nodeview: updates to complete new context paradigm

app/node/node.cpp

@@ -1622,15 +1622,28 @@ void Node::GenerateFrame(FramePtr frame, const GenerateJob &job) const
   Q_UNUSED(job)
 }
 
-bool Node::OutputsTo(Node *n, bool recursively) const
+bool Node::OutputsTo(Node *n, bool recursively, const OutputConnections &ignore_edges, const OutputConnection &added_edge) const
 {
   for (const OutputConnection& conn : output_connections_) {
+    if (std::find(ignore_edges.cbegin(), ignore_edges.cend(), conn) != ignore_edges.cend()) {
+      // If this edge is in the "ignore edges" list, skip it
+      continue;
+    }
+
     Node* connected = conn.second.node();
 
     if (connected == n) {
       return true;
-    } else if (recursively && connected->OutputsTo(n, recursively)) {
+    } else if (recursively && connected->OutputsTo(n, recursively, ignore_edges, added_edge)) {
       return true;
+    } else if (added_edge.first.node() == this) {
+      Node *proposed_connected = added_edge.second.node();
+
+      if (proposed_connected == n) {
+        return true;
+      } else if (recursively && proposed_connected->OutputsTo(n, recursively, ignore_edges, added_edge)) {
+        return true;
+      }
     }
   }
 
@@ -1697,7 +1710,7 @@ bool Node::InputsFrom(const QString &id, bool recursively) const
   return false;
 }
 
-int Node::GetRoutesTo(Node *n) const
+int Node::GetNumberOfRoutesTo(Node *n) const
 {
   bool outputs_directly = false;
   int routes = 0;
@@ -1708,7 +1721,7 @@ int Node::GetRoutesTo(Node *n) const
     if (connected_node == n) {
       outputs_directly = true;
     } else {
-      routes += connected_node->GetRoutesTo(n);
+      routes += connected_node->GetNumberOfRoutesTo(n);
     }
   }
 
@@ -2264,25 +2277,29 @@ void NodeSetPositionAndShiftSurroundingsCommand::redo()
     commands_.append(set_pos_command);
 
     // Get bounding rect
-    QRectF bounding_rect(position_.x() - 0.5, position_.y() - 0.5, 1, 1);
+    qreal bounding_rect_sz = 1.0;
+    qreal bounding_rect_half_sz = bounding_rect_sz * 0.5;
+    QRectF bounding_rect(position_.x() - bounding_rect_half_sz, position_.y() - bounding_rect_half_sz, bounding_rect_sz, bounding_rect_sz);
 
     // Start moving other nodes
     foreach (Node* surrounding, node_->parent()->nodes()) {
-      QPointF surrounding_position = node_->parent()->GetNodePosition(surrounding, relative_);
-      if (bounding_rect.contains(surrounding_position) && surrounding != node_) {
-        QPointF new_pos = surrounding_position;
+      if (surrounding != node_) {
+        QPointF surrounding_position = node_->parent()->GetNodePosition(surrounding, relative_);
+        if (bounding_rect.contains(surrounding_position)) {
+          QPointF new_pos = surrounding_position;
 
-        qreal move_rate = 0.50;
+          qreal move_rate = 0.50;
 
-        if (surrounding_position.y() < position_.y()) {
-          move_rate = -move_rate;
+          if (surrounding_position.y() < position_.y()) {
+            move_rate = -move_rate;
+          }
+
+          new_pos.setY(new_pos.y() + move_rate);
+
+          auto sur_command = new NodeSetPositionAndShiftSurroundingsCommand(surrounding, relative_, new_pos, true);
+          sur_command->redo();
+          commands_.append(sur_command);
         }
-
-        new_pos.setY(new_pos.y() + move_rate);
-
-        auto sur_command = new NodeSetPositionAndShiftSurroundingsCommand(surrounding, relative_, new_pos, true);
-        sur_command->redo();
-        commands_.append(sur_command);
       }
     }
   } else {
@@ -2294,20 +2311,19 @@ void NodeSetPositionAndShiftSurroundingsCommand::redo()
 
 void NodeSetPositionCommand::redo()
 {
-  NodeGraph* graph = node_->parent();
-  if (!(added_ = !graph->NodeMapContainsNode(node_, relevant_))) {
-    old_pos_ = graph->GetNodePosition(node_, relevant_);
+  graph_ = node_->parent();
+  if (!(added_ = !graph_->NodeMapContainsNode(node_, relevant_))) {
+    old_pos_ = graph_->GetNodePosition(node_, relevant_);
   }
-  graph->SetNodePosition(node_, relevant_, pos_);
+  graph_->SetNodePosition(node_, relevant_, pos_);
 }
 
 void NodeSetPositionCommand::undo()
 {
-  NodeGraph* graph = node_->parent();
   if (added_) {
-    graph->RemoveNodePosition(node_, relevant_);
+    graph_->RemoveNodePosition(node_, relevant_);
   } else {
-    graph->SetNodePosition(node_, relevant_, old_pos_);
+    graph_->SetNodePosition(node_, relevant_, old_pos_);
   }
 }
 
