recalculate bounding rect of stroke when adding point

add eraser prototype functionality

lib/canvas/document_types.dart

@@ -3,6 +3,11 @@ import 'dart:ui';
 class Stroke {
   List<Point> points = <Point>[];
 
+  double _minx = double.infinity;
+  double _maxx = double.negativeInfinity;
+  double _miny = double.infinity;
+  double _maxy = double.negativeInfinity;
+
   @override
   String toString() {
     return 'Stroke{points: $points}';
@@ -10,6 +15,16 @@ class Stroke {
 
   void addPoint(Point point) {
     points.add(point);
+
+    // update bounding rect
+    if (point.point.dx < _minx) _minx = point.point.dx;
+    if (point.point.dx > _maxx) _maxx = point.point.dx;
+    if (point.point.dy < _miny) _miny = point.point.dy;
+    if (point.point.dy > _maxy) _maxy = point.point.dy;
+  }
+
+  Rect getBoundingRect() {
+    return Rect.fromPoints(Offset(_minx, _miny), Offset(_maxx, _maxy));
   }
 
   Stroke.fromPoints(this.points);

lib/canvas/drawing_page.dart

@@ -111,6 +111,27 @@ class _DrawingPageState extends State<DrawingPage> {
       return;
     }
 
+    // todo outsource this eraser pen
+    if (eraseractive) {
+      // todo dynamic eraser size
+      final eraserrect = Rect.fromCircle(center: pos, radius: 3);
+      for (final stroke in _strokes) {
+        // check if delete action was within bounding rect of stroke
+        if (stroke.getBoundingRect().contains(pos)) {
+          // check if eraser hit an point within its range
+          for (final pt in stroke.points) {
+            if (eraserrect.contains(pt.point)) {
+              setState(() {
+                _strokes = List.from(_strokes)..remove(stroke);
+              });
+              return;
+            }
+          }
+        }
+      }
+      return;
+    }
+
     if (allowDrawWithFinger || event.kind != PointerDeviceKind.touch) {
       final pts = _strokes.last.points;
 
@@ -134,8 +155,7 @@ class _DrawingPageState extends State<DrawingPage> {
   Widget _buildCanvas() {
     final size = MediaQuery.of(context).size;
 
-    return Scaffold(
-      body: Listener(
+    return Listener(
       behavior: HitTestBehavior.opaque,
       onPointerMove: (e) => _onPointerMove(e, size),
       onPointerSignal: (event) {
@@ -162,6 +182,8 @@ class _DrawingPageState extends State<DrawingPage> {
         }
       },
       onPointerUp: (event) {
+        if (eraseractive) return;
+
         if (allowDrawWithFinger || event.kind != PointerDeviceKind.touch) {
           if (_strokes.last.points.length <= 1) {
             // if the line consists only of one point (point) add endpoint as the same to allow drawing a line
@@ -200,7 +222,6 @@ class _DrawingPageState extends State<DrawingPage> {
           size: Size.infinite,
         ),
       ),
-      ),
     );
   }
 }