or deletion are coalesced into a single user operation.

UndoHistory::UndoHistory() {

        lenActions = 100;
        actions = new Action[lenActions];
        maxAction = 0;
        currentAction = 0;
        undoSequenceDepth = 0;
        savePoint = 0;

        actions[currentAction].Create(startAction);
}

UndoHistory::~UndoHistory() {
        delete []actions;
        actions = 0;
}

void UndoHistory::EnsureUndoRoom() {
        // Have to test that there is room for 2 more actions in the array
        // as two actions may be created by the calling function
        if (currentAction >= (lenActions - 2)) {
                // Run out of undo nodes so extend the array
                int lenActionsNew = lenActions * 2;
                Action *actionsNew = new Action[lenActionsNew];
                if (!actionsNew)
                        return ;
                for (int act = 0; act <= currentAction; act++)
                        actionsNew[act].Grab(&actions[act]);
                delete []actions;
                lenActions = lenActionsNew;
                actions = actionsNew;
        }
}

void UndoHistory::AppendAction(actionType at, int position, char *data, int lengthData) {
        EnsureUndoRoom();
        //Platform::DebugPrintf("%% %d action %d %d %d\n", at, position, lengthData, currentAction);
        //Platform::DebugPrintf("^ %d action %d %d\n", actions[currentAction - 1].at,
        //      actions[currentAction - 1].position, actions[currentAction - 1].lenData);
        if (currentAction >= 1) {
                if (0 == undoSequenceDepth) {
                        // Top level actions may not always be coalesced
                        Action &actPrevious = actions[currentAction - 1];
                        // See if current action can be coalesced into previous action
                        // Will work if both are inserts or deletes and position is same
                        if (at != actPrevious.at) {
                                currentAction++;
                        } else if (currentAction == savePoint) {
                                currentAction++;
                        } else if ((at == insertAction) &&
                                   (position != (actPrevious.position + actPrevious.lenData*2))) {
                                // Insertions must be immediately after to coalesce
                                currentAction++;
                        } else if (!actions[currentAction].mayCoalesce) {
                                // Not allowed to coalesce if this set
                                currentAction++;
                        } else if (at == removeAction) {
                                if ((lengthData == 1) || (lengthData == 2)){
                                        if ((position + lengthData * 2) == actPrevious.position) {
                                                ; // Backspace -> OK
                                        } else if (position == actPrevious.position) {
                                                ; // Delete -> OK
                                        } else {
                                                // Removals must be at same position to coalesce
                                                currentAction++;
                                        }
                                } else {
                                        // Removals must be of one character to coalesce
                                        currentAction++;
                                }
                        } else {
                                //Platform::DebugPrintf("action coalesced\n");
                        }

                } else {
                        // Actions not at top level are always coalesced unless this is after return to top level
                        if (!actions[currentAction].mayCoalesce)
                                currentAction++;
                }
        } else {
                currentAction++;
        }
        actions[currentAction].Create(at, position, data, lengthData);
        currentAction++;
        actions[currentAction].Create(startAction);
        maxAction = currentAction;
}

void UndoHistory::BeginUndoAction() {
        EnsureUndoRoom();
        if (undoSequenceDepth == 0) {
                if (actions[currentAction].at != startAction) {
                        currentAction++;
                        actions[currentAction].Create(startAction);
                        maxAction = currentAction;
                }
                actions[currentAction].mayCoalesce = false;
        }
        undoSequenceDepth++;
}

void UndoHistory::EndUndoAction() {
        EnsureUndoRoom();
        undoSequenceDepth--;
        if (0 == undoSequenceDepth) {
                if (actions[currentAction].at != startAction) {
                        currentAction++;
                        actions[currentAction].Create(startAction);
                        maxAction = currentAction;
                }
                actions[currentAction].mayCoalesce = false;
        }
}

void UndoHistory::DropUndoSequence() {
        undoSequenceDepth = 0;
}

void UndoHistory::DeleteUndoHistory() {
        for (int i = 1; i < maxAction; i++)
                actions[i].Destroy();
        maxAction = 0;
        currentAction = 0;
        actions[currentAction].Create(startAction);
        savePoint = 0;
}

void UndoHistory::SetSavePoint() {
        savePoint = currentAction;
}

bool UndoHistory::IsSavePoint() const {
        return savePoint == currentAction;
}

bool UndoHistory::CanUndo() const {
        return (currentAction > 0) && (maxAction > 0);
}

int UndoHistory::StartUndo() {
        // Drop any trailing startAction
        if (actions[currentAction].at == startAction && currentAction > 0)
                currentAction--;

