Add an empty data layer when user clicks disabled "mode" button

[openstreetmap.org-user-d1g]

If user click mode buttons (on the left), he should be asked with promt

"In order to use modes, you need at least one data layer. Would you like to <s>add one</s> download OSM data for that region now?" yes/no

In code:

• there 0 data layers OR
• there data layers and all of them are invisible

[Don-vip]

vertical toolbar is not shown without layer. And core modes are disabled without data layer. Are you talking about plugin modes? They should all be disabled as well.

[openstreetmap.org-user-d1g]

Replying to Don-vip:

vertical toolbar is not shown without layer.

Yes, there are some some layers added (GPS/imagery) but none of them "data layer". It is possible to see/click at (disabled) vertical toolbar without OSM data layer.

And core modes are disabled without data layer.

Yes, as many other disabled osm data tools they are disabled; but they are still visible and user may still click at them. We can tell user why this action makes no sense (yet) and load data for him (if he agrees).

[stoecker]

Actually I find that strange. A disabled element should not result in any action. That's totally uncommon behaviour.

[openstreetmap.org-user-d1g]

Replying to stoecker:

Actually I find that strange. A disabled element should not result in any action. That's totally uncommon behaviour.

True, maybe text label with explanation(s) would be better (similar to html alt=*)?

"This item (mode) is disabled because there no active data layer. Make sure you have downloaded OSM data".

Because this is one of the first steps in the workflow, it is worth to add it directly in editor(JOSM) IMO. We repeat ourself in Introduction for no real reason.

This one step ("fetch OSM data") is not optional (unlike imagery/video/images/Mapillary/etc). BTW I think we may rework download menu to have more tabs (OSM API/overpassQL/open file) but single activation step (Ctrl+Shift+Down)

[Hb---]

The fewer actions and the fewer bling-bling a GUI needs the better is it. A said above, clicking a deactivated button should do nothing.