ZoomToLayer fix

[ahmadayubi]

Rather than zooming in/out and checking if a layer is within bounds repeatedly, calculate whether a layer would be in or out of bounds after a set number of zoom in/outs, ahead of time.

Before: (flickering, instant movements)

2021-12-14.12-47-01.mp4

After: (no flickering, removing repeated zoom in/out)

2021-12-14.15-15-33.mp4

Closes issue with templatedFeatureLayer duplicates, although that issue may still remain in another form if the underlying bug wasn't the zoomToLayer feature but rather quick successive addition and removal of layers (which the old zoomToLayer feature would do).

Closes #634

#612 (comment)

[prushforth]

It does seem to fix the problem with duplicate markers. The animation is not quite right though: it flashes dramatically. To reproduce/ see what I mean, go to this example. Click on British Columbia. Click on the marker. Use Zoom To Layer for the BC layer.

[ahmadayubi]

The flashing in that certain case is due to the tiles loading in, if you zoom out manually you can see the same effect, the animation is handled by leaflets flyTo function, alternatively you can simply setView to avoid animations altogether.

Removing the flying effect would also reduce bandwidth, as you wouldn't need to make requests for intermediary zoom level tiles. (the duplication and flickering would still be fixed)

[prushforth]

Let's use the direct to location method then

[prushforth]

Pretty abrupt, but functional. Can't afford to get too fancy atm. Makes me think that zooming to a feature is just another word for following a link.

[ahmadayubi]

Maybe a fading effect would help, it would have to be a custom implementation since Leaflet doesn't offer layer fading in, I believe.

[prushforth]

I don't think it makes much difference to non-visual users, so not inclined to spend cycles on it now.

[prushforth]

LGTM -- thanks!