Allow standard io.open to accept UTF-8 paths in Windows

conf.lua

@@ -8,6 +8,7 @@
 
 local love = require("love")
 if love._os == "Android" and jit then jit.on() end
+if love._os == "Windows" then require("io_open_wide") end
 
 local errhand = love.errorhandler or love.errhand
 function love.errorhandler(msg)

io_open_wide.lua

@@ -0,0 +1,75 @@
+-- io.open patch to allow UTF-8 filenames in Windows
+-- Copyright (c) 2020 Miku AuahDark
+-- You can use portion of this code or as a whole without my permission.
+
+local ffi = require("ffi")
+
+if ffi.os ~= "Windows" then
+	-- Not Windows
+	return
+end
+
+-- Safety measures from redefining
+do
+	local function index(t, k)
+		return t[k]
+	end
+
+	if pcall(index, ffi.C, "GetACP") then
+		-- Has been patched!
+		return
+	end
+end
+
+ffi.cdef[[
+uint32_t __stdcall GetACP();
+]]
+
+if ffi.C.GetACP() == 65001 then
+	-- "Use Unicode UTF-8 for worldwide language support" is ticked.
+	-- Don't bother patching it.
+	return
+end
+
+ffi.cdef[[
+int32_t __stdcall MultiByteToWideChar(
+	uint32_t CodePage,
+	uint32_t dwFlags,
+	const char *lpMultiByteStr,
+	int32_t cbMultiByte,
+	wchar_t *lpWideCharStr,
+	int32_t cchWideChar
+);
+void *_wfreopen(wchar_t *path, wchar_t *mode, void *file);
+]]
+
+local MB_ERR_INVALID_CHARS = 0x8
+
+local function toWideChar(ch)
+	local size = ffi.C.MultiByteToWideChar(65001, MB_ERR_INVALID_CHARS, ch, #ch, nil, 0)
+	if size == 0 then
+		error("invalid character sequence")
+	end
+
+	local buf = ffi.new("wchar_t[?]", size + 1)
+	if ffi.C.MultiByteToWideChar(65001, MB_ERR_INVALID_CHARS, ch, #ch, buf, size) == 0 then
+		error("char conversion error")
+	end
+
+	return buf
+end
+
+local open = io.open
+
+function io.open(path, mode)
+	local pathw = toWideChar(path)
+	local modew = toWideChar(mode)
+
+	local file = assert(open("nul", "rb"))
+	if ffi.C._wfreopen(pathw, modew, file) == nil then
+		local msg, errno = select(2, file:close())
+		return nil, path..": "..msg, errno
+	end
+
+	return file
+end

util.lua

@@ -5,6 +5,7 @@
 local love = require("love")
 local Luaoop = require("libs.Luaoop")
 require("libs.ls2x")
+require("io_open_wide")
 local color = require("color")
 local hasLVEP = not(not(package.preload.lvep))
 local lvep