9567if (_scrollData == null) { _scrollData = new ScrollData(); }

455_scrollData._computedOffset.X = startingOffset; 459_scrollData._computedOffset.Y = startingOffset; 489if (!DoubleUtil.AreClose(scrollX, _scrollData._offset.X)) 491Vector oldViewportOffset = _scrollData._offset; 494_scrollData._offset.X = scrollX; 497OnViewportOffsetChanged(oldViewportOffset, _scrollData._offset); 502_scrollData.SetHorizontalScrollType(oldViewportOffset.X, scrollX); 529_scrollData._offset.X = Math.Floor(_scrollData._offset.X); 530_scrollData._computedOffset.X = Math.Floor(_scrollData._computedOffset.X); 538_scrollData._offset.X = UIElement.RoundLayoutValue(_scrollData._offset.X, dpi.DpiScaleX); 539_scrollData._computedOffset.X = UIElement.RoundLayoutValue(_scrollData._computedOffset.X, dpi.DpiScaleX); 561_scrollData._computedOffset.X = startingOffset; 575_scrollData._offset.X = ScrollContentPresenter.CoerceOffset(scrollX, _scrollData._extent.Width, _scrollData._viewport.Width); 576_scrollData._computedOffset.X = _scrollData._offset.X; 584_scrollData._offset, _scrollData._extent, _scrollData._computedOffset); 617if (!DoubleUtil.AreClose(scrollY, _scrollData._offset.Y)) 619Vector oldViewportOffset = _scrollData._offset; 622_scrollData._offset.Y = scrollY; 625OnViewportOffsetChanged(oldViewportOffset, _scrollData._offset); 631_scrollData.SetVerticalScrollType(oldViewportOffset.Y, scrollY); 657_scrollData._offset.Y = Math.Floor(_scrollData._offset.Y); 658_scrollData._computedOffset.Y = Math.Floor(_scrollData._computedOffset.Y); 666_scrollData._offset.Y = UIElement.RoundLayoutValue(_scrollData._offset.Y, dpi.DpiScaleY); 667_scrollData._computedOffset.Y = UIElement.RoundLayoutValue(_scrollData._computedOffset.Y, dpi.DpiScaleY); 689_scrollData._computedOffset.Y = startingOffset; 703_scrollData._offset.Y = ScrollContentPresenter.CoerceOffset(scrollY, _scrollData._extent.Height, _scrollData._viewport.Height); 704_scrollData._computedOffset.Y = _scrollData._offset.Y; 718_scrollData._offset, _scrollData._extent, _scrollData._computedOffset); 756double expectedDistanceBetweenViewports = (isHorizontal ? _scrollData._offset.X - _scrollData._computedOffset.X : _scrollData._offset.Y - _scrollData._computedOffset.Y); 764if (_scrollData._firstContainerInViewport != null) 776_scrollData._offset.X += expectedDistanceBetweenViewports; 780_scrollData._offset.Y += expectedDistanceBetweenViewports; 784if (_scrollData._firstContainerInViewport == null) 786_scrollData._firstContainerInViewport = ComputeFirstContainerInViewport( 797out _scrollData._firstContainerOffsetFromViewport); 799if (_scrollData._firstContainerInViewport != null) 801_scrollData._expectedDistanceBetweenViewports = expectedDistanceBetweenViewports; 810_scrollData._expectedDistanceBetweenViewports += expectedDistanceBetweenViewports; 816_scrollData._expectedDistanceBetweenViewports, 817_scrollData._firstContainerInViewport, 818_scrollData._firstContainerOffsetFromViewport); 835Debug.Assert(_scrollData._firstContainerInViewport != null, "Must have an anchor element"); 839if (itemsControl == null || !VisualTreeHelper.IsAncestorOf(this, _scrollData._firstContainerInViewport)) 850_scrollData._expectedDistanceBetweenViewports, 851_scrollData._firstContainerInViewport); 880FrameworkElement prevFirstContainerInViewport = _scrollData._firstContainerInViewport; 881double prevFirstContainerOffsetFromViewport = _scrollData._firstContainerOffsetFromViewport; 882double prevFirstContainerOffset = FindScrollOffset(_scrollData._firstContainerInViewport); 898bool success = (LayoutDoubleUtil.AreClose(_scrollData._expectedDistanceBetweenViewports, actualDistanceBetweenViewports)); 915double diff = actualDistanceBetweenViewports - _scrollData._expectedDistanceBetweenViewports; 937computedOffset = _scrollData._computedOffset.X; 938maxOffset = _scrollData._extent.Width - _scrollData._viewport.Width; 942computedOffset = _scrollData._computedOffset.Y; 943maxOffset = _scrollData._extent.Height - _scrollData._viewport.Height; 955_scrollData._computedOffset.X = currFirstContainerOffset - currFirstContainerOffsetFromViewport; 956_scrollData._offset.X = _scrollData._computedOffset.X; 960_scrollData._computedOffset.Y = currFirstContainerOffset - currFirstContainerOffsetFromViewport; 961_scrollData._offset.Y = _scrollData._computedOffset.Y; 973_scrollData._offset); 983_scrollData._computedOffset.X = prevFirstContainerOffset - prevFirstContainerOffsetFromViewport; 985actualOffset = _scrollData._computedOffset.X + actualDistanceBetweenViewports; 986expectedOffset = _scrollData._computedOffset.X + _scrollData._expectedDistanceBetweenViewports; 987maxOffset = _scrollData._extent.Width - _scrollData._viewport.Width; 996_scrollData._computedOffset.X = actualOffset; 997_scrollData._offset.X = actualOffset; 1002_scrollData._offset.X = expectedOffset; 1008_scrollData._offset.X = expectedOffset; 1013_scrollData._computedOffset.Y = prevFirstContainerOffset - prevFirstContainerOffsetFromViewport; 1015actualOffset = _scrollData._computedOffset.Y + actualDistanceBetweenViewports; 1016expectedOffset = _scrollData._computedOffset.Y + _scrollData._expectedDistanceBetweenViewports; 1017maxOffset = _scrollData._extent.Height - _scrollData._viewport.Height; 1026_scrollData._computedOffset.Y = actualOffset; 1027_scrollData._offset.Y = actualOffset; 1032_scrollData._offset.Y = expectedOffset; 1038_scrollData._offset.Y = expectedOffset; 1045remeasure, expectedOffset, actualOffset, _scrollData._offset, _scrollData._computedOffset); 1091if (_scrollData == null) 1094if (_scrollData._firstContainerInViewport != null) 1096DependencyObject element = _scrollData._firstContainerInViewport; 1110_scrollData._firstContainerInViewport = null; 1111_scrollData._firstContainerOffsetFromViewport = 0; 1112_scrollData._expectedDistanceBetweenViewports = 0; 1523alignTop = (_scrollData._bringIntoViewLeafContainer == visual && AlignTopOfBringIntoViewContainer); 1524alignBottom = (_scrollData._bringIntoViewLeafContainer == visual && 1541newOffset.X = ScrollContentPresenter.CoerceOffset(newOffset.X, _scrollData._extent.Width, _scrollData._viewport.Width); 1542newOffset.Y = ScrollContentPresenter.CoerceOffset(newOffset.Y, _scrollData._extent.Height, _scrollData._viewport.Height); 1544if (!LayoutDoubleUtil.AreClose(newOffset.X, _scrollData._offset.X) || 1545!LayoutDoubleUtil.AreClose(newOffset.Y, _scrollData._offset.Y)) 1548if (visual != _scrollData._bringIntoViewLeafContainer) 1550_scrollData._bringIntoViewLeafContainer = visual; 1555Vector oldOffset = _scrollData._offset; 1556_scrollData._offset = newOffset; 1561_scrollData._offset, 1563_scrollData._bringIntoViewLeafContainer); 1571_scrollData.SetHorizontalScrollType(oldOffset.X, newOffset.X); 1572_scrollData.SetVerticalScrollType(oldOffset.Y, newOffset.Y); 1581_scrollData._computedOffset = newOffset; 1599_scrollData._bringIntoViewLeafContainer = null; 1826if (_scrollData == null) { return false; } 1827return _scrollData._allowHorizontal; 1832if (_scrollData._allowHorizontal != value) 1834_scrollData._allowHorizontal = value; 1849if (_scrollData == null) { return false; } 1850return _scrollData._allowVertical; 1855if (_scrollData._allowVertical != value) 1857_scrollData._allowVertical = value; 1870if (_scrollData == null) { return 0.0; } 1871return _scrollData._extent.Width; 1882if (_scrollData == null) { return 0.0; } 1883return _scrollData._extent.Height; 1894if (_scrollData == null) { return 0.0; } 1895return _scrollData._viewport.Width; 1906if (_scrollData == null) { return 0.0; } 1907return _scrollData._viewport.Height; 1919if (_scrollData == null) { return 0.0; } 1920return _scrollData._computedOffset.X; 1932if (_scrollData == null) { return 0.0; } 1933return _scrollData._computedOffset.Y; 1946if (_scrollData == null) return null; 1947return _scrollData._scrollOwner; 1952if (value != _scrollData._scrollOwner) 1955_scrollData._scrollOwner = value; 2614if (IsScrolling && _scrollData._firstContainerInViewport != null && !areContainersUniformlySized) 2655_scrollData._offset.X += delta; 2659_scrollData._offset.Y += delta; 2670"newVpOff:", _scrollData._offset); 3276return StackPanel.StackMeasureHelper(this, _scrollData, constraint); 3281return StackPanel.StackArrangeHelper(this, _scrollData, arrangeSize); 