        // Count the steps in this action
        int act = currentAction;
        while (actions[act].at != startAction && act > 0) {
                act--;
        }
        return currentAction - act;
}

const Action &UndoHistory::GetUndoStep() const {
        return actions[currentAction];
}

void UndoHistory::CompletedUndoStep() {
        currentAction--;
}

bool UndoHistory::CanRedo() const {
        return maxAction > currentAction;
}

int UndoHistory::StartRedo() {
        // Drop any leading startAction
        if (actions[currentAction].at == startAction && currentAction < maxAction)
                currentAction++;

        // Count the steps in this action
        int act = currentAction;
        while (actions[act].at != startAction && act < maxAction) {
                act++;
        }
        return act - currentAction;
}

const Action &UndoHistory::GetRedoStep() const {
        return actions[currentAction];
}

void UndoHistory::CompletedRedoStep() {
        currentAction++;
}

CellBuffer::CellBuffer(int initialLength) {
        body = new char[initialLength];
        size = initialLength;
        length = 0;
        part1len = 0;
        gaplen = initialLength;
        part2body = body + gaplen;
        readOnly = false;
        collectingUndo = true;
        growSize = 4000;
}

CellBuffer::~CellBuffer() {
        delete []body;
        body = 0;
}

void CellBuffer::GapTo(int position) {
        if (position == part1len)
                return ;
        if (position < part1len) {
                int diff = part1len - position;
                //Platform::DebugPrintf("Move gap backwards to %d diff = %d part1len=%d length=%d \n", position,diff, part1len, length);
                for (int i = 0; i < diff; i++)
                        body[part1len + gaplen - i - 1] = body[part1len - i - 1];
        } else {        // position > part1len
                int diff = position - part1len;
                //Platform::DebugPrintf("Move gap forwards to %d diff =%d\n", position,diff);
                for (int i = 0; i < diff; i++)
                        body[part1len + i] = body[part1len + gaplen + i];
        }
        part1len = position;
        part2body = body + gaplen;
}

void CellBuffer::RoomFor(int insertionLength) {
        //Platform::DebugPrintf("need room %d %d\n", gaplen, insertionLength);
        if (gaplen <= insertionLength) {
                //Platform::DebugPrintf("need room %d %d\n", gaplen, insertionLength);
                GapTo(length);
                if (growSize * 6 < size)
                        growSize *= 2;
                int newSize = size + insertionLength + growSize;
                //Platform::DebugPrintf("moved gap %d\n", newSize);
                char *newBody = new char[newSize];
                memcpy(newBody, body, size);
                delete []body;
                body = newBody;
                gaplen += newSize - size;
                part2body = body + gaplen;
                size = newSize;
                //Platform::DebugPrintf("end need room %d %d - size=%d length=%d\n", gaplen, insertionLength,size,length);
        }

}

// To make it easier to write code that uses ByteAt, a position outside the range of the buffer
// can be retrieved. All characters outside the range have the value '\0'.
char CellBuffer::ByteAt(int position) {
        if (position < part1len) {
                if (position < 0) {
                        return '\0';
                } else {
                        return body[position];
                }
        } else {
                if (position >= length) {
                        return '\0';
                } else {
                        return part2body[position];
                }
        }
}

void CellBuffer::SetByteAt(int position, char ch) {

        if (position < 0) {
                //Platform::DebugPrintf("Bad position %d\n",position);
                return ;
        }
        if (position >= length + 11) {
                Platform::DebugPrintf("Very Bad position %d of %d\n", position, length);
                //exit(2);
                return ;
        }
        if (position >= length) {
                //Platform::DebugPrintf("Bad position %d of %d\n",position,length);
                return ;
        }

        if (position < part1len) {
                body[position] = ch;
        } else {
                part2body[position] = ch;
        }
}

char CellBuffer::CharAt(int position) {
        return ByteAt(position*2);
}

void CellBuffer::GetCharRange(char *buffer, int position, int lengthRetrieve) {
        if (lengthRetrieve < 0)
                return ;
        if (position < 0)
                return ;
        int bytePos = position * 2;
        if ((bytePos + lengthRetrieve * 2) > length) {
                Platform::DebugPrintf("Bad GetCharRange %d for %d of %d\n", bytePos,
                                      lengthRetrieve, length);
                return ;
        }
        GapTo(0);       // Move the buffer so its easy to subscript into it
        char *pb = part2body + bytePos;
        while (lengthRetrieve--) {
                *buffer++ = *pb;
                pb += 2;
        }
}

