This demo is a fuzzer of sorts, testing in particular our text layout system and painting.

packages/flutter/example/raw/mutating-dom.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import "dart:math" as math;
+import 'dart:sky' as sky;
+
+const kMaxIterations = 100;
+int peakCount = 1000; // this is the number that must be reached for us to start reporting the peak number of nodes in the tree each frame
+
+void report(String s) {
+  // uncomment this if you want to see what the mutations are
+  // print("$s\n");
+}
+
+sky.LayoutRoot layoutRoot = new sky.LayoutRoot();
+sky.Document document = new sky.Document();
+sky.Element root;
+math.Random random = new math.Random();
+
+bool pickThis(double odds) {
+  return random.nextDouble() < odds;
+}
+
+String generateCharacter(int min, int max) {
+  String result = new String.fromCharCode(random.nextInt(max)+min);
+  report("generated character: '$result'");
+  return result;
+}
+
+String colorToCSSString(sky.Color color) {
+  return 'rgba(${color.red}, ${color.green}, ${color.blue}, ${color.alpha / 255.0})';
+}
+
+void doFrame(double timeStamp) {
+  // mutate the DOM randomly
+  int iterationsLeft = kMaxIterations;
+  sky.Node node = root;
+  sky.Node other = null;
+  while (node != null && iterationsLeft > 0) {
+    iterationsLeft -= 1;
+    if (node is sky.Element && pickThis(0.4)) {
+      node = (node as sky.Element).firstChild;
+    } else if (node.nextSibling != null && pickThis(0.5)) {
+      node = node.nextSibling;
+    } else if (other == null && node != root && pickThis(0.1)) {
+      other = node;
+      node = root;
+    } else if (node != root && other != null && pickThis(0.1)) {
+      report("insertBefore()");
+      node.insertBefore([other]);
+      break;
+    } else if (pickThis(0.001)) {
+      report("remove()");
+      node.remove();
+    } else if (node is sky.Element) {
+      if (pickThis(0.1)) {
+        report("appending a new text node (ASCII)");
+        node.appendChild(document.createText(generateCharacter(0x20, 0x7F)));
+        break;
+      } else if (pickThis(0.05)) {
+        report("appending a new text node (Latin1)");
+        node.appendChild(document.createText(generateCharacter(0x20, 0xFF)));
+        break;
+      } else if (pickThis(0.025)) {
+        report("appending a new text node (BMP)");
+        node.appendChild(document.createText(generateCharacter(0x20, 0xFFFF)));
+        break;
+      } else if (pickThis(0.0125)) {
+        report("appending a new text node (Unicode)");
+        node.appendChild(document.createText(generateCharacter(0x20, 0x10FFFF)));
+        break;
+      } else if (pickThis(0.1)) {
+        report("appending a new Element");
+        node.appendChild(document.createElement('t'));
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: color");
+        node.style['color'] = colorToCSSString(new sky.Color(random.nextInt(0xFFFFFFFF) | 0xC0808080));
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: font-size");
+        node.style['font-size'] = "${random.nextDouble() * 48.0}px";
+        break;
+      } else if (pickThis(0.2)) {
+        report("styling: font-weight");
+        node.style['font-weight'] = "${random.nextInt(8)+1}00";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: line-height, dynamic");
+        node.style['line-height'] = "${random.nextDouble()*1.5}";
+        break;
+      } else if (pickThis(0.001)) {
+        report("styling: line-height, fixed");
+        node.style['line-height'] = "${random.nextDouble()*1.5}px";
+        break;
+      } else if (pickThis(0.025)) {
+        report("styling: font-style italic");
+        node.style['font-style'] = "italic";
+        break;
+      } else if (pickThis(0.05)) {
+        report("styling: font-style normal");
+        node.style['font-style'] = "normal";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: text-decoration");
+        node.style['text-decoration-line'] = "none";
+        break;
+      } else if (pickThis(0.01)) {
+        report("styling: text-decoration");
+        node.style['text-decoration-line'] = "underline";
+        break;
+      } else if (pickThis(0.01)) {
+        report("styling: text-decoration");
+        node.style['text-decoration-line'] = "overline";
+        break;
+      } else if (pickThis(0.01)) {
+        report("styling: text-decoration");
+        node.style['text-decoration-line'] = "underline overline";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: text-decoration-style: inherit");
+        node.style['text-decoration-style'] = "inherit";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: text-decoration-style: solid");
+        node.style['text-decoration-style'] = "solid";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: text-decoration-style: double");
+        node.style['text-decoration-style'] = "double";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: text-decoration-style: dotted");
+        node.style['text-decoration-style'] = "dotted";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: text-decoration-style: dashed");
+        node.style['text-decoration-style'] = "dashed";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: text-decoration-style: wavy");
+        node.style['text-decoration-style'] = "wavy";
+        break;
+      } else if (pickThis(0.1)) {
+        report("styling: text-decoration-color");
+        node.style['text-decoration-color'] = colorToCSSString(new sky.Color(random.nextInt(0xFFFFFFFF)));
+        break;
+      }
+    } else {
+      assert(node is sky.Text); // 
+      if (pickThis(0.1)) {
+        report("appending a new text node (ASCII)");
+        node.appendData(generateCharacter(0x20, 0x7F));
+        break;
+      } else if (pickThis(0.05)) {
+        report("appending a new text node (Latin1)");
+        node.appendData(generateCharacter(0x20, 0xFF));
+        break;
+      } else if (pickThis(0.025)) {
+        report("appending a new text node (BMP)");
+        node.appendData(generateCharacter(0x20, 0xFFFF));
+        break;
+      } else if (pickThis(0.0125)) {
+        report("appending a new text node (Unicode)");
+        node.appendData(generateCharacter(0x20, 0x10FFFF));
+        break;
+      } else if (node.length > 1 && pickThis(0.1)) {
+        report("deleting character from Text node");
+        node.deleteData(random.nextInt(node.length), 1);
+        break;
+      }
+    }
+  }
+
+  report("counting...");
+  node = root;
+  int count = 1;
+  while (node != null) {
+    if (node is sky.Element && node.firstChild != null) {
+      node = node.firstChild;
+      count += 1;
+    } else {
+      while (node != null && node.nextSibling == null)
+        node = node.parentNode;
+      if (node != null && node.nextSibling != null) {
+        node = node.nextSibling;
+        count += 1;
+      }
+    }
+  }
+  report("node count: $count\r");
+  if (count > peakCount) {
+    peakCount = count;
+    print("peak node count so far: $count\r");
+  }
+
+  // draw the result
+  report("recording...");
+  sky.PictureRecorder recorder = new sky.PictureRecorder();
+  sky.Canvas canvas = new sky.Canvas(recorder, new sky.Rect.fromLTWH(0.0, 0.0, sky.view.width, sky.view.height));
+  layoutRoot.maxWidth = sky.view.width;
+  layoutRoot.layout();
+  layoutRoot.paint(canvas);
+  report("painting...");
+  sky.view.picture = recorder.endRecording();
+  sky.view.scheduleFrame();
+}
+
+void main() {
+  root = document.createElement('p');
+  root.style['display'] = 'paragraph';
+  root.style['color'] = '#FFFFFF';
+  layoutRoot.rootElement = root;
+  sky.view.setFrameCallback(doFrame);
+  sky.view.scheduleFrame();
+}