URLs do not give same view

[Robinlovelace]

Minor issue for now but thinking for future work this could be really useful. Reproducible example: go to https://actdev.cyipt.bike/lcid/ and follow the steps shown in gif:

I'm trying to share a map showing Kirkgate: https://actdev.cyipt.bike/lcid/routenetwork,buildings,destinations/#16.58/53.79545/-1.535571

Is this a bug or a feature or other @mvl22 ? great that you can share the urls but sad that the zoom is lost when you share it if I understand correctly.

[mvl22]

Currently the logic is that the site moniker, i.e. the first URL component, takes precedence over the zoom location. This is because if you zoom to another location to see a site, e.g. Allerton Bywater, you confusingly would see all the LCID data in the panel.

The correct solution to this is that the zoom should be maintained when it isn't overlapping in a strong sense with another site, but that is significantly more complex logic.

We could set the zoom to dominate, by changing the logic here in the underlying library to have an option that checks for the zoom after doing the region selection:
https://github.com/cyclestreets/Mapboxgljs.LayerViewer/blob/master/src/layerviewer.js#L4334-L4345

In general I'm a strong advocate of persistent URLs, and we worked hard to ensure this happened with both the site and the enabled layers, but maintaining zoom does conflict a bit with the site control concept.

[Robinlovelace]

Thanks for the explanation Martin, that makes sense. I suggest trying to see what happens when the zoom dominates. As long as https://actdev.cyipt.bike/lcid/ goes to the right zoom, as I imagine it would do even if the zoom dominates, I think that it should be fine. We don't have many users atm so could try it out on the main branch.

[mvl22]

Pull requests to the Mapboxgljs.LayerViewer library very welcome.

However, this should be set as a setting which is off by default (see var _settings), as otherwise this could affect other uses of the library.

[Robinlovelace]

Pull requests to the Mapboxgljs.LayerViewer library very welcome.

Great to hear. Are you up for putting in the PR? It's not my area of knowledge. @natesheehan or @Siequnu or you may be better placed, although will take a look...

[Robinlovelace]

will take a look...

Took a look and I'm not sure what needs to change here

					$('#regionswitcher select').change (function () {
						if (this.value) {
							
							// Fit bounds
							_selectedRegion = this.value;
							var options = {};
							if (_settings.regionSwitcherMaxZoom) {
								options.maxZoom = _settings.regionSwitcherMaxZoom;
							}
							
							_map.fitBounds (_regionBounds[_selectedRegion], options);