Render contiguous boundaries

[kostmo]

Closes #1271

Demo

scripts/play.sh --scenario data/scenarios/Testing/1271-wall-boundaries.yaml --autoplay

Implementation

This implements neighbor-aware boundary rendering strictly on the display layer. Underlying entities remain unchanged (for the purpose of world cell contents and e.g. scan). Eventually we should be able to retire all of the niche boundary glyph entities.

Only a single function getBoundaryDisplay is exposed for computing the glyph appropriate for adjacent boundaries. It takes a function from AbsoluteDir -> Bool indicating whether the neighbor cell in a particular direction is (also) a "boundary" entity.

The internal glyphForNeighbors function is implemented with pattern-matching such that exhaustive coverage of cases is guaranteed.

[xsebek]

@kostmo Looks good! 👍

I was initially put off by having the variants hardcoded, but on further thought this simple approach makes sense.

The PR description confused me though, is the discussion up to date?

[byorgey]

Looks good to me, though I can't help thinking that the complication with the orientationMap necessitates adding yet more complication in the form of a boundaryOverride field in a Display.

This is just speculation for a future PR... what if a Display contained just a single Char, and an "orientation map" was stored at a higher level as a function from direction to Display? Likewise, then Display wouldn't have to know anything about boundary overrides --- if you wanted to show a boundary you would just take the Display you got and replace its Char with the appropriate box drawing character. [The reason we can't do that now is that you can't just "replace a Display's character" since it might store a whole orientation map worth of different characters...]