Pass nodename to tnt.burn function where possible to reduce
use of 'get_node'.
Change 'ipairs' to 'pairs'.
Use 'nodeupdate_single(pos)' instead of 'nodeupdate(pos)' to
avoid every node triggering recursion, the loop itself takes
the place of recursion and works upwards through horizontal
planes as required.
Credit to tenplus1 for the suggestion to generalise for mod use.
Mods can add mod nodes to 'group:spreading_dirt_type' enabling the
function to work with mod nodes.
Add some nodes to this group.
Removing 'dirt_with_grass' etc. from 'neighbors' stops the ABM action
running everywhere and constantly, on the dirt nodes immediately below
the surface nodes. Now the action only runs in the rare case of a dirt
node with neighbouring air, grass decorations or snow.
Remove check for air above to allow grass to spread under light-
transmitting nodes such as fences, walls, plants. This causes spread
under slabs, stairs and glass, when near air, but seems worth it.
Remove unnecessary check for nil node.
The collision box still extended into a neighbouring empty node, causing
falling node objects to collide but not transform back into normal nodes.
Completes the fix started in a previous similar commit.
Combine slabs if identical based on orientations using a simple lookup
table if the nodes are identical.
Otherwise relies on place_node() to place the node, which properly
handles rotation compared to adjacent nodes already, and can orient
based on look_dir as well.
Initial slabs placed are oriented based on (1) the orientation of
the pointed "face" (assumes nodes are cubic, of course), and uses
the player look direction to orient the node n/e/w/s if the slab
is horizontal or upside-down. If placed against a vertical face,
the slab is placed against the face without rotation around the axis
perpendicular to that vertical face. This allows upside down placement
and vertical placement without screwdriver.
If a slab is placed on top of an upside down slab, or below a normally
placed slab, the rotation is inverted so that no "floating" slab
is created.
Largely based on kilbith's #807 PR. Slab combining and place_node()
usage by sofar.
Since this relies entirely on `on_place` mechanics, this fails to
combine slabs into a plain node if the space *above* is occupied.
This is unavoidable due to the fact that on_place() happens after
the checks required to see if pointed_thing.above is empty or not.
