framestream2 (with rigtorp/SPSCQueue)

src/CMakeLists.txt

@@ -76,9 +76,14 @@ add_executable(tomato
 	./chat_gui4.cpp
 
 	./content/content.hpp
-	./content/stream_reader.hpp
-	./content/stream_reader_sdl_audio.hpp
-	./content/stream_reader_sdl_audio.cpp
+	#./content/stream_reader.hpp
+	#./content/stream_reader_sdl_audio.hpp
+	#./content/stream_reader_sdl_audio.cpp
+	#./content/stream_reader_sdl_video.hpp
+	#./content/stream_reader_sdl_video.cpp
+	./content/frame_stream2.hpp
+	./content/sdl_video_frame_stream2.hpp
+	./content/sdl_video_frame_stream2.cpp
 )
 
 target_compile_features(tomato PUBLIC cxx_std_17)

src/content/SPSCQueue.h

@@ -0,0 +1,237 @@
+/*
+Copyright (c) 2020 Erik Rigtorp <erik@rigtorp.se>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+ */
+
+#pragma once
+
+#include <atomic>
+#include <cassert>
+#include <cstddef>
+#include <memory> // std::allocator
+#include <new>    // std::hardware_destructive_interference_size
+#include <stdexcept>
+#include <type_traits> // std::enable_if, std::is_*_constructible
+
+#ifdef __has_cpp_attribute
+#if __has_cpp_attribute(nodiscard)
+#define RIGTORP_NODISCARD [[nodiscard]]
+#endif
+#endif
+#ifndef RIGTORP_NODISCARD
+#define RIGTORP_NODISCARD
+#endif
+
+namespace rigtorp {
+
+template <typename T, typename Allocator = std::allocator<T>> class SPSCQueue {
+
+#if defined(__cpp_if_constexpr) && defined(__cpp_lib_void_t)
+  template <typename Alloc2, typename = void>
+  struct has_allocate_at_least : std::false_type {};
+
+  template <typename Alloc2>
+  struct has_allocate_at_least<
+      Alloc2, std::void_t<typename Alloc2::value_type,
+                          decltype(std::declval<Alloc2 &>().allocate_at_least(
+                              size_t{}))>> : std::true_type {};
+#endif
+
+public:
+  explicit SPSCQueue(const size_t capacity,
+                     const Allocator &allocator = Allocator())
+      : capacity_(capacity), allocator_(allocator) {
+    // The queue needs at least one element
+    if (capacity_ < 1) {
+      capacity_ = 1;
+    }
+    capacity_++; // Needs one slack element
+    // Prevent overflowing size_t
+    if (capacity_ > SIZE_MAX - 2 * kPadding) {
+      capacity_ = SIZE_MAX - 2 * kPadding;
+    }
+
+#if defined(__cpp_if_constexpr) && defined(__cpp_lib_void_t)
+    if constexpr (has_allocate_at_least<Allocator>::value) {
+      auto res = allocator_.allocate_at_least(capacity_ + 2 * kPadding);
+      slots_ = res.ptr;
+      capacity_ = res.count - 2 * kPadding;
+    } else {
+      slots_ = std::allocator_traits<Allocator>::allocate(
+          allocator_, capacity_ + 2 * kPadding);
+    }
+#else
+    slots_ = std::allocator_traits<Allocator>::allocate(
+        allocator_, capacity_ + 2 * kPadding);
+#endif
+
+    static_assert(alignof(SPSCQueue<T>) == kCacheLineSize, "");
+    static_assert(sizeof(SPSCQueue<T>) >= 3 * kCacheLineSize, "");
+    assert(reinterpret_cast<char *>(&readIdx_) -
+               reinterpret_cast<char *>(&writeIdx_) >=
+           static_cast<std::ptrdiff_t>(kCacheLineSize));
+  }
+
+  ~SPSCQueue() {
+    while (front()) {
+      pop();
+    }
+    std::allocator_traits<Allocator>::deallocate(allocator_, slots_,
+                                                 capacity_ + 2 * kPadding);
+  }
+
+  // non-copyable and non-movable
+  SPSCQueue(const SPSCQueue &) = delete;
+  SPSCQueue &operator=(const SPSCQueue &) = delete;
+
+  template <typename... Args>
+  void emplace(Args &&...args) noexcept(
+      std::is_nothrow_constructible<T, Args &&...>::value) {
+    static_assert(std::is_constructible<T, Args &&...>::value,
+                  "T must be constructible with Args&&...");
+    auto const writeIdx = writeIdx_.load(std::memory_order_relaxed);
+    auto nextWriteIdx = writeIdx + 1;
+    if (nextWriteIdx == capacity_) {
+      nextWriteIdx = 0;
+    }
+    while (nextWriteIdx == readIdxCache_) {
+      readIdxCache_ = readIdx_.load(std::memory_order_acquire);
+    }
+    new (&slots_[writeIdx + kPadding]) T(std::forward<Args>(args)...);
+    writeIdx_.store(nextWriteIdx, std::memory_order_release);
+  }
+
+  template <typename... Args>
+  RIGTORP_NODISCARD bool try_emplace(Args &&...args) noexcept(
