A few fixes and tweaks

cartbase.lua

@@ -55,8 +55,9 @@ end
 --@param dtime Time since last call, in seconds
 function cartbase.on_step_handler(self, dtime)
 
-    if self.skipnextstep then
-        self.skipnextstep = false
+    if self.skipsteps > 0 then
+        dbg.v3("Skipping step")
+        self.skipsteps = self.skipsteps -1
         self.dtime_debt = self.dtime_debt + dtime
         return
     end
@@ -83,6 +84,10 @@ function cartbase.on_step_handler(self, dtime)
         oldpos = {x=self.pos.x, y=self.pos.y, z=self.pos.z}
     end
 
+    if self.pos and self.speed > 0 then
+        dbg.v3("New step, dtime "..dtime.." at "..minetest.pos_to_string(self.pos))
+    end
+
     -- Keep track of this over all step slices and do it once, otherwise
     -- it goes wrong if it happens twice (i.e. very fast over two close
     -- together curves)
@@ -112,7 +117,7 @@ function cartbase.on_step_handler(self, dtime)
         end
 
     end
-    if dtime >= 0 and not nomore then
+    if dtime > 0 and not nomore then
         nomore = cartbase.update(self, dtime)
         dtime = 0
     end
@@ -120,7 +125,9 @@ function cartbase.on_step_handler(self, dtime)
         -- TODO - seeing if skipping an extra step resolves the mesecons
         --        delay which occasionally causes rails to not be switched
         --        in time
-        self.skipnextstep = true
+        -- TODO - in fact, the switching happens at the *end* of the *next*
+        --        step, so we have to skip two!!
+        self.skipsteps = 2
     end
     self.dtime_debt = dtime
 
@@ -146,15 +153,20 @@ end
 
 
 --- Handle update for a cart.
---@param self The cart
---@param dtime Time since last call, in seconds, which should always be within
---             low enough that the cart doesn't >= 0.5 nodes.
---@return True if something happened which means no further step slices should
---        be processed during this step. (Currently, this is specifically only
---        when a digiline message is sent, because a common usage of that is
---        to pass information to a luacontroller, which then uses mesecons to
---        switch a rail. This will not necessarily have happened until the next
---        server step - and hopefully by then!)
+-- @param self The cart
+-- @param dtime Time since last call, in seconds, which should always be
+--             low enough that the cart doesn't move >= 0.5 nodes.
+-- @return True if something happened which means no further step slices should
+--         be processed during this step. (Currently, this is specifically only
+--         when a digiline message is sent, because a common usage of that is
+--         to pass information to a luacontroller, which then uses mesecons to
+--         switch a rail. This will not necessarily have happened until the next
+--         server step - and hopefully by then!)
+--
+-- Note that although some processing is done before the cart is moved, NOTHING
+-- should set the speed (and in particular, increase it) before the movement,
+-- because this method is called with a dtime calculated to be safe for the
+-- speed at the time of calling.
 function cartbase.update(self, dtime)
 
     local no_more_slices = false
@@ -190,15 +202,6 @@ function cartbase.update(self, dtime)
         return no_more_slices
     end
     
-    -- Eject a player if necessary
-    if (state.railstatus.eject or state.railstatus.onautolauncher)
-        and self.linkedplayer ~= nil then
-        dbg.v1("Ejecting player from cart")
-        self.linkedplayer:set_detach()
-        self.linkedplayer:setpos(state.pos)
-        self.linkedplayer = nil
-    end
-
     -- Grab the cart into something's inventory if necessary
     -- (only allowed when there is no passenger or cargo)
     if state.railstatus.grab and cartbase.is_empty(self) then
@@ -217,15 +220,6 @@ function cartbase.update(self, dtime)
         return no_more_slices
     end
 
-    -- Set speed/direction from launcher
-    if state.railstatus.launch then
-        cartbase.setdirection(self, state, state.railstatus.launch)
-        state.speed = LAUNCH_CART_SPEED
-    elseif state.railstatus.autolaunch and self.linkedplayer ~= nil then
-        cartbase.setdirection(self, state, state.railstatus.autolaunch)
-        state.speed = LAUNCH_CART_SPEED
-    end
-
     -- Handle loading/unloading from/to a hopper
     if (self.carttype == "cargo" or self.carttype == "boring") and state.railstatus.hopper and self.speed == 0 then
         local hpos = state.railstatus.hopper
@@ -302,9 +296,26 @@ function cartbase.update(self, dtime)
         state.speed = 0
     end
 
