internal void RecycleElementAt(int index)
{
UIElement element = _context.GetOrCreateElementAt(index);
_context.RecycleElement(element);
}
/// <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 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 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);
}