Enable async loads of Scenes (#48)

* Move DeltaTime to Glfw

- Don't expose `Glfw::Window` through engine; users should not be able to access `Glfw` directly.
- Return entire state in `Engine::poll()` instead of just delta time.

* Add Engine::load_async

Takes an optional `on_done` callback; loaded scene swapped and callback invoked on poll thread (during `poll()`).

TODO: solve progress notification across the threads.

* Add LoadStatus

* Store only one future and progress

Algorithm for deferring existing requests is buggy: get random malloc "unaligned fastbin chunk detected" crashes, attempts to root cause have been unsuccessful.
Winding back to storing a single request and denying subsequent ones until the stored one is idle.

* Add some comments, fixup minor stuff

Author: karnkaul

lib/engine/include/facade/engine/editor/common.hpp

@@ -90,10 +90,22 @@ class MainMenu : public MenuBar {
 ///
 class Popup : public Openable {
   public:
-	explicit Popup(char const* id, int flags = {});
+	explicit Popup(char const* id, int flags = {}) : Popup(id, false, flags) {}
 	~Popup();
 
+	static void open(char const* id);
 	static void close_current();
+
+  protected:
+	explicit Popup(char const* id, bool modal, int flags);
+};
+
+///
+/// \brief RAII Dear ImGui PopupModal
+///
+class Modal : public Popup {
+  public:
+	explicit Modal(char const* id, int flags = {}) : Popup(id, true, flags) {}
 };
 
 ///

lib/engine/include/facade/engine/engine.hpp

@@ -2,6 +2,7 @@
 #include <facade/glfw/glfw.hpp>
 #include <facade/scene/scene.hpp>
 #include <facade/util/time.hpp>
+#include <facade/util/unique_task.hpp>
 #include <facade/vk/shader.hpp>
 
 namespace facade {
@@ -28,6 +29,7 @@ struct EngineCreateInfo {
 class Engine {
   public:
 	using CreateInfo = EngineCreateInfo;
+	using State = Glfw::State;
 
 	Engine(Engine&&) noexcept;
 	Engine& operator=(Engine&&) noexcept;
@@ -64,9 +66,9 @@ class Engine {
 	///
 	bool running() const;
 	///
-	/// \brief Poll events and obtain delta time
+	/// \brief Poll events and obtain updated state
 	///
-	float poll();
+	State const& poll();
 	///
 	/// \brief Render the scene
 	///
@@ -77,14 +79,29 @@ class Engine {
 	///
 	void request_stop();
 
+	///
+	/// \brief Load a GLTF scene asynchronously
+	///
+	/// Subsequent requests will be rejected if one is in flight
+	///
+	bool load_async(std::string gltf_json_path, UniqueTask<void()> on_loaded = {});
+	///
+	/// \brief Obtain status of in-flight async load request (if active)
+	///
+	LoadStatus load_status() const;
+
+	glm::uvec2 window_extent() const;
+	glm::uvec2 framebuffer_extent() const;
+
 	Scene& scene() const;
-	Gfx const& gfx() const;
-	Glfw::Window const& window() const;
-	Glfw::State const& state() const;
+	State const& state() const;
 	Input const& input() const;
 	Renderer& renderer() const;
+	GLFWwindow* window() const;
 
   private:
+	void update_load_request();
+
 	struct Impl;
 	inline static Impl const* s_instance{};
 	std::unique_ptr<Impl> m_impl{};

lib/engine/src/editor/common.cpp

@@ -37,12 +37,14 @@ MainMenu::~MainMenu() {
 	if (m_open) { ImGui::EndMainMenuBar(); }
 }
 
-Popup::Popup(char const* id, int flags) : Openable(ImGui::BeginPopup(id, flags)) {}
+Popup::Popup(char const* id, bool modal, int flags) : Openable(modal ? ImGui::BeginPopupModal(id, {}, flags) : ImGui::BeginPopup(id, flags)) {}
 
 Popup::~Popup() {
 	if (m_open) { ImGui::EndPopup(); }
 }
 
+void Popup::open(char const* id) { ImGui::OpenPopup(id); }
+
 void Popup::close_current() { ImGui::CloseCurrentPopup(); }
 