@@ -2368,4 +2384,32 @@ void NodeRemovePositionFromContextCommand::undo()
   }
 }
 
+void NodeRemovePositionFromAllContextsCommand::redo()
+{
+  NodeGraph *graph = node_->parent();
+
+  if (points_.empty()) {
+    // No points yet, let's see what points we should remove
+    auto map = graph->GetPositionMap();
+    for (auto it=map.cbegin(); it!=map.cend(); it++) {
+      if (it.value().contains(node_)) {
+        points_.insert({it.key(), it.value().value(node_)});
+      }
+    }
+  }
+
+  for (auto it=points_.cbegin(); it!=points_.cend(); it++) {
+    graph->RemoveNodePosition(node_, it->first);
+  }
+}
+
+void NodeRemovePositionFromAllContextsCommand::undo()
+{
+  NodeGraph *graph = node_->parent();
+
+  for (auto it=points_.crbegin(); it!=points_.crend(); it++) {
+    graph->SetNodePosition(node_, it->first, it->second);
+  }
+}
+
 }

app/node/node.h

@@ -557,7 +557,8 @@ public:
    * Whether to keep traversing down outputs to find this node (TRUE) or stick to immediate outputs
    * (FALSE).
    */
-  bool OutputsTo(Node* n, bool recursively) const;
+  bool OutputsTo(Node* n, bool recursively, const OutputConnections &ignore_edges = OutputConnections(), const OutputConnection &added_edge = OutputConnection()) const;
+
   /**
    * @brief Same as OutputsTo(Node*), but for a node ID rather than a specific instance.
    */
@@ -581,7 +582,7 @@ public:
   /**
    * @brief Determines how many paths go from this node out to another node
    */
-  int GetRoutesTo(Node* n) const;
+  int GetNumberOfRoutesTo(Node* n) const;
 
   /**
    * @brief Severs all input and output connections
@@ -1327,6 +1328,7 @@ private:
   QPointF old_pos_;
   bool added_;
   bool move_deps_;
+  NodeGraph *graph_;
 
 };
 
@@ -1375,7 +1377,7 @@ private:
 class NodeSetPositionAsChildCommand : public UndoCommand
 {
 public:
-  NodeSetPositionAsChildCommand(Node* node, Node* parent, Node *relative, int this_index, int child_count, bool shift_surroundings) :
+  NodeSetPositionAsChildCommand(Node* node, Node* parent, Node *relative, double this_index, int child_count, bool shift_surroundings) :
     node_(node),
     parent_(parent),
     relative_(relative),
@@ -1408,7 +1410,7 @@ private:
   Node* parent_;
   Node *relative_;
 
-  int this_index_;
+  double this_index_;
   int child_count_;
 
   bool shift_surroundings_;
@@ -1417,6 +1419,25 @@ private:
 
 };
 
+class NodePositionCloseChildGapCommand : public UndoCommand
+{
+public:
+  NodePositionCloseChildGapCommand(Node *parent, void *relative, int remove_index, int child_count, bool shift_surroundings);
+
+  virtual Project * GetRelevantProject() const override
+  {
+    return parent_->project();
+  }
+
+  virtual void redo() override;
+
+  virtual void undo() override;
+
+private:
+  Node *parent_;
+
+};
+
 class NodeSetPositionToOffsetOfAnotherNodeCommand : public UndoCommand
 {
 public:
@@ -1474,6 +1495,30 @@ private:
 
 };
 
+class NodeRemovePositionFromAllContextsCommand : public UndoCommand
+{
+public:
+  NodeRemovePositionFromAllContextsCommand(Node *node) :
+    node_(node)
+  {
+  }
+
+  virtual Project * GetRelevantProject() const override
+  {
+    return node_->project();
+  }
+
+  virtual void redo() override;
+
+  virtual void undo() override;
+
+private:
+  Node *node_;
+
+  std::map<Node *, QPointF> points_;
+
+};
+
 }
 
 #endif // NODE_H

app/widget/nodeview/nodeview.cpp

@@ -149,10 +149,10 @@ void NodeView::SetGraph(NodeGraph *graph, const QVector<Node*> &nodes)
             AddNodePosition(it.key(), n);
           }
         }
-
-        // Center on something
-        CenterOnItemsBoundingRect();
       }
+
+      // Center on something
+      QMetaObject::invokeMethod(this, &NodeView::CenterOnItemsBoundingRect, Qt::QueuedConnection);
     }
   }
 }
@@ -171,14 +171,25 @@ void NodeView::DeleteSelected()
   MultiUndoCommand* command = new MultiUndoCommand();
 
   {
+    // First remove any selected edges
     QVector<NodeViewEdge *> selected_edges = scene_.GetSelectedEdges();
 
-    foreach (NodeViewEdge* edge, selected_edges) {
-      command->add_child(new NodeEdgeRemoveCommand(edge->output(), edge->input()));
+    if (!selected_edges.isEmpty()) {
+      Node::OutputConnections removed_connections(selected_edges.size());
+
+      for (int i=0; i<selected_edges.size(); i++) {
+        NodeViewEdge* edge = selected_edges.at(i);
+        command->add_child(new NodeEdgeRemoveCommand(edge->output(), edge->input()));
+        removed_connections[i] = {edge->output(), edge->input()};
+      }
+
+      // Update contexts
+      UpdateContextsFromEdgeRemove(command, removed_connections);
     }
   }
 
   {
+    // Secondly remove any nodes
     QVector<Node*> selected_nodes = scene_.GetSelectedNodes();
 
