nodeview: allow users to place a node on an edge to automatically connect it

between the two nodes

UI convenience. Edge highlights when the cursor is in range to perform this
action.

app/widget/nodeview/nodeview.cpp

@@ -29,7 +29,8 @@
 NodeView::NodeView(QWidget *parent) :
   QGraphicsView(parent),
   graph_(nullptr),
-  attached_item_(nullptr)
+  attached_item_(nullptr),
+  drop_edge_(nullptr)
 {
   setScene(&scene_);
   setDragMode(RubberBandDrag);
@@ -231,7 +232,25 @@ void NodeView::keyPressEvent(QKeyEvent *event)
 void NodeView::mousePressEvent(QMouseEvent *event)
 {
   if (attached_item_) {
+    Node* dropping_node = attached_item_->node();
+
     DetachItemFromCursor();
+
+    if (drop_edge_) {
+      NodeEdgePtr old_edge = drop_edge_->edge();
+
+      // We have everything we need to place the node in between
+      QUndoCommand* command = new QUndoCommand();
+
+      // Remove old edge
+      new NodeEdgeRemoveCommand(old_edge, command);
+
+      // Place new edges
+      new NodeEdgeAddCommand(old_edge->output(), drop_compatible_input_, command);
+      new NodeEdgeAddCommand(dropping_node->output(), old_edge->input(), command);
+
+      Core::instance()->undo_stack()->push(command);
+    }
   }
 
   QGraphicsView::mousePressEvent(event);
@@ -243,6 +262,57 @@ void NodeView::mouseMoveEvent(QMouseEvent *event)
 
   if (attached_item_) {
     attached_item_->setPos(mapToScene(event->pos()));
+
+    // See if the user clicked on an edge
+    QRect edge_detect_rect(event->pos(), event->pos());
+
+    // FIXME: Hardcoded numbers
+    edge_detect_rect.adjust(-20, -20, 20, 20);
+
+    QList<QGraphicsItem*> items = this->items(edge_detect_rect);
+
+    NodeViewEdge* new_drop_edge = nullptr;
+
+    foreach (QGraphicsItem* item, items) {
+      NodeViewEdge* edge = dynamic_cast<NodeViewEdge*>(item);
+
+      if (edge) {
+        // Try to place this node inside this edge
+
+        // See if the node we're dropping has an input of a compatible data type
+        NodeInput* edges_input = edge->edge()->input();
+        NodeParam::DataType input_type = edges_input->data_type();
+
+        NodeInput* compatible_input = nullptr;
+
+        foreach (NodeParam* drop_node_param, attached_item_->node()->parameters()) {
+          if (drop_node_param->type() == NodeParam::kInput
+              && static_cast<NodeInput*>(drop_node_param)->data_type() & input_type) {
+            compatible_input = static_cast<NodeInput*>(drop_node_param);
+            break;
+          }
+        }
+
+        if (compatible_input) {
+          new_drop_edge = edge;
+          drop_compatible_input_ = compatible_input;
+
+          break;
+        }
+      }
+    }
+
+    if (drop_edge_ != new_drop_edge) {
+      if (drop_edge_) {
+        drop_edge_->SetHighlighted(false);
+      }
+
+      drop_edge_ = new_drop_edge;
+
+      if (drop_edge_) {
+        drop_edge_->SetHighlighted(true);
+      }
+    }
   }
 }
 

app/widget/nodeview/nodeview.h

@@ -114,6 +114,9 @@ private:
 
   NodeViewItem* attached_item_;
 
+  NodeViewEdge* drop_edge_;
+  NodeInput* drop_compatible_input_;
+
   QGraphicsScene scene_;
 
   QTimer reorganize_timer_;

app/widget/nodeview/nodeviewedge.cpp

@@ -30,7 +30,8 @@
 NodeViewEdge::NodeViewEdge(QGraphicsItem *parent) :
   QGraphicsLineItem(parent),
   edge_(nullptr),
-  connected_(false)
+  connected_(false),
+  highlighted_(false)
 {
   // Ensures this UI object is drawn behind other objects
   setZValue(-1);
@@ -101,19 +102,29 @@ void NodeViewEdge::Adjust()
 void NodeViewEdge::SetConnected(bool c)
 {
   connected_ = c;
+  update();
+}
+
+void NodeViewEdge::SetHighlighted(bool e)
+{
+  highlighted_ = e;
+  update();
 }
 
 void NodeViewEdge::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
 {
-  QPalette::ColorGroup color_mode;
+  QPalette::ColorGroup color_group = QPalette::Active;
+  QPalette::ColorRole color_role = QPalette::Text;
 
-  if (connected_) {
-    color_mode = QPalette::Active;
-  } else {
-    color_mode = QPalette::Disabled;
+  if (highlighted_) {
+    color_role = QPalette::Highlight;
   }
 
-  setPen(QPen(widget->palette().color(color_mode, QPalette::Text), edge_width_));
+  if (!connected_) {
+    color_group = QPalette::Disabled;
+  }
+
+  setPen(QPen(widget->palette().color(color_group, color_role), edge_width_));
 
   QGraphicsLineItem::paint(painter, option, widget);
 }

app/widget/nodeview/nodeviewedge.h

@@ -68,6 +68,13 @@ public:
    */
   void SetConnected(bool c);
 
+  /**
+   * @brief Set highlighted state
+   *
+   * Changes color of edge.
+   */
+  void SetHighlighted(bool e);
+
 protected:
   virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr) override;
 
@@ -77,6 +84,9 @@ private:
   int edge_width_;
 
   bool connected_;
+
+  bool highlighted_;
+
 };
 
 #endif // NODEEDGEITEM_H

app/widget/nodeview/nodeviewundo.cpp

@@ -45,6 +45,14 @@ NodeEdgeRemoveCommand::NodeEdgeRemoveCommand(NodeOutput *output, NodeInput *inpu
 {
 }
 
+NodeEdgeRemoveCommand::NodeEdgeRemoveCommand(NodeEdgePtr edge, QUndoCommand *parent) :
+  QUndoCommand(parent),
+  output_(edge->output()),
+  input_(edge->input()),
+  done_(false)
+{
+}
+
 void NodeEdgeRemoveCommand::redo()
 {
   if (done_) {

app/widget/nodeview/nodeviewundo.h

@@ -36,6 +36,7 @@ private:
 class NodeEdgeRemoveCommand : public QUndoCommand {
 public:
   NodeEdgeRemoveCommand(NodeOutput* output, NodeInput* input, QUndoCommand* parent = nullptr);
+  NodeEdgeRemoveCommand(NodeEdgePtr edge, QUndoCommand* parent = nullptr);
 
   virtual void redo() override;
   virtual void undo() override;