animated_size.dart 11.2 KB
Newer Older
Ian Hickson's avatar
Ian Hickson committed
1
// Copyright 2014 The Flutter Authors. All rights reserved.
2 3 4 5
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/animation.dart';
6
import 'package:flutter/foundation.dart';
7
import 'package:flutter/scheduler.dart';
8 9

import 'box.dart';
10
import 'layer.dart';
11 12 13
import 'object.dart';
import 'shifted_box.dart';

14 15 16 17 18 19
/// A [RenderAnimatedSize] can be in exactly one of these states.
@visibleForTesting
enum RenderAnimatedSizeState {
  /// The initial state, when we do not yet know what the starting and target
  /// sizes are to animate.
  ///
20
  /// The next state is [stable].
21 22 23 24 25
  start,

  /// At this state the child's size is assumed to be stable and we are either
  /// animating, or waiting for the child's size to change.
  ///
26 27
  /// If the child's size changes, the state will become [changed]. Otherwise,
  /// it remains [stable].
28 29 30 31 32
  stable,

  /// At this state we know that the child has changed once after being assumed
  /// [stable].
  ///
33
  /// The next state will be one of:
34
  ///
35 36 37 38 39
  /// * [stable] if the child's size stabilized immediately. This is a signal
  ///   for the render object to begin animating the size towards the child's new
  ///   size.
  ///
  /// * [unstable] if the child's size continues to change.
40 41
  changed,

42 43
  /// At this state the child's size is assumed to be unstable (changing each
  /// frame).
44
  ///
45 46
  /// Instead of chasing the child's size in this state, the render object
  /// tightly tracks the child's size until it stabilizes.
47
  ///
48 49 50
  /// The render object remains in this state until a frame where the child's
  /// size remains the same as the previous frame. At that time, the next state
  /// is [stable].
51 52 53
  unstable,
}

54
/// A render object that animates its size to its child's size over a given
55 56 57 58 59
/// [duration] and with a given [curve]. If the child's size itself animates
/// (i.e. if it changes size two frames in a row, as opposed to abruptly
/// changing size in one frame then remaining that size in subsequent frames),
/// this render object sizes itself to fit the child instead of animating
/// itself.
60
///
61 62
/// When the child overflows the current animated size of this render object, it
/// is clipped.
63 64
class RenderAnimatedSize extends RenderAligningShiftedBox {
  /// Creates a render object that animates its size to match its child.
65 66 67
  /// The [duration] and [curve] arguments define the animation.
  ///
  /// The [alignment] argument is used to align the child when the parent is not
68 69
  /// (yet) the same size as the child.
  ///
70 71 72 73 74 75 76
  /// The [duration] is required.
  ///
  /// The [vsync] should specify a [TickerProvider] for the animation
  /// controller.
  ///
  /// The arguments [duration], [curve], [alignment], and [vsync] must
  /// not be null.
77
  RenderAnimatedSize({
78 79 80
    required TickerProvider vsync,
    required Duration duration,
    Duration? reverseDuration,
81
    Curve curve = Curves.linear,
82 83 84
    super.alignment,
    super.textDirection,
    super.child,
85
    Clip clipBehavior = Clip.hardEdge,
86 87 88
  }) : assert(vsync != null),
       assert(duration != null),
       assert(curve != null),
89
       assert(clipBehavior != null),
90
       _vsync = vsync,
91
       _clipBehavior = clipBehavior {
92
    _controller = AnimationController(
93 94
      vsync: vsync,
      duration: duration,
95
      reverseDuration: reverseDuration,
96 97 98 99
    )..addListener(() {
      if (_controller.value != _lastValue)
        markNeedsLayout();
    });
100
    _animation = CurvedAnimation(
101
      parent: _controller,
102
      curve: curve,
103 104 105
    );
  }

106 107
  late final AnimationController _controller;
  late final CurvedAnimation _animation;
108
  final SizeTween _sizeTween = SizeTween();
109 110
  late bool _hasVisualOverflow;
  double? _lastValue;
111

112 113 114 115 116 117 118
  /// The state this size animation is in.
  ///
  /// See [RenderAnimatedSizeState] for possible states.
  @visibleForTesting
  RenderAnimatedSizeState get state => _state;
  RenderAnimatedSizeState _state = RenderAnimatedSizeState.start;