char CellBuffer::StyleAt(int position) {
        return ByteAt(position*2 + 1);
}

const char *CellBuffer::InsertString(int position, char *s, int insertLength) {
        char *data = 0;
        // InsertString and DeleteChars are the bottleneck though which all changes occur
        if (!readOnly) {
                if (collectingUndo) {
                        // Save into the undo/redo stack, but only the characters - not the formatting
                        // This takes up about half load time
                        data = new char[insertLength / 2];
                        for (int i = 0; i < insertLength / 2; i++) {
                                data[i] = s[i * 2];
                        }
                        uh.AppendAction(insertAction, position, data, insertLength / 2);
                }

                BasicInsertString(position, s, insertLength);
        }
        return data;
}

void CellBuffer::InsertCharStyle(int position, char ch, char style) {
        char s[2];
        s[0] = ch;
        s[1] = style;
        InsertString(position*2, s, 2);
}

bool CellBuffer::SetStyleAt(int position, char style, char mask) {
        char curVal = ByteAt(position * 2 + 1);
        if ((curVal & mask) != style) {
                SetByteAt(position*2 + 1, static_cast<char>((curVal & ~mask) | style));
                return true;
        } else {
                return false;
        }
}

bool CellBuffer::SetStyleFor(int position, int lengthStyle, char style, char mask) {
        int bytePos = position * 2 + 1;
        bool changed = false;
        PLATFORM_ASSERT(lengthStyle == 0 ||
                (lengthStyle > 0 && lengthStyle + position < length));
        while (lengthStyle--) {
                char curVal = ByteAt(bytePos);
                if ((curVal & mask) != style) {
                        SetByteAt(bytePos, static_cast<char>((curVal & ~mask) | style));
                        changed = true;
                }
                bytePos += 2;
        }
        return changed;
}

const char *CellBuffer::DeleteChars(int position, int deleteLength) {
        // InsertString and DeleteChars are the bottleneck though which all changes occur
        char *data = 0;
        if (!readOnly) {
                if (collectingUndo) {
                        // Save into the undo/redo stack, but only the characters - not the formatting
                        data = new char[deleteLength / 2];
                        for (int i = 0; i < deleteLength / 2; i++) {
                                data[i] = ByteAt(position + i * 2);
                        }
                        uh.AppendAction(removeAction, position, data, deleteLength / 2);
                }

                BasicDeleteChars(position, deleteLength);
        }
        return data;
}

int CellBuffer::ByteLength() {
        return length;
}

int CellBuffer::Length() {
        return ByteLength() / 2;
}

int CellBuffer::Lines() {
        //Platform::DebugPrintf("Lines = %d\n", lv.lines);
        return lv.lines;
}

int CellBuffer::LineStart(int line) {
        if (line < 0)
                return 0;
        else if (line > lv.lines)
                return Length();
        else
                return lv.linesData[line].startPosition;
}

bool CellBuffer::IsReadOnly() {
        return readOnly;
}

void CellBuffer::SetReadOnly(bool set) {
        readOnly = set;
}

void CellBuffer::SetSavePoint() {
        uh.SetSavePoint();
}

bool CellBuffer::IsSavePoint() {
        return uh.IsSavePoint();
}

int CellBuffer::AddMark(int line, int markerNum) {
        if ((line >= 0) && (line < lv.lines)) {
                return lv.AddMark(line, markerNum);
        }
        return - 1;
}

void CellBuffer::DeleteMark(int line, int markerNum) {
        if ((line >= 0) && (line < lv.lines)) {
                lv.DeleteMark(line, markerNum);
        }
}

void CellBuffer::DeleteMarkFromHandle(int markerHandle) {
        lv.DeleteMarkFromHandle(markerHandle);
}

int CellBuffer::GetMark(int line) {
        if ((line >= 0) && (line < lv.lines) && (lv.linesData[line].handleSet))
                return lv.linesData[line].handleSet->MarkValue();
        return 0;
}

void CellBuffer::DeleteAllMarks(int markerNum) {
        for (int line = 0; line < lv.lines; line++) {
                lv.DeleteMark(line, markerNum);
        }
}

int CellBuffer::LineFromHandle(int markerHandle) {
        return lv.LineFromHandle(markerHandle);
}

