/// <summary>
/// Called when a ItemProxy should be displayed in the river. The method will attempt to get data for the item either from the
/// river's data source or the history. If no data is available, the item will not be shown and no attempt will be made to show it
/// until the next loop around the grid.
/// </summary>
/// <param name="proxy">The ItemProxy which should be added.</param>
/// <param name="maintainOrientation">if set to <c>true</c> [maintain orientation].</param>
/// <param name="maintainUnblockedData">if set to <c>true</c> [maintain unblocked data].</param>
private void AttemptToAddToRiver(ItemProxy proxy, bool maintainOrientation, bool maintainUnblockedData)
{
RiverItemState state = GetState(proxy);
if (state == null)
{
return;
}
if (state.DidAttemptToAddToRiver)
{
return;
}
RiverItemBase riverItem = proxy.FindVisualChild<RiverItemBase>();
double orientation = 0;
bool isPortrait = state.RowSpan > state.ColumnSpan;
if (riverItem == null)
{
orientation = isPortrait ? 90 : 0;
}
else
{
int page = (int)Math.Ceiling(_cumulativeScrollChange / (_totalColumns * GridCellSize.Width));
if (GetItemVisibilityInfo(state).IsLooping)
{
page++;
}
RiverItemHistoryInfo history = _history.Where(h => h.State == state && h.Grid == page).FirstOrDefault();
object data = null;
if (history != null)
{
// Use the historical data and orientation if it exists.
data = history.Data;
orientation = history.Orientation;
}
else
{
data = riverItem.GetData(state, maintainUnblockedData);
if (InteractiveSurface.PrimarySurfaceDevice.Tilt == Tilt.Horizontal)
{
// If running on a tabletop, randomly rotate the item.
orientation = _random.NextDouble() > .5 ? 0 : 180;
if (isPortrait)
{
// Rotate vertical items.
orientation += 90 * (_random.NextDouble() > .5 ? 1 : -1);
}
if (state.RowSpan == state.ColumnSpan && _random.NextDouble() > .5)
{
// Maybe rotate square items.
orientation += 90 * (_random.NextDouble() > .5 ? 1 : -1);
}
}
else if (isPortrait)
{
// If running vertically, portrait items still get rotated to portrait.
orientation = _random.NextDouble() > .5 ? 90 : -90;
}
else
{
// If running vertically and not portrait, always render right-side-up.
orientation = 0;
}
history = new RiverItemHistoryInfo { State = state, Grid = page, Orientation = orientation };
_history.Add(history);
}
history.Data = riverItem.RenderData(state, data);
if (history.Data == null)
{
// The item rejected this data and didn't provide new data.
_history.Remove(history);
}
if (data == null)
{
// The item rejected the attempt to add, so don't try again until it's looped around.
state.DidAttemptToAddToRiver = true;
proxy.Visibility = Visibility.Collapsed;
}
}
if (maintainOrientation)
{
// Don't apply the orientation if this was a user-requested refresh.
return;
}
proxy.Orientation = state.OriginalOrientation = orientation;
}
/// <summary>
/// Contains the main logic for creating, destroying, and positioning items. This is called whenever the HorizontalOffset changes.
/// </summary>
/// <param name="proxy">The proxy to update.</param>
/// <param name="state">The state of the proxy.</param>
private void UpdateScrollPosition(ItemProxy proxy, RiverItemState state)
{
if (GridCellSize == Size.Empty || ActualWidth == 0 || ActualHeight == 0 || _totalColumns == 0 || _totalRows == 0)
{
// Not initialized yet.
return;
}
if (state.IsRemovedFromRiver)
{
// This item is pulled from the river, so don't do anything with it.
return;
}
// Get the pool for items of this style.
Style proxyStyle = state.ProxyStyle;
Queue<ItemProxy> pool = null;
if (proxyStyle == null)
{
// There's no style, so use the default pool.
pool = _defaultRiverItemPool;
}
else
{
// There is a style, so create a pool if needed, and use that.
if (!_styledRiverItemPool.ContainsKey(proxyStyle))
{
_styledRiverItemPool[proxyStyle] = new Queue<ItemProxy>();
}
pool = _styledRiverItemPool[proxyStyle];
}
RiverItemVisibilityInfo visibilityInfo = GetItemVisibilityInfo(state);
if (!visibilityInfo.IsVisible)
{
if (proxy != null)
{
RiverItemBase riverItem = proxy.FindVisualChild<RiverItemBase>();
// This definition should not be visible, so hide it.
state.IsAnimatingBackToRiver = false;
state.IsAnimatingToContactOrientation = false;
state.IsAnimatingToRemovedSize = false;
state.DidAttemptToAddToRiver = false;
state.IsRemovedFromRiver = false;
_stateToProxyMap[state] = null;
_sviToProxyMap.Remove(proxy);
proxy.Visibility = Visibility.Hidden;
if (riverItem != null)
{
riverItem.Cleanup();
}
pool.Enqueue(proxy);
}
return;
}
// The definition should be visible, but it's not paired with any ItemProxy yet, so build or recycle one.
if (proxy == null)
{
if (pool.Count > 0)
{
// Use an SVI from the queue.
proxy = pool.Dequeue();
proxy.Visibility = Visibility.Visible;
}
else
{
// Set up a new proxy.
proxy = AddNewItemProxy();
proxy.Style = proxyStyle;
}
// Size the ScatterView item when it's first added to the river.
bool isPortrait = state.RowSpan > state.ColumnSpan;
double itemWidth = state.ColumnSpan * GridCellSize.Width;
double itemHeight = state.RowSpan * GridCellSize.Height;
itemWidth += Plane.GetPlaneFrontPadding(proxy).Left + Plane.GetPlaneFrontPadding(proxy).Right;
itemHeight += Plane.GetPlaneFrontPadding(proxy).Top + Plane.GetPlaneFrontPadding(proxy).Bottom;
proxy.Width = isPortrait ? itemHeight : itemWidth;
proxy.Height = isPortrait ? itemWidth : itemHeight;
proxy.Visibility = Visibility.Visible;
// More setup of added items.
_stateToProxyMap[state] = proxy;
_sviToProxyMap[proxy] = state;
AttemptToAddToRiver(proxy, false, false);
}
if (state.DidAttemptToAddToRiver)
{
// We already tried to add this one and it rejected the add, so wait until it's looped around.
return;
}
// Update the position of the item.
proxy.Center = GetItemCenter(state);
}