Interpolated HUD and radial menu UI.

mods/artifact_base/init.lua

@@ -22,6 +22,30 @@ end
 
 say = minetest.chat_send_all
 
+function extend(dst, src)
+    for k, v in pairs(src) do
+        dst[k] = v
+    end
+    return dst
+end
+
+-- Some kind of promise API. (Forget about async-await, though.)
+function Promise(fn)
+    local p = {resolved = false}
+    p.resolve = function(...)
+        if p.resolved then return end
+        p.resolved = true
+        if p.after then p.after(...) end
+    end
+    fn(p.resolve)
+    return {
+        after = function(fn)
+            p.after = fn
+        end
+    }
+end
+
+
 minetest.register_lbm{
     name = ":artifact:on_load",
     nodenames = {"group:call_on_load"},