@allenjlee: Here's the geo selection issue we discussed. I believe we support single/multi selections with geo projections already but a good first test would be to build out a few examples of each. The flight links example provides a nice base case that you can start adding some interesting interactivity to for both selection types. I'll let you ideate a little here yourself :)

Interval selections are the more trickier ones. As we discussed, these selection generate signals in visual space (vnames that record the x/y coordinates of the region dragged) which are converted to data coordinates (dnames) via scale inversion individually (i.e., visual_x -> scale_x.invert -> data_x; visual_y -> scale_y.invert -> data_y). This approach won't work with geo projections because they are bivariate (i.e., they manipulate both x/y together). In fact, there are some really weird projections out there.

Instead, we added a new intersect expression function in Vega v5 (see the changelog for documentation on its signature) to do bounding box hit testing for us (the function is implemented in the vega-functions package). For now, don't worry about what changes need to be made to the compiler. Instead, start by adding a simple 2D interval selection (i.e., {"type": "interval", "translate": false, "zoom": false}) and to highlight points selected in this example and update the generated Vega spec by modifying signals to use the intersect function instead of scale inversions and removing any unnecessary signals. Once you get that working, try reintroducing the translate and/or zoom properties to see how that changes your spec design. Try and get a good sense of how you think the output Vega spec should change for our next meeting :)

Uh oh!

Support pan and zoom for geoshape mark #3306

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