-    -- Move the cart
     if state.speed > 0 then
 
+        -- Move the cart
+        local movedist = state.speed * dtime
+        dbg.v3("Cart moving "..movedist.." at speed "..state.speed.." and dtime "..dtime)
+        local xz = direction_to_xz(state.direction)
+        local axis, oaxis
+        if xz.x ~= 0 then
+            axis = "x"
+            oaxis = "z"
+        else
+            axis = "z"
+            oaxis = "x"
+        end
+        state.movein = false
+        if (xz[axis] > 0 and state.pos[axis] < state.nodepos[axis]) or
+            (xz[axis] < 0 and state.pos[axis] > state.nodepos[axis]) then
+            state.movein = true
+        end
+
         -- Get the status of the rails at our next location
         cartbase.get_next_railstatus(self, state, false)
         local drop = false
@@ -327,30 +338,14 @@ function cartbase.update(self, dtime)
             return no_more_slices
         end
 
-        local movedist = state.speed * dtime
-        local xz = direction_to_xz(state.direction)
-        local axis, oaxis
-        if xz.x ~= 0 then
-            axis = "x"
-            oaxis = "z"
-        else
-            axis = "z"
-            oaxis = "x"
-        end
-        local movein = false
-        if (xz[axis] > 0 and state.pos[axis] < state.nodepos[axis]) or
-            (xz[axis] < 0 and state.pos[axis] > state.nodepos[axis]) then
-            movein = true
-        end
-
         dbg.v3("Cart on "..state.railstatus.railtype.." at "..minetest.pos_to_string(state.pos)..
                 ", dir:"..state.direction.." speed:"..state.speed..
                 " next rail:"..state.nextrailstatus.railtype..
                  " "..(drop and "(drop)" or "")..
-                 " "..(movein and "(movein)" or "(moveout)"))
+                 " "..(state.movein and "(movein)" or "(moveout)"))
 
         state.pos[axis] = state.pos[axis] + movedist * xz[axis]
-        if movein then
+        if state.movein then
             if (xz[axis] > 0 and state.pos[axis] >= state.nodepos[axis]) or
                 (xz[axis] < 0 and state.pos[axis] <= state.nodepos[axis]) then
 
@@ -362,6 +357,7 @@ function cartbase.update(self, dtime)
                     local detpos = state.railstatus.detector
                     minetest.add_node(detpos, {name="railcarts:cart_detector_on"})
                     mesecon:receptor_on(detpos, mesecon.rules.default)
+                    no_more_slices = true
                     dbg.v2("Triggered cart detector at "..minetest.pos_to_string(detpos))
                 end
 
@@ -490,6 +486,16 @@ function cartbase.update(self, dtime)
         else
             --Moving out
 
+            -- Eject a player if necessary - only when moving out, to avoid
+            -- false ejections when the cart will change direction on a
+            -- switch
+            if state.railstatus.eject and self.linkedplayer ~= nil then
+                dbg.v1("Ejecting player from cart")
+                self.linkedplayer:set_detach()
+                self.linkedplayer:setpos(state.pos)
+                self.linkedplayer = nil
+            end
+
             local newnodepos = vector.round(state.pos)
             if state.nodepos[axis] ~= newnodepos[axis] then
                 dbg.v3("New nodepos "..newnodepos[axis]..", old "..state.nodepos[axis])
@@ -502,6 +508,26 @@ function cartbase.update(self, dtime)
                 end
             end
         end
+
+    else
+        -- speed == 0
+
+        if state.railstatus.onautolauncher and self.linkedplayer ~= nil then
+            dbg.v1("Ejecting player from cart")
+            self.linkedplayer:set_detach()
+            self.linkedplayer:setpos(state.pos)
+            self.linkedplayer = nil
+        end
+
+    end
+
+    -- Set speed/direction from launcher
+    if state.railstatus.launch then
+        cartbase.setdirection(self, state, state.railstatus.launch)
+        state.speed = LAUNCH_CART_SPEED
+    elseif state.railstatus.autolaunch and self.linkedplayer ~= nil then
+        cartbase.setdirection(self, state, state.railstatus.autolaunch)
+        state.speed = LAUNCH_CART_SPEED
     end
 
