Leaflet GridLayer alternative

[bdon]

Ought to investigate a long-term replacement for leaflet.GridLayer

The current leaflet frontend subclasses GridLayer with canvas elements, which is the simplest way to get a working map. By moving away from this we can improve user-perceived latency with more fine grained control over the tile rendering lifecycle.

• remain Leaflet-compatible, but use a single absolutely positioned canvas element for all basemap drawing
• Should work with either zoomAnimation: true or false, false is preferred to achieve 0ms delay on zooming + rendering of overzoomed labels
• Need to test extensively on browsers because this depends heavily on GPU accelerated canvas being available, and not falling back to CPU canvas

[bdon]

Check out the OpenSeadragon example for a good reference point.