private void GetItemsInView(int offset, int viewportWidth, out int leftIndex, out int leftInView, out int centerIndex, out int rightIndex, out int rightInView)
{
leftIndex = leftInView = centerIndex = rightIndex = rightInView = -1;
int count = VisibleChildren.Count;
if (count == 0)
{
return;
}
for (int index = 0; index < count; ++index)
{
StartViewItem child = _visibleChildren[index];
int leftOffset = child.StartPosition + offset;
int rightOffset = leftOffset + child.ItemWidth - 1;
if (leftOffset <= 0 && rightOffset >= 0)
{
leftIndex = index;
leftInView = Math.Min(viewportWidth, child.ItemWidth + leftOffset);
}
if (leftOffset < viewportWidth && rightOffset >= viewportWidth)
{
rightIndex = index;
rightInView = Math.Min(viewportWidth, viewportWidth - leftOffset);
}
if (leftOffset > 0 && rightOffset < viewportWidth)
{
centerIndex = index;
}
if (index == 0 && leftInView == -1)
{
leftInView = leftOffset;
}
if (index == count - 1 && rightInView == -1)
{
rightInView = viewportWidth - rightOffset - 1;
}
}
}
/// <summary>
/// Handles the arrange pass for the control.
/// </summary>
///
/// <returns>
/// Render size.
/// </returns>
/// <param name="finalSize">Final size.</param>
protected override Size ArrangeOverride(Size finalSize)
{
_itemStops.Clear();
double x = 0;
Rect finalRect = new Rect(0, 0, 0, finalSize.Height);
for (int index = 0; index < _visibleChildren.Count; ++index)
{
StartViewItem child = _visibleChildren[index];
finalRect.X = child.StartPosition = (int)x;
_itemStops.Add(new ItemStop(child, child.StartPosition));
finalRect.Width = Owner.ViewportWidth;
child.ItemWidth = (int)finalRect.Width;
child.Arrange(finalRect);
x += finalRect.Width;
}
Owner.RequestAdjustSelection();
return(finalSize);
}
public ItemStop(StartViewItem item, int position)
{
Item = item;
Position = position;
}
internal void GetSnapOffset(int offset, int viewportWidth, int direction, out int snapTo, out int newDirection, out StartViewItem newSelection)
{
int snapThreshold = viewportWidth / SnapThresholdDivisor;
snapTo = offset;
newDirection = direction;
newSelection = _selectedItem;
if (VisibleChildren.Count == 0)
{
return;
}
foreach (ItemStop itemStop in _itemStops)
{
if (itemStop.Position == -offset)
{
newSelection = itemStop.Item;
return;
}
}
int leftIndex;
int leftInView;
int centerIndex;
int rightIndex;
int rightInView;
GetItemsInView(offset, viewportWidth, out leftIndex, out leftInView, out centerIndex, out rightIndex, out rightInView);
if (leftIndex == rightIndex && leftIndex != -1)
{
newSelection = _selectedItem = _visibleChildren[leftIndex];
}
else
{
if (leftIndex == -1)
{
leftIndex = _visibleChildren.Count - 1;
}
if (rightIndex == -1)
{
rightIndex = 0;
}
int index;
if (direction < 0)
{
if (rightInView > snapThreshold)
{
index = GetBestIndex(centerIndex, rightIndex, leftIndex);
newDirection = -1;
}
else
{
index = GetBestIndex(leftIndex, centerIndex, rightIndex);
newDirection = 1;
}
}
else if (direction > 0)
{
if (leftInView > snapThreshold)
{
index = StartViewPanel.GetBestIndex(leftIndex, centerIndex, rightIndex);
newDirection = 1;
}
else
{
index = StartViewPanel.GetBestIndex(centerIndex, rightIndex, leftIndex);
newDirection = -1;
}
}
else if (centerIndex != -1)
{
index = centerIndex;
newDirection = -1;
}
else if (leftInView > rightInView)
{
index = leftIndex;
newDirection = -1;
}
else
{
index = rightIndex;
newDirection = 1;
}
_selectedItem = _visibleChildren[index];
snapTo = -_selectedItem.StartPosition;
newSelection = _selectedItem;
}
}