+      std::is_nothrow_constructible<T, Args &&...>::value) {
+    static_assert(std::is_constructible<T, Args &&...>::value,
+                  "T must be constructible with Args&&...");
+    auto const writeIdx = writeIdx_.load(std::memory_order_relaxed);
+    auto nextWriteIdx = writeIdx + 1;
+    if (nextWriteIdx == capacity_) {
+      nextWriteIdx = 0;
+    }
+    if (nextWriteIdx == readIdxCache_) {
+      readIdxCache_ = readIdx_.load(std::memory_order_acquire);
+      if (nextWriteIdx == readIdxCache_) {
+        return false;
+      }
+    }
+    new (&slots_[writeIdx + kPadding]) T(std::forward<Args>(args)...);
+    writeIdx_.store(nextWriteIdx, std::memory_order_release);
+    return true;
+  }
+
+  void push(const T &v) noexcept(std::is_nothrow_copy_constructible<T>::value) {
+    static_assert(std::is_copy_constructible<T>::value,
+                  "T must be copy constructible");
+    emplace(v);
+  }
+
+  template <typename P, typename = typename std::enable_if<
+                            std::is_constructible<T, P &&>::value>::type>
+  void push(P &&v) noexcept(std::is_nothrow_constructible<T, P &&>::value) {
+    emplace(std::forward<P>(v));
+  }
+
+  RIGTORP_NODISCARD bool
+  try_push(const T &v) noexcept(std::is_nothrow_copy_constructible<T>::value) {
+    static_assert(std::is_copy_constructible<T>::value,
+                  "T must be copy constructible");
+    return try_emplace(v);
+  }
+
+  template <typename P, typename = typename std::enable_if<
+                            std::is_constructible<T, P &&>::value>::type>
+  RIGTORP_NODISCARD bool
+  try_push(P &&v) noexcept(std::is_nothrow_constructible<T, P &&>::value) {
+    return try_emplace(std::forward<P>(v));
+  }
+
+  RIGTORP_NODISCARD T *front() noexcept {
+    auto const readIdx = readIdx_.load(std::memory_order_relaxed);
+    if (readIdx == writeIdxCache_) {
+      writeIdxCache_ = writeIdx_.load(std::memory_order_acquire);
+      if (writeIdxCache_ == readIdx) {
+        return nullptr;
+      }
+    }
+    return &slots_[readIdx + kPadding];
+  }
+
+  void pop() noexcept {
+    static_assert(std::is_nothrow_destructible<T>::value,
+                  "T must be nothrow destructible");
+    auto const readIdx = readIdx_.load(std::memory_order_relaxed);
+    assert(writeIdx_.load(std::memory_order_acquire) != readIdx &&
+           "Can only call pop() after front() has returned a non-nullptr");
+    slots_[readIdx + kPadding].~T();
+    auto nextReadIdx = readIdx + 1;
+    if (nextReadIdx == capacity_) {
+      nextReadIdx = 0;
+    }
+    readIdx_.store(nextReadIdx, std::memory_order_release);
+  }
+
+  RIGTORP_NODISCARD size_t size() const noexcept {
+    std::ptrdiff_t diff = writeIdx_.load(std::memory_order_acquire) -
+                          readIdx_.load(std::memory_order_acquire);
+    if (diff < 0) {
+      diff += capacity_;
+    }
+    return static_cast<size_t>(diff);
+  }
+
+  RIGTORP_NODISCARD bool empty() const noexcept {
+    return writeIdx_.load(std::memory_order_acquire) ==
+           readIdx_.load(std::memory_order_acquire);
+  }
+
+  RIGTORP_NODISCARD size_t capacity() const noexcept { return capacity_ - 1; }
+
+private:
+#ifdef __cpp_lib_hardware_interference_size
+  static constexpr size_t kCacheLineSize =
+      std::hardware_destructive_interference_size;
+#else
+  static constexpr size_t kCacheLineSize = 64;
+#endif
+
+  // Padding to avoid false sharing between slots_ and adjacent allocations
+  static constexpr size_t kPadding = (kCacheLineSize - 1) / sizeof(T) + 1;
+
+private:
+  size_t capacity_;
+  T *slots_;
+#if defined(__has_cpp_attribute) && __has_cpp_attribute(no_unique_address)
+  Allocator allocator_ [[no_unique_address]];
+#else
+  Allocator allocator_;
+#endif
+
+  // Align to cache line size in order to avoid false sharing
+  // readIdxCache_ and writeIdxCache_ is used to reduce the amount of cache
+  // coherency traffic
+  alignas(kCacheLineSize) std::atomic<size_t> writeIdx_ = {0};
+  alignas(kCacheLineSize) size_t readIdxCache_ = 0;
+  alignas(kCacheLineSize) std::atomic<size_t> readIdx_ = {0};
+  alignas(kCacheLineSize) size_t writeIdxCache_ = 0;
+};
+} // namespace rigtorp

