James Westman authored Feb 23, 2023 and Marcus Lundblad committed May 28, 2023

Previously, the renderer connected to the data source's received-data
signal and re-rendered the affected tile(s) when new data arrived.
However, at very low zoom levels (because the same tile is visible
multiple times) and at very high zoom levels (because of overzooming)
sometimes the same data is requested multiple times simultaneously. Each
of these simultaneous requests would emit received-data, which would
cause each tile to re-render. This caused a quadratic slowdown.

Fixed by introducing ShumateDataSourceRequest, which is returned by a
new start_request vfunc in ShumateDataSource. This allows the renderer
to re-render only one tile when new data is received.