public StaggeredLayoutState(VirtualizingLayoutContext context)
{
_context = context;
}
/// <inheritdoc/>
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
if (context.ItemCount == 0)
{
return(new Size(availableSize.Width, 0));
}
if ((context.RealizationRect.Width == 0) && (context.RealizationRect.Height == 0))
{
return(new Size(availableSize.Width, 0.0));
}
var state = (StaggeredLayoutState)context.LayoutState;
double availableWidth = availableSize.Width;
double availableHeight = availableSize.Height;
double columnWidth = Math.Min(DesiredColumnWidth, availableWidth);
if (columnWidth != state.ColumnWidth)
{
// The items will need to be remeasured
state.Clear();
}
state.ColumnWidth = Math.Min(DesiredColumnWidth, availableWidth);
int numColumns = Math.Max(1, (int)Math.Floor(availableWidth / state.ColumnWidth));
// adjust for column spacing on all columns expect the first
double totalWidth = state.ColumnWidth + ((numColumns - 1) * (state.ColumnWidth + ColumnSpacing));
if (totalWidth > availableWidth)
{
numColumns--;
}
else if (double.IsInfinity(availableWidth))
{
availableWidth = totalWidth;
}
if (numColumns != state.NumberOfColumns)
{
// The items will not need to be remeasured, but they will need to go into new columns
state.ClearColumns();
}
if (RowSpacing != state.RowSpacing)
{
// If the RowSpacing changes the height of the rows will be different.
// The columns stores the height so we'll want to clear them out to
// get the proper height
state.ClearColumns();
state.RowSpacing = RowSpacing;
}
var columnHeights = new double[numColumns];
var itemsPerColumn = new int[numColumns];
var deadColumns = new HashSet <int>();
for (int i = 0; i < context.ItemCount; i++)
{
var columnIndex = GetColumnIndex(columnHeights);
bool measured = false;
StaggeredItem item = state.GetItemAt(i);
if (item.Height == 0)
{
// Item has not been measured yet. Get the element and store the values
item.Element = context.GetOrCreateElementAt(i);
item.Element.Measure(new Size(state.ColumnWidth, availableHeight));
item.Height = item.Element.DesiredSize.Height;
measured = true;
}
double spacing = itemsPerColumn[columnIndex] > 0 ? RowSpacing : 0;
item.Top = columnHeights[columnIndex] + spacing;
double bottom = item.Top + item.Height;
columnHeights[columnIndex] = bottom;
itemsPerColumn[columnIndex]++;
state.AddItemToColumn(item, columnIndex);
if (bottom < context.RealizationRect.Top)
{
// The bottom of the element is above the realization area
if (item.Element != null)
{
context.RecycleElement(item.Element);
item.Element = null;
}
}
else if (item.Top > context.RealizationRect.Bottom)
{
// The top of the element is below the realization area
if (item.Element != null)
{
context.RecycleElement(item.Element);
item.Element = null;
}
deadColumns.Add(columnIndex);
}
else if (measured == false)
{
// We ALWAYS want to measure an item that will be in the bounds
item.Element = context.GetOrCreateElementAt(i);
item.Element.Measure(new Size(state.ColumnWidth, availableHeight));
if (item.Height != item.Element.DesiredSize.Height)
{
// this item changed size; we need to recalculate layout for everything after this
state.RemoveFromIndex(i + 1);
item.Height = item.Element.DesiredSize.Height;
columnHeights[columnIndex] = item.Top + item.Height;
}
}
if (deadColumns.Count == numColumns)
{
break;
}
}
double desiredHeight = state.GetHeight();
return(new Size(availableWidth, desiredHeight));
}
/// <inheritdoc/>
protected override void InitializeForContextCore(VirtualizingLayoutContext context)
{
context.LayoutState = new StaggeredLayoutState(context);
base.InitializeForContextCore(context);
}
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
availableSize.Width = availableSize.Width /* - Padding.Left - Padding.Right*/;
availableSize.Height = availableSize.Height /* - Padding.Top - Padding.Bottom*/;
// For when width is even less than desired col width of even one column:
_columnWidth = Math.Min(DesiredColumnWidth, availableSize.Width);
int numColumns = (int)Math.Floor(availableSize.Width / _columnWidth);
_columnWidth = availableSize.Width / numColumns;
if (state == null || state.Width != context.RealizationRect.Width)
{
state = new StaggeredLayoutState(numColumns, _columnWidth, context.RealizationRect.Width);
}
if (context.ItemCount == 0)
{
return(new Size(availableSize.Width, 0));
}
// The viewport consists the current view, one view before, and one view after.
