detect streets:bigpole_tjunction

Treat T-junction as a vertical or horizontal pole (depending
on its orientation), if the sign could be placed flat against
the back or side of the junction.

In this instance, the "front" of the junction is the side with
the middle bit sticking out, and will just get a regular wall
signif targeted, as with any non-pole node.

api.lua

@@ -147,6 +147,78 @@ signs_lib.flip_walldir = {
 	[5] = 4
 }
 
+local htj_north = {
+	[1] = true,
+	[3] = true,
+	[9] = true,
+	[11] = true,
+	[21] = true,
+	[23] = true
+}
+
+local htj_east = {
+	[0] = true,
+	[2] = true,
+	[16] = true,
+	[18] = true,
+	[20] = true,
+	[22] = true
+}
+
+local htj_south = {
+	[1] = true,
+	[3] = true,
+	[5] = true,
+	[7] = true,
+	[21] = true,
+	[23] = true
+}
+
+local htj_west = {
+	[0] = true,
+	[2] = true,
+	[12] = true,
+	[14] = true,
+	[20] = true,
+	[22] = true
+}
+
+local vtj_north = {
+	[8] = true,
+	[10] = true,
+	[13] = true,
+	[15] = true,
+	[17] = true,
+	[19] = true
+}
+
+local vtj_east = {
+	[4] = true,
+	[6] = true,
+	[8] = true,
+	[10] = true,
+	[17] = true,
+	[19] = true
+}
+
+local vtj_south = {
+	[4] = true,
+	[6] = true,
+	[13] = true,
+	[15] = true,
+	[17] = true,
+	[10] = true
+}
+
+local vtj_west = {
+	[4] = true,
+	[6] = true,
+	[8] = true,
+	[10] = true,
+	[13] = true,
+	[15] = true
+}
+
 -- Initialize character texture cache
 local ctexcache = {}
 
@@ -747,6 +819,9 @@ function signs_lib.make_selection_boxes(sizex, sizey, foo, xoffs, yoffs, zoffs,
 end
 
 function signs_lib.check_for_pole(pos, pointed_thing)
+	local node = minetest.get_node(pos)
+	local def = minetest.registered_items[node.name]
+
 	local ppos = minetest.get_pointed_thing_position(pointed_thing)
 	local pnode = minetest.get_node(ppos)
 	local pdef = minetest.registered_items[pnode.name]
@@ -761,6 +836,22 @@ function signs_lib.check_for_pole(pos, pointed_thing)
 	  or (pnode.name == "streets:bigpole" and pnode.param2 > 19 and pnode.param2 < 24) )
 	  and (pos.x ~= ppos.x or pos.z ~= ppos.z) then
 		return true
+	elseif pnode.name == "streets:bigpole_tjunction" then
+		if def.paramtype2 == "wallmounted" then
+			if   (node.param2 == 4 and vtj_north[pnode.param2])
+			  or (node.param2 == 2 and vtj_east[pnode.param2])
+			  or (node.param2 == 5 and vtj_south[pnode.param2])
+			  or (node.param2 == 3 and vtj_west[pnode.param2]) then
+				return true
+			end
+		else
+			if   (node.param2 == 0 and vtj_north[pnode.param2])
+			  or (node.param2 == 1 and vtj_east[pnode.param2])
+			  or (node.param2 == 2 and vtj_south[pnode.param2])
+			  or (node.param2 == 3 and vtj_west[pnode.param2]) then
+				return true
+			end
+		end
 	end
 end
 
@@ -789,6 +880,22 @@ function signs_lib.check_for_horizontal_pole(pos, pointed_thing)
 				return true
 			end
 		end
+	elseif pnode.name == "streets:bigpole_tjunction" then
+		if def.paramtype2 == "wallmounted" then
+			if   (node.param2 == 4 and htj_north[pnode.param2])
+			  or (node.param2 == 2 and htj_east[pnode.param2])
+			  or (node.param2 == 5 and htj_south[pnode.param2])
+			  or (node.param2 == 3 and htj_west[pnode.param2]) then
+				return true
+			end
+		else
+			if   (node.param2 == 0 and htj_north[pnode.param2])
+			  or (node.param2 == 1 and htj_east[pnode.param2])
+			  or (node.param2 == 2 and htj_south[pnode.param2])
+			  or (node.param2 == 3 and htj_west[pnode.param2]) then
+				return true
+			end
+		end
 	end
 end