footageviewer: allow dragging footage from footage viewer

app/widget/viewer/footageviewer.cpp

@@ -1,5 +1,8 @@
 #include "footageviewer.h"
 
+#include <QDrag>
+#include <QMimeData>
+
 #include "project/project.h"
 
 FootageViewerWidget::FootageViewerWidget(QWidget *parent) :
@@ -13,6 +16,8 @@ FootageViewerWidget::FootageViewerWidget(QWidget *parent) :
   NodeParam::ConnectEdge(video_node_->output(), viewer_node_->texture_input());
   NodeParam::ConnectEdge(audio_node_->output(), viewer_node_->samples_input());
   NodeParam::ConnectEdge(video_node_->output(), viewer_node_->length_input());
+
+  connect(gl_widget_, &ViewerGLWidget::DragStarted, this, &FootageViewerWidget::StartFootageDrag);
 }
 
 Footage *FootageViewerWidget::GetFootage() const
@@ -62,3 +67,24 @@ void FootageViewerWidget::SetFootage(Footage *footage)
     audio_renderer_->InvalidateCache(TimeRange(0, viewer_node_->Length()));
   }
 }
+
+void FootageViewerWidget::StartFootageDrag()
+{
+  if (!GetFootage()) {
+    return;
+  }
+
+  qDebug() << "Drag start!";
+  QDrag* drag = new QDrag(this);
+  QMimeData* mimedata = new QMimeData();
+
+  QByteArray encoded_data;
+  QDataStream stream(&encoded_data, QIODevice::WriteOnly);
+
+  stream << -1 << reinterpret_cast<quintptr>(GetFootage());
+
+  mimedata->setData("application/x-oliveprojectitemdata", encoded_data);
+  drag->setMimeData(mimedata);
+
+  drag->exec();
+}

app/widget/viewer/footageviewer.h

@@ -24,6 +24,9 @@ private:
 
   ViewerOutput* viewer_node_;
 
+private slots:
+  void StartFootageDrag();
+
 };
 
 #endif // FOOTAGEVIEWERWIDGET_H

app/widget/viewer/viewer.h

@@ -118,6 +118,8 @@ protected:
   OpenGLBackend* video_renderer_;
   AudioBackend* audio_renderer_;
 
+  ViewerGLWidget* gl_widget_;
+
 private:
   void UpdateTimeInternal(int64_t i);
 
@@ -131,8 +133,6 @@ private:
 
   ViewerSizer* sizer_;
 
-  ViewerGLWidget* gl_widget_;
-
   PlaybackControls* controls_;
 
   qint64 start_msec_;

app/widget/viewer/viewerglwidget.cpp

@@ -167,6 +167,13 @@ const QString &ViewerGLWidget::ocio_look() const
   return ocio_look_;
 }
 
+void ViewerGLWidget::mousePressEvent(QMouseEvent *event)
+{
+  QOpenGLWidget::mousePressEvent(event);
+
+  emit DragStarted();
+}
+
 void ViewerGLWidget::SetOCIOParameters(const QString &display, const QString &view, const QString &look)
 {
   ocio_display_ = display;

app/widget/viewer/viewerglwidget.h

@@ -119,7 +119,15 @@ public slots:
   const QString& ocio_view() const;
   const QString& ocio_look() const;
 
+signals:
+  void DragStarted();
+
 protected:
+  /**
+   * @brief Override the mouse press event simply to emit the DragStarted() signal
+   */
+  virtual void mousePressEvent(QMouseEvent* event) override;
+
   /**
    * @brief Initialize function to set up the OpenGL context upon its construction
    *