double viewUpperBound = context.RealizationRect.Top;
double viewLowerBound = context.RealizationRect.Bottom;
int firstIndex = state.GetFirstItemInView(viewUpperBound);
int lastIndex = state.GetLastItemInView(viewLowerBound);
int index = firstIndex;
while (state.CacheCount < context.ItemCount)
{
Rect rect;
bool cached = state.TryGetRect(lastIndex, out rect);
if (cached)
{
break;
}
// The culpit might be auto recycling. Supressing it solves the problem,
// but defeats virtualization and raises runtime expections, so must fix it.
// Okay, the real problem is the custom image control. Without that this implementation works just fine.
// The culpit is the video control. Even using that alone produces the issue.
// So might consider extract the first frame and put it in an image box.
var child = context.GetOrCreateElementAt(lastIndex /*, ElementRealizationOptions.SuppressAutoRecycle*/);
rect = state.CreateRectForChild(lastIndex, child);
lastIndex++;
if (rect.Top > viewLowerBound)
{
break;
}
}
while (index < lastIndex)
{
var child = context.GetOrCreateElementAt(index);
Rect rect;
if (index < state.CacheCount)
{
rect = state.GetRect(index);
}
else
{
rect = state.CreateRectForChild(index, child);
}
// It turns out this measurement is pretty important for elements to stay within their bounds.
child.Measure(new Size(rect.Width, rect.Height));
// I know this is rather inelegant, but since ItemsRepeater has no click support whatsoever, so...
SubscribeClickEvent(child);
child.Arrange(rect);
index++;
}
// Use this to reproduce bug.
//var firstElement = context.GetOrCreateElementAt(0);
//context.RecycleElement(firstElement);
//firstElement = context.GetOrCreateElementAt(0);
//firstElement.Measure(new Size(_columnWidth, availableSize.Height));
//Rect r = state.GetRect(0);
//firstElement.Arrange(r);
double desiredHeight = state.GetTotalHeight();
return(new Size(availableSize.Width, desiredHeight));
}
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
var requiredSize = new Size(Padding.Left + Padding.Right, Padding.Top + Padding.Bottom);
if (context.ItemCount == 0 ||
context.RealizationRect.Width == 0 ||
context.RealizationRect.Height == 0)
{
return(requiredSize);
}
var state = (AutoFillLayoutState)context.LayoutState;
var clientSize = new Size(
availableSize.Width - Padding.Left - Padding.Right,
availableSize.Height - Padding.Top - Padding.Bottom);
//Save layout properties
//If changed every thing need redo
if (state.SavePropertiesIfChange(Orientation, Padding,
HorizontalSpacing, VerticalSpacing, availableSize))
{
state.Reset();
}
if (!state.Initialized)
{
if (Orientation == Orientation.Horizontal)
{
state.Initialize(
new Rect(Padding.Left, Padding.Top,
clientSize.Width + HorizontalSpacing, double.PositiveInfinity)
);
}
else
{
state.Initialize(
new Rect(Padding.Left, Padding.Top,
double.PositiveInfinity, clientSize.Height + VerticalSpacing)
);
}
}
for (int i = 0; i < context.ItemCount; i++)
{
var item = state.GetOrCreateItemAt(i);
bool measured = false;
if (item.Bounds.IsEmpty())//measure empty
{
item.Element = context.GetOrCreateElementAt(i);
item.Element.Measure(clientSize);
item.Width = item.Element.DesiredSize.Width;
item.Height = item.Element.DesiredSize.Height;
state.FitItem(item);
measured = true;
}
item.ShouldDisplay = context.RealizationRect.IsIntersect(item.Bounds);
if (!item.ShouldDisplay)
{
if (item.Element != null)
{
context.RecycleElement(item.Element);
item.Element = null;
}
}
else if (!measured)//measure in view rect
{
item.Element = context.GetOrCreateElementAt(i);
item.Element.Measure(clientSize);
var childSize = item.Element.DesiredSize;
if (item.Width != childSize.Width || item.Height != childSize.Height) //size changed
{
item.Width = childSize.Width;
item.Height = childSize.Height;
state.RemoveItemsFrom(i + 1);//remove after this
state.FitItem(item);
}
}
}
var size = state.GetTotalSize();
//var size = state.GetVirtualizedSize();
requiredSize.Width += size.Width;
requiredSize.Height += size.Height;
return(requiredSize);
}
