add on_screen_change project script event & fix UIDocument::rebuildIndices & move menu background to project script

src/logic/scripting/lua/libs/libgui.cpp

@@ -79,9 +79,12 @@ static int l_textbox_paste(lua::State* L) {
 
 static int l_container_add(lua::State* L) {
     auto docnode = get_document_node(L);
+    if (docnode.document == nullptr) {
+        throw std::runtime_error("target document not found");
+    }
     auto node = dynamic_cast<Container*>(docnode.node.get());
     if (node == nullptr) {
-        return 0;
+        throw std::runtime_error("target container not found");
     }
     auto xmlsrc = lua::require_string(L, 2);
     try {
@@ -99,7 +102,7 @@ static int l_container_add(lua::State* L) {
         UINode::getIndices(subnode, docnode.document->getMapWriteable());
         node->add(std::move(subnode));
     } catch (const std::exception& err) {
-        throw std::runtime_error(err.what());
+        throw std::runtime_error("container:add(...): " + std::string(err.what()));
     }
     return 0;
 }

src/logic/scripting/lua/lua_engine.cpp

@@ -58,12 +58,8 @@ static void create_libs(State* L, StateType stateType) {
     openlib(L, "vec4", vec4lib);
     openlib(L, "yaml", yamllib);
 
-    if (stateType == StateType::SCRIPT) {
-        openlib(L, "app", applib);
-    } else if (stateType == StateType::BASE) {
-        openlib(L, "__vc_app", applib);
-    }
     if (stateType == StateType::BASE || stateType == StateType::SCRIPT) {
+        openlib(L, "__vc_app", applib);
         openlib(L, "assets", assetslib);
         openlib(L, "audio", audiolib);
         openlib(L, "console", consolelib);

src/logic/scripting/scripting.cpp

@@ -116,11 +116,42 @@ public:
     }
 };
 
-std::unique_ptr<Process> scripting::start_coroutine(
+class LuaProjectScript : public IProjectScript {
+public:
+    LuaProjectScript(lua::State* L, scriptenv env) : L(L), env(std::move(env)) {}
+
+    void onScreenChange(const std::string& name) override {
+        if (!lua::pushenv(L, *env)) {
+            return;
+        }
+        if (!lua::getfield(L, "on_screen_changed")) {
+            lua::pop(L);
+            return;
+        }
+        lua::pushlstring(L, name);
+        lua::call_nothrow(L, 1, 0);
+        lua::pop(L);
+    }
+private:
+    lua::State* L;
+    scriptenv env;
+};
+
+std::unique_ptr<IProjectScript> scripting::load_project_script(
     const io::path& script
 ) {
     auto L = lua::get_main_state();
-    if (lua::getglobal(L, "__vc_start_coroutine")) {
+    auto source = io::read_string(script);
+    auto env = create_environment(nullptr);
+    lua::loadbuffer(L, *env, source, script.name());
+    lua::call(L, 0);
+    return std::make_unique<LuaProjectScript>(L, std::move(env));
+}
+
+std::unique_ptr<Process> scripting::start_coroutine(const io::path& script) {
+    auto L = lua::get_main_state();
+    auto method = "__vc_start_coroutine";
+    if (lua::getglobal(L, method)) {
         auto source = io::read_string(script);
         lua::loadbuffer(L, 0, source, script.name());
         if (lua::call(L, 1)) {

src/logic/scripting/scripting.hpp

@@ -65,9 +65,16 @@ namespace scripting {
 
     void process_post_runnables();
 
-    std::unique_ptr<Process> start_coroutine(
-        const io::path& script
-    );
+    class IProjectScript {
+    public:
+        virtual ~IProjectScript() {}
+
+        virtual void onScreenChange(const std::string& name) = 0;
+    };
+
+    std::unique_ptr<IProjectScript> load_project_script(const io::path& script);
+
+    std::unique_ptr<Process> start_coroutine(const io::path& script);
 
     void on_world_load(LevelController* controller);
     void on_world_tick(int tps);