9543if (_scrollData == null) { _scrollData = new ScrollData(); }

450_scrollData._computedOffset.X = startingOffset; 454_scrollData._computedOffset.Y = startingOffset; 484if (!DoubleUtil.AreClose(scrollX, _scrollData._offset.X)) 486Vector oldViewportOffset = _scrollData._offset; 489_scrollData._offset.X = scrollX; 492OnViewportOffsetChanged(oldViewportOffset, _scrollData._offset); 497_scrollData.SetHorizontalScrollType(oldViewportOffset.X, scrollX); 524_scrollData._offset.X = Math.Floor(_scrollData._offset.X); 525_scrollData._computedOffset.X = Math.Floor(_scrollData._computedOffset.X); 533_scrollData._offset.X = UIElement.RoundLayoutValue(_scrollData._offset.X, dpi.DpiScaleX); 534_scrollData._computedOffset.X = UIElement.RoundLayoutValue(_scrollData._computedOffset.X, dpi.DpiScaleX); 556_scrollData._computedOffset.X = startingOffset; 570_scrollData._offset.X = ScrollContentPresenter.CoerceOffset(scrollX, _scrollData._extent.Width, _scrollData._viewport.Width); 571_scrollData._computedOffset.X = _scrollData._offset.X; 579_scrollData._offset, _scrollData._extent, _scrollData._computedOffset); 612if (!DoubleUtil.AreClose(scrollY, _scrollData._offset.Y)) 614Vector oldViewportOffset = _scrollData._offset; 617_scrollData._offset.Y = scrollY; 620OnViewportOffsetChanged(oldViewportOffset, _scrollData._offset); 626_scrollData.SetVerticalScrollType(oldViewportOffset.Y, scrollY); 652_scrollData._offset.Y = Math.Floor(_scrollData._offset.Y); 653_scrollData._computedOffset.Y = Math.Floor(_scrollData._computedOffset.Y); 661_scrollData._offset.Y = UIElement.RoundLayoutValue(_scrollData._offset.Y, dpi.DpiScaleY); 662_scrollData._computedOffset.Y = UIElement.RoundLayoutValue(_scrollData._computedOffset.Y, dpi.DpiScaleY); 684_scrollData._computedOffset.Y = startingOffset; 698_scrollData._offset.Y = ScrollContentPresenter.CoerceOffset(scrollY, _scrollData._extent.Height, _scrollData._viewport.Height); 699_scrollData._computedOffset.Y = _scrollData._offset.Y; 713_scrollData._offset, _scrollData._extent, _scrollData._computedOffset); 751double expectedDistanceBetweenViewports = (isHorizontal ? _scrollData._offset.X - _scrollData._computedOffset.X : _scrollData._offset.Y - _scrollData._computedOffset.Y); 759if (_scrollData._firstContainerInViewport != null) 771_scrollData._offset.X += expectedDistanceBetweenViewports; 775_scrollData._offset.Y += expectedDistanceBetweenViewports; 779if (_scrollData._firstContainerInViewport == null) 781_scrollData._firstContainerInViewport = ComputeFirstContainerInViewport( 792out _scrollData._firstContainerOffsetFromViewport); 794if (_scrollData._firstContainerInViewport != null) 796_scrollData._expectedDistanceBetweenViewports = expectedDistanceBetweenViewports; 805_scrollData._expectedDistanceBetweenViewports += expectedDistanceBetweenViewports; 811_scrollData._expectedDistanceBetweenViewports, 812_scrollData._firstContainerInViewport, 813_scrollData._firstContainerOffsetFromViewport); 830Debug.Assert(_scrollData._firstContainerInViewport != null, "Must have an anchor element"); 834if (itemsControl == null || !VisualTreeHelper.IsAncestorOf(this, _scrollData._firstContainerInViewport)) 845_scrollData._expectedDistanceBetweenViewports, 846_scrollData._firstContainerInViewport); 875FrameworkElement prevFirstContainerInViewport = _scrollData._firstContainerInViewport; 876double prevFirstContainerOffsetFromViewport = _scrollData._firstContainerOffsetFromViewport; 877double prevFirstContainerOffset = FindScrollOffset(_scrollData._firstContainerInViewport); 893bool success = (LayoutDoubleUtil.AreClose(_scrollData._expectedDistanceBetweenViewports, actualDistanceBetweenViewports)); 910double diff = actualDistanceBetweenViewports - _scrollData._expectedDistanceBetweenViewports; 932computedOffset = _scrollData._computedOffset.X; 933maxOffset = _scrollData._extent.Width - _scrollData._viewport.Width; 937computedOffset = _scrollData._computedOffset.Y; 938maxOffset = _scrollData._extent.Height - _scrollData._viewport.Height; 950_scrollData._computedOffset.X = currFirstContainerOffset - currFirstContainerOffsetFromViewport; 951_scrollData._offset.X = _scrollData._computedOffset.X; 955_scrollData._computedOffset.Y = currFirstContainerOffset - currFirstContainerOffsetFromViewport; 956_scrollData._offset.Y = _scrollData._computedOffset.Y; 968_scrollData._offset); 978_scrollData._computedOffset.X = prevFirstContainerOffset - prevFirstContainerOffsetFromViewport; 980actualOffset = _scrollData._computedOffset.X + actualDistanceBetweenViewports; 981expectedOffset = _scrollData._computedOffset.X + _scrollData._expectedDistanceBetweenViewports; 982maxOffset = _scrollData._extent.Width - _scrollData._viewport.Width; 991_scrollData._computedOffset.X = actualOffset; 992_scrollData._offset.X = actualOffset; 997_scrollData._offset.X = expectedOffset; 1003_scrollData._offset.X = expectedOffset; 1008_scrollData._computedOffset.Y = prevFirstContainerOffset - prevFirstContainerOffsetFromViewport; 1010actualOffset = _scrollData._computedOffset.Y + actualDistanceBetweenViewports; 1011expectedOffset = _scrollData._computedOffset.Y + _scrollData._expectedDistanceBetweenViewports; 1012maxOffset = _scrollData._extent.Height - _scrollData._viewport.Height; 1021_scrollData._computedOffset.Y = actualOffset; 1022_scrollData._offset.Y = actualOffset; 1027_scrollData._offset.Y = expectedOffset; 1033_scrollData._offset.Y = expectedOffset; 1040remeasure, expectedOffset, actualOffset, _scrollData._offset, _scrollData._computedOffset); 1086if (_scrollData == null) 1089if (_scrollData._firstContainerInViewport != null) 1091DependencyObject element = _scrollData._firstContainerInViewport; 1105_scrollData._firstContainerInViewport = null; 1106_scrollData._firstContainerOffsetFromViewport = 0; 1107_scrollData._expectedDistanceBetweenViewports = 0; 1514alignTop = (_scrollData._bringIntoViewLeafContainer == visual && AlignTopOfBringIntoViewContainer); 1515alignBottom = (_scrollData._bringIntoViewLeafContainer == visual && 1532newOffset.X = ScrollContentPresenter.CoerceOffset(newOffset.X, _scrollData._extent.Width, _scrollData._viewport.Width); 1533newOffset.Y = ScrollContentPresenter.CoerceOffset(newOffset.Y, _scrollData._extent.Height, _scrollData._viewport.Height); 1535if (!LayoutDoubleUtil.AreClose(newOffset.X, _scrollData._offset.X) || 1536!LayoutDoubleUtil.AreClose(newOffset.Y, _scrollData._offset.Y)) 1539if (visual != _scrollData._bringIntoViewLeafContainer) 1541_scrollData._bringIntoViewLeafContainer = visual; 1546Vector oldOffset = _scrollData._offset; 1547_scrollData._offset = newOffset; 1552_scrollData._offset, 1554_scrollData._bringIntoViewLeafContainer); 1562_scrollData.SetHorizontalScrollType(oldOffset.X, newOffset.X); 1563_scrollData.SetVerticalScrollType(oldOffset.Y, newOffset.Y); 1572_scrollData._computedOffset = newOffset; 1587_scrollData._bringIntoViewLeafContainer = null; 1811if (_scrollData == null) { return false; } 1812return _scrollData._allowHorizontal; 1817if (_scrollData._allowHorizontal != value) 1819_scrollData._allowHorizontal = value; 1834if (_scrollData == null) { return false; } 1835return _scrollData._allowVertical; 1840if (_scrollData._allowVertical != value) 1842_scrollData._allowVertical = value; 1855if (_scrollData == null) { return 0.0; } 1856return _scrollData._extent.Width; 1867if (_scrollData == null) { return 0.0; } 1868return _scrollData._extent.Height; 1879if (_scrollData == null) { return 0.0; } 1880return _scrollData._viewport.Width; 1891if (_scrollData == null) { return 0.0; } 1892return _scrollData._viewport.Height; 1904if (_scrollData == null) { return 0.0; } 1905return _scrollData._computedOffset.X; 1917if (_scrollData == null) { return 0.0; } 1918return _scrollData._computedOffset.Y; 1931if (_scrollData == null) return null; 1932return _scrollData._scrollOwner; 1937if (value != _scrollData._scrollOwner) 1940_scrollData._scrollOwner = value; 2598if (IsScrolling && _scrollData._firstContainerInViewport != null && !areContainersUniformlySized) 2639_scrollData._offset.X += delta; 2643_scrollData._offset.Y += delta; 2654"newVpOff:", _scrollData._offset); 3257return StackPanel.StackMeasureHelper(this, _scrollData, constraint); 3262return StackPanel.StackArrangeHelper(this, _scrollData, arrangeSize); 