Feature/add measure tool

[LDWiegand]

Summary

Added a measure tool for distances and areas

Instructions for local reproduction and review

npm run snowbox

[warm-coolguy]

With 24e386b gone, there's no documented way on how to subscribe to or otherweise access measurements taken in the map left.

🏓 @dopenguin

[dopenguin]

With 24e386b gone, there's no documented way on how to subscribe to or otherweise access measurements taken in the map left.

🏓 @dopenguin

I've added the information to the featureCollection cc8de51

However, I've encountered an error that stems from the way the draw interaction works and added a todo for that. If you got a lead on how to fix that, let me know. Otherwise, I'll get my thinking cap out 🎩

🏓 @warm-coolguy

[warm-coolguy]

With 24e386b gone, there's no documented way on how to subscribe to or otherweise access measurements taken in the map left.
🏓 @dopenguin

I've added the information to the featureCollection cc8de51

However, I've encountered an error that stems from the way the draw interaction works and added a todo for that. If you got a lead on how to fix that, let me know. Otherwise, I'll get my thinking cap out 🎩

🏓 @warm-coolguy

I don't see a simple solution without digging deeper into this. Have you seen the OL example? Maybe there's some indication on how it could be done in another way. (I also kinda like how much simpler the UI is, even though it has less information – do we need per-line measurements?)

I've also noticed an additional bug where, if you draw e.g. a triangle, enter "Edit" mode, and pull from the last corner, a new side will exist that has no measurement on its own.

🏓 @dopenguin

[dopenguin]

With 24e386b gone, there's no documented way on how to subscribe to or otherweise access measurements taken in the map left.
🏓 @dopenguin

I've added the information to the featureCollection cc8de51
However, I've encountered an error that stems from the way the draw interaction works and added a todo for that. If you got a lead on how to fix that, let me know. Otherwise, I'll get my thinking cap out 🎩
🏓 @warm-coolguy

I don't see a simple solution without digging deeper into this. Have you seen the OL example? Maybe there's some indication on how it could be done in another way. (I also kinda like how much simpler the UI is, even though it has less information – do we need per-line measurements?)

I've also noticed an additional bug where, if you draw e.g. a triangle, enter "Edit" mode, and pull from the last corner, a new side will exist that has no measurement on its own.

🏓 @dopenguin

After further digging it concluded that the issue exists because of the fix for modifying snapped features in packages/plugins/Draw/src/store/createInteractions/createModifyInteractions.ts.
This probably doesn't work because there are multiple dragSegments that need to be modified to be able to modify a Polygon.

I tested multiple different scenarios to change the underlying Collection when modifystart is called. This either involved directly changing event.features or changing event.target.features_.
Somehow, changing either of those to only include one feature by a) setting the whole Collection to be new or b) updating the Collection via the provided methods didn't yield any results; all snapped features where still being modified.

When checking how OpenLayers handles this, one example includes the same issue of not being able to un-snap features while another example fixes this by using a Select interaction to be the base for the features that can be modified.

All in all, this outcome does not seem satifying whatsoever. However, I suggest that we go the route of the second example and use a Select interaction for the whole modification process (not only for text). This is not the best solution UX-wise, but at least it is consistent.

I'd like to tackle this NOT as part of this PR as this issue is not new but only has become clear now. We'd also be able to merge #211.
I'll create an issue to change the modification process to work based on a Select interaction and assign it to myself if you agree.

Edit: The measure issue has been fixed as well dbf946f

[warm-coolguy]

I have found the following additional issues:

• Draw a line of multiple parts. Edit the line by pulling from the middle of line segments or pulling existing points. Sooner or later, no interaction indication is left on some of the fragments; any fragment (no matter if first/last/somewhere in the middle) may be affected. (I.e. the blue dot goes missing and that line segment is no longer editable.)
• The same thing can happen on polygons.
• I was able to "find" that line again on this polygon:
  Note: That dot is the mouse interaction indicator. If clicked, the polygon is drastically altered.
• Since 1km²=1000000m², values are miscalculated:
  I also recommend using decimal places after larger units (km/ha) until values become larger, i.e. 2 decimal places may be used until 10km length are reached or something like that. I furthermore recommend to always give measurements in metres on the exported GeoJSON since that's a more parsable format. Or maybe that and the string, should it only be for display ... but parsing "1km²" versus "100ha" is annoying to distinguish.

@dopenguin According to plan you may change whatever you feel like before the merge. To my understanding, a follow-up PR will clean up the rest.