From 4d3573da9888e5d243c730f20b412be9a98bbcca Mon Sep 17 00:00:00 2001
From: Vishesh Handa <me@vhanda.in>
Date: Sat, 26 Sep 2020 05:35:43 +0200
Subject: [PATCH] GraphView: Tap gestures - get the node position properly

Earlier this was only working as the global and local coordinates were
the same. Now that I've added a SafeArea that is no longer the case.
---
 lib/screens/graph_view.dart | 37 ++++++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/lib/screens/graph_view.dart b/lib/screens/graph_view.dart
index b30d42c7..2e5bf7d2 100644
--- a/lib/screens/graph_view.dart
+++ b/lib/screens/graph_view.dart
@@ -26,7 +26,7 @@ class _GraphViewScreenState extends State<GraphViewScreen> {
       return Container(width: 2500, height: 2500);
     }
 
-    return GraphView(graph);
+    return SafeArea(child: GraphView(graph));
   }
 }
 
@@ -51,6 +51,13 @@ class _GraphViewState extends State<GraphView> {
     });
   }
 
+  Offset _getLocationPosition(Offset globalPos) {
+    RenderBox graphViewRenderBox = context.findRenderObject();
+    assert(graphViewRenderBox != null);
+
+    return graphViewRenderBox.globalToLocal(globalPos);
+  }
+
   @override
   Widget build(BuildContext context) {
     var children = <Widget>[];
@@ -62,12 +69,20 @@ class _GraphViewState extends State<GraphView> {
         child: GestureDetector(
           child: NodeWidget(node, nodeSize),
           onPanStart: (details) {
-            node.x = details.globalPosition.dx;
-            node.y = details.globalPosition.dy;
+            var pos = _getLocationPosition(details.globalPosition);
+            node.x = pos.dx;
+            node.y = pos.dy;
             node.pressed = true;
 
+            if (node.y <= nodeSize / 2) {
+              node.y = nodeSize / 2;
+            }
+            if (node.x <= nodeSize / 2) {
+              node.x = nodeSize / 2;
+            }
+
             widget.graph.notify();
-            print("Pan start ${node.label} $details");
+            print("Pan start ${node.label} $pos");
           },
           onPanEnd: (DragEndDetails details) {
             print("Pan end ${node.label} $details");
@@ -75,11 +90,19 @@ class _GraphViewState extends State<GraphView> {
             widget.graph.notify();
           },
           onPanUpdate: (details) {
-            node.x = details.globalPosition.dx;
-            node.y = details.globalPosition.dy;
+            var pos = _getLocationPosition(details.globalPosition);
+            node.x = pos.dx;
+            node.y = pos.dy;
+
+            if (node.y <= nodeSize / 2) {
+              node.y = nodeSize / 2;
+            }
+            if (node.x <= nodeSize / 2) {
+              node.x = nodeSize / 2;
+            }
 
             widget.graph.notify();
-            print("Pan update ${node.label} ${details.globalPosition}");
+            print("Pan update ${node.label} $pos");
           },
         ),
         left: node.x - (nodeSize / 2),