     // Ensure no nodes are "undeletable"
@@ -408,17 +419,69 @@ void NodeView::ZoomOut()
 
 void NodeView::keyPressEvent(QKeyEvent *event)
 {
-  super::keyPressEvent(event);
+  switch (event->key()) {
+  case Qt::Key_Left:
+  case Qt::Key_Right:
+  case Qt::Key_Up:
+  case Qt::Key_Down:
+  {
+    if (graph_) {
+      MultiUndoCommand *pos_command = new MultiUndoCommand();
+      foreach (Node *n, selected_nodes_) {
+        foreach (Node *context, filter_nodes_) {
+          if (graph_->GetNodesForContext(context).contains(n)) {
+            QPointF old_pos = graph_->GetNodePosition(n, context);
 
-  if (event->key() == Qt::Key_Escape && !attached_items_.isEmpty()) {
-    DetachItemsFromCursor();
+            // Determine one pixel in scene units
+            double movement_amt = 1.0 / scale_;
 
-    // We undo the last action which SHOULD be adding the node
-    if (paste_command_) {
-      paste_command_->undo();
-      delete paste_command_;
-      paste_command_ = nullptr;
+            // Translate to 2D movement
+            QPointF node_movement;
+            switch (event->key()) {
+            case Qt::Key_Left:
+              node_movement.setX(-movement_amt);
+              break;
+            case Qt::Key_Right:
+              node_movement.setX(movement_amt);
+              break;
+            case Qt::Key_Up:
+              node_movement.setY(-movement_amt);
+              break;
+            case Qt::Key_Down:
+              node_movement.setY(movement_amt);
+              break;
+            }
+
+            // Translate from screen units into node units
+            node_movement = NodeViewItem::ScreenToNodePoint(node_movement, scene_.GetFlowDirection());
+
+            // Move command
+            pos_command->add_child(new NodeSetPositionCommand(n, context, old_pos + node_movement, false));
+          }
+        }
+      }
+      Core::instance()->undo_stack()->pushIfHasChildren(pos_command);
     }
+    break;
+  }
+  case Qt::Key_Escape:
+    if (!attached_items_.isEmpty()) {
+      DetachItemsFromCursor();
+
+      // We undo the last action which SHOULD be adding the node
+      if (paste_command_) {
+        paste_command_->undo();
+        delete paste_command_;
+        paste_command_ = nullptr;
+      }
+
+      break;
+    }
+
+    /* fall through */
+  default:
+    super::keyPressEvent(event);
+    break;
   }
 }
 
@@ -426,19 +489,20 @@ void NodeView::mousePressEvent(QMouseEvent *event)
 {
   if (HandPress(event)) return;
 
-  QGraphicsItem* item = itemAt(event->pos());
-
   if (event->button() == Qt::LeftButton) {
-    NodeViewEdge* edge_item = dynamic_cast<NodeViewEdge*>(item);
-    if (edge_item && edge_item->arrow_bounding_rect().contains(mapToScene(event->pos()))) {
-      create_edge_src_ = scene_.NodeToUIObject(edge_item->output().node());
-      create_edge_src_output_ = edge_item->output().output();
-      create_edge_ = edge_item;
-      create_edge_already_exists_ = true;
-      return;
+    foreach (NodeViewEdge *edge_item, scene_.edges()) {
+      if (edge_item->arrow_bounding_rect().contains(mapToScene(event->pos()))) {
+        create_edge_src_ = scene_.NodeToUIObject(edge_item->output().node());
+        create_edge_src_output_ = edge_item->output().output();
+        create_edge_ = edge_item;
+        create_edge_already_exists_ = true;
+        return;
+      }
     }
   }
 
+  QGraphicsItem* item = itemAt(event->pos());
+
   if (event->button() == Qt::RightButton) {
     if (!item || !item->isSelected()) {
       // Qt doesn't do this by default for some reason
@@ -623,13 +687,26 @@ void NodeView::mouseReleaseEvent(QMouseEvent *event)
   if (HandRelease(event)) return;
 
   if (create_edge_) {
+    // We are creating a new edge or moving an existing one
     MultiUndoCommand* command = new MultiUndoCommand();
 
+    Node::OutputConnections removed_edges;
+    Node::OutputConnection added_edge;
+
+    bool reconnected_to_itself = false;
+
     if (create_edge_already_exists_) {
-      if (!create_edge_->IsConnected()) {
+      if (create_edge_dst_input_ == create_edge_->input()) {
+        reconnected_to_itself = true;
+      } else {
+        // We are moving (or removing) an existing edge
         command->add_child(new NodeEdgeRemoveCommand(create_edge_->output(), create_edge_->input()));
+
+        // Update contexts for edge removal
+        removed_edges.push_back({create_edge_->output(), create_edge_->input()});
       }
     } else {
+      // We're creating a new edge, which means this UI object is only temporary
       delete create_edge_;
     }
 
@@ -645,15 +722,37 @@ void NodeView::mouseReleaseEvent(QMouseEvent *event)
         create_edge_dst_->setZValue(0);
       }
 