// Without undo

void CellBuffer::BasicInsertString(int position, char *s, int insertLength) {
        //Platform::DebugPrintf("Inserting at %d for %d\n", position, insertLength);
        if (insertLength == 0)
                return ;
        RoomFor(insertLength);
        GapTo(position);

        memcpy(body + part1len, s, insertLength);
        length += insertLength;
        part1len += insertLength;
        gaplen -= insertLength;
        part2body = body + gaplen;

        int lineInsert = lv.LineFromPosition(position / 2) + 1;
        // Point all the lines after the insertion point further along in the buffer
        for (int lineAfter = lineInsert; lineAfter <= lv.lines; lineAfter++) {
                lv.linesData[lineAfter].startPosition += insertLength / 2;
        }
        char chPrev = ' ';
        if ((position - 2) >= 0)
                chPrev = ByteAt(position - 2);
        char chAfter = ' ';
        if ((position + insertLength) < length)
                chAfter = ByteAt(position + insertLength);
        if (chPrev == '\r' && chAfter == '\n') {
                //Platform::DebugPrintf("Splitting a crlf pair at %d\n", lineInsert);
                // Splitting up a crlf pair at position
                lv.InsertValue(lineInsert, position / 2);
                lineInsert++;
        }
        char ch = ' ';
        for (int i = 0; i < insertLength; i += 2) {
                ch = s[i];
                if (ch == '\r') {
                        //Platform::DebugPrintf("Inserting cr at %d\n", lineInsert);
                        lv.InsertValue(lineInsert, (position + i) / 2 + 1);
                        lineInsert++;
                } else if (ch == '\n') {
                        if (chPrev == '\r') {
                                //Platform::DebugPrintf("Patching cr before lf at %d\n", lineInsert-1);
                                // Patch up what was end of line
                                lv.SetValue(lineInsert - 1, (position + i) / 2 + 1);
                        } else {
                                //Platform::DebugPrintf("Inserting lf at %d\n", lineInsert);
                                lv.InsertValue(lineInsert, (position + i) / 2 + 1);
                                lineInsert++;
                        }
                }
                chPrev = ch;
        }
        // Joining two lines where last insertion is cr and following text starts with lf
        if (chAfter == '\n') {
                if (ch == '\r') {
                        //Platform::DebugPrintf("Joining cr before lf at %d\n", lineInsert-1);
                        // End of line already in buffer so drop the newly created one
                        lv.Remove(lineInsert - 1);
                }
        }
}

void CellBuffer::BasicDeleteChars(int position, int deleteLength) {
        //Platform::DebugPrintf("Deleting at %d for %d\n", position, deleteLength);
        if (deleteLength == 0)
                return ;

        if ((position == 0) && (deleteLength == length)) {
                // If whole buffer is being deleted, faster to reinitialise lines data
                // than to delete each line.
                //printf("Whole buffer being deleted\n");
                lv.Init();
        } else {
                // Have to fix up line positions before doing deletion as looking at text in buffer
                // to work out which lines have been removed

                int lineRemove = lv.LineFromPosition(position / 2) + 1;
                // Point all the lines after the insertion point further along in the buffer
                for (int lineAfter = lineRemove; lineAfter <= lv.lines; lineAfter++) {
                        lv.linesData[lineAfter].startPosition -= deleteLength / 2;
                }
                char chPrev = ' ';
                if (position >= 2)
                        chPrev = ByteAt(position - 2);
                char chBefore = chPrev;
                char chNext = ' ';
                if (position < length)
                        chNext = ByteAt(position);
                bool ignoreNL = false;
                if (chPrev == '\r' && chNext == '\n') {
                        //Platform::DebugPrintf("Deleting lf after cr, move line end to cr at %d\n", lineRemove);
                        // Move back one
                        lv.SetValue(lineRemove, position / 2);
                        lineRemove++;
                        ignoreNL = true;        // First \n is not real deletion
                }

                char ch = chNext;
                for (int i = 0; i < deleteLength; i += 2) {
                        chNext = ' ';
                        if ((position + i + 2) < length)
                                chNext = ByteAt(position + i + 2);
                        //Platform::DebugPrintf("Deleting %d %x\n", i, ch);
                        if (ch == '\r') {
                                if (chNext != '\n') {
                                        //Platform::DebugPrintf("Removing cr end of line\n");
                                        lv.Remove(lineRemove);
                                }
                        } else if ((ch == '\n') && !ignoreNL) {
                                //Platform::DebugPrintf("Removing lf end of line\n");
                                lv.Remove(lineRemove);
                                ignoreNL = false;       // Further \n are not real deletions
                        }

