enhancements to node edge creation

ui/nodeui.cpp

@@ -112,9 +112,47 @@ void NodeUI::mousePressEvent(QGraphicsSceneMouseEvent *event)
   }
 
   if (clicked_socket_ > -1) {
-    drag_line_start_ = pos() + sockets.at(clicked_socket_).center();
+
+    // See if this socket already has an edge connected
+    QVector<NodeEdgePtr> edges = central_widget_->GetEffect()->row(clicked_socket_)->edges();
+    if (!edges.isEmpty()) {
+
+      NodeEdge* e = edges.last().get();
+
+      EffectRow* other_row = (e->input()->GetParentEffect() == central_widget_->GetEffect()) ?
+            e->output() : e->input();
+
+      Node* other_node = other_row->GetParentEffect();
+
+      int other_row_index = other_node->IndexOfRow(other_row);
+
+      NodeUI* other_node_ui = FindUIFromNode(other_node);
+
+      // Start an edge at the opposite end
+      drag_line_start_ = other_node_ui->pos() + other_node_ui->GetNodeSocketRects().at(other_row_index).center();
+
+      drag_source_ = other_row;
+
+      // Disconnect the existing edge, and treat our dynamic one as an edit of that one
+      EffectRow::DisconnectEdge(edges.last());
+
+    } else {
+
+      // Start a new edge here
+      drag_line_start_ = pos() + sockets.at(clicked_socket_).center();
+
+      drag_source_ = central_widget_->GetEffect()->row(clicked_socket_);
+
+    }
+
     drag_line_ = scene()->addPath(NodeEdgeUI::GetEdgePath(drag_line_start_, event->scenePos()));
 
+    if (!edges.isEmpty()) {
+      drag_line_->setPen(QPen(Qt::white, 2));
+    } else {
+      drag_line_->setPen(QPen(Qt::gray, 2));
+    }
+
     event->accept();
   } else {
     QGraphicsItem::mousePressEvent(event);
@@ -135,8 +173,8 @@ void NodeUI::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
 
       // See if the graphics item here is a node
       NodeUI* mouse_node = dynamic_cast<NodeUI*>(mouse_items.at(j));
-
       if (mouse_node != nullptr) {
+
         // If so, get this node's sockets and loop through them
         QVector<QRectF> mouse_nodes_sockets = mouse_node->GetNodeSocketRects();
         for (int i=0;i<mouse_nodes_sockets.size();i++) {
@@ -146,7 +184,7 @@ void NodeUI::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
 
             // If so, see if the two rows can be connected
 
-            EffectRow* local_row = central_widget_->GetEffect()->row(clicked_socket_);
+            EffectRow* local_row = drag_source_;
             EffectRow* remote_row = mouse_node->GetRowFromIndex(i);
 
             // Ensure one is an input and one is an output and whether their data types are compatible
@@ -199,7 +237,7 @@ void NodeUI::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
     event->accept();
 
     if (drag_destination_ != nullptr) {
-      EffectRow::ConnectEdge(central_widget_->GetEffect()->row(clicked_socket_), drag_destination_);
+      EffectRow::ConnectEdge(drag_source_, drag_destination_);
     }
   } else {
     QGraphicsItem::mouseReleaseEvent(event);
@@ -241,3 +279,22 @@ EffectRow *NodeUI::GetRowFromIndex(int i)
   }
   return nullptr;
 }
+
+NodeUI *NodeUI::FindUIFromNode(Node* n)
+{
+  QList<QGraphicsItem*> all_items = scene()->items();
+
+  for (int j=0;j<all_items.size();j++) {
+    NodeUI* node = dynamic_cast<NodeUI*>(all_items.at(j));
+    if (node != nullptr) {
+
+      // Check if this node has the specified
+
+      if (node->Widget()->GetEffect() == n) {
+        return node;
+      }
+    }
+  }
+
+  return nullptr;
+}