| 1 | // Copyright 2014 The Flutter Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | /// @docImport 'package:flutter/widgets.dart'; |
| 6 | /// |
| 7 | /// @docImport 'list_wheel_viewport.dart'; |
| 8 | /// @docImport 'sliver_fixed_extent_list.dart'; |
| 9 | /// @docImport 'sliver_grid.dart'; |
| 10 | /// @docImport 'sliver_list.dart'; |
| 11 | library; |
| 12 | |
| 13 | import 'dart:math' as math; |
| 14 | |
| 15 | import 'package:flutter/animation.dart'; |
| 16 | import 'package:flutter/foundation.dart'; |
| 17 | import 'package:flutter/semantics.dart'; |
| 18 | |
| 19 | import 'box.dart'; |
| 20 | import 'debug.dart'; |
| 21 | import 'layer.dart'; |
| 22 | import 'object.dart'; |
| 23 | import 'sliver.dart'; |
| 24 | import 'viewport_offset.dart'; |
| 25 | |
| 26 | /// The unit of measurement for a [Viewport.cacheExtent]. |
| 27 | enum CacheExtentStyle { |
| 28 | /// Treat the [Viewport.cacheExtent] as logical pixels. |
| 29 | pixel, |
| 30 | |
| 31 | /// Treat the [Viewport.cacheExtent] as a multiplier of the main axis extent. |
| 32 | viewport, |
| 33 | } |
| 34 | |
| 35 | /// An interface for render objects that are bigger on the inside. |
| 36 | /// |
| 37 | /// Some render objects, such as [RenderViewport], present a portion of their |
| 38 | /// content, which can be controlled by a [ViewportOffset]. This interface lets |
| 39 | /// the framework recognize such render objects and interact with them without |
| 40 | /// having specific knowledge of all the various types of viewports. |
| 41 | abstract interface class RenderAbstractViewport extends RenderObject { |
| 42 | /// Returns the [RenderAbstractViewport] that most tightly encloses the given |
| 43 | /// render object. |
| 44 | /// |
| 45 | /// If the object does not have a [RenderAbstractViewport] as an ancestor, |
| 46 | /// this function returns null. |
| 47 | /// |
| 48 | /// See also: |
| 49 | /// |
| 50 | /// * [RenderAbstractViewport.of], which is similar to this method, but |
| 51 | /// asserts if no [RenderAbstractViewport] ancestor is found. |
| 52 | static RenderAbstractViewport? maybeOf(RenderObject? object) { |
| 53 | while (object != null) { |
| 54 | if (object is RenderAbstractViewport) { |
| 55 | return object; |
| 56 | } |
| 57 | object = object.parent; |
| 58 | } |
| 59 | return null; |
| 60 | } |
| 61 | |
| 62 | /// Returns the [RenderAbstractViewport] that most tightly encloses the given |
| 63 | /// render object. |
| 64 | /// |
| 65 | /// If the object does not have a [RenderAbstractViewport] as an ancestor, |
| 66 | /// this function will assert in debug mode, and throw an exception in release |
| 67 | /// mode. |
| 68 | /// |
| 69 | /// See also: |
| 70 | /// |
| 71 | /// * [RenderAbstractViewport.maybeOf], which is similar to this method, but |
| 72 | /// returns null if no [RenderAbstractViewport] ancestor is found. |
| 73 | static RenderAbstractViewport of(RenderObject? object) { |
| 74 | final RenderAbstractViewport? viewport = maybeOf(object); |
| 75 | assert(() { |
| 76 | if (viewport == null) { |
| 77 | throw FlutterError( |
| 78 | 'RenderAbstractViewport.of() was called with a render object that was ' |
| 79 | 'not a descendant of a RenderAbstractViewport.\n' |
| 80 | 'No RenderAbstractViewport render object ancestor could be found starting ' |
| 81 | 'from the object that was passed to RenderAbstractViewport.of().\n' |
| 82 | 'The render object where the viewport search started was:\n' |
| 83 | '$object ', |
| 84 | ); |
| 85 | } |
| 86 | return true; |
| 87 | }()); |
| 88 | return viewport!; |
| 89 | } |
| 90 | |
| 91 | /// Returns the offset that would be needed to reveal the `target` |
| 92 | /// [RenderObject]. |
| 93 | /// |
| 94 | /// This is used by [RenderViewportBase.showInViewport], which is |
| 95 | /// itself used by [RenderObject.showOnScreen] for |
| 96 | /// [RenderViewportBase], which is in turn used by the semantics |
| 97 | /// system to implement scrolling for accessibility tools. |
| 98 | /// |
| 99 | /// The optional `rect` parameter describes which area of that `target` object |
| 100 | /// should be revealed in the viewport. If `rect` is null, the entire |
| 101 | /// `target` [RenderObject] (as defined by its [RenderObject.paintBounds]) |
| 102 | /// will be revealed. If `rect` is provided it has to be given in the |
| 103 | /// coordinate system of the `target` object. |
| 104 | /// |
| 105 | /// The `alignment` argument describes where the target should be positioned |
| 106 | /// after applying the returned offset. If `alignment` is 0.0, the child must |
| 107 | /// be positioned as close to the leading edge of the viewport as possible. If |
| 108 | /// `alignment` is 1.0, the child must be positioned as close to the trailing |
| 109 | /// edge of the viewport as possible. If `alignment` is 0.5, the child must be |
| 110 | /// positioned as close to the center of the viewport as possible. |
| 111 | /// |
| 112 | /// The `target` might not be a direct child of this viewport but it must be a |
| 113 | /// descendant of the viewport. Other viewports in between this viewport and |
| 114 | /// the `target` will not be adjusted. |
| 115 | /// |
| 116 | /// This method assumes that the content of the viewport moves linearly, i.e. |
| 117 | /// when the offset of the viewport is changed by x then `target` also moves |
| 118 | /// by x within the viewport. |
| 119 | /// |
| 120 | /// The optional [Axis] is used by |
| 121 | /// [RenderTwoDimensionalViewport.getOffsetToReveal] to |
| 122 | /// determine which of the two axes to compute an offset for. One dimensional |
| 123 | /// subclasses like [RenderViewportBase] and [RenderListWheelViewport] |
| 124 | /// will ignore the `axis` value if provided, since there is only one [Axis]. |
| 125 | /// |
| 126 | /// If the `axis` is omitted when called on [RenderTwoDimensionalViewport], |
| 127 | /// the [RenderTwoDimensionalViewport.mainAxis] is used. To reveal an object |
| 128 | /// properly in both axes, this method should be called for each [Axis] as the |
| 129 | /// returned [RevealedOffset.offset] only represents the offset of one of the |
| 130 | /// the two [ScrollPosition]s. |
| 131 | /// |
| 132 | /// See also: |
| 133 | /// |
| 134 | /// * [RevealedOffset], which describes the return value of this method. |
| 135 | RevealedOffset getOffsetToReveal(RenderObject target, double alignment, {Rect? rect, Axis? axis}); |
| 136 | |
| 137 | /// The default value for the cache extent of the viewport. |
| 138 | /// |
| 139 | /// This default assumes [CacheExtentStyle.pixel]. |
| 140 | /// |
| 141 | /// See also: |
| 142 | /// |
| 143 | /// * [RenderViewportBase.cacheExtent] for a definition of the cache extent. |
| 144 | static const double defaultCacheExtent = 250.0; |
| 145 | } |
| 146 | |
| 147 | /// Return value for [RenderAbstractViewport.getOffsetToReveal]. |
| 148 | /// |
| 149 | /// It indicates the [offset] required to reveal an element in a viewport and |
| 150 | /// the [rect] position said element would have in the viewport at that |
| 151 | /// [offset]. |
| 152 | class RevealedOffset { |
| 153 | /// Instantiates a return value for [RenderAbstractViewport.getOffsetToReveal]. |
| 154 | const RevealedOffset({required this.offset, required this.rect}); |
| 155 | |
| 156 | /// Offset for the viewport to reveal a specific element in the viewport. |
| 157 | /// |
| 158 | /// See also: |
| 159 | /// |
| 160 | /// * [RenderAbstractViewport.getOffsetToReveal], which calculates this |
| 161 | /// value for a specific element. |
| 162 | final double offset; |
| 163 | |
| 164 | /// The [Rect] in the outer coordinate system of the viewport at which the |
| 165 | /// to-be-revealed element would be located if the viewport's offset is set |
| 166 | /// to [offset]. |
| 167 | /// |
| 168 | /// A viewport usually has two coordinate systems and works as an adapter |
| 169 | /// between the two: |
| 170 | /// |
| 171 | /// The inner coordinate system has its origin at the top left corner of the |
| 172 | /// content that moves inside the viewport. The origin of this coordinate |
| 173 | /// system usually moves around relative to the leading edge of the viewport |
| 174 | /// when the viewport offset changes. |
| 175 | /// |
| 176 | /// The outer coordinate system has its origin at the top left corner of the |
| 177 | /// visible part of the viewport. This origin stays at the same position |
| 178 | /// regardless of the current viewport offset. |
| 179 | /// |
| 180 | /// In other words: [rect] describes where the revealed element would be |
| 181 | /// located relative to the top left corner of the visible part of the |
| 182 | /// viewport if the viewport's offset is set to [offset]. |
| 183 | /// |
| 184 | /// See also: |
| 185 | /// |
| 186 | /// * [RenderAbstractViewport.getOffsetToReveal], which calculates this |
| 187 | /// value for a specific element. |
| 188 | final Rect rect; |
| 189 | |
| 190 | /// Determines which provided leading or trailing edge of the viewport, as |
| 191 | /// [RevealedOffset]s, will be used for [RenderViewportBase.showInViewport] |
| 192 | /// accounting for the size and already visible portion of the [RenderObject] |
| 193 | /// that is being revealed. |
| 194 | /// |
| 195 | /// Also used by [RenderTwoDimensionalViewport.showInViewport] for each |
| 196 | /// horizontal and vertical [Axis]. |
| 197 | /// |
| 198 | /// If the target [RenderObject] is already fully visible, this will return |
| 199 | /// null. |
| 200 | static RevealedOffset? clampOffset({ |
| 201 | required RevealedOffset leadingEdgeOffset, |
| 202 | required RevealedOffset trailingEdgeOffset, |
| 203 | required double currentOffset, |
| 204 | }) { |
| 205 | // scrollOffset |
| 206 | // 0 +---------+ |
| 207 | // | | |
| 208 | // _ | | |
| 209 | // viewport position | | | |
| 210 | // with `descendant` at | | | _ |
| 211 | // trailing edge |_ | xxxxxxx | | viewport position |
| 212 | // | | | with `descendant` at |
| 213 | // | | _| leading edge |
| 214 | // | | |
| 215 | // 800 +---------+ |
| 216 | // |
| 217 | // `trailingEdgeOffset`: Distance from scrollOffset 0 to the start of the |
| 218 | // viewport on the left in image above. |
| 219 | // `leadingEdgeOffset`: Distance from scrollOffset 0 to the start of the |
| 220 | // viewport on the right in image above. |
| 221 | // |
| 222 | // The viewport position on the left is achieved by setting `offset.pixels` |
| 223 | // to `trailingEdgeOffset`, the one on the right by setting it to |
| 224 | // `leadingEdgeOffset`. |
| 225 | final bool inverted = leadingEdgeOffset.offset < trailingEdgeOffset.offset; |
| 226 | final RevealedOffset smaller; |
| 227 | final RevealedOffset larger; |
| 228 | (smaller, larger) = |
| 229 | inverted |
| 230 | ? (leadingEdgeOffset, trailingEdgeOffset) |
| 231 | : (trailingEdgeOffset, leadingEdgeOffset); |
| 232 | if (currentOffset > larger.offset) { |
| 233 | return larger; |
| 234 | } else if (currentOffset < smaller.offset) { |
| 235 | return smaller; |
| 236 | } else { |
| 237 | return null; |
| 238 | } |
| 239 | } |
| 240 | |
| 241 | @override |
| 242 | String toString() { |
| 243 | return '${objectRuntimeType(this, 'RevealedOffset')} (offset:$offset , rect:$rect )'; |
| 244 | } |
| 245 | } |
| 246 | |
| 247 | /// A base class for render objects that are bigger on the inside. |
| 248 | /// |
| 249 | /// This render object provides the shared code for render objects that host |
| 250 | /// [RenderSliver] render objects inside a [RenderBox]. The viewport establishes |
| 251 | /// an [axisDirection], which orients the sliver's coordinate system, which is |
| 252 | /// based on scroll offsets rather than Cartesian coordinates. |
| 253 | /// |
| 254 | /// The viewport also listens to an [offset], which determines the |