-      if (create_edge_dst_input_.IsValid()) {
+      NodeInput &creating_input = create_edge_dst_input_;
+      if (creating_input.IsValid()) {
         // Make connection
-        command->add_child(new NodeEdgeAddCommand(NodeOutput(create_edge_src_->GetNode(), create_edge_src_output_), create_edge_dst_input_));
-        create_edge_dst_input_.Reset();
+        if (!reconnected_to_itself) {
+          NodeOutput creating_output(create_edge_src_->GetNode(), create_edge_src_output_);
+
+          if (creating_input.IsConnected()) {
+            Node::OutputConnection existing_edge_to_remove = {creating_input.GetConnectedOutput(), creating_input};
+            command->add_child(new NodeEdgeRemoveCommand(existing_edge_to_remove.first, existing_edge_to_remove.second));
+            removed_edges.push_back(existing_edge_to_remove);
+          }
+
+          command->add_child(new NodeEdgeAddCommand(creating_output, creating_input));
+          added_edge = {creating_output, creating_input};
+        }
+
+        creating_input.Reset();
       }
 
       create_edge_dst_ = nullptr;
     }
 
+    // Update contexts
+    if (!removed_edges.empty()) {
+      UpdateContextsFromEdgeRemove(command, removed_edges);
+    }
+
+    if (added_edge.first.IsValid()) {
+      UpdateContextsFromEdgeAdd(command, added_edge, removed_edges);
+    }
+
     Core::instance()->undo_stack()->pushIfHasChildren(command);
     return;
   }
@@ -668,44 +767,105 @@ void NodeView::mouseReleaseEvent(QMouseEvent *event)
       command->add_child(paste_command_);
       paste_command_ = nullptr;
     }
-
-    if (attached_items_.size() == 1) {
-      Node* dropping_node = attached_items_.first().item->GetNode();
-
-      if (drop_edge_) {
-        // Remove old edge
-        command->add_child(new NodeEdgeRemoveCommand(drop_edge_->output(), drop_edge_->input()));
-
-        // Place new edges
-        command->add_child(new NodeEdgeAddCommand(drop_edge_->output(), drop_input_));
-        command->add_child(new NodeEdgeAddCommand(dropping_node, drop_edge_->input()));
-      }
-
-      drop_edge_ = nullptr;
-    }
-
-    DetachItemsFromCursor();
   }
 
-  for (auto it=positions_.begin(); it!=positions_.end(); it++) {
-    NodeViewItem *item = it.key();
-    Position &pos_data = it.value();
-    QPointF current_item_pos = item->GetNodePosition();
-    Node *node = pos_data.node;
+  {
+    // If any node positions changed, set them in their contexts now
+    MultiUndoCommand *set_pos_command = new MultiUndoCommand();
+    for (auto it=positions_.begin(); it!=positions_.end(); it++) {
+      NodeViewItem *item = it.key();
+      Position &pos_data = it.value();
+      QPointF current_item_pos = item->GetNodePosition();
+      Node *node = pos_data.node;
 
-    if (pos_data.original_item_pos != current_item_pos) {
-      QPointF diff = current_item_pos - pos_data.original_item_pos;
+      if (pos_data.original_item_pos != current_item_pos) {
+        QPointF diff = current_item_pos - pos_data.original_item_pos;
 
-      foreach (Node *context, filter_nodes_) {
-        if (graph_->ContextContainsNode(node, context)) {
-          QPointF current_node_pos_in_context = graph_->GetNodePosition(node, context);
-          current_node_pos_in_context += diff;
-          command->add_child(new NodeSetPositionCommand(node, context, current_node_pos_in_context, false));
+        foreach (Node *context, filter_nodes_) {
+          if (graph_->ContextContainsNode(node, context)) {
+            QPointF current_node_pos_in_context = graph_->GetNodePosition(node, context);
+            current_node_pos_in_context += diff;
+            set_pos_command->add_child(new NodeSetPositionCommand(node, context, current_node_pos_in_context, false));
+          }
+        }
+
+        pos_data.original_item_pos = current_item_pos;
+      }
+    }
+    if (set_pos_command->child_count()) {
+      set_pos_command->redo();
+      command->add_child(set_pos_command);
+    } else {
+      delete set_pos_command;
+    }
+  }
+
+
+  if (!attached_items_.isEmpty()) {
+    {
+      // Dropped attached item onto an edge, connect it between them
+      MultiUndoCommand *drop_edge_command = new MultiUndoCommand();
+      if (attached_items_.size() == 1) {
+        Node* dropping_node = attached_items_.first().item->GetNode();
+
+        if (drop_edge_) {
+          // Remove old edge
+          drop_edge_command->add_child(new NodeEdgeRemoveCommand(drop_edge_->output(), drop_edge_->input()));
+
+          // Place new edges
+          drop_edge_command->add_child(new NodeEdgeAddCommand(drop_edge_->output(), drop_input_));
+          drop_edge_command->add_child(new NodeEdgeAddCommand(dropping_node, drop_edge_->input()));
+        }
+
+        drop_edge_ = nullptr;
+      }
+      if (drop_edge_command->child_count()) {
+        drop_edge_command->redo();
+        command->add_child(drop_edge_command);
+      } else {
+        delete drop_edge_command;
+      }
+    }
+
+    {
+      // Remove from context any nodes that don't specifically output to said context
+      MultiUndoCommand *remove_pos_command = new MultiUndoCommand();
+
+      foreach (const AttachedItem &attached, attached_items_) {
+        MultiUndoCommand *remove_pos_subcommand = new MultiUndoCommand();
+        Node *attached_node = scene_.item_map().key(attached.item);
+
+        bool removed = false;
+        QVector<Node*> relevant_contexts;
+        foreach (Node *context, filter_nodes_) {
+          if (attached_node->OutputsTo(context, true)) {
+            relevant_contexts.append(context);
+          } else {
+            remove_pos_subcommand->add_child(new NodeRemovePositionFromContextCommand(attached_node, context));
+            removed = true;
+          }
+        }
+
+        if (removed && !relevant_contexts.isEmpty()) {
+          foreach (Node *relevant, relevant_contexts) {
+            remove_pos_subcommand->add_child(new NodeSetPositionCommand(attached_node, relevant, GetEstimatedPositionForContext(attached.item, relevant), false));
+          }
+
+          remove_pos_command->add_child(remove_pos_subcommand);
+        } else {
+          delete remove_pos_subcommand;
         }
       }
 
