implemented reveal in footage viewer option

Fixes #1958

app/widget/viewer/footageviewer.cpp

@@ -38,6 +38,22 @@ FootageViewerWidget::FootageViewerWidget(QWidget *parent) :
   controls_->SetAudioVideoDragButtonsVisible(true);
   connect(controls_, &PlaybackControls::VideoPressed, this, &FootageViewerWidget::StartVideoDrag);
   connect(controls_, &PlaybackControls::AudioPressed, this, &FootageViewerWidget::StartAudioDrag);
+
+  override_workarea_ = new TimelineWorkArea(this);
+}
+
+void FootageViewerWidget::OverrideWorkArea(const TimeRange &r)
+{
+  override_workarea_->set_enabled(true);
+  override_workarea_->set_range(r);
+  this->ConnectWorkArea(override_workarea_);
+}
+
+void FootageViewerWidget::ResetWorkArea()
+{
+  if (GetConnectedWorkArea() == override_workarea_) {
+    this->ConnectWorkArea(GetConnectedNode() ? GetConnectedNode()->GetWorkArea() : nullptr);
+  }
 }
 
 void FootageViewerWidget::ConnectNodeEvent(ViewerOutput *n)

app/widget/viewer/footageviewer.h

@@ -32,6 +32,9 @@ class FootageViewerWidget : public ViewerWidget
 public:
   FootageViewerWidget(QWidget* parent = nullptr);
 
+  void OverrideWorkArea(const TimeRange &r);
+  void ResetWorkArea();
+
 protected:
   virtual void ConnectNodeEvent(ViewerOutput *) override;
 
@@ -42,6 +45,8 @@ private:
 
   QHash<ViewerOutput*, rational> cached_timestamps_;
 
+  TimelineWorkArea *override_workarea_;
+
 private slots:
   void StartFootageDrag();