| 255 | /// [SliverConstraints.scrollOffset] input to the sliver layout protocol. |
| 256 | /// |
| 257 | /// Subclasses typically override [performLayout] and call |
| 258 | /// [layoutChildSequence], perhaps multiple times. |
| 259 | /// |
| 260 | /// See also: |
| 261 | /// |
| 262 | /// * [RenderSliver], which explains more about the Sliver protocol. |
| 263 | /// * [RenderBox], which explains more about the Box protocol. |
| 264 | /// * [RenderSliverToBoxAdapter], which allows a [RenderBox] object to be |
| 265 | /// placed inside a [RenderSliver] (the opposite of this class). |
| 266 | abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMixin<RenderSliver>> |
| 267 | extends RenderBox |
| 268 | with ContainerRenderObjectMixin<RenderSliver, ParentDataClass> |
| 269 | implements RenderAbstractViewport { |
| 270 | /// Initializes fields for subclasses. |
| 271 | /// |
| 272 | /// The [cacheExtent], if null, defaults to [RenderAbstractViewport.defaultCacheExtent]. |
| 273 | /// |
| 274 | /// The [cacheExtent] must be specified if [cacheExtentStyle] is not [CacheExtentStyle.pixel]. |
| 275 | RenderViewportBase({ |
| 276 | AxisDirection axisDirection = AxisDirection.down, |
| 277 | required AxisDirection crossAxisDirection, |
| 278 | required ViewportOffset offset, |
| 279 | double? cacheExtent, |
| 280 | CacheExtentStyle cacheExtentStyle = CacheExtentStyle.pixel, |
| 281 | Clip clipBehavior = Clip.hardEdge, |
| 282 | }) : assert(axisDirectionToAxis(axisDirection) != axisDirectionToAxis(crossAxisDirection)), |
| 283 | assert(cacheExtent != null || cacheExtentStyle == CacheExtentStyle.pixel), |
| 284 | _axisDirection = axisDirection, |
| 285 | _crossAxisDirection = crossAxisDirection, |
| 286 | _offset = offset, |
| 287 | _cacheExtent = cacheExtent ?? RenderAbstractViewport.defaultCacheExtent, |
| 288 | _cacheExtentStyle = cacheExtentStyle, |
| 289 | _clipBehavior = clipBehavior; |
| 290 | |
| 291 | /// Report the semantics of this node, for example for accessibility purposes. |
| 292 | /// |
| 293 | /// [RenderViewportBase] adds [RenderViewport.useTwoPaneSemantics] to the |
| 294 | /// provided [SemanticsConfiguration] to support children using |
| 295 | /// [RenderViewport.excludeFromScrolling]. |
| 296 | /// |
| 297 | /// This method should be overridden by subclasses that have interesting |
| 298 | /// semantic information. Overriding subclasses should call |
| 299 | /// `super.describeSemanticsConfiguration(config)` to ensure |
| 300 | /// [RenderViewport.useTwoPaneSemantics] is still added to `config`. |
| 301 | /// |
| 302 | /// See also: |
| 303 | /// |
| 304 | /// * [RenderObject.describeSemanticsConfiguration], for important |
| 305 | /// details about not mutating a [SemanticsConfiguration] out of context. |
| 306 | @override |
| 307 | void describeSemanticsConfiguration(SemanticsConfiguration config) { |
| 308 | super.describeSemanticsConfiguration(config); |
| 309 | |
| 310 | config.addTagForChildren(RenderViewport.useTwoPaneSemantics); |
| 311 | } |
| 312 | |
| 313 | @override |
| 314 | void visitChildrenForSemantics(RenderObjectVisitor visitor) { |
| 315 | childrenInPaintOrder |
| 316 | .where( |
| 317 | (RenderSliver sliver) => |
| 318 | sliver.geometry!.visible || |
| 319 | sliver.geometry!.cacheExtent > 0.0 || |
| 320 | sliver.ensureSemantics, |
| 321 | ) |
| 322 | .forEach(visitor); |
| 323 | } |
| 324 | |
| 325 | /// The direction in which the [SliverConstraints.scrollOffset] increases. |
| 326 | /// |
| 327 | /// For example, if the [axisDirection] is [AxisDirection.down], a scroll |
| 328 | /// offset of zero is at the top of the viewport and increases towards the |
| 329 | /// bottom of the viewport. |
| 330 | AxisDirection get axisDirection => _axisDirection; |
| 331 | AxisDirection _axisDirection; |
| 332 | set axisDirection(AxisDirection value) { |
| 333 | if (value == _axisDirection) { |
| 334 | return; |
| 335 | } |
| 336 | _axisDirection = value; |
| 337 | markNeedsLayout(); |
| 338 | } |
| 339 | |
| 340 | /// The direction in which child should be laid out in the cross axis. |
| 341 | /// |
| 342 | /// For example, if the [axisDirection] is [AxisDirection.down], this property |
| 343 | /// is typically [AxisDirection.left] if the ambient [TextDirection] is |
| 344 | /// [TextDirection.rtl] and [AxisDirection.right] if the ambient |
| 345 | /// [TextDirection] is [TextDirection.ltr]. |
| 346 | AxisDirection get crossAxisDirection => _crossAxisDirection; |
| 347 | AxisDirection _crossAxisDirection; |
| 348 | set crossAxisDirection(AxisDirection value) { |
| 349 | if (value == _crossAxisDirection) { |
| 350 | return; |
| 351 | } |
| 352 | _crossAxisDirection = value; |
| 353 | markNeedsLayout(); |
| 354 | } |
| 355 | |
| 356 | /// The axis along which the viewport scrolls. |
| 357 | /// |
| 358 | /// For example, if the [axisDirection] is [AxisDirection.down], then the |
| 359 | /// [axis] is [Axis.vertical] and the viewport scrolls vertically. |
| 360 | Axis get axis => axisDirectionToAxis(axisDirection); |
| 361 | |
| 362 | /// Which part of the content inside the viewport should be visible. |
| 363 | /// |
| 364 | /// The [ViewportOffset.pixels] value determines the scroll offset that the |
| 365 | /// viewport uses to select which part of its content to display. As the user |
| 366 | /// scrolls the viewport, this value changes, which changes the content that |
| 367 | /// is displayed. |
| 368 | ViewportOffset get offset => _offset; |
| 369 | ViewportOffset _offset; |
| 370 | set offset(ViewportOffset value) { |
| 371 | if (value == _offset) { |
| 372 | return; |
| 373 | } |
| 374 | if (attached) { |
| 375 | _offset.removeListener(markNeedsLayout); |
| 376 | } |
| 377 | _offset = value; |
| 378 | if (attached) { |
| 379 | _offset.addListener(markNeedsLayout); |
| 380 | } |
| 381 | // We need to go through layout even if the new offset has the same pixels |
| 382 | // value as the old offset so that we will apply our viewport and content |
| 383 | // dimensions. |
| 384 | markNeedsLayout(); |
| 385 | } |
| 386 | |
| 387 | // TODO(ianh): cacheExtent/cacheExtentStyle should be a single |
| 388 | // object that specifies both the scalar value and the unit, not a |
| 389 | // pair of independent setters. Changing that would allow a more |
| 390 | // rational API and would let us make the getter non-nullable. |
| 391 | |
| 392 | /// {@template flutter.rendering.RenderViewportBase.cacheExtent} |
| 393 | /// The viewport has an area before and after the visible area to cache items |
| 394 | /// that are about to become visible when the user scrolls. |
| 395 | /// |
| 396 | /// Items that fall in this cache area are laid out even though they are not |
| 397 | /// (yet) visible on screen. The [cacheExtent] describes how many pixels |
| 398 | /// the cache area extends before the leading edge and after the trailing edge |
| 399 | /// of the viewport. |
| 400 | /// |
| 401 | /// The total extent, which the viewport will try to cover with children, is |
| 402 | /// [cacheExtent] before the leading edge + extent of the main axis + |
| 403 | /// [cacheExtent] after the trailing edge. |
| 404 | /// |
| 405 | /// The cache area is also used to implement implicit accessibility scrolling |
| 406 | /// on iOS: When the accessibility focus moves from an item in the visible |
| 407 | /// viewport to an invisible item in the cache area, the framework will bring |
| 408 | /// that item into view with an (implicit) scroll action. |
| 409 | /// {@endtemplate} |
| 410 | /// |
| 411 | /// The getter can never return null, but the field is nullable |
| 412 | /// because the setter can be set to null to reset the value to |
| 413 | /// [RenderAbstractViewport.defaultCacheExtent] (in which case |
| 414 | /// [cacheExtentStyle] must be [CacheExtentStyle.pixel]). |
| 415 | /// |
| 416 | /// See also: |
| 417 | /// |
| 418 | /// * [cacheExtentStyle], which controls the units of the [cacheExtent]. |
| 419 | double? get cacheExtent => _cacheExtent; |
| 420 | double _cacheExtent; |
| 421 | set cacheExtent(double? value) { |
| 422 | value ??= RenderAbstractViewport.defaultCacheExtent; |
| 423 | if (value == _cacheExtent) { |
| 424 | return; |
| 425 | } |
| 426 | _cacheExtent = value; |
| 427 | markNeedsLayout(); |
| 428 | } |
| 429 | |
| 430 | /// This value is set during layout based on the [CacheExtentStyle]. |
| 431 | /// |
| 432 | /// When the style is [CacheExtentStyle.viewport], it is the main axis extent |
| 433 | /// of the viewport multiplied by the requested cache extent, which is still |
| 434 | /// expressed in pixels. |
| 435 | double? _calculatedCacheExtent; |
| 436 | |
| 437 | /// {@template flutter.rendering.RenderViewportBase.cacheExtentStyle} |
| 438 | /// Controls how the [cacheExtent] is interpreted. |
| 439 | /// |
| 440 | /// If set to [CacheExtentStyle.pixel], the [cacheExtent] will be |
| 441 | /// treated as a logical pixels, and the default [cacheExtent] is |
| 442 | /// [RenderAbstractViewport.defaultCacheExtent]. |
| 443 | /// |
| 444 | /// If set to [CacheExtentStyle.viewport], the [cacheExtent] will be |
| 445 | /// treated as a multiplier for the main axis extent of the |
| 446 | /// viewport. In this case there is no default [cacheExtent]; it |
| 447 | /// must be explicitly specified. |
| 448 | /// {@endtemplate} |
| 449 | /// |
| 450 | /// Changing the [cacheExtentStyle] without also changing the [cacheExtent] |
| 451 | /// is rarely the correct choice. |
| 452 | CacheExtentStyle get cacheExtentStyle => _cacheExtentStyle; |
| 453 | CacheExtentStyle _cacheExtentStyle; |
| 454 | set cacheExtentStyle(CacheExtentStyle value) { |
| 455 | if (value == _cacheExtentStyle) { |
| 456 | return; |
| 457 | } |
| 458 | _cacheExtentStyle = value; |
| 459 | markNeedsLayout(); |
| 460 | } |
| 461 | |
| 462 | /// {@macro flutter.material.Material.clipBehavior} |
| 463 | /// |
| 464 | /// Defaults to [Clip.hardEdge]. |
| 465 | Clip get clipBehavior => _clipBehavior; |
| 466 | Clip _clipBehavior = Clip.hardEdge; |
| 467 | set clipBehavior(Clip value) { |
| 468 | if (value != _clipBehavior) { |
| 469 | _clipBehavior = value; |
| 470 | markNeedsPaint(); |
| 471 | markNeedsSemanticsUpdate(); |
| 472 | } |
| 473 | } |
| 474 | |
| 475 | @override |
| 476 | void attach(PipelineOwner owner) { |
| 477 | super.attach(owner); |
| 478 | _offset.addListener(markNeedsLayout); |
| 479 | } |
| 480 | |
| 481 | @override |
| 482 | void detach() { |
| 483 | _offset.removeListener(markNeedsLayout); |
| 484 | super.detach(); |
| 485 | } |
| 486 | |
| 487 | /// Throws an exception saying that the object does not support returning |
| 488 | /// intrinsic dimensions if, in debug mode, we are not in the |
| 489 | /// [RenderObject.debugCheckingIntrinsics] mode. |
| 490 | /// |
| 491 | /// This is used by [computeMinIntrinsicWidth] et al because viewports do not |
| 492 | /// generally support returning intrinsic dimensions. See the discussion at |
| 493 | /// [computeMinIntrinsicWidth]. |
| 494 | @protected |
| 495 | bool debugThrowIfNotCheckingIntrinsics() { |
| 496 | assert(() { |
| 497 | if (!RenderObject.debugCheckingIntrinsics) { |
| 498 | assert(this is! RenderShrinkWrappingViewport); // it has its own message |
| 499 | throw FlutterError.fromParts(<DiagnosticsNode>[ |
| 500 | ErrorSummary('$runtimeType does not support returning intrinsic dimensions.'), |
| 501 | ErrorDescription( |
| 502 | 'Calculating the intrinsic dimensions would require instantiating every child of ' |
| 503 | 'the viewport, which defeats the point of viewports being lazy.', |
| 504 | ), |
| 505 | ErrorHint( |
| 506 | 'If you are merely trying to shrink-wrap the viewport in the main axis direction, ' |
| 507 | 'consider a RenderShrinkWrappingViewport render object (ShrinkWrappingViewport widget), ' |
| 508 | 'which achieves that effect without implementing the intrinsic dimension API.', |
