    //=============================================================================
    //  MuseScore
    //  Music Composition & Notation
    //
    //  Copyright (C) 2002-2017 Werner Schweer
    //
    //  This program is free software; you can redistribute it and/or modify
    //  it under the terms of the GNU General Public License version 2
    //  as published by the Free Software Foundation and appearing in
    //  the file LICENCE.GPL
    //=============================================================================

    #include "musescore.h"
    #include "scoreview.h"
    #include "texttools.h"
    #include "libmscore/chordrest.h"
    #include "libmscore/figuredbass.h"
    #include "libmscore/score.h"
    #include "libmscore/segment.h"
    #include "libmscore/measure.h"

    namespace Ms {

    //---------------------------------------------------------
    //   ScoreView::figuredBassEndEdit
    //    derived from harmonyEndEdit()
    //    remove the FB if empty
    //---------------------------------------------------------

    void ScoreView::figuredBassEndEdit()
          {
          FiguredBass* fb = static_cast<FiguredBass*>(editData.element);

          if (fb->empty())
                _score->undoRemoveElement(fb);
          }

    //---------------------------------------------------------
    //   ScoreView::figuredBassTab
    //    derived from harmonyTab() (for Harmony)
    //    manages [Space] / [Shift][Space] keys, moving editing to FB of next/prev ChordRest
    //    and [Tab] / [Shift][Tab] keys, moving to FB of next/prev measure
    //---------------------------------------------------------

    void ScoreView::figuredBassTab(bool bMeas, bool bBack)
          {
          FiguredBass* fb   = (FiguredBass*)editData.element;
          Segment* nextSegm;
          Segment* segm     = fb->segment();
          int track         = fb->track();

          if (!segm) {
                qDebug("figuredBassTab: no segment");
                return;
                }

          // if moving to next/prev measure

          if (bMeas) {
                Measure* meas = segm->measure();
                if (meas) {
                      if (bBack)
                            meas = meas->prevMeasure();
                      else
                            meas = meas->nextMeasure();
                      }
                if (!meas) {
                      qDebug("figuredBassTab: no prev/next measure");
                      return;
                      }
                // find initial ChordRest segment
                nextSegm = meas->findSegment(SegmentType::ChordRest, meas->tick());
                if (!nextSegm) {
                      qDebug("figuredBassTab: no ChordRest segment at measure");
                      return;
                      }
                }

          // if moving to next/prev chord segment

          else {
                // search next chord segment in same staff
                nextSegm = bBack ? segm->prev1(SegmentType::ChordRest) : segm->next1(SegmentType::ChordRest);
                int minTrack = (track / VOICES ) * VOICES;
                int maxTrack = minTrack + (VOICES-1);

                while (nextSegm) {                   // look for a ChordRest in the compatible track range
                      if(nextSegm->findAnnotationOrElement(ElementType::FIGURED_BASS, minTrack, maxTrack))
                            break;
                      nextSegm = bBack ? nextSegm->prev1(SegmentType::ChordRest) : nextSegm->next1(SegmentType::ChordRest);
                      }

                if (!nextSegm) {
                      qDebug("figuredBassTab: no prev/next segment");
                      return;
                      }
                }

          changeState(ViewState::NORMAL);

          _score->startCmd();
          bool bNew;
          // add a (new) FB element, using chord duration as default duration
          FiguredBass * fbNew = FiguredBass::addFiguredBassToSegment(nextSegm, track, 0, &bNew);
          if (bNew)
                _score->undoAddElement(fbNew);
          _score->select(fbNew, SelectType::SINGLE, 0);
          startEdit(fbNew, Grip::NO_GRIP);
          mscore->changeState(mscoreState());
          adjustCanvasPosition(fbNew, false);
    //TODO-edit      ((FiguredBass*)editData.element)->moveCursorToEnd();
    //      _score->update();                         // used by lyricsTab() but not by harmonyTab(): needed or not?
          }

    //---------------------------------------------------------
    //   figuredBassTicksTab
    //    manages [Ctrl] [1]-[9], extending current FB of the given number of ticks
    //---------------------------------------------------------

    void ScoreView::figuredBassTicksTab(int ticks)
          {
          FiguredBass* fb   = toFiguredBass(editData.element);
          int track         = fb->track();
          Segment* segm     = fb->segment();
          if (!segm) {
                qDebug("figuredBassTicksTab: no segment");
                return;
                }
          Measure* measure = segm->measure();

          int nextSegTick   = segm->tick() + ticks;

          // find the measure containing the target tick
          while (nextSegTick >= measure->tick() + measure->ticks()) {
                measure = measure->nextMeasure();
                if (!measure) {
                      qDebug("figuredBassTicksTab: no next measure");
                      return;
                      }
                }

          // look for a segment at this tick; if none, create one
          Segment * nextSegm = segm;
          while (nextSegm && nextSegm->tick() < nextSegTick)
                nextSegm = nextSegm->next1(SegmentType::ChordRest);
          if (!nextSegm || nextSegm->tick() > nextSegTick) {      // no ChordRest segm at this tick
                nextSegm = new Segment(measure, SegmentType::ChordRest, nextSegTick - measure->tick());
                if (!nextSegm) {
                      qDebug("figuredBassTicksTab: no next segment");
                      return;
                      }
                _score->undoAddElement(nextSegm);
                }

          changeState(ViewState::NORMAL);

          _score->startCmd();
          bool bNew;
          FiguredBass * fbNew = FiguredBass::addFiguredBassToSegment(nextSegm, track, ticks, &bNew);
          if (bNew)
                _score->undoAddElement(fbNew);
          _score->select(fbNew, SelectType::SINGLE, 0);
          startEdit(fbNew, Grip::NO_GRIP);
          mscore->changeState(mscoreState());
          adjustCanvasPosition(fbNew, false);
    //TODO-edit      fb->moveCursorToEnd();
          }

    }

↑ V668 There is no sense in testing the 'nextSegm' pointer against null, as the memory was allocated using the 'new' operator. The exception will be generated in the case of memory allocation error.