Measure behavior on multiple layers

[mstenta]

If you try to add the measure behavior to multiple layers (eg: in the "current location" and "new location" layers in the animal move quick form map: https://www.drupal.org/project/farm/issues/3156713), it works at first (both layers show their measurements), but if you then try to edit a layer then the other one disappears.

[mstenta]

Dug into this, and it basically comes down to: there is only one layer variable defined in the measure.js behavior code:

farmOS-map/src/behavior/measure.js

Line 16 in d50daf5

let layer;

So whenever addBehavior('measure', { layer }); runs, it replaces the layer that the behavior is looking at:

farmOS-map/src/behavior/measure.js

Line 128 in d50daf5

({ layer } = options);

Then, specifically, whenever stopMeasure() runs, it goes through and removes any measure overlays with IDs that are not found in the layer. So because layer gets overridden, it doesn't find any of the measures in the first layer, and removes them all:

farmOS-map/src/behavior/measure.js

Line 116 in d50daf5

// Remove the overlay.

[mstenta]

Similarly, I don't think the measure behavior would work with multiple maps, for the same reason.