nodeviewedge: use bezier curves instead of straight lines

app/widget/nodeview/nodeviewedge.cpp

@@ -20,6 +20,7 @@
 
 #include "nodeviewedge.h"
 
+#include <QApplication>
 #include <QDebug>
 #include <QGraphicsSceneMouseEvent>
 
@@ -28,10 +29,10 @@
 #include "nodeview.h"
 
 NodeViewEdge::NodeViewEdge(QGraphicsItem *parent) :
-  QGraphicsLineItem(parent),
+  QGraphicsPathItem(parent),
   edge_(nullptr),
-  connected_(false),
-  highlighted_(false)
+  color_group_(QPalette::Active),
+  color_role_(QPalette::Text)
 {
   // Ensures this UI object is drawn behind other objects
   setZValue(-1);
@@ -93,39 +94,44 @@ void NodeViewEdge::Adjust()
   input_point.setY(CalculateEdgeYPoint(input, edge_->input(), output));
 
   // Draw a line between the two
-  setLine(QLineF(
-            output_point,
-            input_point
-            ));
+  SetPoints(output_point, input_point);
 }
 
 void NodeViewEdge::SetConnected(bool c)
 {
-  connected_ = c;
-  update();
+  if (c) {
+    color_group_ = QPalette::Active;
+  } else {
+    color_group_ = QPalette::Disabled;
+  }
+
+  UpdatePen();
 }
 
 void NodeViewEdge::SetHighlighted(bool e)
 {
-  highlighted_ = e;
-  update();
+  if (e) {
+    color_role_ = QPalette::Highlight;
+  } else {
+    color_role_ = QPalette::Text;
+  }
+
+  UpdatePen();
 }
 
-void NodeViewEdge::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
+void NodeViewEdge::SetPoints(const QPointF &start, const QPointF &end)
 {
-  QPalette::ColorGroup color_group = QPalette::Active;
-  QPalette::ColorRole color_role = QPalette::Text;
-
-  if (highlighted_) {
-    color_role = QPalette::Highlight;
-  }
-
-  if (!connected_) {
-    color_group = QPalette::Disabled;
-  }
-
-  setPen(QPen(widget->palette().color(color_group, color_role), edge_width_));
-
-  QGraphicsLineItem::paint(painter, option, widget);
+  QPainterPath path;
+  float half_x = lerp(start.x(), end.x(), 0.5f);
+  path.moveTo(start);
+  path.cubicTo(QPointF(half_x, start.y()), QPointF(half_x, end.y()), end);
+  setPath(path);
+}
+
+void NodeViewEdge::UpdatePen()
+{
+  setPen(QPen(qApp->palette().color(color_group_, color_role_), edge_width_));
+
+  //update();
 }
 

app/widget/nodeview/nodeviewedge.h

@@ -21,7 +21,8 @@
 #ifndef NODEEDGEITEM_H
 #define NODEEDGEITEM_H
 
-#include <QGraphicsLineItem>
+#include <QGraphicsPathItem>
+#include <QPalette>
 
 #include "node/edge.h"
 
@@ -30,7 +31,7 @@
  *
  * A fairly simple line widget use to visualize a connection between two node parameters (a NodeEdge).
  */
-class NodeViewEdge : public QGraphicsLineItem
+class NodeViewEdge : public QGraphicsPathItem
 {
 public:
   NodeViewEdge(QGraphicsItem* parent = nullptr);
@@ -75,17 +76,21 @@ public:
    */
   void SetHighlighted(bool e);
 
-protected:
-  virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr) override;
+  /**
+   * @brief Set points to create curve from
+   */
+  void SetPoints(const QPointF& start, const QPointF& end);
 
 private:
+  void UpdatePen();
+
   NodeEdgePtr edge_;
 
   int edge_width_;
 
-  bool connected_;
+  QPalette::ColorGroup color_group_;
 
-  bool highlighted_;
+  QPalette::ColorRole color_role_;
 
 };
 

app/widget/nodeview/nodeviewitem.cpp

@@ -332,11 +332,13 @@ void NodeViewItem::mousePressEvent(QGraphicsSceneMouseEvent *event)
           // (we use the current coordinates because a complex formula is used for the line's coords if the opposing
           //  node is collapsed, therefore it's easier to just retrieve it from line itself)
           NodeViewEdge* existing_edge_ui = NodeView::EdgeToUIObject(scene(), edge);
-          QLineF existing_edge_line = existing_edge_ui->line();
-          if (existing_edge_ui->contains(existing_edge_line.p1())) {
-            dragging_edge_start_ = existing_edge_line.p1();
+          QPainterPath existing_edge_line = existing_edge_ui->path();
+          QPointF edge_start = existing_edge_line.pointAtPercent(0);
+          QPointF edge_end = existing_edge_line.pointAtPercent(1);
+          if (existing_edge_ui->contains(edge_start)) {
+            dragging_edge_start_ = edge_start;
           } else {
-            dragging_edge_start_ = existing_edge_line.p2();
+            dragging_edge_start_ = edge_end;
           }
 
 
@@ -429,7 +431,7 @@ void NodeViewItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
 
     dragging_edge_->SetConnected(drag_dest_param_ != nullptr);
 
-    dragging_edge_->setLine(QLineF(dragging_edge_start_, end_point));
+    dragging_edge_->SetPoints(dragging_edge_start_, end_point);
 
     return;
   }