private async Task HandleGroundOverlayForTile(TileInfo tileInfo)
{
if (SharedOverlay.IsVisible)
{
int virtualTileSize = Extensions.SKMapExtensions.MercatorMapSize >> tileInfo.Zoom;
int xPixelsStart = tileInfo.X * virtualTileSize;
int yPixelsStart = tileInfo.Y * virtualTileSize;
double zoomScale = SKMapCanvas.MapTileSize / (double)virtualTileSize;
Rectangle mercatorSpan = new Rectangle(xPixelsStart, yPixelsStart, virtualTileSize, virtualTileSize);
SKMapSpan tileSpan = mercatorSpan.ToGps();
if (tileSpan.FastIntersects(SharedOverlay.GpsBounds))
{
SKBitmap bitmap = DrawTileToBitmap(tileSpan, zoomScale);
BitmapDescriptor bitmapDescriptor = BitmapDescriptorFactory.FromBitmap(bitmap.ToBitmap());
TaskCompletionSource <object> drawingTcs = new TaskCompletionSource <object>();
Console.WriteLine($"Refreshing ground tile at ({tileInfo.X}, {tileInfo.Y}) for zoom level {tileInfo.Zoom} ({zoomScale}) with GPS bounds {tileSpan}");
Device.BeginInvokeOnMainThread(() =>
{
GroundOverlay overlay;
lock (_GroundOverlays)
{
overlay = _GroundOverlays.FirstOrDefault(o => (o.Tag as TileInfo)?.Equals(tileInfo) ?? false);
}
if (overlay == null)
{
GroundOverlayOptions overlayOptions = new GroundOverlayOptions().PositionFromBounds(tileSpan.ToLatLng())
.InvokeImage(bitmapDescriptor);
overlay = _NativeMap.AddGroundOverlay(overlayOptions);
overlay.Tag = tileInfo;
lock (_GroundOverlays)
{
_GroundOverlays.Add(overlay);
}
}
else if ((overlay.Tag as TileInfo)?.NeedsRedraw ?? false)
{
overlay.SetImage(bitmapDescriptor);
}
drawingTcs.TrySetResult(null);
});
await drawingTcs.Task.ConfigureAwait(false);
ReleaseOverlayBitmap(bitmap);
}
else
{
Console.WriteLine($"Ground tile at ({tileInfo.X}, {tileInfo.Y}) for zoom level {tileInfo.Zoom} already exists");
}
}
}
public static LatLngBounds ToLatLng(this Rectangle self)
{
SKMapSpan mapSpan = self.ToGps();
return(mapSpan.ToLatLng());
}