Write settings to nvs when changing from the setting screen

Otherwise, settings may not actually be saved if the device crashes/
reboots unexpectedly.

Fixes #148

lua/settings.lua

@@ -13,6 +13,7 @@ local usb = require("usb")
 local font = require("font")
 local main_menu = require("main_menu")
 local img = require("images")
+local nvs = require("nvs")
 
 local settings = {}
 
@@ -33,6 +34,9 @@ local SettingsScreen = widgets.MenuScreen:new {
       pad_left = 4,
       pad_right = 4,
     }
+  end,
+  on_hide = function(self)
+    nvs.write();
   end
 }
 

luals-stubs/nvs.lua

@@ -0,0 +1,9 @@
+--- @meta
+
+--- @class nvs
+local nvs = {}
+
+--- Saves current nvs
+function nvs.write() end
+
+return nvs

src/tangara/lua/bridge.cpp

@@ -25,6 +25,7 @@
 #include "lua/lua_database.hpp"
 #include "lua/lua_filesystem.hpp"
 #include "lua/lua_font.hpp"
+#include "lua/lua_nvs.hpp"
 #include "lua/lua_queue.hpp"
 #include "lua/lua_screen.hpp"
 #include "lua/lua_testing.hpp"
@@ -84,6 +85,7 @@ auto Bridge::installBaseModules(lua_State* L) -> void {
   RegisterVersionModule(L);
   RegisterThemeModule(L);
   RegisterScreenModule(L);
+  RegisterNvsModule(L);
 }
 
 auto Bridge::installLvgl(lua_State* L) -> void {

src/tangara/lua/lua_nvs.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2024 Clayton Craft <clayton@craftyguy.net>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "lua/lua_version.hpp"
+
+#include "lua.hpp"
+#include "lua/bridge.hpp"
+
+#include "lua.h"
+#include "lua/lua_thread.hpp"
+
+namespace lua {
+
+[[maybe_unused]] static constexpr char kTag[] = "lua_nvs";
+
+static auto write(lua_State* L) -> int {
+  Bridge* instance = Bridge::Get(L);
+  instance->services().nvs().Write();
+
+  return 1;
+}
+
+static const struct luaL_Reg kNvsFuncs[] = {{"write", write},
+                                             {NULL, NULL}};
+
+static auto lua_nvs(lua_State* L) -> int {
+  luaL_newlib(L, kNvsFuncs);
+  return 1;
+}
+
+auto RegisterNvsModule(lua_State* L) -> void {
+  luaL_requiref(L, "nvs", lua_nvs, true);
+  lua_pop(L, 1);
+}
+
+}  // namespace lua

src/tangara/lua/lua_nvs.hpp

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2024 Clayton Craft <clayton@craftyguy.net>
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#pragma once
+
+#include "lua.hpp"
+
+namespace lua {
+
+auto RegisterNvsModule(lua_State*) -> void;
+
+}  // namespace lua