119
  /// The duration of the animation.
120
  Duration get duration => _controller.duration!;
121 122 123 124 125 126 127
  set duration(Duration value) {
    assert(value != null);
    if (value == _controller.duration)
      return;
    _controller.duration = value;
  }

128
  /// The duration of the animation when running in reverse.
129 130
  Duration? get reverseDuration => _controller.reverseDuration;
  set reverseDuration(Duration? value) {
131 132 133 134 135
    if (value == _controller.reverseDuration)
      return;
    _controller.reverseDuration = value;
  }

136 137 138 139 140 141 142 143 144
  /// The curve of the animation.
  Curve get curve => _animation.curve;
  set curve(Curve value) {
    assert(value != null);
    if (value == _animation.curve)
      return;
    _animation.curve = value;
  }

145
  /// {@macro flutter.material.Material.clipBehavior}
146 147 148 149 150 151 152 153 154 155 156 157 158
  ///
  /// Defaults to [Clip.hardEdge], and must not be null.
  Clip get clipBehavior => _clipBehavior;
  Clip _clipBehavior = Clip.hardEdge;
  set clipBehavior(Clip value) {
    assert(value != null);
    if (value != _clipBehavior) {
      _clipBehavior = value;
      markNeedsPaint();
      markNeedsSemanticsUpdate();
    }
  }

159 160 161 162 163 164
  /// Whether the size is being currently animated towards the child's size.
  ///
  /// See [RenderAnimatedSizeState] for situations when we may not be animating
  /// the size.
  bool get isAnimating => _controller.isAnimating;

165 166 167 168 169 170 171 172 173 174 175
  /// The [TickerProvider] for the [AnimationController] that runs the animation.
  TickerProvider get vsync => _vsync;
  TickerProvider _vsync;
  set vsync(TickerProvider value) {
    assert(value != null);
    if (value == _vsync)
      return;
    _vsync = value;
    _controller.resync(vsync);
  }

176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
  @override
  void attach(PipelineOwner owner) {
    super.attach(owner);
    switch (state) {
      case RenderAnimatedSizeState.start:
      case RenderAnimatedSizeState.stable:
        break;
      case RenderAnimatedSizeState.changed:
      case RenderAnimatedSizeState.unstable:
        // Call markNeedsLayout in case the RenderObject isn't marked dirty
        // already, to resume interrupted resizing animation.
        markNeedsLayout();
        break;
    }
  }

192 193 194 195 196 197
  @override
  void detach() {
    _controller.stop();
    super.detach();
  }

198
  Size? get _animatedSize {
199 200 201 202 203 204 205
    return _sizeTween.evaluate(_animation);
  }

  @override
  void performLayout() {
    _lastValue = _controller.value;
    _hasVisualOverflow = false;
206
    final BoxConstraints constraints = this.constraints;
207 208
    if (child == null || constraints.isTight) {
      _controller.stop();
209
      size = _sizeTween.begin = _sizeTween.end = constraints.smallest;
210 211
      _state = RenderAnimatedSizeState.start;
      child?.layout(constraints);
212 213 214
      return;
    }

215
    child!.layout(constraints, parentUsesSize: true);
216

217 218
    assert(_state != null);
    switch (_state) {
219 220 221 222 223 224 225 226 227 228 229 230
      case RenderAnimatedSizeState.start:
        _layoutStart();
        break;
      case RenderAnimatedSizeState.stable:
        _layoutStable();
        break;
      case RenderAnimatedSizeState.changed:
        _layoutChanged();
        break;
      case RenderAnimatedSizeState.unstable:
        _layoutUnstable();
        break;
231 232
    }

233
    size = constraints.constrain(_animatedSize!);
234 235
    alignChild();

236 237
    if (size.width < _sizeTween.end!.width ||
        size.height < _sizeTween.end!.height)
238 239 240
      _hasVisualOverflow = true;
  }

241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272
  @override
  Size computeDryLayout(BoxConstraints constraints) {
    if (child == null || constraints.isTight) {
      return constraints.smallest;
    }