/// <inheritdoc />
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
var totalMeasure = UvMeasure.Zero;
var parentMeasure = new UvMeasure(Orientation, availableSize.Width, availableSize.Height);
var spacingMeasure = new UvMeasure(Orientation, HorizontalSpacing, VerticalSpacing);
var realizationBounds = new UvBounds(Orientation, context.RealizationRect);
var position = UvMeasure.Zero;
var state = (WrapLayoutState)context.LayoutState;
if (state.Orientation != Orientation)
{
state.SetOrientation(Orientation);
}
if (spacingMeasure.Equals(state.Spacing) == false)
{
state.ClearPositions();
state.Spacing = spacingMeasure;
}
if (state.AvailableU != parentMeasure.U)
{
state.ClearPositions();
state.AvailableU = parentMeasure.U;
}
double currentV = 0;
for (int i = 0; i < context.ItemCount; i++)
{
bool measured = false;
WrapItem item = state.GetItemAt(i);
if (item.Measure == null)
{
item.Element = context.GetOrCreateElementAt(i);
item.Element.Measure(availableSize);
item.Measure = new UvMeasure(Orientation, item.Element.DesiredSize.Width, item.Element.DesiredSize.Height);
measured = true;
}
UvMeasure currentMeasure = item.Measure.Value;
if (currentMeasure.U == 0)
{
continue; // ignore collapsed items
}
if (item.Position == null)
{
if (parentMeasure.U < position.U + currentMeasure.U)
{
// New Row
position.U = 0;
position.V += currentV + spacingMeasure.V;
currentV = 0;
}
item.Position = position;
}
position = item.Position.Value;
double vEnd = position.V + currentMeasure.V;
if (vEnd < realizationBounds.VMin)
{
// Item is "above" the bounds
if (item.Element != null)
{
context.RecycleElement(item.Element);
item.Element = null;
}
}
else if (position.V > realizationBounds.VMax)
{
// Item is "below" the bounds.
if (item.Element != null)
{
context.RecycleElement(item.Element);
item.Element = null;
}
// We don't need to measure anything below the bounds
break;
}
else if (measured == false)
{
// Always measure elements that are within the bounds
item.Element = context.GetOrCreateElementAt(i);
item.Element.Measure(availableSize);
currentMeasure = new UvMeasure(Orientation, item.Element.DesiredSize.Width, item.Element.DesiredSize.Height);
if (currentMeasure.Equals(item.Measure) == false)
{
// this item changed size; we need to recalculate layout for everything after this
state.RemoveFromIndex(i + 1);
item.Measure = currentMeasure;
// did the change make it go into the new row?
if (parentMeasure.U < position.U + currentMeasure.U)
{
// New Row
position.U = 0;
position.V += currentV + spacingMeasure.V;
currentV = 0;
}
item.Position = position;
}
}
position.U += currentMeasure.U + spacingMeasure.U;
currentV = Math.Max(currentMeasure.V, currentV);
}
// update value with the last line
// if the the last loop is(parentMeasure.U > currentMeasure.U + lineMeasure.U) the total isn't calculated then calculate it
// if the last loop is (parentMeasure.U > currentMeasure.U) the currentMeasure isn't added to the total so add it here
// for the last condition it is zeros so adding it will make no difference
// this way is faster than an if condition in every loop for checking the last item
totalMeasure.U = parentMeasure.U;
// Propagating an infinite size causes a crash. This can happen if the parent is scrollable and infinite in the opposite
// axis to the panel. Clearing to zero prevents the crash.
// This is likely an incorrect use of the control by the developer, however we need stability here so setting a default that wont crash.
if (double.IsInfinity(totalMeasure.U))
{
totalMeasure.U = 0.0;
}
totalMeasure.V = state.GetHeight();
totalMeasure.U = Math.Ceiling(totalMeasure.U);
return(Orientation == Orientation.Horizontal ? new Size(totalMeasure.U, totalMeasure.V) : new Size(totalMeasure.V, totalMeasure.U));
}
protected override Size ArrangeOverride(VirtualizingLayoutContext context, Size finalSize)
{
// Note that you MUST call GetOrCreateElement on any items that are in the realized region... that's how
// the control tracks which elements it shouldn't dispose.
