9562if (_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; 1518alignTop = (_scrollData._bringIntoViewLeafContainer == visual && AlignTopOfBringIntoViewContainer); 1519alignBottom = (_scrollData._bringIntoViewLeafContainer == visual && 1536newOffset.X = ScrollContentPresenter.CoerceOffset(newOffset.X, _scrollData._extent.Width, _scrollData._viewport.Width); 1537newOffset.Y = ScrollContentPresenter.CoerceOffset(newOffset.Y, _scrollData._extent.Height, _scrollData._viewport.Height); 1539if (!LayoutDoubleUtil.AreClose(newOffset.X, _scrollData._offset.X) || 1540!LayoutDoubleUtil.AreClose(newOffset.Y, _scrollData._offset.Y)) 1543if (visual != _scrollData._bringIntoViewLeafContainer) 1545_scrollData._bringIntoViewLeafContainer = visual; 1550Vector oldOffset = _scrollData._offset; 1551_scrollData._offset = newOffset; 1556_scrollData._offset, 1558_scrollData._bringIntoViewLeafContainer); 1566_scrollData.SetHorizontalScrollType(oldOffset.X, newOffset.X); 1567_scrollData.SetVerticalScrollType(oldOffset.Y, newOffset.Y); 1576_scrollData._computedOffset = newOffset; 1594_scrollData._bringIntoViewLeafContainer = null; 1821if (_scrollData == null) { return false; } 1822return _scrollData._allowHorizontal; 1827if (_scrollData._allowHorizontal != value) 1829_scrollData._allowHorizontal = value; 1844if (_scrollData == null) { return false; } 1845return _scrollData._allowVertical; 1850if (_scrollData._allowVertical != value) 1852_scrollData._allowVertical = value; 1865if (_scrollData == null) { return 0.0; } 1866return _scrollData._extent.Width; 1877if (_scrollData == null) { return 0.0; } 1878return _scrollData._extent.Height; 1889if (_scrollData == null) { return 0.0; } 1890return _scrollData._viewport.Width; 1901if (_scrollData == null) { return 0.0; } 1902return _scrollData._viewport.Height; 1914if (_scrollData == null) { return 0.0; } 1915return _scrollData._computedOffset.X; 1927if (_scrollData == null) { return 0.0; } 1928return _scrollData._computedOffset.Y; 1941if (_scrollData == null) return null; 1942return _scrollData._scrollOwner; 1947if (value != _scrollData._scrollOwner) 1950_scrollData._scrollOwner = value; 2609if (IsScrolling && _scrollData._firstContainerInViewport != null && !areContainersUniformlySized) 2650_scrollData._offset.X += delta; 2654_scrollData._offset.Y += delta; 2665"newVpOff:", _scrollData._offset); 3271return StackPanel.StackMeasureHelper(this, _scrollData, constraint); 3276return StackPanel.StackArrangeHelper(this, _scrollData, arrangeSize); 3561"ext:", IsScrolling ? _scrollData._extent : Size.Empty, 3625_scrollData._maxDesiredSize = new Size(); 3893_scrollData._extent.Width = distance; 3897_scrollData._extent.Height = distance; 3902ScrollTracer.Trace(this, ScrollTraceOp.UpdateExtent, "ext:", _scrollData._extent); 4331offsetX = _scrollData._offset.X; 4332offsetY = _scrollData._offset.Y; 4333extent = _scrollData._extent; 4334viewportSize = _scrollData._viewport; 4335scrollGeneration = _scrollData._scrollGeneration; 4339_scrollData._maxDesiredSize = new Size(); 4364WasLastMeasurePassAnchored = (_scrollData._firstContainerInViewport != null) || (_scrollData._bringIntoViewLeafContainer != null); 4668_scrollData._bringIntoViewLeafContainer = null; 4676_scrollData._offset = _scrollData._computedOffset; 4802if (DoubleUtil.GreaterThan(extendedViewport.X + extendedViewport.Width, _scrollData._extent.Width)) 4809extendedViewport.Width = Math.Max(_scrollData._extent.Width - extendedViewport.X, 0.0); 4842if (DoubleUtil.GreaterThan(extendedViewport.X + extendedViewport.Width / approxSizeOfLogicalUnit, _scrollData._extent.Width)) 4849extendedViewport.Width = Math.Max(_scrollData._extent.Width - extendedViewport.X, 0.0) * approxSizeOfLogicalUnit; 4918if (DoubleUtil.GreaterThan(extendedViewport.Y + extendedViewport.Height, _scrollData._extent.Height)) 4925extendedViewport.Height = Math.Max(_scrollData._extent.Height - extendedViewport.Y, 0.0); 4958if (DoubleUtil.GreaterThan(extendedViewport.Y + extendedViewport.Height / approxSizeOfLogicalUnit, _scrollData._extent.Height)) 4965extendedViewport.Height = Math.Max(_scrollData._extent.Height - extendedViewport.Y, 0.0) * approxSizeOfLogicalUnit; 4990if (!