-      pos_data.original_item_pos = current_item_pos;
+      if (remove_pos_command->child_count()) {
+        remove_pos_command->redo();
+        command->add_child(remove_pos_command);
+      } else {
+        delete remove_pos_command;
+      }
     }
+
+    DetachItemsFromCursor();
   }
 
   Core::instance()->undo_stack()->pushIfHasChildren(command);
@@ -991,19 +1151,29 @@ void NodeView::RemoveNodePosition(Node *node, Node *relative)
 {
   if (filter_mode_ == kFilterShowSelective) {
     if (filter_nodes_.contains(relative)) {
-      // Determine if any other contexts have this node
-      bool found = false;
+      NodeViewItem *item = scene_.item_map().value(node);
 
-      foreach (Node *context, filter_nodes_) {
-        if (graph_->ContextContainsNode(node, context)) {
-          found = true;
-          break;
+      if (item && !item->GetPreventRemoving()) {
+        // Determine if any other contexts have this node
+        bool found = false;
+
+        foreach (Node *context, filter_nodes_) {
+          if (graph_->ContextContainsNode(node, context)) {
+            found = true;
+            break;
+          }
         }
-      }
 
-      if (!found) {
-        positions_.remove(scene_.item_map().value(node));
-        scene_.RemoveNode(node);
+        if (!found) {
+          foreach (const Node::OutputConnection &oc, node->output_connections()) {
+            scene_.RemoveEdge(oc.first, oc.second);
+          }
+          for (auto it=node->input_connections().cbegin(); it!=node->input_connections().cend(); it++) {
+            scene_.RemoveEdge(it->second, it->first);
+          }
+          positions_.remove(item);
+          scene_.RemoveNode(node);
+        }
       }
     }
   }
@@ -1098,6 +1268,22 @@ void NodeView::ZoomIntoCursorPosition(QWheelEvent *event, double multiplier, con
   }
 }
 
+bool NodeView::event(QEvent *event)
+{
+  if (event->type() == QEvent::ShortcutOverride) {
+    QKeyEvent *se = static_cast<QKeyEvent *>(event);
+    if (se->key() == Qt::Key_Left
+        || se->key() == Qt::Key_Right
+        || se->key() == Qt::Key_Up
+        || se->key() == Qt::Key_Down) {
+      se->accept();
+      return true;
+    }
+  }
+
+  return super::event(event);
+}
+
 void NodeView::ZoomFromKeyboard(double multiplier)
 {
   QPoint cursor_pos = mapFromGlobal(QCursor::pos());
@@ -1110,6 +1296,149 @@ void NodeView::ZoomFromKeyboard(double multiplier)
   ZoomIntoCursorPosition(nullptr, multiplier, cursor_pos);
 }
 