// It's easier to not support infinite width, and none of my scenarios need it, so not worth spending time implementing it
if (double.IsInfinity(finalSize.Width))
{
throw new ArgumentException("This panel doesn't support infinite width");
}
// If there's no width, there's nothing we can do.
if (finalSize.Width == 0)
{
return(new Size(0, 0));
}
var state = (GroupedLayoutState)context.LayoutState;
var colInfo = GetColumnInfo(finalSize);
bool widthChanged = state.AvailableWidth != finalSize.Width;
double y = 0;
int i = 0;
int col = 0;
double currRowHeight = 0;
while (i < context.ItemCount)
{
if (col >= colInfo.NumberOfColumns)
{
// Start a new row
y += currRowHeight + AfterGroupSpacing;
col = 0;
currRowHeight = 0;
}
var colSize = ArrangeColumn(
context,
state,
colInfo,
col,
headerIndex: i,
startingY: y,
widthChanged: widthChanged,
nextHeaderIndex: out i);
currRowHeight = Math.Max(currRowHeight, colSize.Height);
col++;
}
y += currRowHeight;
var actualFinalSize = new Size(finalSize.Width, y);
if (_currMeasuredSize != actualFinalSize)
{
#if DEBUG
Debugger.Break();
#endif
}
return(actualFinalSize);
}
public WrapLayoutState(VirtualizingLayoutContext context)
{
this._context = context;
}
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
if (MinItemSize == Size.Empty)
{
var firstElement = context.GetOrCreateElementAt(0);
firstElement.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
// setting the member value directly to skip invalidating layout
_minItemSize = firstElement.DesiredSize;
}
// Determine which rows need to be realized. We know every row will have the same height and
// only contain 3 items. Use that to determine the index for the first and last item that
// will be within that realization rect.
var firstRowIndex = Math.Max(
(int)(context.RealizationRect.Y / (MinItemSize.Height + RowSpacing)) - 1,
0);
var lastRowIndex = Math.Min(
(int)(context.RealizationRect.Bottom / (MinItemSize.Height + RowSpacing)) + 1,
context.ItemCount / 3);
// Determine which items will appear on those rows and what the rect will be for each item
var state = context.LayoutState as ActivityFeedLayoutState;
state.LayoutRects.Clear();
// Save the index of the first realized item. We'll use it as a starting point during arrange.
state.FirstRealizedIndex = firstRowIndex * 3;
// ideal item width that will expand/shrink to fill available space
double desiredItemWidth = Math.Max(MinItemSize.Width, (availableSize.Width - ColumnSpacing * 3) / 4);
// Foreach item between the first and last index,
// Call GetElementOrCreateElementAt which causes an element to either be realized or retrieved
// from a recycle pool
// Measure the element using an appropriate size
//
// Any element that was previously realized which we don't retrieve in this pass (via a call to
// GetElementOrCreateAt) will be automatically cleared and set aside for later re-use.
// Note: While this work fine, it does mean that more elements than are required may be
// created because it isn't until after our MeasureOverride completes that the unused elements
// will be recycled and available to use. We could avoid this by choosing to track the first/last
// index from the previous layout pass. The diff between the previous range and current range
// would represent the elements that we can pre-emptively make available for re-use by calling
// context.RecycleElement(element).
for (int rowIndex = firstRowIndex; rowIndex < lastRowIndex; rowIndex++)
{
int firstItemIndex = rowIndex * 3;
var boundsForCurrentRow = CalculateLayoutBoundsForRow(rowIndex, desiredItemWidth);
for (int columnIndex = 0; columnIndex < 3; columnIndex++)
{
var index = firstItemIndex + columnIndex;
var rect = boundsForCurrentRow[index % 3];
var container = context.GetOrCreateElementAt(index);
container.Measure(
new Size(boundsForCurrentRow[columnIndex].Width, boundsForCurrentRow[columnIndex].Height));
state.LayoutRects.Add(boundsForCurrentRow[columnIndex]);
}
}
// Calculate and return the size of all the content (realized or not) by figuring out
// what the bottom/right position of the last item would be.