_scrollData.IsEmpty) 4999if (!_scrollData.IsEmpty) 5749++_scrollData._scrollGeneration; 8432rcChild.Y = -1.0 * _scrollData._computedOffset.Y; 8438rcChild.X = -1.0 * _scrollData._computedOffset.X; 8443rcChild.X = -1.0 * _scrollData._computedOffset.X; 8444rcChild.Y = -1.0 * _scrollData._computedOffset.Y; 9562if (_scrollData == null) { _scrollData = new ScrollData(); } 9572element._scrollData.ClearLayout(); 9614Vector offsetForScrollViewerRemeasure = _scrollData._offset; 9658stackPixelSize.Height = _scrollData._extent.Height; 9665_scrollData._maxDesiredSize.Height = Math.Max(_scrollData._maxDesiredSize.Height, stackPixelSize.Height); 9666stackPixelSize.Height = _scrollData._maxDesiredSize.Height; 9685stackPixelSize.Width = _scrollData._extent.Width; 9692_scrollData._maxDesiredSize.Width = Math.Max(_scrollData._maxDesiredSize.Width, stackPixelSize.Width); 9693stackPixelSize.Width = _scrollData._maxDesiredSize.Width; 9749"o:", _scrollData._offset, 9765isHorizontal ? (!DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X) || 9766(IsScrollActive && computedViewportOffset.X > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.X, _scrollData.Extent.Width-_scrollData.Viewport.Width))) 9767: (!DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y) || 9768(IsScrollActive && computedViewportOffset.Y > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.Y, _scrollData.Extent.Height-_scrollData.Viewport.Height))); 9770isHorizontal ? (!DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y) || 9771(IsScrollActive && computedViewportOffset.Y > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.Y, _scrollData.Extent.Height-_scrollData.Viewport.Height))) 9772: (!DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X) || 9773(IsScrollActive && computedViewportOffset.X > 0.0 && DoubleUtil.GreaterThanOrClose(computedViewportOffset.X, _scrollData.Extent.Width-_scrollData.Viewport.Width))); 9809_scrollData.HorizontalScrollType = ScrollType.ToEnd; 9832_scrollData.VerticalScrollType = ScrollType.ToEnd; 9869bool viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 9870bool extentSizeChanged = !DoubleUtil.AreClose(extentSize, _scrollData._extent); 9871bool computedViewportOffsetChanged = !DoubleUtil.AreClose(computedViewportOffset, _scrollData._computedOffset); 9876extentWidthChanged = !DoubleUtil.AreClose(extentSize.Width, _scrollData._extent.Width); 9877extentHeightChanged = !DoubleUtil.AreClose(extentSize.Height, _scrollData._extent.Height); 10016!DoubleUtil.AreClose(_scrollData._viewport.Width, viewportSize.Width)) 10022"vpSz:", _scrollData._viewport.Width, viewportSize.Width, 10023"newOff:", _scrollData._offset); 10032viewportSize.Width = _scrollData._viewport.Width; 10046if (_scrollData.HorizontalScrollType == ScrollType.ToEnd || 10054"ext:", _scrollData._extent.Width, extentSize.Width, 10060_scrollData.HorizontalScrollType = ScrollType.ToEnd; 10069else if (_scrollData.HorizontalScrollType == ScrollType.Absolute) 10071if (!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10076if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10079viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10085if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.X)/extentSize.Width, Math.Floor(_scrollData._offset.X)/_scrollData._extent.Width)) 10088viewportOffset.X = Math.Floor((extentSize.Width * Math.Floor(_scrollData._offset.X)) / _scrollData._extent.Width); 10096"expRat:", _scrollData._offset.X, _scrollData._extent.Width, (_scrollData._offset.X/_scrollData._extent.Width), 10113if (_scrollData.VerticalScrollType == ScrollType.ToEnd || 10122"ext:", _scrollData._extent.Height, extentSize.Height, 10128_scrollData.VerticalScrollType = ScrollType.ToEnd; 10136else if (_scrollData.VerticalScrollType == ScrollType.Absolute) 10138if (!