src/content/frame_stream2.hpp

@@ -0,0 +1,99 @@
+#pragma once
+
+#include <cstdint>
+#include <memory>
+#include <optional>
+#include <vector>
+#include <mutex>
+
+#include "./SPSCQueue.h"
+
+// Frames ofen consist of:
+// - seq id // incremental sequential id, gaps in ids can be used to detect loss
+// - data // the frame data
+// eg:
+//struct ExampleFrame {
+	//int64_t seq_id {0};
+	//std::vector<uint8_t> data;
+//};
+
+template<typename FrameType>
+struct FrameStream2Reader {
+	// get number of available frames
+	virtual int32_t getSize(void) = 0;
+
+	// get next frame
+	// TODO: optional instead?
+	// data sharing? -> no, data is copied for each fsr, if concurency supported
+	virtual std::optional<FrameType>  getNext(void) = 0;
+};
+
+// needs count frames queue size
+// having ~1-2sec buffer size is often sufficent
+template<typename FrameType>
+struct QueuedFrameStream2Reader : public FrameStream2Reader<FrameType> {
+	using frame_type = FrameType;
+
+	rigtorp::SPSCQueue<FrameType> _queue;
+
+	explicit QueuedFrameStream2Reader(size_t queue_size) : _queue(queue_size) {}
+
+	[[nodiscard]] int32_t getSize(void) override {
+		return _queue.size();
+	}
+
+	[[nodiscard]] std::optional<FrameType> getNext(void) override {
+		auto* ret_ptr = _queue.front();
+		if (ret_ptr == nullptr) {
+			return std::nullopt;
+		}
+
+		// move away
+		FrameType ret = std::move(*ret_ptr);
+
+		_queue.pop();
+
+		return ret;
+	}
+};
+
+template<typename FrameType>
+struct MultiplexedQueuedFrameStream2Writer {
+	using ReaderType = QueuedFrameStream2Reader<FrameType>;
+
+	// TODO: expose
+	const size_t _queue_size {10};
+
+	// pointer stability
+	std::vector<std::unique_ptr<ReaderType>> _readers;
+	std::mutex _readers_lock; // accessing the _readers array needs to be exclusive
+	// a simple lock here is ok, since this tends to be a rare operation,
+	// except for the push, which is always on the same thread
+
+	ReaderType* aquireReader(void) {
+		std::lock_guard lg{_readers_lock};
+		return _readers.emplace_back(std::make_unique<ReaderType>(_queue_size)).get();
+	}
+
+	void releaseReader(ReaderType* reader) {
+		std::lock_guard lg{_readers_lock};
+		for (auto it = _readers.begin(); it != _readers.end(); it++) {
+			if (it->get() == reader) {
+				_readers.erase(it);
+				break;
+			}
+		}
+	}
+
+	// returns true if there are readers
+	bool pushValue(const FrameType& value) {
+		std::lock_guard lg{_readers_lock};
+		bool have_readers{false};
+		for (auto& it : _readers) {
+			[[maybe_unused]] auto _ = it->_queue.try_emplace(value);
+			have_readers = true; // even if queue full, we still continue believing in them
+		}
+		return have_readers;
+	}
+};
+