| 509 | ), |
| 510 | ]); |
| 511 | } |
| 512 | return true; |
| 513 | }()); |
| 514 | return true; |
| 515 | } |
| 516 | |
| 517 | @override |
| 518 | double computeMinIntrinsicWidth(double height) { |
| 519 | assert(debugThrowIfNotCheckingIntrinsics()); |
| 520 | return 0.0; |
| 521 | } |
| 522 | |
| 523 | @override |
| 524 | double computeMaxIntrinsicWidth(double height) { |
| 525 | assert(debugThrowIfNotCheckingIntrinsics()); |
| 526 | return 0.0; |
| 527 | } |
| 528 | |
| 529 | @override |
| 530 | double computeMinIntrinsicHeight(double width) { |
| 531 | assert(debugThrowIfNotCheckingIntrinsics()); |
| 532 | return 0.0; |
| 533 | } |
| 534 | |
| 535 | @override |
| 536 | double computeMaxIntrinsicHeight(double width) { |
| 537 | assert(debugThrowIfNotCheckingIntrinsics()); |
| 538 | return 0.0; |
| 539 | } |
| 540 | |
| 541 | @override |
| 542 | bool get isRepaintBoundary => true; |
| 543 | |
| 544 | /// Determines the size and position of some of the children of the viewport. |
| 545 | /// |
| 546 | /// This function is the workhorse of `performLayout` implementations in |
| 547 | /// subclasses. |
| 548 | /// |
| 549 | /// Layout starts with `child`, proceeds according to the `advance` callback, |
| 550 | /// and stops once `advance` returns null. |
| 551 | /// |
| 552 | /// * `scrollOffset` is the [SliverConstraints.scrollOffset] to pass the |
| 553 | /// first child. The scroll offset is adjusted by |
| 554 | /// [SliverGeometry.scrollExtent] for subsequent children. |
| 555 | /// * `overlap` is the [SliverConstraints.overlap] to pass the first child. |
| 556 | /// The overlay is adjusted by the [SliverGeometry.paintOrigin] and |
| 557 | /// [SliverGeometry.paintExtent] for subsequent children. |
| 558 | /// * `layoutOffset` is the layout offset at which to place the first child. |
| 559 | /// The layout offset is updated by the [SliverGeometry.layoutExtent] for |
| 560 | /// subsequent children. |
| 561 | /// * `remainingPaintExtent` is [SliverConstraints.remainingPaintExtent] to |
| 562 | /// pass the first child. The remaining paint extent is updated by the |
| 563 | /// [SliverGeometry.layoutExtent] for subsequent children. |
| 564 | /// * `mainAxisExtent` is the [SliverConstraints.viewportMainAxisExtent] to |
| 565 | /// pass to each child. |
| 566 | /// * `crossAxisExtent` is the [SliverConstraints.crossAxisExtent] to pass to |
| 567 | /// each child. |
| 568 | /// * `growthDirection` is the [SliverConstraints.growthDirection] to pass to |
| 569 | /// each child. |
| 570 | /// |
| 571 | /// Returns the first non-zero [SliverGeometry.scrollOffsetCorrection] |
| 572 | /// encountered, if any. Otherwise returns 0.0. Typical callers will call this |
| 573 | /// function repeatedly until it returns 0.0. |
| 574 | @protected |
| 575 | double layoutChildSequence({ |
| 576 | required RenderSliver? child, |
| 577 | required double scrollOffset, |
| 578 | required double overlap, |
| 579 | required double layoutOffset, |
| 580 | required double remainingPaintExtent, |
| 581 | required double mainAxisExtent, |
| 582 | required double crossAxisExtent, |
| 583 | required GrowthDirection growthDirection, |
| 584 | required RenderSliver? Function(RenderSliver child) advance, |
| 585 | required double remainingCacheExtent, |
| 586 | required double cacheOrigin, |
| 587 | }) { |
| 588 | assert(scrollOffset.isFinite); |
| 589 | assert(scrollOffset >= 0.0); |
| 590 | final double initialLayoutOffset = layoutOffset; |
| 591 | final ScrollDirection adjustedUserScrollDirection = applyGrowthDirectionToScrollDirection( |
| 592 | offset.userScrollDirection, |
| 593 | growthDirection, |
| 594 | ); |
| 595 | double maxPaintOffset = layoutOffset + overlap; |
| 596 | double precedingScrollExtent = 0.0; |
| 597 | |
| 598 | while (child != null) { |
| 599 | final double sliverScrollOffset = scrollOffset <= 0.0 ? 0.0 : scrollOffset; |
| 600 | // If the scrollOffset is too small we adjust the paddedOrigin because it |
| 601 | // doesn't make sense to ask a sliver for content before its scroll |
| 602 | // offset. |
| 603 | final double correctedCacheOrigin = math.max(cacheOrigin, -sliverScrollOffset); |
| 604 | final double cacheExtentCorrection = cacheOrigin - correctedCacheOrigin; |
| 605 | |
| 606 | assert(sliverScrollOffset >= correctedCacheOrigin.abs()); |
| 607 | assert(correctedCacheOrigin <= 0.0); |
| 608 | assert(sliverScrollOffset >= 0.0); |
| 609 | assert(cacheExtentCorrection <= 0.0); |
| 610 | |
| 611 | child.layout( |
| 612 | SliverConstraints( |
| 613 | axisDirection: axisDirection, |
| 614 | growthDirection: growthDirection, |
| 615 | userScrollDirection: adjustedUserScrollDirection, |
| 616 | scrollOffset: sliverScrollOffset, |
| 617 | precedingScrollExtent: precedingScrollExtent, |
| 618 | overlap: maxPaintOffset - layoutOffset, |
| 619 | remainingPaintExtent: math.max( |
| 620 | 0.0, |
| 621 | remainingPaintExtent - layoutOffset + initialLayoutOffset, |
| 622 | ), |
| 623 | crossAxisExtent: crossAxisExtent, |
| 624 | crossAxisDirection: crossAxisDirection, |
| 625 | viewportMainAxisExtent: mainAxisExtent, |
| 626 | remainingCacheExtent: math.max(0.0, remainingCacheExtent + cacheExtentCorrection), |
| 627 | cacheOrigin: correctedCacheOrigin, |
| 628 | ), |
| 629 | parentUsesSize: true, |
| 630 | ); |
| 631 | |
| 632 | final SliverGeometry childLayoutGeometry = child.geometry!; |
| 633 | assert(childLayoutGeometry.debugAssertIsValid()); |
| 634 | |
| 635 | // If there is a correction to apply, we'll have to start over. |
| 636 | if (childLayoutGeometry.scrollOffsetCorrection != null) { |
| 637 | return childLayoutGeometry.scrollOffsetCorrection!; |
| 638 | } |
| 639 | |
| 640 | // We use the child's paint origin in our coordinate system as the |
| 641 | // layoutOffset we store in the child's parent data. |
| 642 | final double effectiveLayoutOffset = layoutOffset + childLayoutGeometry.paintOrigin; |
| 643 | |
| 644 | // `effectiveLayoutOffset` becomes meaningless once we moved past the trailing edge |
| 645 | // because `childLayoutGeometry.layoutExtent` is zero. Using the still increasing |
| 646 | // 'scrollOffset` to roughly position these invisible slivers in the right order. |
| 647 | if (childLayoutGeometry.visible || scrollOffset > 0) { |
| 648 | updateChildLayoutOffset(child, effectiveLayoutOffset, growthDirection); |
| 649 | } else { |
| 650 | updateChildLayoutOffset(child, -scrollOffset + initialLayoutOffset, growthDirection); |
| 651 | } |
| 652 | |
| 653 | maxPaintOffset = math.max( |
| 654 | effectiveLayoutOffset + childLayoutGeometry.paintExtent, |
| 655 | maxPaintOffset, |
| 656 | ); |
| 657 | scrollOffset -= childLayoutGeometry.scrollExtent; |
| 658 | precedingScrollExtent += childLayoutGeometry.scrollExtent; |
| 659 | layoutOffset += childLayoutGeometry.layoutExtent; |
| 660 | if (childLayoutGeometry.cacheExtent != 0.0) { |
| 661 | remainingCacheExtent -= childLayoutGeometry.cacheExtent - cacheExtentCorrection; |
| 662 | cacheOrigin = math.min(correctedCacheOrigin + childLayoutGeometry.cacheExtent, 0.0); |
| 663 | } |
| 664 | |
| 665 | updateOutOfBandData(growthDirection, childLayoutGeometry); |
| 666 | |
| 667 | // move on to the next child |
| 668 | child = advance(child); |
| 669 | } |
| 670 | |
| 671 | // we made it without a correction, whee! |
| 672 | return 0.0; |
| 673 | } |
| 674 | |
| 675 | @override |
| 676 | Rect? describeApproximatePaintClip(RenderSliver child) { |
| 677 | if (child.ensureSemantics && !(child.geometry!.visible || child.geometry!.cacheExtent > 0.0)) { |
| 678 | // Return null here so we don't end up clipping out a semantics node rect |
| 679 | // for a sliver child when we explicitly want it to be included in the semantics tree. |
| 680 | return null; |
| 681 | } |
| 682 | |
| 683 | switch (clipBehavior) { |
| 684 | case Clip.none: |
| 685 | return null; |
| 686 | case Clip.hardEdge: |
| 687 | case Clip.antiAlias: |
| 688 | case Clip.antiAliasWithSaveLayer: |
| 689 | break; |
| 690 | } |
| 691 | |
| 692 | final Rect viewportClip = Offset.zero & size; |
| 693 | // The child's viewportMainAxisExtent can be infinite when a |
| 694 | // RenderShrinkWrappingViewport is given infinite constraints, such as when |
| 695 | // it is the child of a Row or Column (depending on orientation). |
| 696 | // |
| 697 | // For example, a shrink wrapping render sliver may have infinite |
| 698 | // constraints along the viewport's main axis but may also have bouncing |
| 699 | // scroll physics, which will allow for some scrolling effect to occur. |
| 700 | // We should just use the viewportClip - the start of the overlap is at |
| 701 | // double.infinity and so it is effectively meaningless. |
| 702 | if (child.constraints.overlap == 0 || !child.constraints.viewportMainAxisExtent.isFinite) { |
| 703 | return viewportClip; |
| 704 | } |
| 705 | |
| 706 | // Adjust the clip rect for this sliver by the overlap from the previous sliver. |
| 707 | double left = viewportClip.left; |
| 708 | double right = viewportClip.right; |
| 709 | double top = viewportClip.top; |
| 710 | double bottom = viewportClip.bottom; |
| 711 | final double startOfOverlap = |
| 712 | child.constraints.viewportMainAxisExtent - child.constraints.remainingPaintExtent; |
| 713 | final double overlapCorrection = startOfOverlap + child.constraints.overlap; |
| 714 | switch (applyGrowthDirectionToAxisDirection(axisDirection, child.constraints.growthDirection)) { |
| 715 | case AxisDirection.down: |
| 716 | top += overlapCorrection; |
| 717 | case AxisDirection.up: |
| 718 | bottom -= overlapCorrection; |
| 719 | case AxisDirection.right: |
| 720 | left += overlapCorrection; |
| 721 | case AxisDirection.left: |
| 722 | right -= overlapCorrection; |
| 723 | } |
| 724 | return Rect.fromLTRB(left, top, right, bottom); |
| 725 | } |
| 726 | |
| 727 | @override |
| 728 | Rect? describeSemanticsClip(RenderSliver? child) { |
| 729 | if (child != null && |
| 730 | child.ensureSemantics && |
| 731 | !(child.geometry!.visible || child.geometry!.cacheExtent > 0.0)) { |
| 732 | // Return null here so we don't end up clipping out a semantics node rect |
| 733 | // for a sliver child when we explicitly want it to be included in the semantics tree. |
| 734 | return null; |
| 735 | } |
| 736 | if (_calculatedCacheExtent == null) { |
| 737 | return semanticBounds; |
| 738 | } |
| 739 | |
| 740 | switch (axis) { |
| 741 | case Axis.vertical: |
| 742 | return Rect.fromLTRB( |
| 743 | semanticBounds.left, |
| 744 | semanticBounds.top - _calculatedCacheExtent!, |
| 745 | semanticBounds.right, |
| 746 | semanticBounds.bottom + _calculatedCacheExtent!, |
| 747 | ); |
| 748 | case Axis.horizontal: |
| 749 | return Rect.fromLTRB( |
| 750 | semanticBounds.left - _calculatedCacheExtent!, |
| 751 | semanticBounds.top, |
| 752 | semanticBounds.right + _calculatedCacheExtent!, |
| 753 | semanticBounds.bottom, |
| 754 | ); |
| 755 | } |
| 756 | } |
| 757 | |
| 758 | @override |
| 759 | void paint(PaintingContext context, Offset offset) { |
| 760 | if (firstChild == null) { |
| 761 | return; |
| 762 | } |
| 763 | if (hasVisualOverflow && clipBehavior != Clip.none) { |
| 764 | _clipRectLayer.layer = context.pushClipRect( |
| 765 | needsCompositing, |
| 766 | offset, |
| 767 | Offset.zero & size, |
| 768 | _paintContents, |
| 769 | clipBehavior: clipBehavior, |
| 770 | oldLayer: _clipRectLayer.layer, |
| 771 | ); |
| 772 | } else { |
| 773 | _clipRectLayer.layer = null; |
| 774 | _paintContents(context, offset); |
| 775 | } |
| 776 | } |
| 777 | |
| 778 | final LayerHandle<ClipRectLayer> _clipRectLayer = LayerHandle<ClipRectLayer>(); |
| 779 | |
| 780 | @override |
| 781 | void dispose() { |
| 782 | _clipRectLayer.layer = null; |
| 783 | super.dispose(); |
| 784 | } |
| 785 | |
