Some minor but required fixes

example/main.dart

@@ -3,29 +3,29 @@ import "package:p5/p5.dart";
 import "sketch.dart";
 
 void main() {
-  runApp(new MyApp());
+  runApp(MyApp());
 }
 
 class MyHomePage extends StatefulWidget {
-  MyHomePage({Key? key, this.title}) : super(key: key);
+  const MyHomePage({Key? key, this.title}) : super(key: key);
   final String? title;
   @override
   _MyHomePageState createState() {
-    return new _MyHomePageState();
+    return _MyHomePageState();
   }
 }
 
 class MyApp extends StatelessWidget {
   // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
-    return new MaterialApp(
+    return MaterialApp(
       title: 'P5 Demo',
-      theme: new ThemeData(
+      theme: ThemeData(
         // This is the theme of your application.
         primarySwatch: Colors.blue,
       ),
-      home: new MyHomePage(title: 'P5 Demo Home Page'),
+      home: const MyHomePage(title: 'P5 Demo Home Page'),
     );
   }
 }
@@ -38,10 +38,10 @@ class _MyHomePageState extends State<MyHomePage>
   @override
   void initState() {
     super.initState();
-    sketch = new MySketch();
+    sketch = MySketch();
     // Need an animator to call the draw() method in the sketch continuously,
     // otherwise it will be called only when touch events are detected.
-    animator = new PAnimator(this);
+    animator = PAnimator(this);
     animator.addListener(() {
       setState(() {
         sketch!.redraw();
@@ -52,11 +52,11 @@ class _MyHomePageState extends State<MyHomePage>
 
   @override
   Widget build(BuildContext context) {
-    return new Scaffold(
-      appBar: new AppBar(title: new Text("P5 Draw!")),
+    return Scaffold(
+      appBar: AppBar(title: const Text("P5 Draw!")),
       backgroundColor: const Color.fromRGBO(200, 200, 200, 1.0),
-      body: new Center(
-        child: new PWidget(sketch),
+      body: Center(
+        child: PWidget(sketch),
       ),
     );
   }

example/sketch.dart

@@ -25,11 +25,11 @@ class MySketch extends PPainter {
   }
 
   void mousePressed() {
-    strokes.add([new PVector(mouseX, mouseY)]);
+    strokes.add([PVector(mouseX, mouseY)]);
   }
 
   void mouseDragged() {
     var stroke = strokes.last;
-    stroke.add(new PVector(mouseX, mouseY));
+    stroke.add(PVector(mouseX, mouseY));
   }
 }

lib/PApplet.dart

@@ -16,9 +16,7 @@ abstract class PApplet {
       return 0;
     }
 
-    if (internalRandom == null) {
-      internalRandom = math.Random();
-    }
+    internalRandom ??= math.Random();
 
     // for some reason (rounding error?) Math.random() * 3
     // can sometimes return '3' (once in ~30 million tries)

lib/PVector.dart

@@ -14,17 +14,13 @@ class PVector {
     return PVector(0, 0, 0);
   }
 
-  PVector(double x, double y, [double z = 0.0]) {
-    this.x = x;
-    this.y = y;
-    this.z = z;
-  }
+  PVector(this.x, this.y, [this.z = 0.0]);
 
   /// Subtract one vector from another and store in another vector
   /// @param target PVector in which to store the result
   static PVector? sub3(PVector v1, PVector v2, PVector? target) {
     if (target == null) {
-      target = new PVector(v1.x - v2.x, v1.y - v2.y, v1.z - v2.z);
+      target = PVector(v1.x - v2.x, v1.y - v2.y, v1.z - v2.z);
     } else {
       target.set(v1.x - v2.x, v1.y - v2.y, v1.z - v2.z);
     }
@@ -91,7 +87,7 @@ class PVector {
   /// @param target the target vector (if null, a new vector will be created)
   static PVector add3(PVector v1, PVector v2, PVector? target) {
     if (target == null) {
-      target = new PVector(v1.x + v2.x, v1.y + v2.y, v1.z + v2.z);
+      target = PVector(v1.x + v2.x, v1.y + v2.y, v1.z + v2.z);
     } else {
       target.set(v1.x + v2.x, v1.y + v2.y, v1.z + v2.z);
     }
@@ -224,7 +220,7 @@ class PVector {
   /// @param target PVector in which to store the result
   static PVector? div3(PVector v, double n, PVector? target) {
     if (target == null) {
-      target = new PVector(v.x / n, v.y / n, v.z / n);
+      target = PVector(v.x / n, v.y / n, v.z / n);
     } else {
       target.set(v.x / n, v.y / n, v.z / n);
     }
@@ -248,7 +244,7 @@ class PVector {
   /// @usage web_application
   /// @brief Get a copy of the vector
   PVector copy() {
-    return new PVector(x, y, z);
+    return PVector(x, y, z);
   }
 
   ///  @Deprecated use copy
@@ -353,7 +349,7 @@ class PVector {
   /// @return the PVector
   static PVector fromAngle_v2(double angle, PVector? target) {
     if (target == null) {
-      target = new PVector(math.cos(angle), math.sin(angle));
+      target = PVector(math.cos(angle), math.sin(angle));
     } else {
       target.set(math.cos(angle), math.sin(angle), 0);
     }

lib/p5.dart

@@ -21,16 +21,16 @@ class PWidget extends StatelessWidget {
 //    print("BUILDING WIDGET...");
 
