From a7d7515ba730be0cef9e2b01b6f177bce437aad8 Mon Sep 17 00:00:00 2001
From: itsmattkc <itsmattkc@gmail.com>
Date: Tue, 27 Apr 2021 18:48:40 +1000
Subject: [PATCH] nodeview: allow dragging edges from their arrows

Fixes #1594
---
 app/widget/nodeview/nodeview.cpp     | 31 +++++++++++++++++++++-------
 app/widget/nodeview/nodeview.h       |  3 +++
 app/widget/nodeview/nodeviewedge.cpp |  6 +++++-
 app/widget/nodeview/nodeviewedge.h   |  7 +++++++
 4 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/app/widget/nodeview/nodeview.cpp b/app/widget/nodeview/nodeview.cpp
index 8f6f224c8..1b07d691e 100644
--- a/app/widget/nodeview/nodeview.cpp
+++ b/app/widget/nodeview/nodeview.cpp
@@ -363,9 +363,20 @@ void NodeView::mousePressEvent(QMouseEvent *event)
 {
   if (HandPress(event)) return;
 
-  if (event->button() == Qt::RightButton) {
-    QGraphicsItem* item = itemAt(event->pos());
+  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;
+    }
+  }
+
+  if (event->button() == Qt::RightButton) {
     if (!item || !item->isSelected()) {
       // Qt doesn't do this by default for some reason
       if (!(event->modifiers() & Qt::ShiftModifier)) {
@@ -380,11 +391,12 @@ void NodeView::mousePressEvent(QMouseEvent *event)
   }
 
   if (event->modifiers() & Qt::ControlModifier) {
-    NodeViewItem* item = dynamic_cast<NodeViewItem*>(itemAt(event->pos()));
-
-    if (item) {
+    NodeViewItem* node_item = dynamic_cast<NodeViewItem*>(item);
+    if (node_item) {
       create_edge_ = new NodeViewEdge();
-      create_edge_src_ = item;
+      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());
@@ -551,7 +563,10 @@ void NodeView::mouseReleaseEvent(QMouseEvent *event)
   if (HandRelease(event)) return;
 
   if (create_edge_) {
-    delete create_edge_;
+    if (!create_edge_already_exists_) {
+      delete create_edge_;
+    }
+
     create_edge_ = nullptr;
 
     if (create_edge_dst_) {
@@ -566,7 +581,7 @@ void NodeView::mouseReleaseEvent(QMouseEvent *event)
 
       if (create_edge_dst_input_.IsValid()) {
         // Make connection
-        Core::instance()->undo_stack()->push(new NodeEdgeAddCommand(create_edge_src_->GetNode(), create_edge_dst_input_));
+        Core::instance()->undo_stack()->push(new NodeEdgeAddCommand(NodeOutput(create_edge_src_->GetNode(), create_edge_src_output_), create_edge_dst_input_));
         create_edge_dst_input_.Reset();
       }
 
diff --git a/app/widget/nodeview/nodeview.h b/app/widget/nodeview/nodeview.h
index c654bf72b..e1edc1990 100644
--- a/app/widget/nodeview/nodeview.h
+++ b/app/widget/nodeview/nodeview.h
@@ -142,6 +142,7 @@ private:
 
   NodeViewEdge* create_edge_;
   NodeViewItem* create_edge_src_;
+  QString create_edge_src_output_;
   NodeViewItem* create_edge_dst_;
   NodeInput create_edge_dst_input_;
   bool create_edge_dst_temp_expanded_;
@@ -161,6 +162,8 @@ private:
 
   double scale_;
 
+  bool create_edge_already_exists_;
+
   static const double kMinimumScale;
 
 private slots:
diff --git a/app/widget/nodeview/nodeviewedge.cpp b/app/widget/nodeview/nodeviewedge.cpp
index 4d26fec0e..46357aa4e 100644
--- a/app/widget/nodeview/nodeviewedge.cpp
+++ b/app/widget/nodeview/nodeviewedge.cpp
@@ -33,10 +33,12 @@
 
 namespace olive {
 
+#define super QGraphicsPathItem
+
 NodeViewEdge::NodeViewEdge(const NodeOutput &output, const NodeInput &input,
                            NodeViewItem* from_item, NodeViewItem* to_item,
                            QGraphicsItem* parent) :
-  QGraphicsPathItem(parent),
+  super(parent),
   output_(output),
   input_(input),
   from_item_(from_item),
@@ -150,6 +152,8 @@ void NodeViewEdge::SetPoints(const QPointF &start, const QPointF &end, bool inpu
   arrow_points[3] = end;
 
   arrow_ = QPolygonF(arrow_points);
+  arrow_bounding_rect_ = arrow_.boundingRect();
+  arrow_bounding_rect_.adjust(-arrow_size_, -arrow_size_, arrow_size_, arrow_size_);
 }
 
 void NodeViewEdge::SetFlowDirection(NodeViewCommon::FlowDirection dir)
diff --git a/app/widget/nodeview/nodeviewedge.h b/app/widget/nodeview/nodeviewedge.h
index 6719349db..96ab31578 100644
--- a/app/widget/nodeview/nodeviewedge.h
+++ b/app/widget/nodeview/nodeviewedge.h
@@ -70,6 +70,11 @@ public:
     return to_item_;
   }
 
+  const QRectF arrow_bounding_rect() const
+  {
+    return arrow_bounding_rect_;
+  }
+
   void Adjust();
 
   /**
@@ -136,6 +141,8 @@ private:
 
   int arrow_size_;
 
+  QRectF arrow_bounding_rect_;
+
 };
 
 }