| 786 | void _paintContents(PaintingContext context, Offset offset) { |
| 787 | for (final RenderSliver child in childrenInPaintOrder) { |
| 788 | if (child.geometry!.visible) { |
| 789 | context.paintChild(child, offset + paintOffsetOf(child)); |
| 790 | } |
| 791 | } |
| 792 | } |
| 793 | |
| 794 | @override |
| 795 | void debugPaintSize(PaintingContext context, Offset offset) { |
| 796 | assert(() { |
| 797 | super.debugPaintSize(context, offset); |
| 798 | final Paint paint = |
| 799 | Paint() |
| 800 | ..style = PaintingStyle.stroke |
| 801 | ..strokeWidth = 1.0 |
| 802 | ..color = const Color(0xFF00FF00); |
| 803 | final Canvas canvas = context.canvas; |
| 804 | RenderSliver? child = firstChild; |
| 805 | while (child != null) { |
| 806 | final Size size = switch (axis) { |
| 807 | Axis.vertical => Size(child.constraints.crossAxisExtent, child.geometry!.layoutExtent), |
| 808 | Axis.horizontal => Size(child.geometry!.layoutExtent, child.constraints.crossAxisExtent), |
| 809 | }; |
| 810 | canvas.drawRect(((offset + paintOffsetOf(child)) & size).deflate(0.5), paint); |
| 811 | child = childAfter(child); |
| 812 | } |
| 813 | return true; |
| 814 | }()); |
| 815 | } |
| 816 | |
| 817 | @override |
| 818 | bool hitTestChildren(BoxHitTestResult result, {required Offset position}) { |
| 819 | final (double mainAxisPosition, double crossAxisPosition) = switch (axis) { |
| 820 | Axis.vertical => (position.dy, position.dx), |
| 821 | Axis.horizontal => (position.dx, position.dy), |
| 822 | }; |
| 823 | final SliverHitTestResult sliverResult = SliverHitTestResult.wrap(result); |
| 824 | for (final RenderSliver child in childrenInHitTestOrder) { |
| 825 | if (!child.geometry!.visible) { |
| 826 | continue; |
| 827 | } |
| 828 | final Matrix4 transform = Matrix4.identity(); |
| 829 | applyPaintTransform(child, transform); // must be invertible |
| 830 | final bool isHit = result.addWithOutOfBandPosition( |
| 831 | paintTransform: transform, |
| 832 | hitTest: (BoxHitTestResult result) { |
| 833 | return child.hitTest( |
| 834 | sliverResult, |
| 835 | mainAxisPosition: computeChildMainAxisPosition(child, mainAxisPosition), |
| 836 | crossAxisPosition: crossAxisPosition, |
| 837 | ); |
| 838 | }, |
| 839 | ); |
| 840 | if (isHit) { |
| 841 | return true; |
| 842 | } |
| 843 | } |
| 844 | return false; |
| 845 | } |
| 846 | |
| 847 | @override |
| 848 | RevealedOffset getOffsetToReveal( |
| 849 | RenderObject target, |
| 850 | double alignment, { |
| 851 | Rect? rect, |
| 852 | Axis? axis, |
| 853 | }) { |
| 854 | // One dimensional viewport has only one axis, override if it was |
| 855 | // provided/may be mismatched. |
| 856 | axis = this.axis; |
| 857 | |
| 858 | // Steps to convert `rect` (from a RenderBox coordinate system) to its |
| 859 | // scroll offset within this viewport (not in the exact order): |
| 860 | // |
| 861 | // 1. Pick the outermost RenderBox (between which, and the viewport, there |
| 862 | // is nothing but RenderSlivers) as an intermediate reference frame |
| 863 | // (the `pivot`), convert `rect` to that coordinate space. |
| 864 | // |
| 865 | // 2. Convert `rect` from the `pivot` coordinate space to its sliver |
| 866 | // parent's sliver coordinate system (i.e., to a scroll offset), based on |
| 867 | // the axis direction and growth direction of the parent. |
| 868 | // |
| 869 | // 3. Convert the scroll offset to its sliver parent's coordinate space |
| 870 | // using `childScrollOffset`, until we reach the viewport. |
| 871 | // |
| 872 | // 4. Make the final conversion from the outmost sliver to the viewport |
| 873 | // using `scrollOffsetOf`. |
| 874 | |
| 875 | double leadingScrollOffset = 0.0; |
| 876 | // Starting at `target` and walking towards the root: |
| 877 | // - `child` will be the last object before we reach this viewport, and |
| 878 | // - `pivot` will be the last RenderBox before we reach this viewport. |
| 879 | RenderObject child = target; |
| 880 | RenderBox? pivot; |
| 881 | bool onlySlivers = |
| 882 | target is RenderSliver; // ... between viewport and `target` (`target` included). |
| 883 | while (child.parent != this) { |
| 884 | final RenderObject parent = child.parent!; |
| 885 | if (child is RenderBox) { |
| 886 | pivot = child; |
| 887 | } |
| 888 | if (parent is RenderSliver) { |
| 889 | leadingScrollOffset += parent.childScrollOffset(child)!; |
| 890 | } else { |
| 891 | onlySlivers = false; |
| 892 | leadingScrollOffset = 0.0; |
| 893 | } |
| 894 | child = parent; |
| 895 | } |
| 896 | |
| 897 | // `rect` in the new intermediate coordinate system. |
| 898 | final Rect rectLocal; |
| 899 | // Our new reference frame render object's main axis extent. |
| 900 | final double pivotExtent; |
| 901 | final GrowthDirection growthDirection; |
| 902 | |
| 903 | // `leadingScrollOffset` is currently the scrollOffset of our new reference |
| 904 | // frame (`pivot` or `target`), within `child`. |
| 905 | if (pivot != null) { |
| 906 | assert(pivot.parent != null); |
| 907 | assert(pivot.parent != this); |
| 908 | assert(pivot != this); |
| 909 | assert( |
| 910 | pivot.parent is RenderSliver, |
| 911 | ); // TODO(abarth): Support other kinds of render objects besides slivers. |
| 912 | final RenderSliver pivotParent = pivot.parent! as RenderSliver; |
| 913 | growthDirection = pivotParent.constraints.growthDirection; |
| 914 | pivotExtent = switch (axis) { |
| 915 | Axis.horizontal => pivot.size.width, |
| 916 | Axis.vertical => pivot.size.height, |
| 917 | }; |
| 918 | rect ??= target.paintBounds; |
| 919 | rectLocal = MatrixUtils.transformRect(target.getTransformTo(pivot), rect); |
| 920 | } else if (onlySlivers) { |
| 921 | // `pivot` does not exist. We'll have to make up one from `target`, the |
| 922 | // innermost sliver. |
| 923 | final RenderSliver targetSliver = target as RenderSliver; |
| 924 | growthDirection = targetSliver.constraints.growthDirection; |
| 925 | // TODO(LongCatIsLooong): make sure this works if `targetSliver` is a |
| 926 | // persistent header, when #56413 relands. |
| 927 | pivotExtent = targetSliver.geometry!.scrollExtent; |
| 928 | if (rect == null) { |
| 929 | switch (axis) { |
| 930 | case Axis.horizontal: |
| 931 | rect = Rect.fromLTWH( |
| 932 | 0, |
| 933 | 0, |
| 934 | targetSliver.geometry!.scrollExtent, |
| 935 | targetSliver.constraints.crossAxisExtent, |
| 936 | ); |
| 937 | case Axis.vertical: |
| 938 | rect = Rect.fromLTWH( |
| 939 | 0, |
| 940 | 0, |
| 941 | targetSliver.constraints.crossAxisExtent, |
| 942 | targetSliver.geometry!.scrollExtent, |
| 943 | ); |
| 944 | } |
| 945 | } |
| 946 | rectLocal = rect; |
| 947 | } else { |
| 948 | assert(rect != null); |
| 949 | return RevealedOffset(offset: offset.pixels, rect: rect!); |
| 950 | } |
| 951 | |
| 952 | assert(child.parent == this); |
| 953 | assert(child is RenderSliver); |
| 954 | final RenderSliver sliver = child as RenderSliver; |
| 955 | |
| 956 | // The scroll offset of `rect` within `child`. |
| 957 | leadingScrollOffset += switch (applyGrowthDirectionToAxisDirection( |
| 958 | axisDirection, |
| 959 | growthDirection, |
| 960 | )) { |
| 961 | AxisDirection.up => pivotExtent - rectLocal.bottom, |
| 962 | AxisDirection.left => pivotExtent - rectLocal.right, |
| 963 | AxisDirection.right => rectLocal.left, |
| 964 | AxisDirection.down => rectLocal.top, |
| 965 | }; |
| 966 | |
| 967 | // So far leadingScrollOffset is the scroll offset of `rect` in the `child` |
| 968 | // sliver's sliver coordinate system. The sign of this value indicates |
| 969 | // whether the `rect` protrudes the leading edge of the `child` sliver. When |
| 970 | // this value is non-negative and `child`'s `maxScrollObstructionExtent` is |
| 971 | // greater than 0, we assume `rect` can't be obstructed by the leading edge |
| 972 | // of the viewport (i.e. its pinned to the leading edge). |
| 973 | final bool isPinned = |
| 974 | sliver.geometry!.maxScrollObstructionExtent > 0 && leadingScrollOffset >= 0; |
| 975 | |
| 976 | // The scroll offset in the viewport to `rect`. |
| 977 | leadingScrollOffset = scrollOffsetOf(sliver, leadingScrollOffset); |
| 978 | |
| 979 | // This step assumes the viewport's layout is up-to-date, i.e., if |
| 980 | // offset.pixels is changed after the last performLayout, the new scroll |
| 981 | // position will not be accounted for. |
| 982 | final Matrix4 transform = target.getTransformTo(this); |
| 983 | Rect targetRect = MatrixUtils.transformRect(transform, rect); |
| 984 | final double extentOfPinnedSlivers = maxScrollObstructionExtentBefore(sliver); |
| 985 | |
| 986 | switch (sliver.constraints.growthDirection) { |
| 987 | case GrowthDirection.forward: |
| 988 | if (isPinned && alignment <= 0) { |
| 989 | return RevealedOffset(offset: double.infinity, rect: targetRect); |
| 990 | } |
| 991 | leadingScrollOffset -= extentOfPinnedSlivers; |
| 992 | case GrowthDirection.reverse: |
| 993 | if (isPinned && alignment >= 1) { |
| 994 | return RevealedOffset(offset: double.negativeInfinity, rect: targetRect); |
| 995 | } |
| 996 | // If child's growth direction is reverse, when viewport.offset is |
| 997 | // `leadingScrollOffset`, it is positioned just outside of the leading |
| 998 | // edge of the viewport. |
| 999 | leadingScrollOffset -= switch (axis) { |
| 1000 | Axis.vertical => targetRect.height, |
| 1001 | Axis.horizontal => targetRect.width, |
| 1002 | }; |
| 1003 | } |
| 1004 | |
| 1005 | final double mainAxisExtentDifference = switch (axis) { |
| 1006 | Axis.horizontal => size.width - extentOfPinnedSlivers - rectLocal.width, |
| 1007 | Axis.vertical => size.height - extentOfPinnedSlivers - rectLocal.height, |
| 1008 | }; |
| 1009 | |
| 1010 | final double targetOffset = leadingScrollOffset - mainAxisExtentDifference * alignment; |
| 1011 | final double offsetDifference = offset.pixels - targetOffset; |
| 1012 | |
| 1013 | targetRect = switch (axisDirection) { |
| 1014 | AxisDirection.up => targetRect.translate(0.0, -offsetDifference), |
| 1015 | AxisDirection.down => targetRect.translate(0.0, offsetDifference), |
| 1016 | AxisDirection.left => targetRect.translate(-offsetDifference, 0.0), |
| 1017 | AxisDirection.right => targetRect.translate(offsetDifference, 0.0), |
| 1018 | }; |
| 1019 | |
| 1020 | return RevealedOffset(offset: targetOffset, rect: targetRect); |
| 1021 | } |
| 1022 | |
| 1023 | /// The offset at which the given `child` should be painted. |
| 1024 | /// |
| 1025 | /// The returned offset is from the top left corner of the inside of the |
| 1026 | /// viewport to the top left corner of the paint coordinate system of the |
| 1027 | /// `child`. |
| 1028 | /// |
| 1029 | /// See also: |
| 1030 | /// |
| 1031 | /// * [paintOffsetOf], which uses the layout offset and growth direction |
| 1032 | /// computed for the child during layout. |
| 1033 | @protected |
| 1034 | Offset computeAbsolutePaintOffset( |
| 1035 | RenderSliver child, |
| 1036 | double layoutOffset, |
| 1037 | GrowthDirection growthDirection, |
| 1038 | ) { |
| 1039 | assert(hasSize); // this is only usable once we have a size |
| 1040 | assert(child.geometry != null); |
| 1041 | return switch (applyGrowthDirectionToAxisDirection(axisDirection, growthDirection)) { |
| 1042 | AxisDirection.up => Offset(0.0, size.height - layoutOffset - child.geometry!.paintExtent), |
| 1043 | AxisDirection.left => Offset(size.width - layoutOffset - child.geometry!.paintExtent, 0.0), |
| 1044 | AxisDirection.right => Offset(layoutOffset, 0.0), |
| 1045 | AxisDirection.down => Offset(0.0, layoutOffset), |
| 1046 | }; |
| 1047 | } |
| 1048 | |
| 1049 | @override |
| 1050 | void debugFillProperties(DiagnosticPropertiesBuilder properties) { |
| 1051 | super.debugFillProperties(properties); |
| 1052 | properties.add(EnumProperty<AxisDirection>('axisDirection', axisDirection)); |
