Work around wrong character bone rotations on Luanti 5.11+ (#6)

Fixes head turning more than 90 degrees during minor lag, which appears unnatural.

init.lua

@@ -22,10 +22,17 @@ end
 
 -- stop player_api from messing stuff up (since 5.3)
 if minetest.global_exists("player_api") then
-	for _, v in pairs(player_api.registered_models["character.b3d"].animations) do
+	minetest.register_on_mods_loaded(function()
-		v.x = 0
+		for _, model in pairs(player_api.registered_models) do
-		v.y = 0
+			if model.animations then
+				for _, animation in pairs(model.animations) do
+					animation.x = 0
+					animation.y = 0
 				end
+			end
+		end
+	end)
+
 	minetest.register_on_joinplayer(function(player)
 		player:set_local_animation(nil, nil, nil, nil, 0)
 	end)
@@ -118,6 +125,17 @@ minetest.register_on_joinplayer(function(player)
 	players_animation_data:init_player(player)
 end)
 
+-- HACK work around https://github.com/luanti-org/luanti/issues/15692
+-- Scales corresponding to default perfect 180° rotations in the character b3d model
+local bone_workaround_scales = {
+	Body = vector.new(-1, 1, -1),
+	Arm_Left = vector.new(1, -1, -1),
+	Arm_Right = vector.new(1, -1, -1),
+	Leg_Left = vector.new(1, -1, -1),
+	Leg_Right = vector.new(1, -1, -1),
+	Cape = vector.new(1, -1, -1),
+}
+
 local vector_add, vector_equals = vector.add, vector.equals
 local function rotate_bone(player, bone, rotation, position_optional)
 	local previous_rotation = players_animation_data:get_bone_rotation(player, bone)
@@ -133,10 +151,18 @@ local function rotate_bone(player, bone, rotation, position_optional)
 	or not previous_position
 	or not vector_equals(rotation, previous_rotation)
 	or not vector_equals(position, previous_position) then
+		if player.set_bone_override then -- Luanti 5.9+
+			player:set_bone_override(bone, {
+				position = {vec = position, absolute = true},
+				rotation = {vec = rotation:apply(math.rad), absolute = true},
+				scale = {vec = bone_workaround_scales[bone], absolute = true},
+			})
+		else
 			player:set_bone_position(bone, position, rotation)
 			players_animation_data:set_bone_rotation(player, bone, rotation)
 			players_animation_data:set_bone_position(player, bone, position)
 		end
+	end
 end
 
 -- Animation alias
@@ -254,7 +280,14 @@ local function rotate_body_and_head(player)
 		if #yaw_history > BODY_ROTATION_DELAY then
 			local body_yaw = table_remove(yaw_history, 1)
 			local player_yaw = player:get_look_horizontal()
-			return math_deg(player_yaw - body_yaw)
+			-- Get the difference and normalize it to [-180,180) range.
+			-- This will give the shortest rotation between head and body angles.
+			local angle = ((player_yaw - body_yaw + 3.0*math_pi) % (2.0*math_pi)) - math_pi
+			-- Arbitrary limit of the head turn angle
+			local limit = math_pi*0.3 -- value from 0 to pi, less than 0.45*pi looks good
+			-- Clamp the value to the limit
+			angle = math.max(math.min(angle, limit), -limit)
+			return math_deg(angle)
 		end
 		return 0
 	end)()
@@ -267,7 +300,15 @@ end
 
 
 local function animate_player(player, dtime)
-	local animation = get_animation(player).animation
+	local data = get_animation(player)
+	if not data then
+		-- Minetest Engine workaround for 5.6.0-dev and older
+		-- minetest.register_globalstep may call to this function before the player is
+		-- initialized by minetest.register_on_joinplayer in player_api
+		return
+	end
+
+	local animation = data.animation
 
 	-- Yaw history
 	if animation == "lay" or animation == "sit" then