/// <summary>
/// Gets a given tile at a specific zoom level.
/// Checks the current caching provider for the file. If the file is present within
/// the caching provider, a stream to it's contents is returned. This stream should be disposed as soon as the
/// data from it is fully used.
///
/// If the tile is not present within the tile cache, it is checked if the tile is currently being downloaded.
/// If not so, a download job to download the tile is enqueued.
///
/// In both cases - tile being downloaded or not - null is returned.
/// </summary>
/// <param name="zoom">The zoom level to get the tile from.</param>
/// <param name="tile">The tile X/Y coordinates.</param>
/// <returns>A stream to the tiles contents or null.</returns>
public Stream GetTile(int zoom, MapVector tile)
{
TileDescriptor desc = new TileDescriptor(zoom, tile);
if (_cachingProvider.HasTile(desc))
{
return(_cachingProvider.GetTile(desc));
}
else if (!_enqueuedTiles.Contains(desc))
{
DownloadJob job = new DownloadJob(_mapProvider.GetTileUrl(GetNextServer(), desc.Zoom, desc.Tile), desc);
job.OnFinished += Job_OnFinished;
job.OnFailed += Job_OnFailed;
try
{
_downloadMutex.WaitOne();
_enqueuedTiles.Add(desc);
}
finally
{
_downloadMutex.ReleaseMutex();
}
_download.AddJob(job);
}
return(null);
}