| 1053 | properties.add(EnumProperty<AxisDirection>('crossAxisDirection', crossAxisDirection)); |
| 1054 | properties.add(DiagnosticsProperty<ViewportOffset>('offset', offset)); |
| 1055 | } |
| 1056 | |
| 1057 | @override |
| 1058 | List<DiagnosticsNode> debugDescribeChildren() { |
| 1059 | final List<DiagnosticsNode> children = <DiagnosticsNode>[]; |
| 1060 | RenderSliver? child = firstChild; |
| 1061 | if (child == null) { |
| 1062 | return children; |
| 1063 | } |
| 1064 | |
| 1065 | int count = indexOfFirstChild; |
| 1066 | while (true) { |
| 1067 | children.add(child!.toDiagnosticsNode(name: labelForChild(count))); |
| 1068 | if (child == lastChild) { |
| 1069 | break; |
| 1070 | } |
| 1071 | count += 1; |
| 1072 | child = childAfter(child); |
| 1073 | } |
| 1074 | return children; |
| 1075 | } |
| 1076 | |
| 1077 | // API TO BE IMPLEMENTED BY SUBCLASSES |
| 1078 | |
| 1079 | // setupParentData |
| 1080 | |
| 1081 | // performLayout (and optionally sizedByParent and performResize) |
| 1082 | |
| 1083 | /// Whether the contents of this viewport would paint outside the bounds of |
| 1084 | /// the viewport if [paint] did not clip. |
| 1085 | /// |
| 1086 | /// This property enables an optimization whereby [paint] can skip apply a |
| 1087 | /// clip of the contents of the viewport are known to paint entirely within |
| 1088 | /// the bounds of the viewport. |
| 1089 | @protected |
| 1090 | bool get hasVisualOverflow; |
| 1091 | |
| 1092 | /// Called during [layoutChildSequence] for each child. |
| 1093 | /// |
| 1094 | /// Typically used by subclasses to update any out-of-band data, such as the |
| 1095 | /// max scroll extent, for each child. |
| 1096 | @protected |
| 1097 | void updateOutOfBandData(GrowthDirection growthDirection, SliverGeometry childLayoutGeometry); |
| 1098 | |
| 1099 | /// Called during [layoutChildSequence] to store the layout offset for the |
| 1100 | /// given child. |
| 1101 | /// |
| 1102 | /// Different subclasses using different representations for their children's |
| 1103 | /// layout offset (e.g., logical or physical coordinates). This function lets |
| 1104 | /// subclasses transform the child's layout offset before storing it in the |
| 1105 | /// child's parent data. |
| 1106 | @protected |
| 1107 | void updateChildLayoutOffset( |
| 1108 | RenderSliver child, |
| 1109 | double layoutOffset, |
| 1110 | GrowthDirection growthDirection, |
| 1111 | ); |
| 1112 | |
| 1113 | /// The offset at which the given `child` should be painted. |
| 1114 | /// |
| 1115 | /// The returned offset is from the top left corner of the inside of the |
| 1116 | /// viewport to the top left corner of the paint coordinate system of the |
| 1117 | /// `child`. |
| 1118 | /// |
| 1119 | /// See also: |
| 1120 | /// |
| 1121 | /// * [computeAbsolutePaintOffset], which computes the paint offset from an |
| 1122 | /// explicit layout offset and growth direction instead of using the values |
| 1123 | /// computed for the child during layout. |
| 1124 | @protected |
| 1125 | Offset paintOffsetOf(RenderSliver child); |
| 1126 | |
| 1127 | /// Returns the scroll offset within the viewport for the given |
| 1128 | /// `scrollOffsetWithinChild` within the given `child`. |
| 1129 | /// |
| 1130 | /// The returned value is an estimate that assumes the slivers within the |
| 1131 | /// viewport do not change the layout extent in response to changes in their |
| 1132 | /// scroll offset. |
| 1133 | @protected |
| 1134 | double scrollOffsetOf(RenderSliver child, double scrollOffsetWithinChild); |
| 1135 | |
| 1136 | /// Returns the total scroll obstruction extent of all slivers in the viewport |
| 1137 | /// before [child]. |
| 1138 | /// |
| 1139 | /// This is the extent by which the actual area in which content can scroll |
| 1140 | /// is reduced. For example, an app bar that is pinned at the top will reduce |
| 1141 | /// the area in which content can actually scroll by the height of the app bar. |
| 1142 | @protected |
| 1143 | double maxScrollObstructionExtentBefore(RenderSliver child); |
| 1144 | |
| 1145 | /// Converts the `parentMainAxisPosition` into the child's coordinate system. |
| 1146 | /// |
| 1147 | /// The `parentMainAxisPosition` is a distance from the top edge (for vertical |
| 1148 | /// viewports) or left edge (for horizontal viewports) of the viewport bounds. |
| 1149 | /// This describes a line, perpendicular to the viewport's main axis, heretofore |
| 1150 | /// known as the target line. |
| 1151 | /// |
| 1152 | /// The child's coordinate system's origin in the main axis is at the leading |
| 1153 | /// edge of the given child, as given by the child's |
| 1154 | /// [SliverConstraints.axisDirection] and [SliverConstraints.growthDirection]. |
| 1155 | /// |
| 1156 | /// This method returns the distance from the leading edge of the given child to |
| 1157 | /// the target line described above. |
| 1158 | /// |
| 1159 | /// (The `parentMainAxisPosition` is not from the leading edge of the |
| 1160 | /// viewport, it's always the top or left edge.) |
| 1161 | @protected |
| 1162 | double computeChildMainAxisPosition(RenderSliver child, double parentMainAxisPosition); |
| 1163 | |
| 1164 | /// The index of the first child of the viewport relative to the center child. |
| 1165 | /// |
| 1166 | /// For example, the center child has index zero and the first child in the |
| 1167 | /// reverse growth direction has index -1. |
| 1168 | @protected |
| 1169 | int get indexOfFirstChild; |
| 1170 | |
| 1171 | /// A short string to identify the child with the given index. |
| 1172 | /// |
| 1173 | /// Used by [debugDescribeChildren] to label the children. |
| 1174 | @protected |
| 1175 | String labelForChild(int index); |
| 1176 | |
| 1177 | /// Provides an iterable that walks the children of the viewport, in the order |
| 1178 | /// that they should be painted. |
| 1179 | /// |
| 1180 | /// This should be the reverse order of [childrenInHitTestOrder]. |
| 1181 | @protected |
| 1182 | Iterable<RenderSliver> get childrenInPaintOrder; |
| 1183 | |
| 1184 | /// Provides an iterable that walks the children of the viewport, in the order |
| 1185 | /// that hit-testing should use. |
| 1186 | /// |
| 1187 | /// This should be the reverse order of [childrenInPaintOrder]. |
| 1188 | @protected |
| 1189 | Iterable<RenderSliver> get childrenInHitTestOrder; |
| 1190 | |
| 1191 | @override |
| 1192 | void showOnScreen({ |
| 1193 | RenderObject? descendant, |
| 1194 | Rect? rect, |
| 1195 | Duration duration = Duration.zero, |
| 1196 | Curve curve = Curves.ease, |
| 1197 | }) { |
| 1198 | if (!offset.allowImplicitScrolling) { |
| 1199 | return super.showOnScreen( |
| 1200 | descendant: descendant, |
| 1201 | rect: rect, |
| 1202 | duration: duration, |
| 1203 | curve: curve, |
| 1204 | ); |
| 1205 | } |
| 1206 | |
| 1207 | final Rect? newRect = RenderViewportBase.showInViewport( |
| 1208 | descendant: descendant, |
| 1209 | viewport: this, |
| 1210 | offset: offset, |
| 1211 | rect: rect, |
| 1212 | duration: duration, |
| 1213 | curve: curve, |
| 1214 | ); |
| 1215 | super.showOnScreen(rect: newRect, duration: duration, curve: curve); |
| 1216 | } |
| 1217 | |
| 1218 | /// Make (a portion of) the given `descendant` of the given `viewport` fully |
| 1219 | /// visible in the `viewport` by manipulating the provided [ViewportOffset] |
| 1220 | /// `offset`. |
| 1221 | /// |
| 1222 | /// The optional `rect` parameter describes which area of the `descendant` |
| 1223 | /// should be shown in the viewport. If `rect` is null, the entire |
| 1224 | /// `descendant` will be revealed. The `rect` parameter is interpreted |
| 1225 | /// relative to the coordinate system of `descendant`. |
| 1226 | /// |
| 1227 | /// The returned [Rect] describes the new location of `descendant` or `rect` |
| 1228 | /// in the viewport after it has been revealed. See [RevealedOffset.rect] |
| 1229 | /// for a full definition of this [Rect]. |
| 1230 | /// |
| 1231 | /// If `descendant` is null, this is a no-op and `rect` is returned. |
| 1232 | /// |
| 1233 | /// If both `descendant` and `rect` are null, null is returned because there is |
| 1234 | /// nothing to be shown in the viewport. |
| 1235 | /// |
| 1236 | /// The `duration` parameter can be set to a non-zero value to animate the |
| 1237 | /// target object into the viewport with an animation defined by `curve`. |
| 1238 | /// |
| 1239 | /// See also: |
| 1240 | /// |
| 1241 | /// * [RenderObject.showOnScreen], overridden by [RenderViewportBase] and the |
| 1242 | /// renderer for [SingleChildScrollView] to delegate to this method. |
| 1243 | static Rect? showInViewport({ |
| 1244 | RenderObject? descendant, |
| 1245 | Rect? rect, |
| 1246 | required RenderAbstractViewport viewport, |
| 1247 | required ViewportOffset offset, |
| 1248 | Duration duration = Duration.zero, |
| 1249 | Curve curve = Curves.ease, |
| 1250 | }) { |
| 1251 | if (descendant == null) { |
| 1252 | return rect; |
| 1253 | } |
| 1254 | final RevealedOffset leadingEdgeOffset = viewport.getOffsetToReveal( |
| 1255 | descendant, |
| 1256 | 0.0, |
| 1257 | rect: rect, |
| 1258 | ); |
| 1259 | final RevealedOffset trailingEdgeOffset = viewport.getOffsetToReveal( |
| 1260 | descendant, |
| 1261 | 1.0, |
| 1262 | rect: rect, |
| 1263 | ); |
| 1264 | final double currentOffset = offset.pixels; |
| 1265 | final RevealedOffset? targetOffset = RevealedOffset.clampOffset( |
| 1266 | leadingEdgeOffset: leadingEdgeOffset, |
| 1267 | trailingEdgeOffset: trailingEdgeOffset, |
| 1268 | currentOffset: currentOffset, |
| 1269 | ); |
| 1270 | if (targetOffset == null) { |
| 1271 | // `descendant` is between leading and trailing edge and hence already |
| 1272 | // fully shown on screen. No action necessary. |
| 1273 | assert(viewport.parent != null); |
| 1274 | final Matrix4 transform = descendant.getTransformTo(viewport.parent); |
| 1275 | return MatrixUtils.transformRect(transform, rect ?? descendant.paintBounds); |
| 1276 | } |
| 1277 | |
| 1278 | offset.moveTo(targetOffset.offset, duration: duration, curve: curve); |
| 1279 | return targetOffset.rect; |
| 1280 | } |
| 1281 | } |
| 1282 | |
| 1283 | /// A render object that is bigger on the inside. |
| 1284 | /// |
| 1285 | /// [RenderViewport] is the visual workhorse of the scrolling machinery. It |
| 1286 | /// displays a subset of its children according to its own dimensions and the |
| 1287 | /// given [offset]. As the offset varies, different children are visible through |
| 1288 | /// the viewport. |
| 1289 | /// |
| 1290 | /// [RenderViewport] hosts a bidirectional list of slivers in a single shared |
| 1291 | /// [Axis], anchored on a [center] sliver, which is placed at the zero scroll |
| 1292 | /// offset. The center widget is displayed in the viewport according to the |
| 1293 | /// [anchor] property. |
| 1294 | /// |
| 1295 | /// Slivers that are earlier in the child list than [center] are displayed in |
| 1296 | /// reverse order in the reverse [axisDirection] starting from the [center]. For |
| 1297 | /// example, if the [axisDirection] is [AxisDirection.down], the first sliver |
| 1298 | /// before [center] is placed above the [center]. The slivers that are later in |
| 1299 | /// the child list than [center] are placed in order in the [axisDirection]. For |
| 1300 | /// example, in the preceding scenario, the first sliver after [center] is |
| 1301 | /// placed below the [center]. |
| 1302 | /// |
| 1303 | /// {@macro flutter.rendering.GrowthDirection.sample} |
| 1304 | /// |
| 1305 | /// [RenderViewport] cannot contain [RenderBox] children directly. Instead, use |
| 1306 | /// a [RenderSliverList], [RenderSliverFixedExtentList], [RenderSliverGrid], or |
| 1307 | /// a [RenderSliverToBoxAdapter], for example. |
| 1308 | /// |
| 1309 | /// See also: |
| 1310 | /// |