+bool NodeView::DetermineIfNodeIsFloatingInContext(Node *node, Node *context, Node *source, const Node::OutputConnections &removed_edges, const Node::OutputConnection &added_edge)
+{
+  // Determines whether `node` outputs to another node in `context` besides `source`
+  foreach (const Node::OutputConnection &conn, node->output_connections()) {
+    Node *output_candidate = conn.second.node();
+
+    if (output_candidate == source) {
+      continue;
+    }
+
+    if (graph_->ContextContainsNode(output_candidate, context)) {
+      if (!output_candidate->OutputsTo(source, true, removed_edges, added_edge)) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+void NodeView::UpdateContextsFromEdgeRemove(MultiUndoCommand *command, const Node::OutputConnections &remove_edges)
+{
+  // For each edge we remove, determine if we should remove the node from a context as well
+  foreach (const Node::OutputConnection &edge, remove_edges) {
+    Node *output_node = edge.first.node();
+    QVector<Node *> contexts_to_remove_from;
+    int contexts_containing = 0;
+
+    for (auto it=graph_->GetPositionMap().cbegin(); it!=graph_->GetPositionMap().cend(); it++) {
+      Node *context = it.key();
+
+      if (it.value().contains(output_node)) {
+        bool currently_outputs = output_node->OutputsTo(context, true);
+        bool will_output_after_operation = output_node->OutputsTo(context, true, remove_edges);
+
+        if (currently_outputs && !will_output_after_operation) {
+          // Will remove
+          contexts_to_remove_from.append(context);
+        }
+
+        contexts_containing++;
+      }
+    }
+
+    // Removing from all current contexts, convert to a floating node (i.e. don't remove from the context)
+    if (contexts_to_remove_from.size() != contexts_containing) {
+      // Not removing from all contexts, can remove
+      bool removing_from_all_current_contexts = true;
+
+      foreach (Node *context, filter_nodes_) {
+        if (graph_->ContextContainsNode(output_node, context)) {
+          if (!contexts_to_remove_from.contains(context)) {
+            removing_from_all_current_contexts = false;
+            break;
+          }
+        }
+      }
+
+      foreach (Node *context, contexts_to_remove_from) {
+        RecursivelyRemoveFloatingNodeFromContext(command, output_node, context, output_node, remove_edges, Node::OutputConnection(), removing_from_all_current_contexts);
+      }
+    }
+  }
+}
+
+void NodeView::RecursivelyRemoveFloatingNodeFromContext(MultiUndoCommand *command, Node *node, Node *context, Node *source, const Node::OutputConnections &removed_edges, const Node::OutputConnection &added_edge, bool prevent_removing)
+{
+  if (prevent_removing) {
+    command->add_child(new NodeViewItemPreventRemovingCommand(this, node, true));
+  }
+
+  command->add_child(new NodeRemovePositionFromContextCommand(node, context));
+
+  // Remove any dependency from the context that's also floating
+  for (auto it=node->input_connections().cbegin(); it!=node->input_connections().cend(); it++) {
+    Node *dependency = it->second.node();
+
+    // Determine if this node happens to output to anything else in the context (which may be
+    // another floating node that won't be removed by this operation)
+    if (!DetermineIfNodeIsFloatingInContext(dependency, context, source, removed_edges, added_edge)) {
+      RecursivelyRemoveFloatingNodeFromContext(command, dependency, context, source, removed_edges, added_edge, prevent_removing);
+    }
+  }
+}
+
+void NodeView::RecursivelyAddNodeToContext(MultiUndoCommand *command, Node *node, Node *context)
+{
+  command->add_child(new NodeSetPositionCommand(node, context, GetEstimatedPositionForContext(scene_.item_map().value(node), context), false));
+
+  // Add dependency
+  for (auto it=node->input_connections().cbegin(); it!=node->input_connections().cend(); it++) {
+    Node *dependency = it->second.node();
+    RecursivelyAddNodeToContext(command, dependency, context);
+  }
+}
+
+void NodeView::UpdateContextsFromEdgeAdd(MultiUndoCommand *command, const Node::OutputConnection &added_edge, const Node::OutputConnections &removed_edges)
+{
+  // Determine if node currently does NOT output to a context that it WILL after this operation
+  QVector<Node*> contexts_to_add_to;
+  Node *connecting_node = added_edge.first.node();
+  Node *input_node = added_edge.second.node();
+  for (auto it=graph_->GetPositionMap().cbegin(); it!=graph_->GetPositionMap().cend(); it++) {
+    if (it.value().contains(input_node)) {
+      contexts_to_add_to.append(it.key());
+    }
+  }
+
+  if (!contexts_to_add_to.isEmpty()) {
+    // Determine whether the node is currently "floating", i.e. it outputs to none of the contexts
+    // that it currently belongs to. If so, we will take ownership of it with this node.
+    bool node_is_floating = true;
+    QVector<Node*> current_contexts;
+    for (auto it=graph_->GetPositionMap().cbegin(); it!=graph_->GetPositionMap().cend(); it++) {
+      if (it.value().contains(connecting_node)) {
+        if (connecting_node->OutputsTo(it.key(), true, removed_edges)) {
+          node_is_floating = false;
+          break;
+        } else {
+          current_contexts.append(it.key());
+        }
+      }
+    }
+
+    if (node_is_floating) {
+      // This action will unfloat this node, so remove it from all current contexts
+      foreach (Node *context, current_contexts) {
+        RecursivelyRemoveFloatingNodeFromContext(command, connecting_node, context, connecting_node, removed_edges, added_edge, false);
+      }
+    }
+
+    // Add nodes to contexts
+    foreach (Node *context, contexts_to_add_to) {
+      RecursivelyAddNodeToContext(command, connecting_node, context);
+    }
+  }
+}
+
+QPointF NodeView::GetEstimatedPositionForContext(NodeViewItem *item, Node *context) const
+{
+  return item->GetNodePosition() - context_offsets_.value(context);
+}
+
 NodeView::NodeViewAttachNodesToCursor::NodeViewAttachNodesToCursor(NodeView *view, const QVector<Node *> &nodes) :
   view_(view),
   nodes_(nodes)
@@ -1132,4 +1461,23 @@ Project *NodeView::NodeViewAttachNodesToCursor::GetRelevantProject() const
   return dynamic_cast<Project*>(view_->graph_);
 }
 
+void NodeView::NodeViewItemPreventRemovingCommand::redo()
+{
+  NodeViewItem *item = view_->scene_.item_map().value(node_);
+
+  if (item) {
+    old_prevent_removing_ = item->GetPreventRemoving();
+    item->SetPreventRemoving(new_prevent_removing_);
+  }
+}
+
+void NodeView::NodeViewItemPreventRemovingCommand::undo()
+{
+  NodeViewItem *item = view_->scene_.item_map().value(node_);
+
+  if (item) {
+    item->SetPreventRemoving(old_prevent_removing_);
+  }
+}
+
 }

app/widget/nodeview/nodeview.h

@@ -91,6 +91,8 @@ protected:
 
   virtual void ZoomIntoCursorPosition(QWheelEvent *event, double multiplier, const QPointF &cursor_pos) override;
 
+  virtual bool event(QEvent *event) override;
+
 private:
   void AttachNodesToCursor(const QVector<Node *> &nodes);
 
@@ -107,6 +109,14 @@ private:
 
   void ZoomFromKeyboard(double multiplier);
 
