Add lua function gui.switch_theme() to allow add-ons to switch themes in the middle of a scenario

src/scripting/lua_gui2.cpp

@@ -15,6 +15,7 @@
 
 #include "scripting/lua_gui2.hpp"
 
+#include "gui/gui.hpp"
 #include "gui/core/gui_definition.hpp"
 #include "gui/dialogs/drop_down_menu.hpp"
 #include "gui/dialogs/gamestate_inspector.hpp"
@@ -168,6 +169,16 @@ int show_story(lua_State* L) {
 	return 0;
 }
 
+/**
+ * Changes the current ui(gui2) theme
+ * - Arg 1: The id of the theme to switch to
+ */
+int switch_theme(lua_State* L) {
+	std::string theme_id = luaL_checkstring(L, 1);
+	gui2::switch_theme(theme_id);
+	return 0;
+}
+
 /**
  * Displays a popup menu at the current mouse position
  * Best used from a [set_menu_item], to show a submenu
@@ -281,6 +292,7 @@ int luaW_open(lua_State* L)
 		{ "show_story",         &show_story },
 		{ "show_prompt",        &show_message_box },
 		{ "show_help",          &show_help   },
+		{ "switch_theme",             &switch_theme   },
 		{ "add_widget_definition",    &intf_add_widget_definition },
 		{ "show_dialog",              &intf_show_dialog   },
 		{ nullptr, nullptr },

src/scripting/lua_gui2.hpp

@@ -28,6 +28,7 @@ namespace lua_gui2 {
 int intf_add_widget_definition(lua_State *L);
 int show_message_dialog(lua_State *L);
 int show_popup_dialog(lua_State *L);
+int switch_theme(lua_State* L);
 int show_menu(lua_State* L);
 int show_story(lua_State* L);
 int show_message_box(lua_State* L);

utils/emmylua/gui.lua

@@ -88,6 +88,10 @@ function gui.show_lua_console() end
 ---@return integer
 function gui.show_dialog(cfg, preshow, postshow) end
 
+---Changes the current ui (gui2) theme
+---@param theme_id string The id of the gui2 theme to switch to
+function gui.switch_theme(theme_id) end
+
 -- Add a custom widget definition, for use in a custom dialog
 ---@param type string The type of widget the definition applies to
 ---@param id string An ID for the definition, to be referenced from WML