3566"ext:", IsScrolling ? _scrollData._extent : Size.Empty, 3630_scrollData._maxDesiredSize = new Size(); 3898_scrollData._extent.Width = distance; 3902_scrollData._extent.Height = distance; 3907ScrollTracer.Trace(this, ScrollTraceOp.UpdateExtent, "ext:", _scrollData._extent); 4336offsetX = _scrollData._offset.X; 4337offsetY = _scrollData._offset.Y; 4338extent = _scrollData._extent; 4339viewportSize = _scrollData._viewport; 4340scrollGeneration = _scrollData._scrollGeneration; 4344_scrollData._maxDesiredSize = new Size(); 4369WasLastMeasurePassAnchored = (_scrollData._firstContainerInViewport != null) || (_scrollData._bringIntoViewLeafContainer != null); 4673_scrollData._bringIntoViewLeafContainer = null; 4681_scrollData._offset = _scrollData._computedOffset; 4807if (DoubleUtil.GreaterThan(extendedViewport.X + extendedViewport.Width, _scrollData._extent.Width)) 4814extendedViewport.Width = Math.Max(_scrollData._extent.Width - extendedViewport.X, 0.0); 4847if (DoubleUtil.GreaterThan(extendedViewport.X + extendedViewport.Width / approxSizeOfLogicalUnit, _scrollData._extent.Width)) 4854extendedViewport.Width = Math.Max(_scrollData._extent.Width - extendedViewport.X, 0.0) * approxSizeOfLogicalUnit; 4923if (DoubleUtil.GreaterThan(extendedViewport.Y + extendedViewport.Height, _scrollData._extent.Height)) 4930extendedViewport.Height = Math.Max(_scrollData._extent.Height - extendedViewport.Y, 0.0); 4963if (DoubleUtil.GreaterThan(extendedViewport.Y + extendedViewport.Height / approxSizeOfLogicalUnit, _scrollData._extent.Height)) 4970extendedViewport.Height = Math.Max(_scrollData._extent.Height - extendedViewport.Y, 0.0) * approxSizeOfLogicalUnit; 4995if (!_scrollData.IsEmpty) 5004if (!_scrollData.IsEmpty) 5754++_scrollData._scrollGeneration; 8437rcChild.Y = -1.0 * _scrollData._computedOffset.Y; 8443rcChild.X = -1.0 * _scrollData._computedOffset.X; 8448rcChild.X = -1.0 * _scrollData._computedOffset.X; 8449rcChild.Y = -1.0 * _scrollData._computedOffset.Y; 9567if (_scrollData == null) { _scrollData = new ScrollData(); } 9577element._scrollData.ClearLayout(); 9619Vector offsetForScrollViewerRemeasure = _scrollData._offset; 9663stackPixelSize.Height = _scrollData._extent.Height; 9670_scrollData._maxDesiredSize.Height = Math.Max(_scrollData._maxDesiredSize.Height, stackPixelSize.Height); 9671stackPixelSize.Height = _scrollData._maxDesiredSize.Height; 9690stackPixelSize.Width = _scrollData._extent.Width; 9697_scrollData._maxDesiredSize.Width = Math.Max(_scrollData._maxDesiredSize.Width, stackPixelSize.Width); 9698stackPixelSize.Width = _scrollData._maxDesiredSize.Width; 9754"o:", _scrollData._offset, 9770isHorizontal ? (!DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X) || 9771(IsScrollActive && computedViewportOffset.X > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.X, _scrollData.Extent.Width-_scrollData.Viewport.Width))) 9772: (!DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y) || 9773(IsScrollActive && computedViewportOffset.Y > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.Y, _scrollData.Extent.Height-_scrollData.Viewport.Height))); 9775isHorizontal ? (!DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y) || 9776(IsScrollActive && computedViewportOffset.Y > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.Y, _scrollData.Extent.Height-_scrollData.Viewport.Height))) 9777: (!DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X) || 9778(IsScrollActive && computedViewportOffset.X > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.X, _scrollData.Extent.Width-_scrollData.Viewport.Width))); 9814_scrollData.HorizontalScrollType = ScrollType.ToEnd; 9837_scrollData.VerticalScrollType = ScrollType.ToEnd; 9874bool viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 9875bool extentSizeChanged = !DoubleUtil.AreClose(extentSize, _scrollData._extent); 9876bool computedViewportOffsetChanged = !DoubleUtil.AreClose(computedViewportOffset, _scrollData._computedOffset); 9881extentWidthChanged = !DoubleUtil.AreClose(extentSize.Width, _scrollData._extent.Width); 9882extentHeightChanged = !DoubleUtil.AreClose(extentSize.Height, _scrollData._extent.Height); 10021!DoubleUtil.AreClose(_scrollData._viewport.Width, viewportSize.Width)) 10027"vpSz:", _scrollData._viewport.Width, viewportSize.Width, 10028"newOff:", _scrollData._offset); 10037viewportSize.Width = _scrollData._viewport.Width; 10051if (_scrollData.HorizontalScrollType == ScrollType.ToEnd || 10059"ext:", _scrollData._extent.Width, extentSize.Width, 10065_scrollData.HorizontalScrollType = ScrollType.ToEnd; 10074else if (_scrollData.HorizontalScrollType == ScrollType.Absolute) 10076if (!