 Menu::Menu(NotClosed<MenuBar>, char const* label, bool enabled) : Openable(ImGui::BeginMenu(label, enabled)) {}

lib/engine/src/engine.cpp

@@ -1,18 +1,25 @@
 #include <backends/imgui_impl_glfw.h>
 #include <backends/imgui_impl_vulkan.h>
 #include <imgui.h>
+#include <djson/json.hpp>
 #include <facade/defines.hpp>
 #include <facade/engine/engine.hpp>
 #include <facade/engine/scene_renderer.hpp>
 #include <facade/glfw/glfw_wsi.hpp>
 #include <facade/render/renderer.hpp>
+#include <facade/util/data_provider.hpp>
 #include <facade/util/error.hpp>
+#include <facade/util/logger.hpp>
 #include <facade/vk/cmd.hpp>
 #include <facade/vk/vk.hpp>
 #include <glm/gtc/color_space.hpp>
 #include <glm/mat4x4.hpp>
+#include <filesystem>
+#include <future>
 
 namespace facade {
+namespace fs = std::filesystem;
+
 namespace {
 static constexpr std::size_t command_buffers_v{1};
 
@@ -150,6 +157,34 @@ struct RenderWindow {
 		: window(std::move(window)), vulkan(GlfwWsi{this->window}, validation), gfx(vulkan.gfx()),
 		  renderer(gfx, this->window, gui.get(), Renderer::CreateInfo{command_buffers_v, msaa}), gui(std::move(gui)) {}
 };
+
+bool load_gltf(Scene& out_scene, char const* path, std::atomic<LoadStatus>* out_status) {
+	auto const provider = FileDataProvider::mount_parent_dir(path);
+	auto json = dj::Json::from_file(path);
+	return out_scene.load_gltf(json, provider, out_status);
+}
+
+template <typename T>
+bool ready(std::future<T> const& future) {
+	return future.valid() && future.wait_for(std::chrono::seconds{}) == std::future_status::ready;
+}
+
+template <typename T>
+bool timeout(std::future<T> const& future) {
+	return future.valid() && future.wait_for(std::chrono::seconds{}) == std::future_status::timeout;
+}
+
+template <typename T>
+bool busy(std::future<T> const& future) {
+	return future.valid() && future.wait_for(std::chrono::seconds{}) == std::future_status::deferred;
+}
+
+struct LoadRequest {
+	std::string path{};
+	std::future<Scene> future{};
+	std::atomic<LoadStatus> status{};
+	float start_time{};
+};
 } // namespace
 
 struct Engine::Impl {
@@ -158,14 +193,21 @@ struct Engine::Impl {
 	Scene scene;
 
 	std::uint8_t msaa;
-	DeltaTime dt{};
+
+	std::mutex mutex{};
+
+	struct {
+		LoadRequest request{};
+		UniqueTask<void()> callback{};
+	} load{};
 
 	Impl(UniqueWin window, std::uint8_t msaa, bool validation)
 		: window(std::move(window), std::make_unique<DearImGui>(), msaa, validation), renderer(this->window.gfx), scene(this->window.gfx), msaa(msaa) {
 		s_instance = this;
 	}
 
 	~Impl() {
+		load.request.future = {};
 		window.gfx.device.waitIdle();
 		s_instance = {};
 	}
@@ -189,32 +231,96 @@ void Engine::add_shader(Shader shader) { m_impl->window.renderer.add_shader(std:
 
 void Engine::show(bool reset_dt) {
 	glfwShowWindow(window());
-	if (reset_dt) { m_impl->dt = {}; }
+	if (reset_dt) { m_impl->window.window.get().glfw->reset_dt(); }
 }
 
 void Engine::hide() { glfwHideWindow(window()); }
 
 bool Engine::running() const { return !glfwWindowShouldClose(window()); }
 
-float Engine::poll() {
-	window().glfw->poll_events();
+auto Engine::poll() -> State const& {
+	// the code in this call locks the mutex, so it's not inlined here
+	update_load_request();
+	// ImGui wants all widget calls within BeginFrame() / EndFrame(), so begin here
 	m_impl->window.gui->new_frame();
-	return m_impl->dt();
+	m_impl->window.window.get().glfw->poll_events();
+	return m_impl.get()->window.window.get().state();
 }
 
 void Engine::render() {
 	auto cb = vk::CommandBuffer{};
+	// we skip rendering the scene if acquiring a swapchain image fails (unlikely)
 	if (m_impl->window.renderer.next_frame({&cb, 1})) { m_impl->renderer.render(scene(), renderer(), cb); }
 	m_impl->window.gui->end_frame();
 	m_impl->window.renderer.render();
 }
 