     -- Set ourselves autonomous if necessary (requires minetest patch)
@@ -528,7 +554,15 @@ end
 
 --- Get the status of the rails at the next node
 --@param state The current state, which will have a next_railstatus
---       field added. (And only railstatus, pos, speed and direction are relevant)
+--       field added. (And only railstatus, pos, speed, movein and
+--       direction are relevant)
+--
+--       If movein is true, the track is used to determine the
+--       outbound direction (e.g. curves, switches)
+--       If movein is false, the current direction is used instead.
+--       This is to ensure that movement isn't messed up by the 
+--       track switching underneath the cart.
+--
 --@param below True to look below instead of at the same level
 function cartbase.get_next_railstatus(self, state, below)
 
@@ -552,7 +586,7 @@ function cartbase.get_next_railstatus(self, state, below)
         end
     end
 
-    if is_curve(state.railstatus.railtype) then
+    if is_curve(state.railstatus.railtype) and state.movein then
         if state.railstatus.railtype == "x+" then
             if state.direction == 0 or state.direction == 1 then
                 xz = {x=1,z=0}
@@ -642,7 +676,7 @@ function cartbase.punch_move(self, own_pos, hitterpos)
             return
         end
 
-        state = {direction=newdir, speed=1, railstatus=railstatus, pos=self.pos}
+        state = {direction=newdir, speed=1, railstatus=railstatus, pos=self.pos, movein=true}
         cartbase.get_next_railstatus(self, state, false)
         if state.nextrailstatus.railtype == "inv" then
             -- check below, so we can push down a hill
@@ -684,7 +718,7 @@ function cartbase.on_activate_handler(self, staticdata)
     self.tag = nil
     self.wait = 0
     self.loadwait = 0
-    self.skipnextstep = false
+    self.skipsteps = 0
     self.lastmove = 0
     self.dtime_debt = 0
 

items.lua

@@ -1,4 +1,7 @@
 
+local dbg
+if moddebug then dbg=moddebug.dbg("railcarts") else dbg={v1=function() end,v2=function() end,v3=function() end} end
+
 minetest.register_craft({
     output = "railcarts:cart",
     recipe = {
@@ -115,11 +118,10 @@ minetest.register_node(":default:rail", {
     mesecons = {
         effector = {
             rules = railrules,
-            action_on =
-            function(pos, node)
+            action_on = function(pos, node)
                 node.name = "railcarts:rail_switched"
                 minetest.swap_node(pos, node)
-                debug.v2("Rails switched at "..minetest.pos_to_string(pos))
+                dbg.v2("Rails switched at "..minetest.pos_to_string(pos))
             end
         }
     }
@@ -141,11 +143,10 @@ minetest.register_node("railcarts:rail_switched", {
     mesecons = {
         effector = {
             rules = railrules,
-            action_off = 
-            function(pos, node)
+            action_off = function(pos, node)
                 node.name = "default:rail"
                 minetest.swap_node(pos, node)
-                debug.v2("Rails switched back at "..minetest.pos_to_string(pos))
+                dbg.v2("Rails switched back at "..minetest.pos_to_string(pos))
             end
         }
     }

rail.lua

@@ -107,7 +107,7 @@ end
 --          that caused the unloaded status
 --   slope, if the rail is sloped, the up direction, 0-3 (and railtype can only
 --          be "x" or "z"
---   eject, which if true means any player in the cart should be
+--   eject, which if true means any player in the cart should be ejected
 --   grab, which if it exists is the position of a node which should 'grab' the
 --         cart into its inventory (i.e. an autolauncher)
 --   launch, which is a launch direction
@@ -238,8 +238,8 @@ function get_railstatus(fppos, direction, speed)
         end
 
         if direction then
-            -- Check if a player should be ejected
             if speed > 0 then
+                -- Check if a player should be ejected
                 if direction == 1 and is_ejector(surrounds.x_next_above) and is_rail(surrounds.x_next) then
                     status.eject = true
                 elseif direction == 3 and is_ejector(surrounds.x_prev_above) and is_rail(surrounds.x_prev) then