| 1311 | /// * [RenderSliver], which explains more about the Sliver protocol. |
| 1312 | /// * [RenderBox], which explains more about the Box protocol. |
| 1313 | /// * [RenderSliverToBoxAdapter], which allows a [RenderBox] object to be |
| 1314 | /// placed inside a [RenderSliver] (the opposite of this class). |
| 1315 | /// * [RenderShrinkWrappingViewport], a variant of [RenderViewport] that |
| 1316 | /// shrink-wraps its contents along the main axis. |
| 1317 | class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentData> { |
| 1318 | /// Creates a viewport for [RenderSliver] objects. |
| 1319 | /// |
| 1320 | /// If the [center] is not specified, then the first child in the `children` |
| 1321 | /// list, if any, is used. |
| 1322 | /// |
| 1323 | /// The [offset] must be specified. For testing purposes, consider passing a |
| 1324 | /// [ViewportOffset.zero] or [ViewportOffset.fixed]. |
| 1325 | RenderViewport({ |
| 1326 | super.axisDirection, |
| 1327 | required super.crossAxisDirection, |
| 1328 | required super.offset, |
| 1329 | double anchor = 0.0, |
| 1330 | List<RenderSliver>? children, |
| 1331 | RenderSliver? center, |
| 1332 | super.cacheExtent, |
| 1333 | super.cacheExtentStyle, |
| 1334 | super.clipBehavior, |
| 1335 | }) : assert(anchor >= 0.0 && anchor <= 1.0), |
| 1336 | assert(cacheExtentStyle != CacheExtentStyle.viewport || cacheExtent != null), |
| 1337 | _anchor = anchor, |
| 1338 | _center = center { |
| 1339 | addAll(children); |
| 1340 | if (center == null && firstChild != null) { |
| 1341 | _center = firstChild; |
| 1342 | } |
| 1343 | } |
| 1344 | |
| 1345 | /// If a [RenderAbstractViewport] overrides |
| 1346 | /// [RenderObject.describeSemanticsConfiguration] to add the [SemanticsTag] |
| 1347 | /// [useTwoPaneSemantics] to its [SemanticsConfiguration], two semantics nodes |
| 1348 | /// will be used to represent the viewport with its associated scrolling |
| 1349 | /// actions in the semantics tree. |
| 1350 | /// |
| 1351 | /// Two semantics nodes (an inner and an outer node) are necessary to exclude |
| 1352 | /// certain child nodes (via the [excludeFromScrolling] tag) from the |
| 1353 | /// scrollable area for semantic purposes: The [SemanticsNode]s of children |
| 1354 | /// that should be excluded from scrolling will be attached to the outer node. |
| 1355 | /// The semantic scrolling actions and the [SemanticsNode]s of scrollable |
| 1356 | /// children will be attached to the inner node, which itself is a child of |
| 1357 | /// the outer node. |
| 1358 | /// |
| 1359 | /// See also: |
| 1360 | /// |
| 1361 | /// * [RenderViewportBase.describeSemanticsConfiguration], which adds this |
| 1362 | /// tag to its [SemanticsConfiguration]. |
| 1363 | static const SemanticsTag useTwoPaneSemantics = SemanticsTag('RenderViewport.twoPane'); |
| 1364 | |
| 1365 | /// When a top-level [SemanticsNode] below a [RenderAbstractViewport] is |
| 1366 | /// tagged with [excludeFromScrolling] it will not be part of the scrolling |
| 1367 | /// area for semantic purposes. |
| 1368 | /// |
| 1369 | /// This behavior is only active if the [RenderAbstractViewport] |
| 1370 | /// tagged its [SemanticsConfiguration] with [useTwoPaneSemantics]. |
| 1371 | /// Otherwise, the [excludeFromScrolling] tag is ignored. |
| 1372 | /// |
| 1373 | /// As an example, a [RenderSliver] that stays on the screen within a |
| 1374 | /// [Scrollable] even though the user has scrolled past it (e.g. a pinned app |
| 1375 | /// bar) can tag its [SemanticsNode] with [excludeFromScrolling] to indicate |
| 1376 | /// that it should no longer be considered for semantic actions related to |
| 1377 | /// scrolling. |
| 1378 | static const SemanticsTag excludeFromScrolling = SemanticsTag( |
| 1379 | 'RenderViewport.excludeFromScrolling', |
| 1380 | ); |
| 1381 | |
| 1382 | @override |
| 1383 | void setupParentData(RenderObject child) { |
| 1384 | if (child.parentData is! SliverPhysicalContainerParentData) { |
| 1385 | child.parentData = SliverPhysicalContainerParentData(); |
| 1386 | } |
| 1387 | } |
| 1388 | |
| 1389 | /// The relative position of the zero scroll offset. |
| 1390 | /// |
| 1391 | /// For example, if [anchor] is 0.5 and the [axisDirection] is |
| 1392 | /// [AxisDirection.down] or [AxisDirection.up], then the zero scroll offset is |
| 1393 | /// vertically centered within the viewport. If the [anchor] is 1.0, and the |
| 1394 | /// [axisDirection] is [AxisDirection.right], then the zero scroll offset is |
| 1395 | /// on the left edge of the viewport. |
| 1396 | /// |
| 1397 | /// {@macro flutter.rendering.GrowthDirection.sample} |
| 1398 | double get anchor => _anchor; |
| 1399 | double _anchor; |
| 1400 | set anchor(double value) { |
| 1401 | assert(value >= 0.0 && value <= 1.0); |
| 1402 | if (value == _anchor) { |
| 1403 | return; |
| 1404 | } |
| 1405 | _anchor = value; |
| 1406 | markNeedsLayout(); |
| 1407 | } |
| 1408 | |
| 1409 | /// The first child in the [GrowthDirection.forward] growth direction. |
| 1410 | /// |
| 1411 | /// This child that will be at the position defined by [anchor] when the |
| 1412 | /// [ViewportOffset.pixels] of [offset] is `0`. |
| 1413 | /// |
| 1414 | /// Children after [center] will be placed in the [axisDirection] relative to |
| 1415 | /// the [center]. |
| 1416 | /// |
| 1417 | /// Children before [center] will be placed in the opposite of |
| 1418 | /// the [axisDirection] relative to the [center]. These children above |
| 1419 | /// [center] will have a growth direction of [GrowthDirection.reverse]. |
| 1420 | /// |
| 1421 | /// The [center] must be a direct child of the viewport. |
| 1422 | /// |
| 1423 | /// {@macro flutter.rendering.GrowthDirection.sample} |
| 1424 | RenderSliver? get center => _center; |
| 1425 | RenderSliver? _center; |
| 1426 | set center(RenderSliver? value) { |
| 1427 | if (value == _center) { |
| 1428 | return; |
| 1429 | } |
| 1430 | _center = value; |
| 1431 | markNeedsLayout(); |
| 1432 | } |
| 1433 | |
| 1434 | @override |
| 1435 | bool get sizedByParent => true; |
| 1436 | |
| 1437 | @override |
| 1438 | @protected |
| 1439 | Size computeDryLayout(covariant BoxConstraints constraints) { |
| 1440 | assert(debugCheckHasBoundedAxis(axis, constraints)); |
| 1441 | return constraints.biggest; |
| 1442 | } |
| 1443 | |
| 1444 | static const int _maxLayoutCyclesPerChild = 10; |
| 1445 | |
| 1446 | // Out-of-band data computed during layout. |
| 1447 | late double _minScrollExtent; |
| 1448 | late double _maxScrollExtent; |
| 1449 | bool _hasVisualOverflow = false; |
| 1450 | |
| 1451 | @override |
| 1452 | void performLayout() { |
| 1453 | // Ignore the return value of applyViewportDimension because we are |
| 1454 | // doing a layout regardless. |
| 1455 | switch (axis) { |
| 1456 | case Axis.vertical: |
| 1457 | offset.applyViewportDimension(size.height); |
| 1458 | case Axis.horizontal: |
| 1459 | offset.applyViewportDimension(size.width); |
| 1460 | } |
| 1461 | |
| 1462 | if (center == null) { |
| 1463 | assert(firstChild == null); |
| 1464 | _minScrollExtent = 0.0; |
| 1465 | _maxScrollExtent = 0.0; |
| 1466 | _hasVisualOverflow = false; |
| 1467 | offset.applyContentDimensions(0.0, 0.0); |
| 1468 | return; |
| 1469 | } |
| 1470 | assert(center!.parent == this); |
| 1471 | |
| 1472 | final (double mainAxisExtent, double crossAxisExtent) = switch (axis) { |
| 1473 | Axis.vertical => (size.height, size.width), |
| 1474 | Axis.horizontal => (size.width, size.height), |
| 1475 | }; |
| 1476 | |
| 1477 | final double centerOffsetAdjustment = center!.centerOffsetAdjustment; |
| 1478 | final int maxLayoutCycles = _maxLayoutCyclesPerChild * childCount; |
| 1479 | |
| 1480 | double correction; |
| 1481 | int count = 0; |
| 1482 | do { |
| 1483 | correction = _attemptLayout( |
| 1484 | mainAxisExtent, |
| 1485 | crossAxisExtent, |
| 1486 | offset.pixels + centerOffsetAdjustment, |
| 1487 | ); |
| 1488 | if (correction != 0.0) { |
| 1489 | offset.correctBy(correction); |
| 1490 | } else { |
| 1491 | if (offset.applyContentDimensions( |
| 1492 | math.min(0.0, _minScrollExtent + mainAxisExtent * anchor), |
| 1493 | math.max(0.0, _maxScrollExtent - mainAxisExtent * (1.0 - anchor)), |
| 1494 | )) { |
| 1495 | break; |
| 1496 | } |
| 1497 | } |
| 1498 | count += 1; |
| 1499 | } while (count < maxLayoutCycles); |
| 1500 | assert(() { |
| 1501 | if (count >= maxLayoutCycles) { |
| 1502 | assert(count != 1); |
| 1503 | throw FlutterError( |
| 1504 | 'A RenderViewport exceeded its maximum number of layout cycles.\n' |
| 1505 | 'RenderViewport render objects, during layout, can retry if either their ' |
| 1506 | 'slivers or their ViewportOffset decide that the offset should be corrected ' |
| 1507 | 'to take into account information collected during that layout.\n' |
| 1508 | 'In the case of this RenderViewport object, however, this happened$count ' |
| 1509 | 'times and still there was no consensus on the scroll offset. This usually ' |
| 1510 | 'indicates a bug. Specifically, it means that one of the following three ' |
| 1511 | 'problems is being experienced by the RenderViewport object:\n' |
| 1512 | ' * One of the RenderSliver children or the ViewportOffset have a bug such' |
| 1513 | ' that they always think that they need to correct the offset regardless.\n' |
| 1514 | ' * Some combination of the RenderSliver children and the ViewportOffset' |
| 1515 | ' have a bad interaction such that one applies a correction then another' |
| 1516 | ' applies a reverse correction, leading to an infinite loop of corrections.\n' |
| 1517 | ' * There is a pathological case that would eventually resolve, but it is' |
| 1518 | ' so complicated that it cannot be resolved in any reasonable number of' |
| 1519 | ' layout passes.', |
| 1520 | ); |
| 1521 | } |
| 1522 | return true; |
| 1523 | }()); |
| 1524 | } |
| 1525 | |
| 1526 | double _attemptLayout(double mainAxisExtent, double crossAxisExtent, double correctedOffset) { |
| 1527 | assert(!mainAxisExtent.isNaN); |
| 1528 | assert(mainAxisExtent >= 0.0); |
| 1529 | assert(crossAxisExtent.isFinite); |
| 1530 | assert(crossAxisExtent >= 0.0); |
| 1531 | assert(correctedOffset.isFinite); |
| 1532 | _minScrollExtent = 0.0; |
| 1533 | _maxScrollExtent = 0.0; |
| 1534 | _hasVisualOverflow = false; |
| 1535 | |
| 1536 | // centerOffset is the offset from the leading edge of the RenderViewport |
| 1537 | // to the zero scroll offset (the line between the forward slivers and the |
| 1538 | // reverse slivers). |
| 1539 | final double centerOffset = mainAxisExtent * anchor - correctedOffset; |
| 1540 | final double reverseDirectionRemainingPaintExtent = clampDouble( |
| 1541 | centerOffset, |
| 1542 | 0.0, |
| 1543 | mainAxisExtent, |
| 1544 | ); |
| 1545 | final double forwardDirectionRemainingPaintExtent = clampDouble( |
| 1546 | mainAxisExtent - centerOffset, |
| 1547 | 0.0, |
| 1548 | mainAxisExtent, |
| 1549 | ); |
| 1550 | |
| 1551 | _calculatedCacheExtent = switch (cacheExtentStyle) { |
| 1552 | CacheExtentStyle.pixel => cacheExtent, |
| 1553 | CacheExtentStyle.viewport => mainAxisExtent * _cacheExtent, |
| 1554 | }; |
| 1555 | |
| 1556 | final double fullCacheExtent = mainAxisExtent + 2 * _calculatedCacheExtent!; |
| 1557 | final double centerCacheOffset = centerOffset + _calculatedCacheExtent!; |
| 1558 | final double reverseDirectionRemainingCacheExtent = clampDouble( |
| 1559 | centerCacheOffset, |
| 1560 | 0.0, |
| 1561 | fullCacheExtent, |
| 1562 | ); |
| 1563 | final double forwardDirectionRemainingCacheExtent = clampDouble( |
| 1564 | fullCacheExtent - centerCacheOffset, |
| 1565 | 0.0, |
| 1566 | fullCacheExtent, |
| 1567 | ); |
| 1568 | |
| 1569 | final RenderSliver? leadingNegativeChild = childBefore(center!); |
| 1570 | |
| 1571 | if (leadingNegativeChild != null) { |
| 1572 | // negative scroll offsets |