 void Engine::request_stop() { glfwSetWindowShouldClose(window(), GLFW_TRUE); }
 
+glm::uvec2 Engine::window_extent() const { return m_impl->window.window.get().window_extent(); }
+glm::uvec2 Engine::framebuffer_extent() const { return m_impl->window.window.get().framebuffer_extent(); }
+
+bool Engine::load_async(std::string gltf_json_path, UniqueTask<void()> on_loaded) {
+	if (!fs::is_regular_file(gltf_json_path)) {
+		// early return if file will fail to load anyway
+		logger::error("[Engine] Invalid GLTF JSON path: [{}]", gltf_json_path);
+		return false;
+	}
+	// shared state will need to be accessed, lock the mutex
+	auto lock = std::scoped_lock{m_impl->mutex};
+	if (m_impl->load.request.future.valid()) {
+		// we don't support discarding in-flight requests
+		logger::warn("[Engine] Denied attempt to load_async when a load request is already in flight");
+		return false;
+	}
+
+	// ready to start loading
+	logger::info("[Engine] Loading GLTF [{}]...", State::to_filename(gltf_json_path));
+	// populate load request
+	m_impl->load.callback = std::move(on_loaded);
+	m_impl->load.request.path = std::move(gltf_json_path);
+	m_impl->load.request.status.store(LoadStatus::eStartingThread);
+	m_impl->load.request.start_time = time::since_start();
+	auto func = [path = m_impl->load.request.path, gfx = m_impl->window.gfx, status = &m_impl->load.request.status] {
+		auto scene = Scene{gfx};
+		if (!load_gltf(scene, path.c_str(), status)) { logger::error("[Engine] Failed to load GLTF: [{}]", path); }
+		// return the scene even on failure, it will be empty but valid
+		return scene;
+	};
+	// store future
+	m_impl->load.request.future = std::async(std::launch::async, func);
+	return true;
+}
+
+LoadStatus Engine::load_status() const {
+	auto lock = std::scoped_lock{m_impl->mutex};
+	return m_impl->load.request.status.load();
+}
+
 Scene& Engine::scene() const { return m_impl->scene; }
-Gfx const& Engine::gfx() const { return m_impl->window.gfx; }
-Glfw::Window const& Engine::window() const { return m_impl->window.window; }
-Glfw::State const& Engine::state() const { return window().state(); }
+GLFWwindow* Engine::window() const { return m_impl->window.window.get(); }
+Glfw::State const& Engine::state() const { return m_impl->window.window.get().state(); }
 Input const& Engine::input() const { return state().input; }
 Renderer& Engine::renderer() const { return m_impl->window.renderer; }
+
+void Engine::update_load_request() {
+	auto lock = std::unique_lock{m_impl->mutex};
+	// early return if future isn't valid or is still busy
+	if (!ready(m_impl->load.request.future)) { return; }
+
+	// transfer scene (under mutex lock)
+	m_impl->scene = m_impl->load.request.future.get();
+	// reset load status
+	m_impl->load.request.status.store(LoadStatus::eNone);
+	// move out the path
+	auto path = std::move(m_impl->load.request.path);
+	// move out the callback
+	auto callback = std::move(m_impl->load.callback);
+	auto const duration = time::since_start() - m_impl->load.request.start_time;
+	// unlock mutex to prevent possible deadlock (eg callback calls load_gltf again)
+	lock.unlock();
+	logger::info("...GLTF [{}] loaded in [{:.2f}s]", State::to_filename(path), duration);
+	// invoke callback
+	if (callback) { callback(); }
+}
 } // namespace facade

lib/glfw/include/facade/glfw/glfw.hpp

@@ -18,6 +18,7 @@ struct Glfw {
 
 	std::vector<char const*> vk_extensions() const;
 	void poll_events();
+	void reset_dt();
 
 	bool operator==(Glfw const&) const = default;
 };
@@ -27,6 +28,9 @@ using UniqueWin = Unique<Glfw::Window, Glfw::Deleter>;
 struct Glfw::State {
 	Input input{};
 	std::vector<std::string> file_drops{};
+	float dt{};
+
+	static std::string to_filename(std::string_view path);
 };
 
 struct Glfw::Window {

lib/glfw/src/glfw.cpp

@@ -1,14 +1,22 @@
 #include <facade/glfw/glfw.hpp>
 #include <facade/util/error.hpp>
+#include <facade/util/time.hpp>
+#include <filesystem>
 #include <mutex>
 #include <unordered_map>
 
 namespace facade {
+namespace fs = std::filesystem;
+
 namespace {
 std::weak_ptr<Glfw> g_glfw{};
 std::mutex g_mutex{};
 