                        ch = chNext;
                }
                // May have to fix up end if last deletion causes cr to be next to lf
                // or removes one of a crlf pair
                char chAfter = ' ';
                if ((position + deleteLength) < length)
                        chAfter = ByteAt(position + deleteLength);
                if (chBefore == '\r' && chAfter == '\n') {
                        //d.printf("Joining cr before lf at %d\n", lineRemove);
                        // Using lineRemove-1 as cr ended line before start of deletion
                        lv.Remove(lineRemove - 1);
                        lv.SetValue(lineRemove - 1, position / 2 + 1);
                }
        }
        GapTo(position);
        length -= deleteLength;
        gaplen += deleteLength;
        part2body = body + gaplen;
}

bool CellBuffer::SetUndoCollection(bool collectUndo) {
        collectingUndo = collectUndo;
        uh.DropUndoSequence();
        return collectingUndo;
}

bool CellBuffer::IsCollectingUndo() {
        return collectingUndo;
}

void CellBuffer::BeginUndoAction() {
        uh.BeginUndoAction();
}

void CellBuffer::EndUndoAction() {
        uh.EndUndoAction();
}

void CellBuffer::DeleteUndoHistory() {
        uh.DeleteUndoHistory();
}

bool CellBuffer::CanUndo() {
        return (!readOnly) && (uh.CanUndo());
}

int CellBuffer::StartUndo() {
        return uh.StartUndo();
}

const Action &CellBuffer::GetUndoStep() const {
        return uh.GetUndoStep();
}

void CellBuffer::PerformUndoStep() {
        const Action &actionStep = uh.GetUndoStep();
        if (actionStep.at == insertAction) {
                BasicDeleteChars(actionStep.position, actionStep.lenData*2);
        } else if (actionStep.at == removeAction) {
                char *styledData = new char[actionStep.lenData * 2];
                for (int i = 0; i < actionStep.lenData; i++) {
                        styledData[i*2] = actionStep.data[i];
                        styledData[i*2 + 1] = 0;
                }
                BasicInsertString(actionStep.position, styledData, actionStep.lenData*2);
                delete []styledData;
        }
        uh.CompletedUndoStep();
}

bool CellBuffer::CanRedo() {
        return (!readOnly) && (uh.CanRedo());
}

int CellBuffer::StartRedo() {
        return uh.StartRedo();
}

const Action &CellBuffer::GetRedoStep() const {
        return uh.GetRedoStep();
}

void CellBuffer::PerformRedoStep() {
        const Action &actionStep = uh.GetRedoStep();
        if (actionStep.at == insertAction) {
                char *styledData = new char[actionStep.lenData * 2];
                for (int i = 0; i < actionStep.lenData; i++) {
                        styledData[i*2] = actionStep.data[i];
                        styledData[i*2 + 1] = 0;
                }
                BasicInsertString(actionStep.position, styledData, actionStep.lenData*2);
                delete []styledData;
        } else if (actionStep.at == removeAction) {
                BasicDeleteChars(actionStep.position, actionStep.lenData*2);
        }
        uh.CompletedRedoStep();
}

int CellBuffer::SetLineState(int line, int state) {
        int stateOld = lineStates[line];
        lineStates[line] = state;
        return stateOld;
}

int CellBuffer::GetLineState(int line) {
        return lineStates[line];
}

int CellBuffer::GetMaxLineState() {
        return lineStates.Length();
}

int CellBuffer::SetLevel(int line, int level) {
        int prev = 0;
        if ((line >= 0) && (line < lv.lines)) {
                if (!lv.levels) {
                        lv.ExpandLevels();
                }
                prev = lv.levels[line];
                if (lv.levels[line] != level) {
                        lv.levels[line] = level;
                }
        }
        return prev;
}

int CellBuffer::GetLevel(int line) {
        if (lv.levels && (line >= 0) && (line < lv.lines)) {
                return lv.levels[line];
        } else {
                return SC_FOLDLEVELBASE;
        }
}

void CellBuffer::ClearLevels() {
        lv.ClearLevels();
}