3547"ext:", IsScrolling ? _scrollData._extent : Size.Empty, 3611_scrollData._maxDesiredSize = new Size(); 3879_scrollData._extent.Width = distance; 3883_scrollData._extent.Height = distance; 3888ScrollTracer.Trace(this, ScrollTraceOp.UpdateExtent, "ext:", _scrollData._extent); 4311offsetX = _scrollData._offset.X; 4312offsetY = _scrollData._offset.Y; 4313extent = _scrollData._extent; 4314viewportSize = _scrollData._viewport; 4315scrollGeneration = _scrollData._scrollGeneration; 4319_scrollData._maxDesiredSize = new Size(); 4344WasLastMeasurePassAnchored = (_scrollData._firstContainerInViewport != null) || (_scrollData._bringIntoViewLeafContainer != null); 4645_scrollData._bringIntoViewLeafContainer = null; 4653_scrollData._offset = _scrollData._computedOffset; 4779if (DoubleUtil.GreaterThan(extendedViewport.X + extendedViewport.Width, _scrollData._extent.Width)) 4786extendedViewport.Width = Math.Max(_scrollData._extent.Width - extendedViewport.X, 0.0); 4819if (DoubleUtil.GreaterThan(extendedViewport.X + extendedViewport.Width / approxSizeOfLogicalUnit, _scrollData._extent.Width)) 4826extendedViewport.Width = Math.Max(_scrollData._extent.Width - extendedViewport.X, 0.0) * approxSizeOfLogicalUnit; 4895if (DoubleUtil.GreaterThan(extendedViewport.Y + extendedViewport.Height, _scrollData._extent.Height)) 4902extendedViewport.Height = Math.Max(_scrollData._extent.Height - extendedViewport.Y, 0.0); 4935if (DoubleUtil.GreaterThan(extendedViewport.Y + extendedViewport.Height / approxSizeOfLogicalUnit, _scrollData._extent.Height)) 4942extendedViewport.Height = Math.Max(_scrollData._extent.Height - extendedViewport.Y, 0.0) * approxSizeOfLogicalUnit; 4967if (!_scrollData.IsEmpty) 4976if (!_scrollData.IsEmpty) 5726++_scrollData._scrollGeneration; 8411rcChild.Y = -1.0 * _scrollData._computedOffset.Y; 8417rcChild.X = -1.0 * _scrollData._computedOffset.X; 8422rcChild.X = -1.0 * _scrollData._computedOffset.X; 8423rcChild.Y = -1.0 * _scrollData._computedOffset.Y; 9543if (_scrollData == null) { _scrollData = new ScrollData(); } 9553element._scrollData.ClearLayout(); 9595Vector offsetForScrollViewerRemeasure = _scrollData._offset; 9639stackPixelSize.Height = _scrollData._extent.Height; 9646_scrollData._maxDesiredSize.Height = Math.Max(_scrollData._maxDesiredSize.Height, stackPixelSize.Height); 9647stackPixelSize.Height = _scrollData._maxDesiredSize.Height; 9666stackPixelSize.Width = _scrollData._extent.Width; 9673_scrollData._maxDesiredSize.Width = Math.Max(_scrollData._maxDesiredSize.Width, stackPixelSize.Width); 9674stackPixelSize.Width = _scrollData._maxDesiredSize.Width; 9730"o:", _scrollData._offset, 9746isHorizontal ? (!DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X) || 9747(IsScrollActive && computedViewportOffset.X > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.X, _scrollData.Extent.Width-_scrollData.Viewport.Width))) 9748: (!DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y) || 9749(IsScrollActive && computedViewportOffset.Y > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.Y, _scrollData.Extent.Height-_scrollData.Viewport.Height))); 9751isHorizontal ? (!DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y) || 9752(IsScrollActive && computedViewportOffset.Y > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.Y, _scrollData.Extent.Height-_scrollData.Viewport.Height))) 9753: (!DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X) || 9754(IsScrollActive && computedViewportOffset.X > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.X, _scrollData.Extent.Width-_scrollData.Viewport.Width))); 9790_scrollData.HorizontalScrollType = ScrollType.ToEnd; 9813_scrollData.VerticalScrollType = ScrollType.ToEnd; 9847bool viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 9848bool extentSizeChanged = !DoubleUtil.AreClose(extentSize, _scrollData._extent); 9849bool computedViewportOffsetChanged = !DoubleUtil.AreClose(computedViewportOffset, _scrollData._computedOffset); 9854extentWidthChanged = !DoubleUtil.AreClose(extentSize.Width, _scrollData._extent.Width); 9855extentHeightChanged = !DoubleUtil.AreClose(extentSize.Height, _scrollData._extent.Height); 9994!DoubleUtil.AreClose(_scrollData._viewport.Width, viewportSize.Width)) 10000"vpSz:", _scrollData._viewport.Width, viewportSize.Width, 10001"newOff:", _scrollData._offset); 10010viewportSize.Width = _scrollData._viewport.Width; 10024if (_scrollData.HorizontalScrollType == ScrollType.ToEnd || 10032"ext:", _scrollData._extent.Width, extentSize.Width, 10038_scrollData.HorizontalScrollType = ScrollType.ToEnd; 10047else if (_scrollData.HorizontalScrollType == ScrollType.Absolute) 10049if (!