It allows you to draw simple graphics on the world map similarly to RoomVisual API. You can use it to display helpful infographics, debug info, multi-room paths visualizations, etc. It is available only in the new alpha version of the world map.

Check out the documentation for Game.map.visual.

On room visuals I would do fill: null, but that gives me a black fill on the map.

Anything I am missing?

@artch, is there any chance whilst you're working on the new map interface that you could make it so ctrl-clicking opens rooms in a new tab?

The new map interface is a big improvement!

For example: I could draw a status of every room on the map based on scouting info. It'd be great for me to see what's going on at a glance. I'm probably not going to do it, and certainly not always on, because it's just too much CPU to run every tick. On the other hand, the data does not go stale quickly. Updating it once every 100 ticks would be more than sufficient for me.

I'm not sure how visuals are implemented. The server tells the client something. I don't think it'd be too hard for the client to track persistence - wouldn't add server load and the 100kb limit could still be per-tick (ie. persisting visuals don't count).

It would be nice if we could pass a persistence option to visuals

For map visuals this makes so much sense. They're often very expensive to generate, and they change infrequently.

This mechanism would be somewhat useful for room visuals, but it seems critical for map visuals.

Without that you've got to recreate the object every tick. That's going to be expensive using the API calls for extensive visuals.

Thank you for implementing it!