Progressive data rendering with zoom event
Large data sets may well include more data than can be presented, given the pixel size of the display. When a user zooms in on the data, more information would then be needed to display detail data.
A progressive mechanism would be useful to allow more detail to be requested and sent to the client via an ajax call, triggered from a zoom event. This progressive rendering might show a lag on zoom, but in some cases this lag would be preferred to a long delay for initial data display for very large data sets. It might also perform better with large data sets.
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