    // This simplified version of performLayout only calculates the current
    // size without modifying global state. See performLayout for comments
    // explaining the rational behind the implementation.
    final Size childSize = child!.getDryLayout(constraints);
    assert(_state != null);
    switch (_state) {
      case RenderAnimatedSizeState.start:
        return constraints.constrain(childSize);
      case RenderAnimatedSizeState.stable:
        if (_sizeTween.end != childSize) {
          return constraints.constrain(size);
        } else if (_controller.value == _controller.upperBound) {
          return constraints.constrain(childSize);
        }
        break;
      case RenderAnimatedSizeState.unstable:
      case RenderAnimatedSizeState.changed:
        if (_sizeTween.end != childSize) {
          return constraints.constrain(childSize);
        }
        break;
    }

    return constraints.constrain(_animatedSize!);
  }

273 274 275 276 277 278 279 280 281 282
  void _restartAnimation() {
    _lastValue = 0.0;
    _controller.forward(from: 0.0);
  }

  /// Laying out the child for the first time.
  ///
  /// We have the initial size to animate from, but we do not have the target
  /// size to animate to, so we set both ends to child's size.
  void _layoutStart() {
283
    _sizeTween.begin = _sizeTween.end = debugAdoptSize(child!.size);
284 285 286 287 288 289 290 291 292
    _state = RenderAnimatedSizeState.stable;
  }

  /// At this state we're assuming the child size is stable and letting the
  /// animation run its course.
  ///
  /// If during animation the size of the child changes we restart the
  /// animation.
  void _layoutStable() {
293
    if (_sizeTween.end != child!.size) {
294
      _sizeTween.begin = size;
295
      _sizeTween.end = debugAdoptSize(child!.size);
296 297 298 299
      _restartAnimation();
      _state = RenderAnimatedSizeState.changed;
    } else if (_controller.value == _controller.upperBound) {
      // Animation finished. Reset target sizes.
300
      _sizeTween.begin = _sizeTween.end = debugAdoptSize(child!.size);
301 302
    } else if (!_controller.isAnimating) {
      _controller.forward(); // resume the animation after being detached
303 304 305 306 307 308 309 310 311 312
    }
  }

  /// This state indicates that the size of the child changed once after being
  /// considered stable.
  ///
  /// If the child stabilizes immediately, we go back to stable state. If it
  /// changes again, we match the child's size, restart animation and go to
  /// unstable state.
  void _layoutChanged() {
313
    if (_sizeTween.end != child!.size) {
314
      // Child size changed again. Match the child's size and restart animation.
315
      _sizeTween.begin = _sizeTween.end = debugAdoptSize(child!.size);
316 317 318 319 320
      _restartAnimation();
      _state = RenderAnimatedSizeState.unstable;
    } else {
      // Child size stabilized.
      _state = RenderAnimatedSizeState.stable;
321 322
      if (!_controller.isAnimating)
        _controller.forward(); // resume the animation after being detached
323 324 325 326 327 328 329
    }
  }

  /// The child's size is not stable.
  ///
  /// Continue tracking the child's size until is stabilizes.
  void _layoutUnstable() {
330
    if (_sizeTween.end != child!.size) {
331
      // Still unstable. Continue tracking the child.
332
      _sizeTween.begin = _sizeTween.end = debugAdoptSize(child!.size);
333 334 335 336 337 338 339 340
      _restartAnimation();
    } else {
      // Child size stabilized.
      _controller.stop();
      _state = RenderAnimatedSizeState.stable;
    }
  }

341 342
  @override
  void paint(PaintingContext context, Offset offset) {
343
    if (child != null && _hasVisualOverflow && clipBehavior != Clip.none) {
344
      final Rect rect = Offset.zero & size;
345
      _clipRectLayer.layer = context.pushClipRect(
346 347 348 349 350
        needsCompositing,
        offset,
        rect,
        super.paint,
        clipBehavior: clipBehavior,
351
        oldLayer: _clipRectLayer.layer,
352
      );
353
    } else {
354
      _clipRectLayer.layer = null;
355 356 357
      super.paint(context, offset);
    }
  }
358

359 360 361 362 363 364 365
  final LayerHandle<ClipRectLayer> _clipRectLayer = LayerHandle<ClipRectLayer>();

  @override
  void dispose() {
    _clipRectLayer.layer = null;
    super.dispose();
  }
366
}