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10054if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10057viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10063if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.X)/extentSize.Width, Math.Floor(_scrollData._offset.X)/_scrollData._extent.Width)) 10066viewportOffset.X = Math.Floor((extentSize.Width * Math.Floor(_scrollData._offset.X)) / _scrollData._extent.Width); 10074"expRat:", _scrollData._offset.X, _scrollData._extent.Width, (_scrollData._offset.X/_scrollData._extent.Width), 10091if (_scrollData.VerticalScrollType == ScrollType.ToEnd || 10100"ext:", _scrollData._extent.Height, extentSize.Height, 10106_scrollData.VerticalScrollType = ScrollType.ToEnd; 10114else if (_scrollData.VerticalScrollType == ScrollType.Absolute) 10116if (!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10119if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10122viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10129"expRat:", _scrollData._offset.Y, _scrollData._extent.Height, (_scrollData._offset.Y/_scrollData._extent.Height), 10211!DoubleUtil.AreClose(_scrollData._viewport.Height, viewportSize.Height)) 10217"vpSz:", _scrollData._viewport.Height, viewportSize.Height, 10218"newOff:", _scrollData._offset); 10227viewportSize.Height = _scrollData._viewport.Height; 10241if (_scrollData.VerticalScrollType == ScrollType.ToEnd || 10249"ext:", _scrollData._extent.Height, extentSize.Height, 10255_scrollData.VerticalScrollType = ScrollType.ToEnd; 10264else if (_scrollData.VerticalScrollType == ScrollType.Absolute) 10266if (!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10271if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10274viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10280if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.Y)/extentSize.Height, Math.Floor(_scrollData._offset.Y)/_scrollData._extent.Height)) 10283viewportOffset.Y = Math.Floor((extentSize.Height * Math.Floor(_scrollData._offset.Y)) / _scrollData._extent.Height); 10290"expRat:", _scrollData._offset.Y, _scrollData._extent.Height, (_scrollData._offset.Y/_scrollData._extent.Height), 10307if (_scrollData.HorizontalScrollType == ScrollType.ToEnd || 10316"ext:", _scrollData._extent.Width, extentSize.Width, 10322_scrollData.HorizontalScrollType = ScrollType.ToEnd; 10330else if (_scrollData.HorizontalScrollType == ScrollType.Absolute) 10332if (!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10335if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10338viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10345"expRat:", _scrollData._offset.X, _scrollData._extent.Width, (_scrollData._offset.X/_scrollData._extent.Width), 10361if (isHorizontal && _scrollData.HorizontalScrollType == ScrollType.ToEnd) 10365if (!isHorizontal && _scrollData.VerticalScrollType == ScrollType.ToEnd) 10379viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10384"off:", _scrollData._offset, viewportOffset, 10385"ext:", _scrollData._extent, extentSize, 10386"co:", _scrollData._computedOffset, computedViewportOffset, 10387"vp:", _scrollData._viewport, viewportSize); 10393Vector oldViewportOffset = _scrollData._computedOffset; 10394Size oldViewportSize = _scrollData._viewport; 10396_scrollData._viewport = viewportSize; 10397_scrollData._extent = extentSize; 10398_scrollData._computedOffset = computedViewportOffset; 10415_scrollData._offset = viewportOffset; 10488stackPixelSize.Height = _scrollData._extent.Height; 10495_scrollData._maxDesiredSize.Height = Math.Max(_scrollData._maxDesiredSize.Height, stackPixelSize.Height); 