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10081if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10084viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10090if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.X)/extentSize.Width, Math.Floor(_scrollData._offset.X)/_scrollData._extent.Width)) 10093viewportOffset.X = Math.Floor((extentSize.Width * Math.Floor(_scrollData._offset.X)) / _scrollData._extent.Width); 10101"expRat:", _scrollData._offset.X, _scrollData._extent.Width, (_scrollData._offset.X/_scrollData._extent.Width), 10118if (_scrollData.VerticalScrollType == ScrollType.ToEnd || 10127"ext:", _scrollData._extent.Height, extentSize.Height, 10133_scrollData.VerticalScrollType = ScrollType.ToEnd; 10141else if (_scrollData.VerticalScrollType == ScrollType.Absolute) 10143if (!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10146if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10149viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10156"expRat:", _scrollData._offset.Y, _scrollData._extent.Height, (_scrollData._offset.Y/_scrollData._extent.Height), 10238!DoubleUtil.AreClose(_scrollData._viewport.Height, viewportSize.Height)) 10244"vpSz:", _scrollData._viewport.Height, viewportSize.Height, 10245"newOff:", _scrollData._offset); 10254viewportSize.Height = _scrollData._viewport.Height; 10268if (_scrollData.VerticalScrollType == ScrollType.ToEnd || 10276"ext:", _scrollData._extent.Height, extentSize.Height, 10282_scrollData.VerticalScrollType = ScrollType.ToEnd; 10291else if (_scrollData.VerticalScrollType == ScrollType.Absolute) 10293if (!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10298if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10301viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10307if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.Y)/extentSize.Height, Math.Floor(_scrollData._offset.Y)/_scrollData._extent.Height)) 10310viewportOffset.Y = Math.Floor((extentSize.Height * Math.Floor(_scrollData._offset.Y)) / _scrollData._extent.Height); 10317"expRat:", _scrollData._offset.Y, _scrollData._extent.Height, (_scrollData._offset.Y/_scrollData._extent.Height), 10334if (_scrollData.HorizontalScrollType == ScrollType.ToEnd || 10343"ext:", _scrollData._extent.Width, extentSize.Width, 10349_scrollData.HorizontalScrollType = ScrollType.ToEnd; 10357else if (_scrollData.HorizontalScrollType == ScrollType.Absolute) 10359if (!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10362if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10365viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10372"expRat:", _scrollData._offset.X, _scrollData._extent.Width, (_scrollData._offset.X/_scrollData._extent.Width), 10388if (isHorizontal && _scrollData.HorizontalScrollType == ScrollType.ToEnd) 10392if (!isHorizontal && _scrollData.VerticalScrollType == ScrollType.ToEnd) 10406viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10411"off:", _scrollData._offset, viewportOffset, 10412"ext:", _scrollData._extent, extentSize, 10413"co:", _scrollData._computedOffset, computedViewportOffset, 10414"vp:", _scrollData._viewport, viewportSize); 10420Vector oldViewportOffset = _scrollData._computedOffset; 10421Size oldViewportSize = _scrollData._viewport; 10423_scrollData._viewport = viewportSize; 10424_scrollData._extent = extentSize; 10425_scrollData._computedOffset = computedViewportOffset; 10442_scrollData._offset = viewportOffset; 10515stackPixelSize.Height = _scrollData._extent.Height; 10522_scrollData._maxDesiredSize.Height = Math.Max(_scrollData._maxDesiredSize.Height, stackPixelSize.Height); 