ToME WikiDescribe IdeaArchive/Interface/DTrap Indicator suggestion here.
The green 'DTrap' at the bottom of the screen showing whether you're in a trap detected zone or not should change colours relative to how far away the closest non-detected tile is.
Dark red: 1 tile Red: 2 tiles Orange: 3-4 tiles Yellow: 5-8 tiles Green: 9 or more tiles
Hopefully a colour-changing indicator will prevent leaving-trap-detected-zone-then-immediately-stepping-on-a-trap type annoyances.
NeilStevens: I like it.
ShrikeDeCil: Currently, it looks like traps.lua has the actual map being marked with a boolean flag which is what the display portion picks up on. I don't know if making that a counter (squares-to-edge) might slow things down. A second way is to dynamically hook 'ON_MOVE' and recalculate the distance every step. But while I was looking at this, I had a different thought. There was something called "Temporary Terrain" added recently - what if the effect was applied to the floor directly, instead of as information lingering around the edge of the map. That is, actually 'make' the completely safe tiles greener, and the ring around the edge yellower-then-redder?
PatashuPatashu: That was my other idea. Add a key that, when hit, changes the map to tint 'safe' tiles in green.
DarkGod: The floor changing stuff is not really possible, temporary terrains replace terrains by others, so you'd have to duplicate ALL the game features for each shades of green 
The DTrap changing color on the other hand is quite possible, just have a hook on MOVE_POST that tells the DTrap thing in display/display.lua to redisplay, and have this compute distance. This will slowdown but not noticably I think, except maybe when running
ReenenLaurie: Any chance of just "switching off" this feature while running?
PatashuPatashu: Cool, any chance it'll be in the next version of tome/tome 3?
Sirrocco: It's looking like you already have an answer to this one, but just for the theory's sake - would it be possible to run a floor-coloring scheme off of some variant on "torchlit/visible grids are different colors"?