Fix scene switching flipbook crash

toonz/sources/include/toonz/tscenehandle.h

@@ -42,6 +42,7 @@ public:
     emit sceneChanged();
     if (setDirty) setDirtyFlag(true);
   }
+  void notifySceneSwitching() { emit sceneSwitching(); }
   void notifySceneSwitched() {
     emit sceneSwitched();
     setDirtyFlag(false);
@@ -76,6 +77,7 @@ public slots:
   }
 
 signals:
+  void sceneSwitching();
   void sceneSwitched();
   void sceneChanged();
   void castChanged();

toonz/sources/toonz/flipbook.cpp

@@ -236,6 +236,10 @@ FlipBook::FlipBook(QWidget *parent, QString viewerTitle,
 
   m_previewUpdateTimer.setSingleShot(true);
 
+  TSceneHandle *sceneHandle = TApp::instance()->getCurrentScene();
+
+  ret = ret && connect(sceneHandle, SIGNAL(sceneSwitching()), this,
+                       SLOT(onSceneSwitching()));
   ret = ret && connect(parentWidget(), SIGNAL(closeButtonPressed()), this,
                        SLOT(onCloseButtonPressed()));
   ret = ret && connect(parentWidget(), SIGNAL(doubleClick(QMouseEvent *)), this,
@@ -549,6 +553,10 @@ void FlipBook::loadImages() {
 
 //=============================================================================
 
+void FlipBook::clearImages() { reset(); }
+
+//=============================================================================
+
 bool FlipBook::canAppend() {
   // Images can be appended if:
   //  a) There is a name (in particular, an extension) representing currently
@@ -1862,6 +1870,9 @@ void FlipBook::reset() {
   else
     PreviewFxManager::instance()->detach(this);
 
+  m_snd = 0;
+  m_xl  = 0;
+
   m_levelNames.clear();
   m_levels.clear();
   m_framesCount = 0;
@@ -2264,3 +2275,7 @@ FlipBook *viewFile(const TFilePath &path, int from, int to, int step,
 }
 
 //-----------------------------------------------------------------------------
+
+void FlipBook::onSceneSwitching() {
+  if (m_xl || m_isPreviewFx) reset();
+}

toonz/sources/toonz/flipbook.h

@@ -299,6 +299,7 @@ public slots:
 
   void saveImages();
   void loadImages();
+  void clearImages();
 
   void performFxUpdate();
   void regenerate();
@@ -306,6 +307,8 @@ public slots:
   void clonePreview();
   void freezePreview();
   void unfreezePreview();
+
+  void onSceneSwitching();
 };
 
 // utility

toonz/sources/toonz/imageviewer.cpp

@@ -307,6 +307,9 @@ void ImageViewer::contextMenuEvent(QContextMenuEvent *event) {
     menu->addAction(action);
     action->setParent(m_flipbook);
 
+    action = menu->addAction(tr("Clear Images"));
+    connect(action, SIGNAL(triggered()), m_flipbook, SLOT(clearImages()));
+
     menu->addSeparator();
   }
 

toonz/sources/toonzlib/tscenehandle.cpp

@@ -23,6 +23,7 @@ ToonzScene *TSceneHandle::getScene() const { return m_scene; }
 
 void TSceneHandle::setScene(ToonzScene *scene) {
   if (m_scene == scene) return;
+  emit sceneSwitching();
   delete m_scene;
   m_scene = scene;
   if (m_scene) emit sceneSwitched();