-std::unordered_map<GLFWwindow*, Glfw::State> g_states{};
+struct {
+	std::unordered_map<GLFWwindow*, Glfw::State> states{};
+	// polling / dt is shared across all windows
+	DeltaTime dt{};
+} g_states{};
 
 std::shared_ptr<Glfw> get_or_make_glfw() {
 	auto lock = std::scoped_lock{g_mutex};
@@ -35,14 +43,23 @@ constexpr Action to_action(int glfw_action) {
 } // namespace
 
 void Glfw::poll_events() {
-	for (auto& [_, state] : g_states) {
+	auto const dt = g_states.dt();
+	for (auto& [_, state] : g_states.states) {
 		state.input.keyboard.next_frame();
 		state.input.mouse.next_frame();
 		state.file_drops.clear();
+		state.dt = dt;
 	}
 	glfwPollEvents();
 }
 
+void Glfw::reset_dt() { g_states.dt = {}; }
+
+std::string Glfw::State::to_filename(std::string_view path) {
+	if (auto const i = path.find_last_of('/'); i != std::string_view::npos) { path = path.substr(i + 1); }
+	return std::string{path};
+}
+
 auto Glfw::Window::make() -> UniqueWin {
 	auto ret = Window{};
 	ret.glfw = get_or_make_glfw();
@@ -52,13 +69,13 @@ auto Glfw::Window::make() -> UniqueWin {
 	ret.win = glfwCreateWindow(1, 1, "[untitled]", nullptr, nullptr);
 	if (!ret.win) { throw InitError{"GLFW window creation failed"}; }
 	if (glfwRawMouseMotionSupported()) { glfwSetInputMode(ret, GLFW_RAW_MOUSE_MOTION, GLFW_TRUE); }
-	glfwSetKeyCallback(ret, [](GLFWwindow* w, int key, int, int action, int) { g_states[w].input.keyboard.on_key(key, to_action(action)); });
-	glfwSetMouseButtonCallback(ret, [](GLFWwindow* w, int button, int action, int) { g_states[w].input.mouse.on_button(button, to_action(action)); });
-	glfwSetCursorPosCallback(ret, [](GLFWwindow* w, double x, double y) { g_states[w].input.mouse.on_position(glm::tvec2<double>{x, y}); });
-	glfwSetScrollCallback(ret, [](GLFWwindow* w, double x, double y) { g_states[w].input.mouse.on_scroll(glm::tvec2<double>{x, y}); });
+	glfwSetKeyCallback(ret, [](GLFWwindow* w, int key, int, int action, int) { g_states.states[w].input.keyboard.on_key(key, to_action(action)); });
+	glfwSetMouseButtonCallback(ret, [](GLFWwindow* w, int button, int action, int) { g_states.states[w].input.mouse.on_button(button, to_action(action)); });
+	glfwSetCursorPosCallback(ret, [](GLFWwindow* w, double x, double y) { g_states.states[w].input.mouse.on_position(glm::tvec2<double>{x, y}); });
+	glfwSetScrollCallback(ret, [](GLFWwindow* w, double x, double y) { g_states.states[w].input.mouse.on_scroll(glm::tvec2<double>{x, y}); });
 	glfwSetDropCallback(ret, [](GLFWwindow* w, int count, char const** paths) {
-		auto& file_drops = g_states[w].file_drops;
-		for (int i = 0; i < count; ++i) { file_drops.push_back(paths[i]); }
+		auto& file_drops = g_states.states[w].file_drops;
+		for (int i = 0; i < count; ++i) { file_drops.push_back(fs::absolute(paths[i]).generic_string()); }
 	});
 	return ret;
 }
@@ -70,7 +87,7 @@ void Glfw::Deleter::operator()(Glfw const& glfw) const {
 
 void Glfw::Deleter::operator()(Window const& window) const {
 	glfwDestroyWindow(window.win);
-	g_states.erase(window.win);
+	g_states.states.erase(window.win);
 }
 
 std::vector<char const*> Glfw::vk_extensions() const {
@@ -95,6 +112,6 @@ glm::uvec2 Glfw::Window::framebuffer_extent() const {
 
 Glfw::State const& Glfw::Window::state() const {
 	auto lock = std::scoped_lock{g_mutex};
-	return g_states[win];
+	return g_states.states[win];
 }
 } // namespace facade