| 1573 | final double result = layoutChildSequence( |
| 1574 | child: leadingNegativeChild, |
| 1575 | scrollOffset: math.max(mainAxisExtent, centerOffset) - mainAxisExtent, |
| 1576 | overlap: 0.0, |
| 1577 | layoutOffset: forwardDirectionRemainingPaintExtent, |
| 1578 | remainingPaintExtent: reverseDirectionRemainingPaintExtent, |
| 1579 | mainAxisExtent: mainAxisExtent, |
| 1580 | crossAxisExtent: crossAxisExtent, |
| 1581 | growthDirection: GrowthDirection.reverse, |
| 1582 | advance: childBefore, |
| 1583 | remainingCacheExtent: reverseDirectionRemainingCacheExtent, |
| 1584 | cacheOrigin: clampDouble(mainAxisExtent - centerOffset, -_calculatedCacheExtent!, 0.0), |
| 1585 | ); |
| 1586 | if (result != 0.0) { |
| 1587 | return -result; |
| 1588 | } |
| 1589 | } |
| 1590 | |
| 1591 | // positive scroll offsets |
| 1592 | return layoutChildSequence( |
| 1593 | child: center, |
| 1594 | scrollOffset: math.max(0.0, -centerOffset), |
| 1595 | overlap: leadingNegativeChild == null ? math.min(0.0, -centerOffset) : 0.0, |
| 1596 | layoutOffset: |
| 1597 | centerOffset >= mainAxisExtent ? centerOffset : reverseDirectionRemainingPaintExtent, |
| 1598 | remainingPaintExtent: forwardDirectionRemainingPaintExtent, |
| 1599 | mainAxisExtent: mainAxisExtent, |
| 1600 | crossAxisExtent: crossAxisExtent, |
| 1601 | growthDirection: GrowthDirection.forward, |
| 1602 | advance: childAfter, |
| 1603 | remainingCacheExtent: forwardDirectionRemainingCacheExtent, |
| 1604 | cacheOrigin: clampDouble(centerOffset, -_calculatedCacheExtent!, 0.0), |
| 1605 | ); |
| 1606 | } |
| 1607 | |
| 1608 | @override |
| 1609 | bool get hasVisualOverflow => _hasVisualOverflow; |
| 1610 | |
| 1611 | @override |
| 1612 | void updateOutOfBandData(GrowthDirection growthDirection, SliverGeometry childLayoutGeometry) { |
| 1613 | switch (growthDirection) { |
| 1614 | case GrowthDirection.forward: |
| 1615 | _maxScrollExtent += childLayoutGeometry.scrollExtent; |
| 1616 | case GrowthDirection.reverse: |
| 1617 | _minScrollExtent -= childLayoutGeometry.scrollExtent; |
| 1618 | } |
| 1619 | if (childLayoutGeometry.hasVisualOverflow) { |
| 1620 | _hasVisualOverflow = true; |
| 1621 | } |
| 1622 | } |
| 1623 | |
| 1624 | @override |
| 1625 | void updateChildLayoutOffset( |
| 1626 | RenderSliver child, |
| 1627 | double layoutOffset, |
| 1628 | GrowthDirection growthDirection, |
| 1629 | ) { |
| 1630 | final SliverPhysicalParentData childParentData = child.parentData! as SliverPhysicalParentData; |
| 1631 | childParentData.paintOffset = computeAbsolutePaintOffset(child, layoutOffset, growthDirection); |
| 1632 | } |
| 1633 | |
| 1634 | @override |
| 1635 | Offset paintOffsetOf(RenderSliver child) { |
| 1636 | final SliverPhysicalParentData childParentData = child.parentData! as SliverPhysicalParentData; |
| 1637 | return childParentData.paintOffset; |
| 1638 | } |
| 1639 | |
| 1640 | @override |
| 1641 | double scrollOffsetOf(RenderSliver child, double scrollOffsetWithinChild) { |
| 1642 | assert(child.parent == this); |
| 1643 | final GrowthDirection growthDirection = child.constraints.growthDirection; |
| 1644 | switch (growthDirection) { |
| 1645 | case GrowthDirection.forward: |
| 1646 | double scrollOffsetToChild = 0.0; |
| 1647 | RenderSliver? current = center; |
| 1648 | while (current != child) { |
| 1649 | scrollOffsetToChild += current!.geometry!.scrollExtent; |
| 1650 | current = childAfter(current); |
| 1651 | } |
| 1652 | return scrollOffsetToChild + scrollOffsetWithinChild; |
| 1653 | case GrowthDirection.reverse: |
| 1654 | double scrollOffsetToChild = 0.0; |
| 1655 | RenderSliver? current = childBefore(center!); |
| 1656 | while (current != child) { |
| 1657 | scrollOffsetToChild -= current!.geometry!.scrollExtent; |
| 1658 | current = childBefore(current); |
| 1659 | } |
| 1660 | return scrollOffsetToChild - scrollOffsetWithinChild; |
| 1661 | } |
| 1662 | } |
| 1663 | |
| 1664 | @override |
| 1665 | double maxScrollObstructionExtentBefore(RenderSliver child) { |
| 1666 | assert(child.parent == this); |
| 1667 | final GrowthDirection growthDirection = child.constraints.growthDirection; |
| 1668 | switch (growthDirection) { |
| 1669 | case GrowthDirection.forward: |
| 1670 | double pinnedExtent = 0.0; |
| 1671 | RenderSliver? current = center; |
| 1672 | while (current != child) { |
| 1673 | pinnedExtent += current!.geometry!.maxScrollObstructionExtent; |
| 1674 | current = childAfter(current); |
| 1675 | } |
| 1676 | return pinnedExtent; |
| 1677 | case GrowthDirection.reverse: |
| 1678 | double pinnedExtent = 0.0; |
| 1679 | RenderSliver? current = childBefore(center!); |
| 1680 | while (current != child) { |
| 1681 | pinnedExtent += current!.geometry!.maxScrollObstructionExtent; |
| 1682 | current = childBefore(current); |
| 1683 | } |
| 1684 | return pinnedExtent; |
| 1685 | } |
| 1686 | } |
| 1687 | |
| 1688 | @override |
| 1689 | void applyPaintTransform(RenderObject child, Matrix4 transform) { |
| 1690 | // Hit test logic relies on this always providing an invertible matrix. |
| 1691 | final SliverPhysicalParentData childParentData = child.parentData! as SliverPhysicalParentData; |
| 1692 | childParentData.applyPaintTransform(transform); |
| 1693 | } |
| 1694 | |
| 1695 | @override |
| 1696 | double computeChildMainAxisPosition(RenderSliver child, double parentMainAxisPosition) { |
| 1697 | final Offset paintOffset = (child.parentData! as SliverPhysicalParentData).paintOffset; |
| 1698 | return switch (applyGrowthDirectionToAxisDirection( |
| 1699 | child.constraints.axisDirection, |
| 1700 | child.constraints.growthDirection, |
| 1701 | )) { |
| 1702 | AxisDirection.down => parentMainAxisPosition - paintOffset.dy, |
| 1703 | AxisDirection.right => parentMainAxisPosition - paintOffset.dx, |
| 1704 | AxisDirection.up => child.geometry!.paintExtent - (parentMainAxisPosition - paintOffset.dy), |
| 1705 | AxisDirection.left => child.geometry!.paintExtent - (parentMainAxisPosition - paintOffset.dx), |
| 1706 | }; |
| 1707 | } |
| 1708 | |
| 1709 | @override |
| 1710 | int get indexOfFirstChild { |
| 1711 | assert(center != null); |
| 1712 | assert(center!.parent == this); |
| 1713 | assert(firstChild != null); |
| 1714 | int count = 0; |
| 1715 | RenderSliver? child = center; |
| 1716 | while (child != firstChild) { |
| 1717 | count -= 1; |
| 1718 | child = childBefore(child!); |
| 1719 | } |
| 1720 | return count; |
| 1721 | } |
| 1722 | |
| 1723 | @override |
| 1724 | String labelForChild(int index) { |
| 1725 | if (index == 0) { |
| 1726 | return 'center child'; |
| 1727 | } |
| 1728 | return 'child$index '; |
| 1729 | } |
| 1730 | |
| 1731 | @override |
| 1732 | Iterable<RenderSliver> get childrenInPaintOrder { |
| 1733 | final List<RenderSliver> children = <RenderSliver>[]; |
| 1734 | if (firstChild == null) { |
| 1735 | return children; |
| 1736 | } |
| 1737 | RenderSliver? child = firstChild; |
| 1738 | while (child != center) { |
| 1739 | children.add(child!); |
| 1740 | child = childAfter(child); |
| 1741 | } |
| 1742 | child = lastChild; |
| 1743 | while (true) { |
| 1744 | children.add(child!); |
| 1745 | if (child == center) { |
| 1746 | return children; |
| 1747 | } |
| 1748 | child = childBefore(child); |
| 1749 | } |
| 1750 | } |
| 1751 | |
| 1752 | @override |
| 1753 | Iterable<RenderSliver> get childrenInHitTestOrder { |
| 1754 | final List<RenderSliver> children = <RenderSliver>[]; |
| 1755 | if (firstChild == null) { |
| 1756 | return children; |
| 1757 | } |
| 1758 | RenderSliver? child = center; |
| 1759 | while (child != null) { |
| 1760 | children.add(child); |
| 1761 | child = childAfter(child); |
| 1762 | } |
| 1763 | child = childBefore(center!); |
| 1764 | while (child != null) { |
| 1765 | children.add(child); |
| 1766 | child = childBefore(child); |
| 1767 | } |
| 1768 | return children; |
| 1769 | } |
| 1770 | |
| 1771 | @override |
| 1772 | void debugFillProperties(DiagnosticPropertiesBuilder properties) { |
| 1773 | super.debugFillProperties(properties); |
| 1774 | properties.add(DoubleProperty('anchor', anchor)); |
| 1775 | } |
| 1776 | } |
| 1777 | |
| 1778 | /// A render object that is bigger on the inside and shrink wraps its children |
| 1779 | /// in the main axis. |
| 1780 | /// |
| 1781 | /// [RenderShrinkWrappingViewport] displays a subset of its children according |
| 1782 | /// to its own dimensions and the given [offset]. As the offset varies, different |
| 1783 | /// children are visible through the viewport. |
| 1784 | /// |
| 1785 | /// [RenderShrinkWrappingViewport] differs from [RenderViewport] in that |
| 1786 | /// [RenderViewport] expands to fill the main axis whereas |
| 1787 | /// [RenderShrinkWrappingViewport] sizes itself to match its children in the |
| 1788 | /// main axis. This shrink wrapping behavior is expensive because the children, |
| 1789 | /// and hence the viewport, could potentially change size whenever the [offset] |
| 1790 | /// changes (e.g., because of a collapsing header). |
| 1791 | /// |
| 1792 | /// [RenderShrinkWrappingViewport] cannot contain [RenderBox] children directly. |
| 1793 | /// Instead, use a [RenderSliverList], [RenderSliverFixedExtentList], |
| 1794 | /// [RenderSliverGrid], or a [RenderSliverToBoxAdapter], for example. |
| 1795 | /// |
| 1796 | /// See also: |
| 1797 | /// |
| 1798 | /// * [RenderViewport], a viewport that does not shrink-wrap its contents. |
| 1799 | /// * [RenderSliver], which explains more about the Sliver protocol. |
| 1800 | /// * [RenderBox], which explains more about the Box protocol. |
| 1801 | /// * [RenderSliverToBoxAdapter], which allows a [RenderBox] object to be |
| 1802 | /// placed inside a [RenderSliver] (the opposite of this class). |
| 1803 | class RenderShrinkWrappingViewport extends RenderViewportBase<SliverLogicalContainerParentData> { |
| 1804 | /// Creates a viewport (for [RenderSliver] objects) that shrink-wraps its |
| 1805 | /// contents. |
| 1806 | /// |
| 1807 | /// The [offset] must be specified. For testing purposes, consider passing a |
| 1808 | /// [ViewportOffset.zero] or [ViewportOffset.fixed]. |
| 1809 | RenderShrinkWrappingViewport({ |
| 1810 | super.axisDirection, |
| 1811 | required super.crossAxisDirection, |
| 1812 | required super.offset, |
| 1813 | super.clipBehavior, |
| 1814 | List<RenderSliver>? children, |
| 1815 | }) { |
| 1816 | addAll(children); |
| 1817 | } |
| 1818 | |
| 1819 | @override |
| 1820 | void setupParentData(RenderObject child) { |
| 1821 | if (child.parentData is! SliverLogicalContainerParentData) { |
| 1822 | child.parentData = SliverLogicalContainerParentData(); |
| 1823 | } |
| 1824 | } |
| 1825 | |
| 1826 | @override |
| 1827 | bool debugThrowIfNotCheckingIntrinsics() { |
| 1828 | assert(() { |
| 1829 | if (!RenderObject.debugCheckingIntrinsics) { |
| 1830 | throw FlutterError.fromParts(<DiagnosticsNode>[ |
| 1831 | ErrorSummary('$runtimeType does not support returning intrinsic dimensions.'), |
| 1832 | ErrorDescription( |
| 1833 | 'Calculating the intrinsic dimensions would require instantiating every child of ' |
| 1834 | 'the viewport, which defeats the point of viewports being lazy.', |
| 1835 | ), |
| 1836 | ErrorHint( |
| 1837 | 'If you are merely trying to shrink-wrap the viewport in the main axis direction, ' |
| 1838 | 'you should be able to achieve that effect by just giving the viewport loose ' |
| 1839 | 'constraints, without needing to measure its intrinsic dimensions.', |
| 1840 | ), |
| 1841 | ]); |
| 1842 | } |
| 1843 | return true; |
| 1844 | }()); |
| 1845 | return true; |
| 1846 | } |
| 1847 | |
| 1848 | // Out-of-band data computed during layout. |
| 1849 | late double _maxScrollExtent; |
| 1850 | late double _shrinkWrapExtent; |
| 1851 | bool _hasVisualOverflow = false; |
| 1852 | |
| 1853 | bool _debugCheckHasBoundedCrossAxis() { |
