pointer event

https://github.com/kyorohiro/hello_skyengine/tree/master/dartui_event

// following code is checked in 2016/01/13
import 'dart:ui' as ui;
import 'package:vector_math/vector_math_64.dart';
import 'dart:typed_data';
import 'package:mojo/bindings.dart' as bindings;
import 'package:mojo/core.dart' as core;
import 'package:sky_services/pointer/pointer.mojom.dart';

// ex 3:4 game screen
double stageWidth = 800.0;
double stageHeight = 600.0;
ui.Rect stageSize = new ui.Rect.fromLTWH(0.0, 0.0, stageWidth, stageHeight);

//
//
double widthPaddingless = 0.0;
double heightPaddingless = 0.0;
double stageRatio = 0.0;
double stageTop = ui.window.padding.top;
double stageLeft = ui.window.padding.left + (widthPaddingless - stageWidth * stageRatio) / 2.0;

//
//
Map<int, PointerInfo> pointerInfos = {};

void onPaint(Duration timeStamp) {
  ui.PictureRecorder recorder = new ui.PictureRecorder();
  ui.Canvas canvas = new ui.Canvas(recorder, stageSize);

  //
  for (PointerInfo i in pointerInfos.values) {
    ui.Paint paint = new ui.Paint();
    paint.color = new ui.Color.fromARGB(0xff, 0xff, 0xaa, 0x77);
    double size = i.pressure * 100;
    ui.Rect drawRectSize = new ui.Rect.fromLTWH(i.x - size / 2.0, i.y - size / 2.0, size, size);
    canvas.drawRect(drawRectSize, paint);
  }
  ui.Picture picture = recorder.endRecording();
  ui.window.render(createScene(picture));
}

/*
void onEvent(ui.Event event) {
  if (event is ui.PointerEvent) {
    onPointerEvent(event);
  }
  if (event is ui.KeyboardEvent) {
    onKeyboardEvent(event);
  }
  if (event is ui.WheelEvent) {
    onWheelEvent(event);
  }
  ui.window.scheduleFrame();
}
*/
void handlePointerPacket(ByteData serializedPacket) {
  bindings.Message message = new bindings.Message(
      serializedPacket, <core.MojoHandle>[], serializedPacket.lengthInBytes, 0);
  PointerPacket packet = PointerPacket.deserialize(message);

  for (Pointer pointer in packet.pointers) {
    onPointerEvent(pointer);
  }
  ui.window.scheduleFrame();
}

void onPointerEvent(Pointer event) {
  if (!pointerInfos.containsKey(event.pointer)) {
    pointerInfos[event.pointer] = new PointerInfo()
      ..x = event.x - stageLeft
      ..y = event.y - stageTop;
  }

  pointerInfos[event.pointer].x = (event.x / stageRatio) - stageLeft;
  pointerInfos[event.pointer].y = (event.y / stageRatio) - stageTop;
  pointerInfos[event.pointer].pressure = event.pressure / event.pressureMax;

  switch (event.type) {
    case PointerType.UP:
      pointerInfos.remove(event.pointer);
      break;
    case PointerType.CANCEL:
      pointerInfos.clear();
      break;
  }
}

/*
void onKeyboardEvent(ui.KeyboardEvent event) {}
void onWheelEvent(ui.WheelEvent event) {}
*/
void main() {
  update();
  ui.window.onBeginFrame = onPaint;
  ui.window.onMetricsChanged = () {
    update();
    ui.window.scheduleFrame();
  };
  ui.window.onPointerPacket = handlePointerPacket;
//  ui.window.onEvent = onEvent;
  ui.window.scheduleFrame();
}

class PointerInfo {
  double x = 0.0;
  double y = 0.0;
  double pressure = 0.0;
}

void update() {
  widthPaddingless =
      ui.window.size.width - ui.window.padding.left - ui.window.padding.right;
  heightPaddingless =
      ui.window.size.height - ui.window.padding.top - ui.window.padding.bottom;
  double rw = widthPaddingless / stageWidth;
  double rh = heightPaddingless / stageHeight;
  stageRatio = (rw < rh ? rw : rh);
  stageTop = ui.window.padding.top;
  stageLeft = ui.window.padding.left +
      (widthPaddingless - stageWidth * stageRatio) / 2.0;
}

ui.Scene createScene(ui.Picture picture) {
  ui.Rect sceneBounds = new ui.Rect.fromLTWH(
      0.0,
      0.0,
      ui.window.size.width * ui.window.devicePixelRatio,
      ui.window.size.height * ui.window.devicePixelRatio);

  Matrix4 mat = new Matrix4.identity();
  mat.translate(stageLeft * ui.window.devicePixelRatio, stageTop * ui.window.devicePixelRatio);
  mat.scale(stageRatio * ui.window.devicePixelRatio, stageRatio * ui.window.devicePixelRatio, 1.0);

  ui.SceneBuilder sceneBuilder = new ui.SceneBuilder(sceneBounds);
  sceneBuilder.pushTransform(mat.storage);
  sceneBuilder.pushClipRect(stageSize);
  sceneBuilder.addPicture(ui.Offset.zero, picture, stageSize);
  sceneBuilder.pop();
  sceneBuilder.pop();
  return sceneBuilder.build();
}