 //    print(painter);
-    return new Container(
+    return Container(
       width: painter!.fillParent ? null : painter!.width.toDouble(),
       height: painter!.fillParent ? null : painter!.height.toDouble(),
-      constraints: painter!.fillParent ? BoxConstraints.expand() : null,
+      constraints: painter!.fillParent ? const BoxConstraints.expand() : null,
       //new
       margin: const EdgeInsets.all(0.0),
-      child: new ClipRect(
-          child: new CustomPaint(
+      child: ClipRect(
+          child: CustomPaint(
         painter: painter,
-        child: new GestureDetector(
+        child: GestureDetector(
           // The gesture detector needs to be declared here so it can
           // access the context from the CustomPaint, which allows to
           // transforms global positions into local positions relative
@@ -108,7 +108,7 @@ class PPainter extends ChangeNotifier implements CustomPainter {
   bool useStroke = true;
 
   var vertices = <Offset>[];
-  Path path = new Path();
+  Path path = Path();
   var shapeMode = PConstants.POLYGON;
 
   PPainter() {
@@ -117,6 +117,7 @@ class PPainter extends ChangeNotifier implements CustomPainter {
     redraw();
   }
 
+  @override
   bool? hitTest(Offset position) => null;
 
   @override
@@ -136,9 +137,9 @@ class PPainter extends ChangeNotifier implements CustomPainter {
       var rect = Offset.zero & size;
       rect = const Alignment(0.0, 0.0).inscribe(size, rect);
       return [
-        new CustomPainterSemantics(
+        CustomPainterSemantics(
           rect: rect,
-          properties: new SemanticsProperties(
+          properties: const SemanticsProperties(
             label: 'P5 Sketch',
             textDirection: TextDirection.ltr,
           ),
@@ -315,7 +316,7 @@ class PPainter extends ChangeNotifier implements CustomPainter {
   }
 
   void ellipse(double x, double y, double w, double h) {
-    final rect = new Offset(x - w / 2, y - h / 2) & new Size(w, h);
+    final rect = Offset(x - w / 2, y - h / 2) & Size(w, h);
     if (useFill) {
       paintCanvas.drawOval(rect, fillPaint);
     }
@@ -326,13 +327,13 @@ class PPainter extends ChangeNotifier implements CustomPainter {
 
   void line(double x1, double y1, double x2, double y2) {
     if (useStroke) {
-      paintCanvas.drawLine(new Offset(x1, y1), new Offset(x2, y2), strokePaint);
+      paintCanvas.drawLine(Offset(x1, y1), Offset(x2, y2), strokePaint);
     }
   }
 
   void point(num x, num y) {
     if (useStroke) {
-      var points = [new Offset(x as double, y as double)];
+      var points = [Offset(x as double, y as double)];
       paintCanvas.drawPoints(PointMode.points, points, strokePaint);
     }
   }
@@ -347,7 +348,7 @@ class PPainter extends ChangeNotifier implements CustomPainter {
   }
 
   void rect(double x, double y, double w, double h) {
-    final rect = new Offset(x, y) & new Size(w, h);
+    final rect = Offset(x, y) & Size(w, h);
     if (useFill) {
       paintCanvas.drawRect(rect, fillPaint);
     }
@@ -374,28 +375,26 @@ class PPainter extends ChangeNotifier implements CustomPainter {
   }
 
   void endShape([int mode = 0]) {
-    if (0 < vertices.length) {
-      if (shapeMode == PConstants.POINTS || shapeMode == PConstants.LINES) {
-        var vlist = <double>[];
-        for (var v in vertices) {
-          vlist.add(v.dx);
-          vlist.add(v.dy);
-        }
-        var raw = Float32List.fromList(vlist);
-        if (shapeMode == PConstants.POINTS) {
-          paintCanvas.drawRawPoints(PointMode.points, raw, strokePaint);
-        } else {
-          paintCanvas.drawRawPoints(PointMode.lines, raw, strokePaint);
-        }
+    if (shapeMode == PConstants.POINTS || shapeMode == PConstants.LINES) {
+      var vlist = <double>[];
+      for (var v in vertices) {
+        vlist.add(v.dx);
+        vlist.add(v.dy);
+      }
+      var raw = Float32List.fromList(vlist);
+      if (shapeMode == PConstants.POINTS) {
+        paintCanvas.drawRawPoints(PointMode.points, raw, strokePaint);
       } else {
-        path.reset();
-        path.addPolygon(vertices, mode == PConstants.CLOSE);
-        if (useFill) {
-          paintCanvas.drawPath(path, fillPaint);
-        }
-        if (useStroke) {
-          paintCanvas.drawPath(path, strokePaint);
-        }
+        paintCanvas.drawRawPoints(PointMode.lines, raw, strokePaint);
+      }
+    } else {
+      path.reset();
+      path.addPolygon(vertices, mode == PConstants.CLOSE);
+      if (useFill) {
+        paintCanvas.drawPath(path, fillPaint);
+      }
+      if (useStroke) {
+        paintCanvas.drawPath(path, strokePaint);
       }
     }
   }