+  bool DetermineIfNodeIsFloatingInContext(Node *node, Node *context, Node *source, const Node::OutputConnections &removed_edges, const Node::OutputConnection &added_edge);
+  void UpdateContextsFromEdgeRemove(MultiUndoCommand *command, const Node::OutputConnections &remove_edges);
+  void UpdateContextsFromEdgeAdd(MultiUndoCommand *command, const Node::OutputConnection &added_edge, const Node::OutputConnections &removed_edges = Node::OutputConnections());
+  void RecursivelyAddNodeToContext(MultiUndoCommand *command, Node *node, Node *context);
+  void RecursivelyRemoveFloatingNodeFromContext(MultiUndoCommand *command, Node *node, Node *context, Node *source, const Node::OutputConnections &removed_edges, const Node::OutputConnection &added_edge, bool prevent_removing);
+
+  QPointF GetEstimatedPositionForContext(NodeViewItem *item, Node *context) const;
+
   class NodeViewAttachNodesToCursor : public UndoCommand
   {
   public:
@@ -132,6 +142,32 @@ private:
     QPointF original_pos;
   };
 
+  class NodeViewItemPreventRemovingCommand : public UndoCommand
+  {
+  public:
+    NodeViewItemPreventRemovingCommand(NodeView *view, Node *node, bool prevent_removing) :
+      view_(view),
+      node_(node),
+      new_prevent_removing_(prevent_removing)
+    {}
+
+    virtual void redo() override;
+
+    virtual void undo() override;
+
+    virtual Project * GetRelevantProject() const override
+    {
+      return node_->project();
+    }
+
+  private:
+    NodeView *view_;
+    Node *node_;
+    bool new_prevent_removing_;
+    bool old_prevent_removing_;
+
+  };
+
   QList<AttachedItem> attached_items_;
 
   NodeViewEdge* drop_edge_;

app/widget/nodeview/nodeviewitem.cpp

@@ -45,7 +45,8 @@ NodeViewItem::NodeViewItem(QGraphicsItem *parent) :
   expanded_(false),
   hide_titlebar_(false),
   highlighted_index_(-1),
-  flow_dir_(NodeViewCommon::kLeftToRight)
+  flow_dir_(NodeViewCommon::kLeftToRight),
+  prevent_removing_(false)
 {
   // Set flags for this widget
   setFlag(QGraphicsItem::ItemIsMovable);
@@ -68,31 +69,7 @@ NodeViewItem::NodeViewItem(QGraphicsItem *parent) :
 
 QPointF NodeViewItem::GetNodePosition() const
 {
-  QPointF node_pos;
-
-  qreal adjusted_x = pos().x() / DefaultItemHorizontalPadding();
-  qreal adjusted_y = pos().y() / DefaultItemVerticalPadding();
-
-  switch (flow_dir_) {
-  case NodeViewCommon::kLeftToRight:
-    node_pos.setX(adjusted_x);
-    node_pos.setY(adjusted_y);
-    break;
-  case NodeViewCommon::kRightToLeft:
-    node_pos.setX(-adjusted_x);
-    node_pos.setY(adjusted_y);
-    break;
-  case NodeViewCommon::kTopToBottom:
-    node_pos.setX(adjusted_y);
-    node_pos.setY(adjusted_x);
-    break;
-  case NodeViewCommon::kBottomToTop:
-    node_pos.setX(-adjusted_y);
-    node_pos.setY(adjusted_x);
-    break;
-  }
-
-  return node_pos;
+  return ScreenToNodePoint(pos(), flow_dir_);
 }
 
 void NodeViewItem::SetNodePosition(const QPointF &pos)
@@ -122,24 +99,88 @@ int NodeViewItem::DefaultItemBorder()
   return QFontMetrics(QFont()).height() / 12;
 }
 
-qreal NodeViewItem::DefaultItemHorizontalPadding() const
+QPointF NodeViewItem::NodeToScreenPoint(QPointF p, NodeViewCommon::FlowDirection direction)
 {
-  if (NodeViewCommon::GetFlowOrientation(flow_dir_) == Qt::Horizontal) {
+  switch (direction) {
+  case NodeViewCommon::kLeftToRight:
+    // NodeGraphs are always left-to-right internally, no need to translate
+    break;
+  case NodeViewCommon::kRightToLeft:
+    // Invert X value
+    p.setX(-p.x());
+    break;
+  case NodeViewCommon::kTopToBottom:
+    // Swap X/Y
+    p = QPointF(p.y(), p.x());
+    break;
+  case NodeViewCommon::kBottomToTop:
+    // Swap X/Y and invert Y
+    p = QPointF(p.y(), -p.x());
+    break;
+  }
+
+  // Multiply by item sizes for this direction
+  p.setX(p.x() * DefaultItemHorizontalPadding(direction));
+  p.setY(p.y() * DefaultItemVerticalPadding(direction));
+
+  return p;
+}
+
+QPointF NodeViewItem::ScreenToNodePoint(QPointF p, NodeViewCommon::FlowDirection direction)
+{
+  // Divide by item sizes for this direction
+  p.setX(p.x() / DefaultItemHorizontalPadding(direction));
+  p.setY(p.y() / DefaultItemVerticalPadding(direction));
+
+  switch (direction) {
+  case NodeViewCommon::kLeftToRight:
+    // NodeGraphs are always left-to-right internally, no need to translate
+    break;
+  case NodeViewCommon::kRightToLeft:
+    // Invert X value
+    p.setX(-p.x());
+    break;
+  case NodeViewCommon::kTopToBottom:
+    // Swap X/Y
+      p = QPointF(p.y(), p.x());
+    break;
+  case NodeViewCommon::kBottomToTop:
+    // Swap X/Y and invert Y
+    p = QPointF(-p.y(), p.x());
+    break;
+  }
+
+  return p;
+}
+
+qreal NodeViewItem::DefaultItemHorizontalPadding(NodeViewCommon::FlowDirection dir)
+{
+  if (NodeViewCommon::GetFlowOrientation(dir) == Qt::Horizontal) {
     return DefaultItemWidth() * 1.5;
   } else {
     return DefaultItemWidth() * 1.25;
   }
 }
 