10523stackPixelSize.Height = _scrollData._maxDesiredSize.Height; 10542stackPixelSize.Width = _scrollData._extent.Width; 10549_scrollData._maxDesiredSize.Width = Math.Max(_scrollData._maxDesiredSize.Width, stackPixelSize.Width); 10550stackPixelSize.Width = _scrollData._maxDesiredSize.Width; 10602bool viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10603bool extentSizeChanged = !DoubleUtil.AreClose(extentSize, _scrollData._extent); 10604bool computedViewportOffsetChanged = !DoubleUtil.AreClose(computedViewportOffset, _scrollData._computedOffset); 10632viewportOffset = _scrollData._offset; 10648viewportOffset = _scrollData._offset; 10661bool wasViewportOffsetCoerced = !DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X); 10694!DoubleUtil.AreClose(_scrollData._viewport.Width, viewportSize.Width)) 10697viewportOffset.X = _scrollData._offset.X; 10702viewportSize.Width = _scrollData._viewport.Width; 10707if (!remeasure && extentSizeChanged && !DoubleUtil.AreClose(_scrollData._extent.Width, extentSize.Width)) 10730viewportOffset.X = _scrollData._offset.X; 10744(_scrollData._firstContainerInViewport == null && computedViewportOffsetChanged && !LayoutDoubleUtil.AreClose(computedViewportOffset.X, _scrollData._computedOffset.X)); 10747!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10752if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10755viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10761if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.X)/extentSize.Width, Math.Floor(_scrollData._offset.X)/_scrollData._extent.Width)) 10764viewportOffset.X = Math.Floor((extentSize.Width * Math.Floor(_scrollData._offset.X)) / _scrollData._extent.Width); 10792bool wasViewportOffsetCoerced = !DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y); 10825!DoubleUtil.AreClose(_scrollData._viewport.Height, viewportSize.Height)) 10828viewportOffset.Y = _scrollData._offset.Y; 10833viewportSize.Height = _scrollData._viewport.Height; 10838if (!remeasure && extentSizeChanged && !DoubleUtil.AreClose(_scrollData._extent.Height, extentSize.Height)) 10861viewportOffset.Y = _scrollData._offset.Y; 10875(_scrollData._firstContainerInViewport == null && computedViewportOffsetChanged && !LayoutDoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._computedOffset.Y)); 10878!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10883if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10886viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10892if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.Y)/extentSize.Height, Math.Floor(_scrollData._offset.Y)/_scrollData._extent.Height)) 10895viewportOffset.Y = Math.Floor((extentSize.Height * Math.Floor(_scrollData._offset.Y)) / _scrollData._extent.Height); 10918viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10923Vector oldViewportOffset = _scrollData._computedOffset; 10924Size oldViewportSize = _scrollData._viewport; 10926_scrollData._viewport = viewportSize; 10927_scrollData._extent = extentSize; 10928_scrollData._computedOffset = computedViewportOffset; 10945_scrollData._offset = viewportOffset; 11172viewportOffset = _scrollData._computedOffset.X; 11179viewportOffset = _scrollData._computedOffset.Y; 11220firstChildInView = (int)_scrollData._computedOffset.X; 11221viewportSize = (int)_scrollData._viewport.Width; 11225firstChildInView = (int)_scrollData._computedOffset.Y; 11226viewportSize = (int)_scrollData._viewport.Height; 11351get { return (_scrollData != null) && (_scrollData._scrollOwner != null); } 11518_scrollData.HorizontalScrollType = ScrollType.None; 11519_scrollData.VerticalScrollType = ScrollType.None; 11623get { return _scrollData?._bringIntoViewLeafContainer ?? null; } 11628get { return _scrollData?._firstContainerInViewport ?? null; } 11633get { return _scrollData?._firstContainerOffsetFromViewport ?? 0.0; } 11638get { return _scrollData?._expectedDistanceBetweenViewports ?? 0.0; } 12998s._scrollData._offset = _scrollData._offset; 12999s._scrollData._extent = _scrollData._extent; 13000s._scrollData._computedOffset = _scrollData._computedOffset; 13001s._scrollData._viewport = _scrollData._viewport;