Better rendering for tags with left/right semantics (e.g. coastline, cliff)

[simonpoole]

The following tags make ways "non-reversible":(aka the semantics depend on way direction) natural=cliff, natural=coastline, barrier=retaining_wall and man_made=embankment.

There is no "good" way of handling these outside of showing an "are you sure" alert or similar, this needs to be done for both explicit reversal and implicit (when merging ways).

Updated list of tags:

natural=cliff
natural=coastline
barrier=retaining_wall
barrier=kerb
barrier=guard_rail
man_made=embankment.
barrier=city_wall if two_sided != yes

some people believe that waterway=* belongs in this list too

[simonpoole]

Tag 5: barrier=city_wall if two_sided != yes

[ajashton]

I would think most times someone explicitly reverses one of these would be to fix an incorrect direction. All of these objects should be styled so that the result of a reversal is obvious without a warning.

[malenki]

waterway=* and oneway=* should be issued, too

[jfirebaugh]

We're not planning to add any warnings for reversing ways. Warnings may be well intentioned, but they run counter to iD's goal of encouraging new users to contribute to the map because they make them feel insecure, even when their edits are perfectly legitimate. "I might break something, I better not touch." Not to mention they are an annoyance for experienced mappers, who think "of course I want to reverse it", and click through without reading.

Fortunately, careful design makes users feel MORE secure AND less likely to break something. The best way to do it is show them, in a way they can understand without a deep knowledge of OSM data structures, what's on the map and what changes they are making to it. We're planning to add styles for natural=coastline that indicate the water/land sides (#1465), and we can do the same for cliffs, embankments and barriers. Waterways and oneways already have a clear direction indicator.

[malenki]

For the warnings I know from JOSM there is a checkbox for users feeling nagged:
[ ] Do not show again
or similar
Just my last 2 cent

[simonpoole]

Updated list of problematic tags.

[slhh]

@bhousel Better rendering is useful, but it is not a full solution.
We should considerer the normal safe reversal, which is not changing any meaning of data, and the reversal, which is intentionally swapping left/right properties, as two different operations with different icons. A merge operation should only use the normal safe reversal and be unavailable otherwise. If required the user can swap left/right first and merge afterwards.
Both reversal operations can share the same place in the radial menu because they can't be available both.

[lakedistrictOSM]

Cliffs could be rendered like osm-carto does or with a thick line at top and a glow on the bottom. Would save me having to check the wiki each time!

[tordans]

Ideas for the rendering in iD:

I looked for an easy way to draw a css-border with triangles but apparently there is none. (Except for some (crazy?) svg+border-image workarounds.)

However iD has the ability to draw arrows over a line:

(Left waterway=stream, Right selected highway=unclassified)

So, there might be a way to use this, to draw arrows above (or next to) the line for this usecase?

A very (very) rough scribble for natural=cliff and man_made=embankment:

The arrows are already direction-aware.

With this it should be possible to – more or less – recreate styles like in this OSM-Wiki-Image:

---

Something different: To further point out, that the way is direction aware, we could try to find a place for the "switch direction" button that is used for the "oneway=yes"-preset. However, I don't see a good place for that in tags like natural=cliff and man_made=embankment.

[tordans]

Thanks a lot for adding this @huonw!

Btw, it can be viewed on http://preview.ideditor.com/master/#background=Berlin-2018&disable_features=boundaries&map=19.05/52.47535/13.45292 already.

As a follow up: I wonder if the styling and behaviour of barrier=kerb should be tuned down a bit.

What I notice:

• The arrows are not visible on areas, only on just barrier=kerb-tags. So eg. having a landuse=residential + barrier=kerb does not show arrows. That is both good (looks better) and bad (we loose the direction info).
• Maybe the kerb arrows should only be visible for selected objects?
• Maybe the kerb design in iD should be tuned down (thinner line, softer gray, smaller arrows)?

An example of a not-ideal place (source link above):

What do you think, is this worth creating an issue to discuss and improve it further?

[huonw]

That does look rather overwhelmingly busy! It wouldn't be very hard to give the kerb tag a different style/size of arrows. For instance, natural=coastline is special cased, and adding more special cases should involve changing only two places, following the coastline example.