-qreal NodeViewItem::DefaultItemVerticalPadding() const
+qreal NodeViewItem::DefaultItemVerticalPadding(NodeViewCommon::FlowDirection dir)
 {
-  if (NodeViewCommon::GetFlowOrientation(flow_dir_) == Qt::Horizontal) {
+  if (NodeViewCommon::GetFlowOrientation(dir) == Qt::Horizontal) {
     return DefaultItemHeight() * 1.5;
   } else {
     return DefaultItemHeight() * 2.0;
   }
 }
 
+qreal NodeViewItem::DefaultItemHorizontalPadding() const
+{
+  return DefaultItemHorizontalPadding(flow_dir_);
+}
+
+qreal NodeViewItem::DefaultItemVerticalPadding() const
+{
+  return DefaultItemVerticalPadding(flow_dir_);
+}
+
 void NodeViewItem::AddEdge(NodeViewEdge *edge)
 {
   edges_.append(edge);
@@ -479,26 +520,7 @@ QPointF NodeViewItem::GetInputPointInternal(int index, const QPointF& source_pos
 
 void NodeViewItem::UpdateNodePosition()
 {
-  const QPointF &pos = cached_node_pos_;
-
-  switch (flow_dir_) {
-  case NodeViewCommon::kLeftToRight:
-    setPos(pos.x() * DefaultItemHorizontalPadding(),
-           pos.y() * DefaultItemVerticalPadding());
-    break;
-  case NodeViewCommon::kRightToLeft:
-    setPos(-pos.x() * DefaultItemHorizontalPadding(),
-           pos.y() * DefaultItemVerticalPadding());
-    break;
-  case NodeViewCommon::kTopToBottom:
-    setPos(pos.y() * DefaultItemHorizontalPadding(),
-           pos.x() * DefaultItemVerticalPadding());
-    break;
-  case NodeViewCommon::kBottomToTop:
-    setPos(pos.y() * DefaultItemHorizontalPadding(),
-           -pos.x() * DefaultItemVerticalPadding());
-    break;
-  }
+  setPos(NodeToScreenPoint(cached_node_pos_, flow_dir_));
 }
 
 }

app/widget/nodeview/nodeviewitem.h

@@ -95,8 +95,12 @@ public:
 
   static int DefaultItemBorder();
 
-  qreal DefaultItemHorizontalPadding() const;
+  static QPointF NodeToScreenPoint(QPointF p, NodeViewCommon::FlowDirection direction);
+  static QPointF ScreenToNodePoint(QPointF p, NodeViewCommon::FlowDirection direction);
 
+  static qreal DefaultItemHorizontalPadding(NodeViewCommon::FlowDirection dir);
+  static qreal DefaultItemVerticalPadding(NodeViewCommon::FlowDirection dir);
+  qreal DefaultItemHorizontalPadding() const;
   qreal DefaultItemVerticalPadding() const;
 
   void AddEdge(NodeViewEdge* edge);
@@ -111,6 +115,16 @@ public:
 
   void SetHighlightedIndex(int index);
 
+  void SetPreventRemoving(bool e)
+  {
+    prevent_removing_ = e;
+  }
+
+  bool GetPreventRemoving() const
+  {
+    return prevent_removing_;
+  }
+
 protected:
   virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr) override;
 
@@ -174,6 +188,8 @@ private:
 
   QPointF cached_node_pos_;
 
+  bool prevent_removing_;
+
 };
 
 }

app/widget/nodeview/nodeviewscene.cpp

@@ -200,7 +200,7 @@ int NodeViewScene::DetermineWeight(Node *n)
   int weight = 0;
 
   foreach (Node* i, inputs) {
-    if (i->GetRoutesTo(n) == 1) {
+    if (i->GetNumberOfRoutesTo(n) == 1) {
       weight += DetermineWeight(i);
     }
   }

app/window/mainwindow/mainwindow.cpp

@@ -754,9 +754,15 @@ void MainWindow::FocusedPanelChanged(PanelWidget *panel)
     // Signal project panel focus
     UpdateTitle();
     if (project->project()) {
-      QVector<Node*> context = {project->project()->root()};
-      node_panel_->SetGraph(project->project(), context);
-      node_panel_->SelectWithDependencies(context, false);
+      node_panel_->SetGraph(project->project(), {project->project()->root()});
+
+      bool center = true;
+      auto selected = project->SelectedItems();
+      if (selected.isEmpty()) {
+        selected.append(project->project()->root());
+        center = false;
+      }
+      node_panel_->Select(selected, center);
     }
   }
 }