src/content/sdl_video_frame_stream2.cpp

@@ -0,0 +1,81 @@
+#include "./sdl_video_frame_stream2.hpp"
+
+#include <chrono>
+#include <cstdint>
+#include <iostream>
+#include <memory>
+#include <thread>
+
+SDLVideoCameraContent::SDLVideoCameraContent(void) {
+	int devcount = 0;
+	SDL_CameraDeviceID *devices = SDL_GetCameraDevices(&devcount);
+
+	if (devices == nullptr || devcount < 1) {
+		throw int(1); // TODO: proper exception?
+	}
+
+	std::cout << "### found cameras:\n";
+	for (int i = 0; i < devcount; i++) {
+		const SDL_CameraDeviceID device = devices[i];
+		char *name = SDL_GetCameraDeviceName(device);
+
+		std::cout << "  - Camera #" << i << ": " << name << "\n";
+
+		SDL_free(name);
+	}
+
+	_camera = {
+		SDL_OpenCameraDevice(devices[0], nullptr),
+		&SDL_CloseCamera
+	};
+	if (!static_cast<bool>(_camera)) {
+		throw int(2);
+	}
+
+	SDL_CameraSpec spec;
+	float interval {0.1f};
+	if (SDL_GetCameraFormat(_camera.get(), &spec) < 0) {
+		// meh
+	} else {
+		// interval
+		interval = float(spec.interval_numerator)/float(spec.interval_denominator);
+		std::cout << "camera interval: " << interval*1000 << "ms\n";
+	}
+
+	_thread = std::thread([this, interval](void) {
+		while (!_thread_should_quit) {
+			Uint64 timestampNS = 0;
+			SDL_Surface* sdl_frame_next = SDL_AcquireCameraFrame(_camera.get(), &timestampNS);
+
+			// no new frame yet, or error
+			if (sdl_frame_next == nullptr) {
+				// only sleep 1/10, we expected a frame
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval*1000 / 10)));
+				continue;
+			}
+
+			SDLVideoFrame new_frame {
+				timestampNS,
+				sdl_frame_next
+			};
+
+			bool someone_listening = pushValue(new_frame);
+
+			SDL_ReleaseCameraFrame(_camera.get(), sdl_frame_next);
+
+			if (someone_listening) {
+				// TODO: maybe double the freq?
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval*1000)));
+			} else {
+				// we just sleep 4x as long, bc no one is listening
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval*1000*4)));
+			}
+		}
+	});
+}
+
+SDLVideoCameraContent::~SDLVideoCameraContent(void) {
+	_thread_should_quit = true;
+	_thread.join();
+	// TODO: what to do if readers are still present?
+}

src/content/sdl_video_frame_stream2.hpp

@@ -0,0 +1,66 @@
+#pragma once
+
+#include "./frame_stream2.hpp"
+#include "SDL_surface.h"
+
+#include <SDL3/SDL.h>
+
+#include <cstdint>
+#include <thread>
+
+inline void nopSurfaceDestructor(SDL_Surface*) {}
+
+// this is very sdl specific
+struct SDLVideoFrame {
+	// TODO: sequence numbering?
+	uint64_t timestampNS {0};
+
+	std::unique_ptr<SDL_Surface, decltype(&SDL_DestroySurface)> surface {nullptr, &SDL_DestroySurface};
+
+	// special non-owning constructor?
+	SDLVideoFrame(
+		uint64_t ts,
+		SDL_Surface* surf
+	) {
+		timestampNS = ts;
+		surface = {surf, &nopSurfaceDestructor};
+	}
+	// copy
+	SDLVideoFrame(const SDLVideoFrame& other) {
+		timestampNS = other.timestampNS;
+		if (static_cast<bool>(other.surface)) {
+			surface = {
+				SDL_CreateSurface(
+					other.surface->w,
+					other.surface->h,
+					SDL_PIXELFORMAT_RGBA8888 // meh
+				),
+				&SDL_DestroySurface
+			};
+			SDL_BlitSurface(other.surface.get(), nullptr, surface.get(), nullptr);
+		}
+	}
+	SDLVideoFrame& operator=(const SDLVideoFrame& other) = delete;
+};
+
+using SDLVideoFrameStream2Writer = MultiplexedQueuedFrameStream2Writer<SDLVideoFrame>;
+using SDLVideoFrameStream2Reader = SDLVideoFrameStream2Writer::ReaderType;
+
+struct SDLVideoCameraContent : protected SDLVideoFrameStream2Writer {
+	// meh, empty default
+	std::unique_ptr<SDL_Camera, decltype(&SDL_CloseCamera)> _camera {nullptr, &SDL_CloseCamera};
+	std::atomic<bool> _thread_should_quit {false};
+	std::thread _thread;
+
+	// construct source and start thread
+	// TODO: optimize so the thread is not always running
+	SDLVideoCameraContent(void);
+
+	// stops the thread and closes the camera
+	~SDLVideoCameraContent(void);
+
+	// make only some of writer public
+	using SDLVideoFrameStream2Writer::aquireReader;
+	using SDLVideoFrameStream2Writer::releaseReader;
+};
+

