Lua_api.txt: Warn of errors possible with VoxelArea:index()/indexp() (#7422)

diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index d9cf96800beb858de846f8e9817304e98fc4fa6c..29befca5298c1b23286a14d7015b41a69b66097d 100644 (file)
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -4736,9 +4736,14 @@ The coordinates are *inclusive*, like most other things in Minetest.
   `MaxEdge`.
 * `index(x, y, z)`: returns the index of an absolute position in a flat array
   starting at `1`.
-    * useful for things like `VoxelManip`, raw Schematic specifiers,
+    * `x`, `y` and `z` must be integers to avoid an incorrect index result.
+    * The position (x, y, z) is not checked for being inside the area volume,
+      being outside can cause an incorrect index result.
+    * Useful for things like `VoxelManip`, raw Schematic specifiers,
       `PerlinNoiseMap:get2d`/`3dMap`, and so on.
-* `indexp(p)`: same as above, except takes a vector
+* `indexp(p)`: same functionality as `index(x, y, z)` but takes a vector.
+    * As with `index(x, y, z)`, the components of `p` must be integers, and `p`
+      is not checked for being inside the area volume.
 * `position(i)`: returns the absolute position vector corresponding to index
   `i`.
 * `contains(x, y, z)`: check if (`x`,`y`,`z`) is inside area formed by