Mangrove dryad vines in deep water are invisible and burn as if on ground

[tmewett]

This creates a very large amount of steam, seemingly from nowhere.

[pender]

I suspect this can be fixed by adding (DFF_BLOCKED_BY_OTHER_LAYERS) to the dungeon feature flags for the Dryad grass DF, although it may prevent dryad grass from spawning on shallow water too.

[brturn]

While looking into #372, I also looked at this issue.

Verified the bug - the burning vines generate an enormous amount of steam (fills an entire dungeon level if doors don't block it).

DFF_BLOCKED_BY_OTHER_LAYERS does not fix the issue, it still spawns over deep water. Interestingly, after burning it also leaves grass over the water.

Looked at how/why things can burn over water. Appears that the "priority" field of a floorTileType determines whether a feature ignites or extinguishes (where lower priority is stronger). G_VINE has a very strong priority (19) and can catch fire, while water is in the range of 40-55 and can extinguish it. So it will always ignite even when it is over water.

Adjusting the priority to 58 gave a more reasonable burn behavior (does not ignite over water), but also places the vines 'under' the water layer. Not sure what the desired behavior is.

[tmewett]

Appears that the "priority" field of a floorTileType determines whether a feature ignites or extinguishes

I wonder if this is needed anywhere, or if we can do the check without priority?