packages/flutter/lib/src/rendering/view.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:developer';
import 'dart:io' show Platform;
import 'dart:ui' as ui show Scene, SceneBuilder, window;

import 'package:flutter/foundation.dart';
import 'package:vector_math/vector_math_64.dart';

import 'binding.dart';
import 'box.dart';
import 'debug.dart';
import 'layer.dart';
import 'object.dart';

/// The layout constraints for the root render object.
@immutable
class ViewConfiguration {
  /// Creates a view configuration.
  ///
  /// By default, the view has zero [size] and a [devicePixelRatio] of 1.0.
  const ViewConfiguration({
    this.size = Size.zero,
    this.devicePixelRatio = 1.0,
  });

  /// The size of the output surface.
  final Size size;

  /// The pixel density of the output surface.
  final double devicePixelRatio;

  /// Creates a transformation matrix that applies the [devicePixelRatio].
  Matrix4 toMatrix() {
    return new Matrix4.diagonal3Values(devicePixelRatio, devicePixelRatio, 1.0);
  }

  @override
  String toString() => '$size at ${devicePixelRatio}x';
}

/// The root of the render tree.
///
/// The view represents the total output surface of the render tree and handles
/// bootstrapping the rendering pipeline. The view has a unique child
/// [RenderBox], which is required to fill the entire output surface.
class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox> {
  /// Creates the root of the render tree.
  ///
  /// Typically created by the binding (e.g., [RendererBinding]).
  ///
  /// The [configuration] must not be null.
  RenderView({
    RenderBox child,
    @required ViewConfiguration configuration,
  }) : assert(configuration != null),
       _configuration = configuration {
    this.child = child;
  }

  /// The current layout size of the view.
  Size get size => _size;
  Size _size = Size.zero;

  /// The constraints used for the root layout.
  ViewConfiguration get configuration => _configuration;
  ViewConfiguration _configuration;
  /// The configuration is initially set by the `configuration` argument
  /// passed to the constructor.
  ///
  /// Always call [scheduleInitialFrame] before changing the configuration.
  set configuration(ViewConfiguration value) {
    assert(value != null);
    if (configuration == value)
      return;
    _configuration = value;
    replaceRootLayer(_updateMatricesAndCreateNewRootLayer());
    assert(_rootTransform != null);
    markNeedsLayout();
  }

  /// Bootstrap the rendering pipeline by scheduling the first frame.
  ///
  /// This should only be called once, and must be called before changing
  /// [configuration]. It is typically called immediately after calling the
  /// constructor.
  void scheduleInitialFrame() {
    assert(owner != null);
    assert(_rootTransform == null);
    scheduleInitialLayout();
    scheduleInitialPaint(_updateMatricesAndCreateNewRootLayer());
    assert(_rootTransform != null);
    owner.requestVisualUpdate();
  }

  Matrix4 _rootTransform;

  Layer _updateMatricesAndCreateNewRootLayer() {
    _rootTransform = configuration.toMatrix();
    final ContainerLayer rootLayer = new TransformLayer(transform: _rootTransform);
    rootLayer.attach(this);
    assert(_rootTransform != null);
    return rootLayer;
  }

  // We never call layout() on this class, so this should never get
  // checked. (This class is laid out using scheduleInitialLayout().)
  @override
  void debugAssertDoesMeetConstraints() { assert(false); }

  @override
  void performResize() {
    assert(false);
  }

  @override
  void performLayout() {
    assert(_rootTransform != null);
    _size = configuration.size;
    assert(_size.isFinite);

    if (child != null)
      child.layout(new BoxConstraints.tight(_size));
  }

  @override
  void rotate({ int oldAngle, int newAngle, Duration time }) {
    assert(false); // nobody tells the screen to rotate, the whole rotate() dance is started from our performResize()
  }

  /// Determines the set of render objects located at the given position.
  ///
  /// Returns true if the given point is contained in this render object or one
  /// of its descendants. Adds any render objects that contain the point to the
  /// given hit test result.
  ///
  /// The [position] argument is in the coordinate system of the render view,
  /// which is to say, in logical pixels. This is not necessarily the same
  /// coordinate system as that expected by the root [Layer], which will
  /// normally be in physical (device) pixels.
  bool hitTest(HitTestResult result, { Offset position }) {
    if (child != null)
      child.hitTest(result, position: position);
    result.add(new HitTestEntry(this));
    return true;
  }

  @override
  bool get isRepaintBoundary => true;

  @override
  void paint(PaintingContext context, Offset offset) {
    if (child != null)
      context.paintChild(child, offset);
  }

  @override
  void applyPaintTransform(RenderBox child, Matrix4 transform) {
    assert(_rootTransform != null);
    transform.multiply(_rootTransform);
    super.applyPaintTransform(child, transform);
  }

  /// Uploads the composited layer tree to the engine.
  ///
  /// Actually causes the output of the rendering pipeline to appear on screen.
  void compositeFrame() {
    Timeline.startSync('Compositing', arguments: timelineWhitelistArguments);
    try {
      final ui.SceneBuilder builder = new ui.SceneBuilder();
      layer.addToScene(builder, Offset.zero);
      final ui.Scene scene = builder.build();
      ui.window.render(scene);
      scene.dispose();
      assert(() {
        if (debugRepaintRainbowEnabled || debugRepaintTextRainbowEnabled)
          debugCurrentRepaintColor = debugCurrentRepaintColor.withHue(debugCurrentRepaintColor.hue + 2.0);
        return true;
      }());
    } finally {
      Timeline.finishSync();
    }
  }

  @override
  Rect get paintBounds => Offset.zero & (size * configuration.devicePixelRatio);

  @override
  Rect get semanticBounds {
    assert(_rootTransform != null);
    return MatrixUtils.transformRect(_rootTransform, Offset.zero & size);
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    // call to ${super.debugFillProperties(description)} is omitted because the
    // root superclasses don't include any interesting information for this
    // class
    assert(() {
      properties.add(new DiagnosticsNode.message('debug mode enabled - ${Platform.operatingSystem}'));
      return true;
    }());
    properties.add(new DiagnosticsProperty<Size>('window size', ui.window.physicalSize, tooltip: 'in physical pixels'));
    properties.add(new DoubleProperty('device pixel ratio', ui.window.devicePixelRatio, tooltip: 'physical pixels per logical pixel'));
    properties.add(new DiagnosticsProperty<ViewConfiguration>('configuration', configuration, tooltip: 'in logical pixels'));
    if (ui.window.semanticsEnabled)
      properties.add(new DiagnosticsNode.message('semantics enabled'));
  }
}