10496stackPixelSize.Height = _scrollData._maxDesiredSize.Height; 10515stackPixelSize.Width = _scrollData._extent.Width; 10522_scrollData._maxDesiredSize.Width = Math.Max(_scrollData._maxDesiredSize.Width, stackPixelSize.Width); 10523stackPixelSize.Width = _scrollData._maxDesiredSize.Width; 10575bool viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10576bool extentSizeChanged = !DoubleUtil.AreClose(extentSize, _scrollData._extent); 10577bool computedViewportOffsetChanged = !DoubleUtil.AreClose(computedViewportOffset, _scrollData._computedOffset); 10605viewportOffset = _scrollData._offset; 10621viewportOffset = _scrollData._offset; 10634bool wasViewportOffsetCoerced = !DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X); 10667!DoubleUtil.AreClose(_scrollData._viewport.Width, viewportSize.Width)) 10670viewportOffset.X = _scrollData._offset.X; 10675viewportSize.Width = _scrollData._viewport.Width; 10680if (!remeasure && extentSizeChanged && !DoubleUtil.AreClose(_scrollData._extent.Width, extentSize.Width)) 10703viewportOffset.X = _scrollData._offset.X; 10717(_scrollData._firstContainerInViewport == null && computedViewportOffsetChanged && !LayoutDoubleUtil.AreClose(computedViewportOffset.X, _scrollData._computedOffset.X)); 10720!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10725if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10728viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10734if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.X)/extentSize.Width, Math.Floor(_scrollData._offset.X)/_scrollData._extent.Width)) 10737viewportOffset.X = Math.Floor((extentSize.Width * Math.Floor(_scrollData._offset.X)) / _scrollData._extent.Width); 10765bool wasViewportOffsetCoerced = !DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y); 10798!DoubleUtil.AreClose(_scrollData._viewport.Height, viewportSize.Height)) 10801viewportOffset.Y = _scrollData._offset.Y; 10806viewportSize.Height = _scrollData._viewport.Height; 10811if (!remeasure && extentSizeChanged && !DoubleUtil.AreClose(_scrollData._extent.Height, extentSize.Height)) 10834viewportOffset.Y = _scrollData._offset.Y; 10848(_scrollData._firstContainerInViewport == null && computedViewportOffsetChanged && !LayoutDoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._computedOffset.Y)); 10851!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10856if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10859viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10865if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.Y)/extentSize.Height, Math.Floor(_scrollData._offset.Y)/_scrollData._extent.Height)) 10868viewportOffset.Y = Math.Floor((extentSize.Height * Math.Floor(_scrollData._offset.Y)) / _scrollData._extent.Height); 10891viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10896Vector oldViewportOffset = _scrollData._computedOffset; 10897Size oldViewportSize = _scrollData._viewport; 10899_scrollData._viewport = viewportSize; 10900_scrollData._extent = extentSize; 10901_scrollData._computedOffset = computedViewportOffset; 10918_scrollData._offset = viewportOffset; 11145viewportOffset = _scrollData._computedOffset.X; 11152viewportOffset = _scrollData._computedOffset.Y; 11193firstChildInView = (int)_scrollData._computedOffset.X; 11194viewportSize = (int)_scrollData._viewport.Width; 11198firstChildInView = (int)_scrollData._computedOffset.Y; 11199viewportSize = (int)_scrollData._viewport.Height; 11324get { return (_scrollData != null) && (_scrollData._scrollOwner != null); } 11491_scrollData.HorizontalScrollType = ScrollType.None; 11492_scrollData.VerticalScrollType = ScrollType.None; 11596get { return _scrollData?._bringIntoViewLeafContainer ?? null; } 11601get { return _scrollData?._firstContainerInViewport ?? null; } 11606get { return _scrollData?._firstContainerOffsetFromViewport ?? 0.0; } 11611get { return _scrollData?._expectedDistanceBetweenViewports ?? 0.0; } 12965_offset = _scrollData._offset, 12966_extent = _scrollData._extent, 12967_computedOffset = _scrollData._computedOffset, 12968_viewport = _scrollData._viewport