| 1854 | assert(() { |
| 1855 | switch (axis) { |
| 1856 | case Axis.vertical: |
| 1857 | if (!constraints.hasBoundedWidth) { |
| 1858 | throw FlutterError( |
| 1859 | 'Vertical viewport was given unbounded width.\n' |
| 1860 | 'Viewports expand in the cross axis to fill their container and ' |
| 1861 | 'constrain their children to match their extent in the cross axis. ' |
| 1862 | 'In this case, a vertical shrinkwrapping viewport was given an ' |
| 1863 | 'unlimited amount of horizontal space in which to expand.', |
| 1864 | ); |
| 1865 | } |
| 1866 | case Axis.horizontal: |
| 1867 | if (!constraints.hasBoundedHeight) { |
| 1868 | throw FlutterError( |
| 1869 | 'Horizontal viewport was given unbounded height.\n' |
| 1870 | 'Viewports expand in the cross axis to fill their container and ' |
| 1871 | 'constrain their children to match their extent in the cross axis. ' |
| 1872 | 'In this case, a horizontal shrinkwrapping viewport was given an ' |
| 1873 | 'unlimited amount of vertical space in which to expand.', |
| 1874 | ); |
| 1875 | } |
| 1876 | } |
| 1877 | return true; |
| 1878 | }()); |
| 1879 | return true; |
| 1880 | } |
| 1881 | |
| 1882 | @override |
| 1883 | void performLayout() { |
| 1884 | final BoxConstraints constraints = this.constraints; |
| 1885 | if (firstChild == null) { |
| 1886 | // Shrinkwrapping viewport only requires the cross axis to be bounded. |
| 1887 | assert(_debugCheckHasBoundedCrossAxis()); |
| 1888 | size = switch (axis) { |
| 1889 | Axis.vertical => Size(constraints.maxWidth, constraints.minHeight), |
| 1890 | Axis.horizontal => Size(constraints.minWidth, constraints.maxHeight), |
| 1891 | }; |
| 1892 | offset.applyViewportDimension(0.0); |
| 1893 | _maxScrollExtent = 0.0; |
| 1894 | _shrinkWrapExtent = 0.0; |
| 1895 | _hasVisualOverflow = false; |
| 1896 | offset.applyContentDimensions(0.0, 0.0); |
| 1897 | return; |
| 1898 | } |
| 1899 | |
| 1900 | // Shrinkwrapping viewport only requires the cross axis to be bounded. |
| 1901 | assert(_debugCheckHasBoundedCrossAxis()); |
| 1902 | final (double mainAxisExtent, double crossAxisExtent) = switch (axis) { |
| 1903 | Axis.vertical => (constraints.maxHeight, constraints.maxWidth), |
| 1904 | Axis.horizontal => (constraints.maxWidth, constraints.maxHeight), |
| 1905 | }; |
| 1906 | |
| 1907 | double correction; |
| 1908 | double effectiveExtent; |
| 1909 | while (true) { |
| 1910 | correction = _attemptLayout(mainAxisExtent, crossAxisExtent, offset.pixels); |
| 1911 | if (correction != 0.0) { |
| 1912 | offset.correctBy(correction); |
| 1913 | } else { |
| 1914 | effectiveExtent = switch (axis) { |
| 1915 | Axis.vertical => constraints.constrainHeight(_shrinkWrapExtent), |
| 1916 | Axis.horizontal => constraints.constrainWidth(_shrinkWrapExtent), |
| 1917 | }; |
| 1918 | final bool didAcceptViewportDimension = offset.applyViewportDimension(effectiveExtent); |
| 1919 | final bool didAcceptContentDimension = offset.applyContentDimensions( |
| 1920 | 0.0, |
| 1921 | math.max(0.0, _maxScrollExtent - effectiveExtent), |
| 1922 | ); |
| 1923 | if (didAcceptViewportDimension && didAcceptContentDimension) { |
| 1924 | break; |
| 1925 | } |
| 1926 | } |
| 1927 | } |
| 1928 | size = switch (axis) { |
| 1929 | Axis.vertical => constraints.constrainDimensions(crossAxisExtent, effectiveExtent), |
| 1930 | Axis.horizontal => constraints.constrainDimensions(effectiveExtent, crossAxisExtent), |
| 1931 | }; |
| 1932 | } |
| 1933 | |
| 1934 | double _attemptLayout(double mainAxisExtent, double crossAxisExtent, double correctedOffset) { |
| 1935 | // We can't assert mainAxisExtent is finite, because it could be infinite if |
| 1936 | // it is within a column or row for example. In such a case, there's not |
| 1937 | // even any scrolling to do, although some scroll physics (i.e. |
| 1938 | // BouncingScrollPhysics) could still temporarily scroll the content in a |
| 1939 | // simulation. |
| 1940 | assert(!mainAxisExtent.isNaN); |
| 1941 | assert(mainAxisExtent >= 0.0); |
| 1942 | assert(crossAxisExtent.isFinite); |
| 1943 | assert(crossAxisExtent >= 0.0); |
| 1944 | assert(correctedOffset.isFinite); |
| 1945 | _maxScrollExtent = 0.0; |
| 1946 | _shrinkWrapExtent = 0.0; |
| 1947 | // Since the viewport is shrinkwrapped, we know that any negative overscroll |
| 1948 | // into the potentially infinite mainAxisExtent will overflow the end of |
| 1949 | // the viewport. |
| 1950 | _hasVisualOverflow = correctedOffset < 0.0; |
| 1951 | _calculatedCacheExtent = switch (cacheExtentStyle) { |
| 1952 | CacheExtentStyle.pixel => cacheExtent, |
| 1953 | CacheExtentStyle.viewport => mainAxisExtent * _cacheExtent, |
| 1954 | }; |
| 1955 | |
| 1956 | return layoutChildSequence( |
| 1957 | child: firstChild, |
| 1958 | scrollOffset: math.max(0.0, correctedOffset), |
| 1959 | overlap: math.min(0.0, correctedOffset), |
| 1960 | layoutOffset: math.max(0.0, -correctedOffset), |
| 1961 | remainingPaintExtent: mainAxisExtent + math.min(0.0, correctedOffset), |
| 1962 | mainAxisExtent: mainAxisExtent, |
| 1963 | crossAxisExtent: crossAxisExtent, |
| 1964 | growthDirection: GrowthDirection.forward, |
| 1965 | advance: childAfter, |
| 1966 | remainingCacheExtent: mainAxisExtent + 2 * _calculatedCacheExtent!, |
| 1967 | cacheOrigin: -_calculatedCacheExtent!, |
| 1968 | ); |
| 1969 | } |
| 1970 | |
| 1971 | @override |
| 1972 | bool get hasVisualOverflow => _hasVisualOverflow; |
| 1973 | |
| 1974 | @override |
| 1975 | void updateOutOfBandData(GrowthDirection growthDirection, SliverGeometry childLayoutGeometry) { |
| 1976 | assert(growthDirection == GrowthDirection.forward); |
| 1977 | _maxScrollExtent += childLayoutGeometry.scrollExtent; |
| 1978 | if (childLayoutGeometry.hasVisualOverflow) { |
| 1979 | _hasVisualOverflow = true; |
| 1980 | } |
| 1981 | _shrinkWrapExtent += childLayoutGeometry.maxPaintExtent; |
| 1982 | } |
| 1983 | |
| 1984 | @override |
| 1985 | void updateChildLayoutOffset( |
| 1986 | RenderSliver child, |
| 1987 | double layoutOffset, |
| 1988 | GrowthDirection growthDirection, |
| 1989 | ) { |
| 1990 | assert(growthDirection == GrowthDirection.forward); |
| 1991 | final SliverLogicalParentData childParentData = child.parentData! as SliverLogicalParentData; |
| 1992 | childParentData.layoutOffset = layoutOffset; |
| 1993 | } |
| 1994 | |
| 1995 | @override |
| 1996 | Offset paintOffsetOf(RenderSliver child) { |
| 1997 | final SliverLogicalParentData childParentData = child.parentData! as SliverLogicalParentData; |
| 1998 | return computeAbsolutePaintOffset( |
| 1999 | child, |
| 2000 | childParentData.layoutOffset!, |
| 2001 | GrowthDirection.forward, |
| 2002 | ); |
| 2003 | } |
| 2004 | |
| 2005 | @override |
| 2006 | double scrollOffsetOf(RenderSliver child, double scrollOffsetWithinChild) { |
| 2007 | assert(child.parent == this); |
| 2008 | assert(child.constraints.growthDirection == GrowthDirection.forward); |
| 2009 | double scrollOffsetToChild = 0.0; |
| 2010 | RenderSliver? current = firstChild; |
| 2011 | while (current != child) { |
| 2012 | scrollOffsetToChild += current!.geometry!.scrollExtent; |
| 2013 | current = childAfter(current); |
| 2014 | } |
| 2015 | return scrollOffsetToChild + scrollOffsetWithinChild; |
| 2016 | } |
| 2017 | |
| 2018 | @override |
| 2019 | double maxScrollObstructionExtentBefore(RenderSliver child) { |
| 2020 | assert(child.parent == this); |
| 2021 | assert(child.constraints.growthDirection == GrowthDirection.forward); |
| 2022 | double pinnedExtent = 0.0; |
| 2023 | RenderSliver? current = firstChild; |
| 2024 | while (current != child) { |
| 2025 | pinnedExtent += current!.geometry!.maxScrollObstructionExtent; |
| 2026 | current = childAfter(current); |
| 2027 | } |
| 2028 | return pinnedExtent; |
| 2029 | } |
| 2030 | |
| 2031 | @override |
| 2032 | void applyPaintTransform(RenderObject child, Matrix4 transform) { |
| 2033 | // Hit test logic relies on this always providing an invertible matrix. |
| 2034 | final Offset offset = paintOffsetOf(child as RenderSliver); |
| 2035 | transform.translate(offset.dx, offset.dy); |
| 2036 | } |
| 2037 | |
| 2038 | @override |
| 2039 | double computeChildMainAxisPosition(RenderSliver child, double parentMainAxisPosition) { |
| 2040 | assert(hasSize); |
| 2041 | final double layoutOffset = (child.parentData! as SliverLogicalParentData).layoutOffset!; |
| 2042 | return switch (applyGrowthDirectionToAxisDirection( |
| 2043 | child.constraints.axisDirection, |
| 2044 | child.constraints.growthDirection, |
| 2045 | )) { |
| 2046 | AxisDirection.down || AxisDirection.right => parentMainAxisPosition - layoutOffset, |
| 2047 | AxisDirection.up => size.height - parentMainAxisPosition - layoutOffset, |
| 2048 | AxisDirection.left => size.width - parentMainAxisPosition - layoutOffset, |
| 2049 | }; |
| 2050 | } |
| 2051 | |
| 2052 | @override |
| 2053 | int get indexOfFirstChild => 0; |
| 2054 | |
| 2055 | @override |
| 2056 | String labelForChild(int index) => 'child$index '; |
| 2057 | |
| 2058 | @override |
| 2059 | Iterable<RenderSliver> get childrenInPaintOrder { |
| 2060 | final List<RenderSliver> children = <RenderSliver>[]; |
| 2061 | RenderSliver? child = lastChild; |
| 2062 | while (child != null) { |
| 2063 | children.add(child); |
| 2064 | child = childBefore(child); |
| 2065 | } |
| 2066 | return children; |
| 2067 | } |
| 2068 | |
| 2069 | @override |
| 2070 | Iterable<RenderSliver> get childrenInHitTestOrder { |
| 2071 | final List<RenderSliver> children = <RenderSliver>[]; |
| 2072 | RenderSliver? child = firstChild; |
| 2073 | while (child != null) { |
| 2074 | children.add(child); |
| 2075 | child = childAfter(child); |
| 2076 | } |
| 2077 | return children; |
| 2078 | } |
| 2079 | } |
| 2080 |
Definitions
- CacheExtentStyle
- RenderAbstractViewport
- maybeOf
- of
- getOffsetToReveal
- RevealedOffset
- RevealedOffset
- clampOffset
- toString
- RenderViewportBase
- RenderViewportBase
- describeSemanticsConfiguration
- visitChildrenForSemantics
- axisDirection
- axisDirection
- crossAxisDirection
- crossAxisDirection
- axis
- offset
- offset
- cacheExtent
- cacheExtent
- cacheExtentStyle
- cacheExtentStyle
- clipBehavior
- clipBehavior
- attach
- detach
- debugThrowIfNotCheckingIntrinsics
- computeMinIntrinsicWidth
- computeMaxIntrinsicWidth
- computeMinIntrinsicHeight
- computeMaxIntrinsicHeight
- isRepaintBoundary
- layoutChildSequence
- describeApproximatePaintClip
- describeSemanticsClip
- paint
- dispose
- _paintContents
- debugPaintSize
- hitTestChildren
- getOffsetToReveal
- computeAbsolutePaintOffset
- debugFillProperties
- debugDescribeChildren
- hasVisualOverflow
- updateOutOfBandData
- updateChildLayoutOffset
- paintOffsetOf
- scrollOffsetOf
- maxScrollObstructionExtentBefore
- computeChildMainAxisPosition
- indexOfFirstChild
- labelForChild
- childrenInPaintOrder
- childrenInHitTestOrder
- showOnScreen
- showInViewport
- RenderViewport
- RenderViewport
- setupParentData
- anchor
- anchor
- center
- center
- sizedByParent
- computeDryLayout
- performLayout
- _attemptLayout
- hasVisualOverflow
- updateOutOfBandData
- updateChildLayoutOffset
- paintOffsetOf
- scrollOffsetOf
- maxScrollObstructionExtentBefore
- applyPaintTransform
- computeChildMainAxisPosition
- indexOfFirstChild
- labelForChild
- childrenInPaintOrder
- childrenInHitTestOrder
- debugFillProperties
- RenderShrinkWrappingViewport
- RenderShrinkWrappingViewport
- setupParentData
- debugThrowIfNotCheckingIntrinsics
- _debugCheckHasBoundedCrossAxis
- performLayout
- _attemptLayout
- hasVisualOverflow
- updateOutOfBandData
- updateChildLayoutOffset
- paintOffsetOf
- scrollOffsetOf
- maxScrollObstructionExtentBefore
- applyPaintTransform
- computeChildMainAxisPosition
- indexOfFirstChild
- labelForChild
- childrenInPaintOrder
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