Make it possible to synchronize map navigation

[tschaub]

As the current side-by-side example demonstrates, using one view with two maps doesn't work for animated zoom/pan/rotate.

We should be able to provide a way for applications to have more than one map that share the rendered view state. As the examples below demonstrate, this is possible, but it requires the use of non-exported code and some awkwardness.

This pull request is meant to serve as a discussion point for making map synchronization easier.

[twpayne]

Note that the example only synchronises navigation, not API calls. For example, executing

map1.getView().getView2D().setCenter([1e7, 1e7]);

causes the maps to desynchronise.

[tschaub]

Right, I tried to be careful about saying "synchronized navigation" (as opposed to synchronized view).

I'm experimenting with an alternative that would allow synchronized views.

[pagameba]

@tschaub did you get anywhere with this? I'm curious because I made a little app with two maps which could benefit :)

[tonio]

Kinda duplicate of #298, or maybe achievable with listening to postcompose on the map, & synchronize center & resolution.

[tonio]

Didn’t saw that was a PR :/ Maybe could be updated??

[tschaub]

This should be closed. I think the correct solution is to animate views instead. Working separately on that.