protected override SizeRequest OnMeasure(double widthConstraint, double heightConstraint)
{
WrapLayoutData layoutData = GetLayoutData(widthConstraint, heightConstraint);
if (layoutData.VisibleChildCount == 0)
{
return(new SizeRequest());
}
Size totalSize = new Size(layoutData.CellSize.Width * layoutData.Columns + ColumnSpacing * (layoutData.Columns - 1),
layoutData.CellSize.Height * layoutData.Rows + RowSpacing * (layoutData.Rows - 1));
return(new SizeRequest(totalSize));
}
protected override void LayoutChildren(double x, double y, double width, double height)
{
WrapLayoutData layoutData = GetLayoutData(width, height);
if (layoutData.VisibleChildCount == 0)
{
return;
}
double xChild = x;
double yChild = y;
int row = 0;
int column = 0;
foreach (View child in Children)
{
if (!child.IsVisible)
{
continue;
}
LayoutChildIntoBoundingRegion(child, new Rectangle(new Point(xChild, yChild), layoutData.CellSize));
if (++column == layoutData.Columns)
{
column = 0;
row++;
xChild = x;
yChild += RowSpacing + layoutData.CellSize.Height;
}
else
{
xChild += ColumnSpacing + layoutData.CellSize.Width;
}
}
}
WrapLayoutData GetLayoutData(double width, double height)
{
Size size = new Size(width, height);
// Check if cached information is available.
if (wrapLayoutDataCache.ContainsKey(size))
{
return(wrapLayoutDataCache[size]);
}
int visibleChildCount = 0;
Size maxChildSize = new Size();
int rows = 0;
int columns = 0;
WrapLayoutData layoutData = new WrapLayoutData();
// Enumerate through all the children.
foreach (View child in Children)
{
// Skip invisible children.
if (!child.IsVisible)
{
continue;
}
// Count the visible children.
visibleChildCount++;
// Get the child's requested size.
SizeRequest childSizeRequest = child.Measure(Double.PositiveInfinity, Double.PositiveInfinity);
// Accumulate the maximum child size.
maxChildSize.Width = Math.Max(maxChildSize.Width, childSizeRequest.Request.Width);
maxChildSize.Height = Math.Max(maxChildSize.Height, childSizeRequest.Request.Height);
}
if (visibleChildCount != 0)
{
// Calculate the number of rows and columns.
if (Double.IsPositiveInfinity(width))
{
columns = visibleChildCount;
rows = 1;
}
else
{
columns = (int)((width + ColumnSpacing) / (maxChildSize.Width + ColumnSpacing));
columns = Math.Max(1, columns);
rows = (visibleChildCount + columns - 1) / columns;
}
// Now maximize the cell size based on the layout size.
Size cellSize = new Size();
if (Double.IsPositiveInfinity(width))
{
cellSize.Width = maxChildSize.Width;
}
else
{
cellSize.Width = (width - ColumnSpacing * (columns - 1)) / columns;
}
if (Double.IsPositiveInfinity(height))
{
cellSize.Height = maxChildSize.Height;
}
else
{
cellSize.Height = (height - RowSpacing * (rows - 1)) / rows;
}
layoutData = new WrapLayoutData(visibleChildCount, cellSize, rows, columns);
}
wrapLayoutDataCache.Add(size, layoutData);
return(layoutData);
}