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10141if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10144viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10151"expRat:", _scrollData._offset.Y, _scrollData._extent.Height, (_scrollData._offset.Y/_scrollData._extent.Height), 10233!DoubleUtil.AreClose(_scrollData._viewport.Height, viewportSize.Height)) 10239"vpSz:", _scrollData._viewport.Height, viewportSize.Height, 10240"newOff:", _scrollData._offset); 10249viewportSize.Height = _scrollData._viewport.Height; 10263if (_scrollData.VerticalScrollType == ScrollType.ToEnd || 10271"ext:", _scrollData._extent.Height, extentSize.Height, 10277_scrollData.VerticalScrollType = ScrollType.ToEnd; 10286else if (_scrollData.VerticalScrollType == ScrollType.Absolute) 10288if (!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10293if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10296viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10302if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.Y)/extentSize.Height, Math.Floor(_scrollData._offset.Y)/_scrollData._extent.Height)) 10305viewportOffset.Y = Math.Floor((extentSize.Height * Math.Floor(_scrollData._offset.Y)) / _scrollData._extent.Height); 10312"expRat:", _scrollData._offset.Y, _scrollData._extent.Height, (_scrollData._offset.Y/_scrollData._extent.Height), 10329if (_scrollData.HorizontalScrollType == ScrollType.ToEnd || 10338"ext:", _scrollData._extent.Width, extentSize.Width, 10344_scrollData.HorizontalScrollType = ScrollType.ToEnd; 10352else if (_scrollData.HorizontalScrollType == ScrollType.Absolute) 10354if (!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10357if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10360viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10367"expRat:", _scrollData._offset.X, _scrollData._extent.Width, (_scrollData._offset.X/_scrollData._extent.Width), 10383if (isHorizontal && _scrollData.HorizontalScrollType == ScrollType.ToEnd) 10387if (!isHorizontal && _scrollData.VerticalScrollType == ScrollType.ToEnd) 10401viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10406"off:", _scrollData._offset, viewportOffset, 10407"ext:", _scrollData._extent, extentSize, 10408"co:", _scrollData._computedOffset, computedViewportOffset, 10409"vp:", _scrollData._viewport, viewportSize); 10415Vector oldViewportOffset = _scrollData._computedOffset; 10416Size oldViewportSize = _scrollData._viewport; 10418_scrollData._viewport = viewportSize; 10419_scrollData._extent = extentSize; 10420_scrollData._computedOffset = computedViewportOffset; 10437_scrollData._offset = viewportOffset; 10510stackPixelSize.Height = _scrollData._extent.Height; 10517_scrollData._maxDesiredSize.Height = Math.Max(_scrollData._maxDesiredSize.Height, stackPixelSize.Height); 10518stackPixelSize.Height = _scrollData._maxDesiredSize.Height; 10537stackPixelSize.Width = _scrollData._extent.Width; 10544_scrollData._maxDesiredSize.Width = Math.Max(_scrollData._maxDesiredSize.Width, stackPixelSize.Width); 10545stackPixelSize.Width = _scrollData._maxDesiredSize.Width; 10597bool viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10598bool extentSizeChanged = !DoubleUtil.AreClose(extentSize, _scrollData._extent); 10599bool computedViewportOffsetChanged = !DoubleUtil.AreClose(computedViewportOffset, _scrollData._computedOffset); 10627viewportOffset = _scrollData._offset; 10643viewportOffset = _scrollData._offset; 10656bool wasViewportOffsetCoerced = !DoubleUtil.AreClose(computedViewportOffset.X, _scrollData._offset.X); 10689!DoubleUtil.AreClose(_scrollData._viewport.Width, viewportSize.Width)) 10692viewportOffset.X = _scrollData._offset.X; 10697viewportSize.Width = _scrollData._viewport.Width; 10702if (!remeasure && extentSizeChanged && !DoubleUtil.AreClose(_scrollData._extent.Width, extentSize.Width)) 10725viewportOffset.X = _scrollData._offset.X; 10739(_scrollData._firstContainerInViewport == null && computedViewportOffsetChanged && !LayoutDoubleUtil.AreClose(computedViewportOffset.X, _scrollData._computedOffset.X)); 10742!DoubleUtil.AreClose(_scrollData._extent.Width, 0) && 10747if (!LayoutDoubleUtil.AreClose(computedViewportOffset.X/extentSize.Width, _scrollData._offset.X/_scrollData._extent.Width)) 10750viewportOffset.X = (extentSize.Width * _scrollData._offset.X) / _scrollData._extent.Width; 10756if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.X)/extentSize.Width, Math.Floor(_scrollData._offset.X)/_scrollData._extent.Width)) 10759viewportOffset.X = Math.Floor((extentSize.Width * Math.Floor(_scrollData._offset.X)) / _scrollData._extent.Width); 10787bool wasViewportOffsetCoerced = !DoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._offset.Y); 10820!DoubleUtil.AreClose(_scrollData._viewport.Height, viewportSize.Height)) 10823viewportOffset.Y = _scrollData._offset.Y; 10828viewportSize.Height = _scrollData._viewport.Height; 10833if (!remeasure && extentSizeChanged && !DoubleUtil.AreClose(_scrollData._extent.Height, extentSize.Height)) 10856viewportOffset.Y = _scrollData._offset.Y; 10870(_scrollData._firstContainerInViewport == null && computedViewportOffsetChanged && !LayoutDoubleUtil.AreClose(computedViewportOffset.Y, _scrollData._computedOffset.Y)); 10873!DoubleUtil.AreClose(_scrollData._extent.Height, 0) && 10878if (!LayoutDoubleUtil.AreClose(computedViewportOffset.Y/extentSize.Height, _scrollData._offset.Y/_scrollData._extent.Height)) 10881viewportOffset.Y = (extentSize.Height * _scrollData._offset.Y) / _scrollData._extent.Height; 10887if (!LayoutDoubleUtil.AreClose(Math.Floor(computedViewportOffset.Y)/extentSize.Height, Math.Floor(_scrollData._offset.Y)/_scrollData._extent.Height)) 10890viewportOffset.Y = Math.Floor((extentSize.Height * Math.Floor(_scrollData._offset.Y)) / _scrollData._extent.Height); 10913viewportSizeChanged = !DoubleUtil.AreClose(viewportSize, _scrollData._viewport); 10918Vector oldViewportOffset = _scrollData._computedOffset; 10919Size oldViewportSize = _scrollData._viewport; 10921_scrollData._viewport = viewportSize; 10922_scrollData._extent = extentSize; 10923_scrollData._computedOffset = computedViewportOffset; 10940_scrollData._offset = viewportOffset; 11167viewportOffset = _scrollData._computedOffset.X; 11174viewportOffset = _scrollData._computedOffset.Y; 11215firstChildInView = (int)_scrollData._computedOffset.X; 11216viewportSize = (int)_scrollData._viewport.Width; 11220firstChildInView = (int)_scrollData._computedOffset.Y; 11221viewportSize = (int)_scrollData._viewport.Height; 11346get { return (_scrollData != null) && (_scrollData._scrollOwner != null); } 11513_scrollData.HorizontalScrollType = ScrollType.None; 11514_scrollData.VerticalScrollType = ScrollType.None; 11618get { return _scrollData?._bringIntoViewLeafContainer ?? null; } 11623get { return _scrollData?._firstContainerInViewport ?? null; } 11628get { return _scrollData?._firstContainerOffsetFromViewport ?? 0.0; } 11633get { return _scrollData?._expectedDistanceBetweenViewports ?? 0.0; } 12993s._scrollData._offset = _scrollData._offset; 12994s._scrollData._extent = _scrollData._extent; 12995s._scrollData._computedOffset = _scrollData._computedOffset; 12996s._scrollData._viewport = _scrollData._viewport;