Multiple related changes to string handling

1) Convert most formspec elements to use string.format(), when the
result would be more readable, or less messy, or at least makes the line
shorter, assuming it looked like it really needed it to begin with.

2) Convert all long `foo..","..bar..";"..baz..bleh..` types of excessive
string concatenation into tables that then get concated only once, when
their containing functions return the final formspec string.

3) In some places in the code, such tables were already being used, and
were named "formspec", while others were named "fs".  I settled on just
one name, "formspec", as it's more readable, if longer.

4) There was a mix of styles of adding items to those tables:

* Some places used line after line of `t[#t + 1] = foo/bar/baz`.
* Others places used the form `t[1] = foo, t[2] = bar, ...`.
* Still others used the form `t[n] = foo, t[n+1] = bar...`,
  with `n` being increased or reset every so often.

Most of them should now be of the third form, with a few of the second.

waypoints.lua

@@ -29,21 +29,24 @@ ui.register_page("waypoints", {
 		if not waypoints_temp[player_name] then waypoints_temp[player_name] = {hud = 1} end
 
 		local waypoints = datastorage.get(player_name, "waypoints")
-		local formspec = ui.style_full.standard_inv_bg..
-			"label["..ui.style_full.form_header_x..","..ui.style_full.form_header_y..";" .. F(S("Waypoints")) .. "]"..
+		local formspec = { ui.style_full.standard_inv_bg,
+			string.format("label[%f,%f;%s]",
+				ui.style_full.form_header_x, ui.style_full.form_header_y,
+				F(S("Waypoints"))),
 			"image["..wp_info_x..","..wp_info_y..";1,1;ui_waypoints_icon.png]"
+		}
+		local n=4
 
 		-- Tabs buttons:
 		for i = 1, 5 do
-			formspec = formspec ..
-				"image_button["..ui.style_full.main_button_x..","..
-				(wp_bottom_row - (5-i) * ui.style_full.btn_spc)..";"..
-				ui.style_full.btn_size..","..ui.style_full.btn_size..";" ..
-				(i == waypoints.selected and "ui_blue_icon_background.png^" or "") ..
-				"ui_" .. i .. "_icon.png;" ..
-				"select_waypoint" .. i .. ";]" ..
-				"tooltip[select_waypoint" .. i .. ";"
-					.. S("Select Waypoint #@1", i).."]"
+			local sw="select_waypoint"..i
+			formspec[n] = string.format("image_button[%f,%f;%f,%f;%sui_%i_icon.png;%s;]",
+				ui.style_full.main_button_x, wp_bottom_row - (5-i) * ui.style_full.btn_spc,
+				ui.style_full.btn_size, ui.style_full.btn_size,
+				(i == waypoints.selected) and "ui_blue_icon_background.png^" or "",
+				i, sw)
+			formspec[n+1] = "tooltip["..sw..";"..S("Select Waypoint #@1", i).."]"
+			n = n + 2
 		end
 
 		local i = waypoints.selected or 1
@@ -63,44 +66,44 @@ ui.register_page("waypoints", {
 
 		local x = 4
 		for _, b in pairs(btnlist) do
-			formspec = formspec ..
-				"image_button["..(wp_buttons_rj - ui.style_full.btn_spc * x)..","..
-				wp_bottom_row..";"..
-				ui.style_full.btn_size..","..ui.style_full.btn_size..";"..
-				b[1]..";"..
-				b[2]..i..";]"..
-				"tooltip["..b[2]..i..";"..F(S(b[3], b[4] or "")).."]"
+			formspec[n] = string.format("image_button[%f,%f;%f,%f;%s;%s%i;]",
+				wp_buttons_rj - ui.style_full.btn_spc * x, wp_bottom_row,
+				ui.style_full.btn_size, ui.style_full.btn_size,
+				b[1], b[2], i)
+			formspec[n+1] = "tooltip["..b[2]..i..";"..F(S(b[3], b[4] or "")).."]"
 			x = x - 1
+			n = n + 2
 		end
 
 		-- Waypoint's info:
-		formspec = formspec.."label["..wp_info_x..","..(wp_info_y+1.1)..";"
+		formspec[n] = "label["..wp_info_x..","..(wp_info_y+1.1)..";"
 		if waypoint.active then
-			formspec = formspec ..F(S("Waypoint active")).."]"
+			formspec[n+1] = F(S("Waypoint active")).."]"
 		else
-			formspec = formspec ..F(S("Waypoint inactive")).."]"
+			formspec[n+1] = F(S("Waypoint inactive")).."]"
 		end
+		n = n + 2
 
 		if temp.edit then
-			formspec = formspec ..
-				"field["..(wp_buttons_rj - wp_edit_w - 0.1)..","..(wp_bottom_row - ui.style_full.btn_spc)..";"..
-				wp_edit_w..","..ui.style_full.btn_size..";rename_box" .. i .. ";;"..
-				(waypoint.name or default_name).."]" ..
-				"image_button["..wp_buttons_rj..","..(wp_bottom_row - ui.style_full.btn_spc)..";"..
-				ui.style_full.btn_size..","..ui.style_full.btn_size..";"..
-				"ui_ok_icon.png;"..
-				"confirm_rename"..i.. ";]"..
-				"tooltip[confirm_rename" .. i .. ";"
-					.. F(S("Finish editing")).."]"
+			formspec[n] = string.format("field[%f,%f;%f,%f;rename_box%i;;%s]",
+				wp_buttons_rj - wp_edit_w - 0.1, wp_bottom_row - ui.style_full.btn_spc,
+				wp_edit_w, ui.style_full.btn_size, i, (waypoint.name or default_name))
+			formspec[n+1] = string.format("image_button[%f,%f;%f,%f;ui_ok_icon.png;confirm_rename%i;]",
+				wp_buttons_rj, wp_bottom_row - ui.style_full.btn_spc,
+				ui.style_full.btn_size, ui.style_full.btn_size, i)
+			formspec[n+2] = "tooltip[confirm_rename"..i..";"..F(S("Finish editing")).."]"
+			n = n + 3
 		end
 
-		formspec = formspec .. "label["..wp_info_x..","..(wp_info_y+1.6)..";"..F(S("World position"))..": " ..
-			minetest.pos_to_string(waypoint.world_pos or vector.new()) .. "]" ..
-			"label["..wp_info_x..","..(wp_info_y+2.10)..";"..F(S("Name"))..": ".. (waypoint.name or default_name) .. "]" ..
-			"label["..wp_info_x..","..(wp_info_y+2.60)..";"..F(S("HUD text color"))..": " ..
-			hud_colors[waypoint.color or 1][3] .. "]"
+		formspec[n] = string.format("label[%f,%f;%s: %s]",
+			wp_info_x, wp_info_y+1.6, F(S("World position")),
+			minetest.pos_to_string(waypoint.world_pos or vector.new()))
+		formspec[n+1] = string.format("label[%f,%f;%s: %s]",
+			wp_info_x, wp_info_y+2.10, F(S("Name")), (waypoint.name or default_name))
+		formspec[n+2] = string.format("label[%f,%f;%s: %s]",
+			wp_info_x, wp_info_y+2.60, F(S("HUD text color")), hud_colors[waypoint.color or 1][3])
 
-		return {formspec=formspec}
+		return {formspec=table.concat(formspec)}
 	end,
 })