User-initiated map-move events

[sqcsabbey]

What we need:
Events that specifically trigger when a user gesture starts a pan, zoom, tilt, or rotate action.

My use case:
We have a flutter-maplibre-gl app that automatically follows an external location with panning, zooming, and rotating. When users interact with the map, we want to yield control to them by disabling this automatic following.

Current challenges:
Events like 'onZoom' don't distinguish between our programmatic zooming and user-initiated zooming, which could happen simultaneously.

Events like 'onDoubleClick' need to be combined with others, like 'onDrag', to guess if the user is zooming or rotating, and we might not always guess correctly.

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Is there a more straightforward way to detect when users begin these map interactions?

[josxha]

Hello @sqcsabbey, are you asking to find a solution for fluttermaplibre-gl or are you looking for a solution in this package flutter-maplibre?
For flutter-maplibre you can use the CameraChangeReason flag of the MapEventStartMoveCamera event.

[sqcsabbey]

I don't think that handles my use-case— if there's a code-started pan and a user-started zoom, I wouldn't be able to tell which was user-initiated.

I could suggest other approaches, like a separate start event for each map move change (one for the pan, one for the zoom, ...), but I don't know enough about this package to tell if that makes sense.

[josxha]

Makes sense. Maybe we can implement something similar as maplibre_gl. What callbacks are you currently using?

[sqcsabbey]

It's not currently available in maplibre_gl, so we're capturing the mouse events with a TransparentPointer and interpreting those. The TransparentPointer allows both our code and maplibre_gl to view the mouse events.

There are a couple of issues with this approach:

1. Our interpretation of the mouse events (e.g., what constitutes a rotate) doesn't perfectly match maplibre_gl's.
2. It's complicated code.

That's our fallback position, but we were hoping for something cleaner.

[josxha]

Thanks for the insights. Did you look into maplibre native how it would be solved there? Because the flutter packages are built on it (and maplibre gl js) both package rely on the data they receive from it.
And, is there a reason to assume that the if a move-camera-start event occurs, the next camera-move events are not caused by this start event until another move-camera-start event fires?

[sqcsabbey]

No, we haven't dug into the source. We just tried implementing this on flutter_mapbox_gl (before switching to maplibre_gl), and we didn't find any satisfactory events to use, which is why we wrote our own user event interpreter.

This package looks like such an improvement over maplibre_gl, that I think we'll try switching our code over to it (probably after a 1.0 release), and trying to use the events this package gives us for this at that point.

But, to answer your question, if a user and developer-code both start moving the map at just about the same time, and there are 2 events, just checking the camera state before and after a user's map move start event sounds like it could also see changes from the other event. Race conditions like this tend to be very hard to test for, and very hard to debug.

Thank you for all of your time with this. I was hoping for a 'yes, here's how you can do that'; you've really gone above and beyond with support on this one.