Allow random menu images for subgames

builtin/common/misc_helpers.lua

@@ -159,6 +159,7 @@ function dump(o, indent, nested, level)
 	return "{"..table.concat(t, ", ").."}"
 end
 
+--------------------------------------------------------------------------------
 function string.split(str, delim, include_empty, max_splits, sep_is_pattern)
 	delim = delim or ","
 	max_splits = max_splits or -1
@@ -183,6 +184,19 @@ function string.split(str, delim, include_empty, max_splits, sep_is_pattern)
 	return items
 end
 
+--------------------------------------------------------------------------------
+function table.indexof(list, val)
+	for i = 1, #list do
+		if list[i] == val then
+			return i
+		end
+	end
+	return -1
+end
+
+assert(table.indexof({"foo", "bar"}, "foo") == 1)
+assert(table.indexof({"foo", "bar"}, "baz") == -1)
+
 --------------------------------------------------------------------------------
 function file_exists(filename)
 	local f = io.open(filename, "r")

builtin/mainmenu/textures.lua

@@ -143,8 +143,26 @@ function mm_texture.set_game(identifier,gamedetails)
 		end
 	end
 	
+	-- Find out how many randomized textures the subgame provides
+	local n, filename
+	local menu_files = core.get_dir_list(gamedetails.path .. DIR_DELIM .. "menu", false)
+	for i = 1, #menu_files do
+		local filename = identifier .. "." .. i .. ".png"
+		if table.indexof(menu_files, filename) == -1 then
+			n = i - 1
+			break
+		end
+	end
+	-- Select random texture, 0 means standard texture
+	n = math.random(0, n)
+	if n == 0 then
+		filename = identifier .. ".png"
+	else
+		filename = identifier .. "." .. n .. ".png"
+	end
+
 	local path = gamedetails.path .. DIR_DELIM .. "menu" ..
-									 DIR_DELIM .. identifier .. ".png"
+		DIR_DELIM .. filename
 	if core.set_background(identifier, path) then
 		return true
 	end