var extentHeight = (context.ItemCount / 3 - 1) * (MinItemSize.Height + RowSpacing) + MinItemSize.Height;
// Report this as the desired size for the layout
return(new Size(desiredItemWidth * 4 + ColumnSpacing * 2, extentHeight));
}
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
return(base.MeasureOverride(context, availableSize));
}
protected override void InitializeForContextCore(VirtualizingLayoutContext context)
{
context.LayoutState = new WaterFallLayoutState();
}
protected override Size ArrangeOverride(VirtualizingLayoutContext context, Size finalSize)
{
return(base.ArrangeOverride(context, finalSize));
}
protected override void OnItemsChangedCore(VirtualizingLayoutContext context, object source, NotifyCollectionChangedEventArgs args)
{
base.OnItemsChangedCore(context, source, args);
}
public GroupedLayoutState(VirtualizingLayoutContext context)
{
this._context = context;
}
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
var viewport = context.RealizationRect;
Debug.WriteLine("Measure: " + viewport);
if (availableSize.Width != m_lastAvailableWidth)
{
UpdateCachedBounds(availableSize);
m_lastAvailableWidth = availableSize.Width;
}
// Initialize column offsets
int numColumns = (int)(availableSize.Width / Width);
if (m_columnOffsets.Count == 0)
{
for (int i = 0; i < numColumns; i++)
{
m_columnOffsets.Add(0);
}
}
m_firstIndex = GetStartIndex(viewport);
int currentIndex = m_firstIndex;
double nextOffset = -1.0;
// Measure items from start index to when we hit the end of the viewport.
while (currentIndex < context.ItemCount && nextOffset < viewport.Bottom)
{
Debug.WriteLine("Measuring " + currentIndex);
var child = context.GetOrCreateElementAt(currentIndex);
child.Measure(new Size(Width, availableSize.Height));
if (currentIndex >= m_cachedBounds.Count)
{
// We do not have bounds for this index. Lay it out and cache it.
int columnIndex = GetIndexOfLowestColumn(m_columnOffsets, out nextOffset);
m_cachedBounds.Add(new Rect(columnIndex * Width, nextOffset, Width, child.DesiredSize.Height));
m_columnOffsets[columnIndex] += child.DesiredSize.Height;
}
else
{
if (currentIndex + 1 == m_cachedBounds.Count)
{
// Last element. Use the next offset.
GetIndexOfLowestColumn(m_columnOffsets, out nextOffset);
}
else
{
nextOffset = m_cachedBounds[currentIndex + 1].Top;
}
}
child.Arrange(m_cachedBounds[currentIndex]);
m_lastIndex = currentIndex;
currentIndex++;
}
var extent = GetExtentSize(availableSize);
return(extent);
}
protected override Size MeasureOverride(VirtualizingLayoutContext context, Size availableSize)
{
if (context.ItemCount < 1)
{
return(new Size(0, 0));
}
// Item size is 96 + 2px of margin
var state = context.LayoutState as MosaicLayoutState;
if (state.LayoutRects.Count < 1)
{
state.LayoutRects.Clear();
state.ActualWidth = availableSize.Width;
var items = GetItems(context);
var mosaic = MosaicMedia.Calculate(items);
var top = 0d;
foreach (var row in mosaic)
{
var left = 0d;
foreach (var item in row)
{
state.LayoutRects.Add(new Rect(left, top, item.Width, 98));
left += item.Width;
}
top += 98;
}
state.Rows = mosaic;
state.ExtentHeight = top - 2;
}
if (state.LayoutRects.Count < 1)
{
return(new Size(0, 0));
}
var firstRowIndex = Math.Min(Math.Max((int)(context.RealizationRect.Y / 98) - 1, 0), state.Rows.Count - 1);
var lastRowIndex = Math.Max(Math.Min((int)(context.RealizationRect.Bottom / 98) + 1, state.Rows.Count - 1), 0);
var firstItemIndex = state.Rows[firstRowIndex][0].Index;
var lastItemIndex = state.Rows[lastRowIndex].Last().Index;
var availableWidth = availableSize.Width + 2;
for (int i = firstItemIndex; i <= lastItemIndex; i++)
{
var container = context.GetOrCreateElementAt(i);
container.Measure(new Size(
state.LayoutRects[i].Width * availableWidth,
state.LayoutRects[i].Height));
}
state.FirstRealizedIndex = firstItemIndex;
