nodeview: implemented dragger to create edge without holding key

app/widget/nodeview/nodeview.cpp

@@ -505,8 +505,11 @@ void NodeView::mousePressEvent(QMouseEvent *event)
   if (HandPress(event)) return;
 
   if (event->button() == Qt::LeftButton) {
+    // See if we're dragging the arrow of an edge
+    QPointF scene_pt = mapToScene(event->pos());
+
     foreach (NodeViewEdge *edge_item, scene_.edges()) {
-      if (edge_item->arrow_bounding_rect().contains(mapToScene(event->pos()))) {
+      if (edge_item->arrow_bounding_rect().contains(scene_pt)) {
         create_edge_src_ = scene_.NodeToUIObject(edge_item->output().node());
         create_edge_src_output_ = edge_item->output().output();
         create_edge_ = edge_item;
@@ -514,6 +517,14 @@ void NodeView::mousePressEvent(QMouseEvent *event)
         return;
       }
     }
+
+    // See if we're dragging the arrow of a node
+    foreach (NodeViewItem *node_item, scene_.item_map()) {
+      if (node_item->GetOutputTriangle().boundingRect().translated(node_item->pos()).contains(scene_pt)) {
+        CreateNewEdge(node_item);
+        return;
+      }
+    }
   }
 
   QGraphicsItem* item = itemAt(event->pos());
@@ -535,15 +546,7 @@ void NodeView::mousePressEvent(QMouseEvent *event)
   if (event->modifiers() & Qt::ControlModifier) {
     NodeViewItem* node_item = dynamic_cast<NodeViewItem*>(item);
     if (node_item) {
-      create_edge_ = new NodeViewEdge();
-      create_edge_src_ = node_item;
-      create_edge_src_output_ = Node::kDefaultOutput;
-      create_edge_already_exists_ = false;
-
-      create_edge_->SetCurved(scene_.GetEdgesAreCurved());
-      create_edge_->SetFlowDirection(scene_.GetFlowDirection());
-
-      scene_.addItem(create_edge_);
+      CreateNewEdge(node_item);
       return;
     }
   }
@@ -1501,6 +1504,19 @@ Menu *NodeView::CreateAddMenu(Menu *parent)
   return add_menu;
 }
 
+void NodeView::CreateNewEdge(NodeViewItem *output_item)
+{
+  create_edge_ = new NodeViewEdge();
+  create_edge_src_ = output_item;
+  create_edge_src_output_ = Node::kDefaultOutput;
+  create_edge_already_exists_ = false;
+
+  create_edge_->SetCurved(scene_.GetEdgesAreCurved());
+  create_edge_->SetFlowDirection(scene_.GetFlowDirection());
+
+  scene_.addItem(create_edge_);
+}
+
 NodeView::NodeViewAttachNodesToCursor::NodeViewAttachNodesToCursor(NodeView *view, const QVector<Node *> &nodes) :
   view_(view),
   nodes_(nodes)

app/widget/nodeview/nodeview.h

@@ -136,6 +136,8 @@ private:
 
   Menu *CreateAddMenu(Menu *parent);
 
+  void CreateNewEdge(NodeViewItem *output_item);
+
   class NodeViewAttachNodesToCursor : public UndoCommand
   {
   public:

app/widget/nodeview/nodeviewitem.cpp

@@ -65,6 +65,8 @@ NodeViewItem::NodeViewItem(QGraphicsItem *parent) :
 
   title_bar_rect_ = QRectF(-widget_width/2, -widget_height/2, widget_width, widget_height);
   setRect(title_bar_rect_);
+
+  output_triangle_.resize(3);
 }
 
 QPointF NodeViewItem::GetNodePosition() const
@@ -341,6 +343,41 @@ void NodeViewItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *opti
   painter->setBrush(Qt::NoBrush);
 
   painter->drawRect(rect());
+
+  // Draw output triangle
+  painter->setPen(Qt::NoPen);
+  painter->setBrush(app_pal.color(QPalette::Text));
+  int triangle_sz = qMin(rect().width(), rect().height()) / 2;
+  int triangle_sz_half = triangle_sz / 2;
+
+  switch (flow_dir_) {
+  case NodeViewCommon::kLeftToRight:
+    // Triangle pointing right
+    output_triangle_[0] = QPointF(rect().right(), rect().center().y() - triangle_sz_half);
+    output_triangle_[1] = QPointF(rect().right() + triangle_sz_half, rect().center().y());
+    output_triangle_[2] = QPointF(rect().right(), rect().center().y() + triangle_sz_half);
+    break;
+  case NodeViewCommon::kTopToBottom:
+    // Triangle pointing down
+    output_triangle_[0] = QPointF(rect().center().x() - triangle_sz_half, rect().bottom());
+    output_triangle_[1] = QPointF(rect().center().x(), rect().bottom() + triangle_sz_half);
+    output_triangle_[2] = QPointF(rect().center().x() + triangle_sz_half, rect().bottom());
+    break;
+  case NodeViewCommon::kBottomToTop:
+    // Triangle pointing up
+    output_triangle_[0] = QPointF(rect().center().x() - triangle_sz_half, rect().top());
+    output_triangle_[1] = QPointF(rect().center().x(), rect().top() - triangle_sz_half);
+    output_triangle_[2] = QPointF(rect().center().x() + triangle_sz_half, rect().top());
+    break;
+  case NodeViewCommon::kRightToLeft:
+    // Triangle pointing left
+    output_triangle_[0] = QPointF(rect().left(), rect().center().y() - triangle_sz_half);
+    output_triangle_[1] = QPointF(rect().left() - triangle_sz_half, rect().center().y());
+    output_triangle_[2] = QPointF(rect().left(), rect().center().y() + triangle_sz_half);
+    break;
+  }
+
+  painter->drawPolygon(output_triangle_);
 }
 
 void NodeViewItem::mousePressEvent(QGraphicsSceneMouseEvent *event)

app/widget/nodeview/nodeviewitem.h

@@ -125,6 +125,11 @@ public:
     return prevent_removing_;
   }
 
+  const QPolygonF &GetOutputTriangle() const
+  {
+    return output_triangle_;
+  }
+
 protected:
   virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr) override;
 
@@ -190,6 +195,8 @@ private:
 
   bool prevent_removing_;
 
+  QPolygonF output_triangle_;
+
 };
 
 }