Add custom compare feature

API.md

@@ -7,7 +7,7 @@ to check for the mod's existence first (`minetest.get_modpath`
 returns non-`nil` value).
 
 ## Functions
-### `select_item.show_dialog(playername, dialogname, filter)`
+### `select_item.show_dialog(playername, dialogname, filter, compare)`
 Shows an item selection dialog to a player. The player can choose
 one item (which triggers a callback) or abort selection
 (in which case nothing happens).
@@ -21,13 +21,20 @@ to filter out unwanted items.
 #### Parameters
 * `playername`: Name of player to show dialog to
 * `dialogname`: Identifier of the dialog (must not contain “%%”)
-* `filter`: Optional filter function to narrow down the visible
-   items (see below)
+* `filter`: (optional) Filter function to narrow down the visible
+            items (see below)
+* `compare`: (optional) Custom compare function for sorting,
+             used in `table.sort`.
 
 Recommended form of `dialogname` is “`<modname>:<name>`”. Almost all
 names are allowed, but they must never contain the substring “%%”.
 Example: `example:select_my_item`
 
+Default sorting sorts items alphabetically by itemstring. It
+moves items with empty description to the end, preceded by items
+with description, but `not_in_creative_inventory=1`, and then
+everything else to the beginning.
+
 #### Filter function
 The filter function has the function signature `filter(itemstring)`.
 This function will be called for each item with the itemstring

init.lua

@@ -3,11 +3,13 @@ select_item = {}
 -- Cache for result of item filters
 local player_filters = {}
 local player_filter_results = {}
+local player_compares = {}
 local player_maxpage = {}
 
 local reset_player_info = function(playername)
 	player_filters[playername] = nil
 	player_filter_results[playername] = nil
+	player_compares[playername] = nil
 	player_maxpage[playername] = nil
 end
 
@@ -49,33 +51,40 @@ local check_item = function(itemstring, filter)
 	return true
 end
 
-local get_items = function(filter)
+local get_items = function(filter, compare)
 	local it = {}
 	for itemstring, itemdef in pairs(minetest.registered_items) do
 		if check_item(itemstring, filter) then
 			table.insert(it, {itemstring=itemstring, itemdef=itemdef})
 		end
 	end
-	-- Default sorting: Move description-less items and
-	-- items not_in_creative_inventory=1 to the end, then sort by itemstring.
-	local compare = function(t1, t2)
-		local t1d = minetest.registered_items[t1.itemstring].description
-		local t2d = minetest.registered_items[t2.itemstring].description
-		local t1g = minetest.get_item_group(t1.itemstring, "not_in_creative_inventory")
-		local t2g = minetest.get_item_group(t2.itemstring, "not_in_creative_inventory")
-		if (t1d == "" and t2d ~= "") then
-			return false
-		elseif (t1d ~= "" and t2d == "") then
-			return true
+	local internal_compare
+	if not compare then
+		-- Default sorting: Move description-less items and
+		-- items not_in_creative_inventory=1 to the end, then sort by itemstring.
+		internal_compare = function(t1, t2)
+			local t1d = minetest.registered_items[t1.itemstring].description
+			local t2d = minetest.registered_items[t2.itemstring].description
+			local t1g = minetest.get_item_group(t1.itemstring, "not_in_creative_inventory")
+			local t2g = minetest.get_item_group(t2.itemstring, "not_in_creative_inventory")
+			if (t1d == "" and t2d ~= "") then
+				return false
+			elseif (t1d ~= "" and t2d == "") then
+				return true
+			end
+			if (t1g == 1 and t2g == 0) then
+				return false
+			elseif (t1g == 0 and t2g == 1) then
+				return true
+			end
+			return t1.itemstring < t2.itemstring
 		end
-		if (t1g == 1 and t2g == 0) then
-			return false
-		elseif (t1g == 0 and t2g == 1) then
-			return true
+	else
+		internal_compare = function(t1, t2)
+			return compare(t1.itemstring, t2.itemstring)
 		end
-		return t1.itemstring < t2.itemstring
 	end
-	table.sort(it, compare)
+	table.sort(it, internal_compare)
 	return it
 end
 
@@ -85,11 +94,12 @@ local ysize_norm = 9
 -- Opens the item selection dialog for player with the given filter function at page.
 -- The dialog has unique identifier dialogname.
 -- Returns: Number of items it displays.
-local show_dialog_page = function(playername, dialogname, filter, page)
+local show_dialog_page = function(playername, dialogname, filter, compare, page)
 	local items
 	if player_filters[playername] == nil then
 		player_filters[playername] = filter
-		items = get_items(filter)
+		player_compares[playername] = compare
+		items = get_items(filter, compare)
 		player_filter_results[playername] = items
 	end
 	items = player_filter_results[playername]
@@ -151,8 +161,8 @@ local show_dialog_page = function(playername, dialogname, filter, page)
 	return #items
 end
 
-select_item.show_dialog = function(playername, dialogname, filter)
-	show_dialog_page(playername, dialogname, filter, 1)
+select_item.show_dialog = function(playername, dialogname, filter, compare)
+	show_dialog_page(playername, dialogname, filter, compare, 1)
 end
 
 local callbacks = {}
@@ -194,11 +204,11 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 		end
 		if page ~= nil then
 			if fields.previous and page > 1 then
-				show_dialog_page(player:get_player_name(), dialogname, player_filters[playername], page - 1)
+				show_dialog_page(player:get_player_name(), dialogname, player_filters[playername], player_compares[playername], page - 1)
 			elseif fields.next then
 				local maxpage = player_maxpage[playername]
 				if maxpage and (page + 1 <= maxpage) then
-					show_dialog_page(playername, dialogname, player_filters[playername], page + 1)
+					show_dialog_page(playername, dialogname, player_filters[playername], player_compares[playername], page + 1)
 				end
 				if not maxpage then
 					minetest.log("warning", "[select_item] Player "..playername.." managed to navigate select_item menu without maxpage set!")