state.LastRealizedIndex = lastItemIndex;
// Report this as the desired size for the layout
return(new Size(availableSize.Width, state.ExtentHeight));
}
/// <inheritdoc />
protected override void UninitializeForContextCore(VirtualizingLayoutContext context)
{
context.LayoutState = null;
base.UninitializeForContextCore(context);
}
protected override void InitializeForContextCore(VirtualizingLayoutContext context)
{
context.LayoutState = new CustomGridLayoutState(this);
base.InitializeForContextCore(context);
}
/// <inheritdoc />
protected override Size ArrangeOverride(VirtualizingLayoutContext context, Size finalSize)
{
if (context.ItemCount > 0)
{
var parentMeasure = new UvMeasure(Orientation, finalSize.Width, finalSize.Height);
var spacingMeasure = new UvMeasure(Orientation, HorizontalSpacing, VerticalSpacing);
var realizationBounds = new UvBounds(Orientation, context.RealizationRect);
var state = (WrapLayoutState)context.LayoutState;
bool Arrange(WrapItem item, bool isLast = false)
{
if (item.Measure.HasValue == false)
{
return(false);
}
if (item.Position == null)
{
return(false);
}
var desiredMeasure = item.Measure.Value;
if (desiredMeasure.U == 0)
{
return(true); // if an item is collapsed, avoid adding the spacing
}
UvMeasure position = item.Position.Value;
// Stretch the last item to fill the available space
if (isLast)
{
desiredMeasure.U = parentMeasure.U - position.U;
}
if (((position.V + desiredMeasure.V) >= realizationBounds.VMin) && (position.V <= realizationBounds.VMax))
{
// place the item
UIElement child = context.GetOrCreateElementAt(item.Index);
if (Orientation == Orientation.Horizontal)
{
child.Arrange(new Rect(position.U, position.V, desiredMeasure.U, desiredMeasure.V));
}
else
{
child.Arrange(new Rect(position.V, position.U, desiredMeasure.V, desiredMeasure.U));
}
}
else if (position.V > realizationBounds.VMax)
{
return(false);
}
return(true);
}
for (var i = 0; i < context.ItemCount; i++)
{
bool continueArranging = Arrange(state.GetItemAt(i));
if (continueArranging == false)
{
break;
}
}
}
return(finalSize);
}
private Size MeasureColumn(VirtualizingLayoutContext context, GroupedLayoutState state, Size availableSizeForElements, int headerIndex, double startingY, bool widthChanged, out int nextHeaderIndex)
{
// Note that you MUST call GetOrCreateElement on any items that are in the realized region... that's how
// the control tracks which elements it shouldn't dispose.
double y = startingY;
int i = headerIndex;
var header = state.GetItemAt(headerIndex);
//if (widthChanged || header.Height == null)
{
var headerEl = context.GetOrCreateElementAt(headerIndex);
headerEl.Measure(availableSizeForElements);
header.Height = headerEl.DesiredSize.Height;
}
y += header.Height.Value + AfterHeaderSpacing;
i++;
while (i < context.ItemCount)
{
if (!(context.GetItemAt(i) is ViewItemTaskOrEvent))
{
// End of column
break;
}
var item = state.GetItemAt(i);
// Logic technically ignores height of item, but heights are short enough it shouldn't matter
if (y < context.RealizationRect.Top ||
y > context.RealizationRect.Bottom)
{
y += item.Height.GetValueOrDefault(40);
}
else
{
// Theoretically since tasks/events are removed and then added back when edited, we know they can never change size...
// Therefore we can store their measured size, and only call measure if their width changed or height unknown...
// However this didn't work in reality, not sure why.
//if (widthChanged || item.Height == null)
{
var itemEl = context.GetOrCreateElementAt(i);
itemEl.Measure(availableSizeForElements);
item.Height = itemEl.DesiredSize.Height;
}
y += item.Height.Value;
}
// Include item spacing
y += ItemSpacing;
i++;
}
// Remove last item spacing (since no item after it)
y -= ItemSpacing;
nextHeaderIndex = i;
return(new Size(availableSizeForElements.Width, y - startingY));
}