src/content/stream_reader_sdl_video.cpp

@@ -0,0 +1,84 @@
+#include "./stream_reader_sdl_video.hpp"
+
+#include <iostream>
+
+SDLVideoFrameStreamReader::SDLVideoFrameStreamReader() : _camera{nullptr, &SDL_CloseCamera}, _surface{nullptr, &SDL_DestroySurface} {
+	// enumerate
+	int devcount = 0;
+	SDL_CameraDeviceID *devices = SDL_GetCameraDevices(&devcount);
+
+	if (devices == nullptr || devcount < 1) {
+		throw int(1); // TODO: proper exception?
+	}
+
+	std::cout << "### found cameras:\n";
+	for (int i = 0; i < devcount; i++) {
+		const SDL_CameraDeviceID device = devices[i];
+		char *name = SDL_GetCameraDeviceName(device);
+
+		std::cout << "  - Camera #" << i << ": " << name << "\n";
+
+		SDL_free(name);
+	}
+
+	_camera = {
+		SDL_OpenCameraDevice(devices[0], nullptr),
+		&SDL_CloseCamera
+	};
+	if (!static_cast<bool>(_camera)) {
+		throw int(2);
+	}
+
+	SDL_CameraSpec spec;
+	if (SDL_GetCameraFormat(_camera.get(), &spec) < 0) {
+		// meh
+	} else {
+		// interval
+		float interval = float(spec.interval_numerator)/float(spec.interval_denominator);
+		std::cout << "camera interval: " << interval*1000 << "ms\n";
+	}
+}
+
+SDLVideoFrameStreamReader::VideoFrame SDLVideoFrameStreamReader::getNextVideoFrameRGBA(void) {
+	if (!static_cast<bool>(_camera)) {
+		return {};
+	}
+
+	Uint64 timestampNS = 0;
+	SDL_Surface* frame_next = SDL_AcquireCameraFrame(_camera.get(), &timestampNS);
+
+	// no new frame yet, or error
+	if (frame_next == nullptr) {
+		//std::cout << "failed acquiring frame\n";
+		return {};
+	}
+
+	// TODO: investigate zero copy
+	_surface = {
+		SDL_ConvertSurfaceFormat(frame_next, SDL_PIXELFORMAT_RGBA8888),
+		&SDL_DestroySurface
+	};
+
+	SDL_ReleaseCameraFrame(_camera.get(), frame_next);
+
+	SDL_LockSurface(_surface.get());
+
+	return {
+		_surface->w,
+		_surface->h,
+		timestampNS,
+		{
+			reinterpret_cast<const uint8_t*>(_surface->pixels),
+			uint64_t(_surface->w*_surface->h*4) // rgba
+		}
+	};
+}
+
+int64_t SDLVideoFrameStreamReader::have(void) {
+	return -1;
+}
+
+ByteSpan SDLVideoFrameStreamReader::getNext(void) {
+	return {};
+}
+

src/content/stream_reader_sdl_video.hpp

@@ -0,0 +1,34 @@
+#pragma once
+
+#include "./stream_reader.hpp"
+
+#include <SDL3/SDL.h>
+
+#include <cstdint>
+#include <cstdio>
+#include <memory>
+
+struct SDLVideoFrameStreamReader : public RawFrameStreamReaderI {
+	// meh, empty default
+	std::unique_ptr<SDL_Camera, decltype(&SDL_CloseCamera)> _camera;
+	std::unique_ptr<SDL_Surface, decltype(&SDL_DestroySurface)> _surface;
+
+	SDLVideoFrameStreamReader(void);
+
+	struct VideoFrame {
+		int32_t width {0};
+		int32_t height {0};
+
+		uint64_t timestampNS {0};
+
+		ByteSpan data;
+	};
+
+	// data owned by StreamReader, overwritten by next call to getNext*()
+	VideoFrame getNextVideoFrameRGBA(void);
+
+	public: // interface
+		int64_t have(void) override;
+		ByteSpan getNext(void) override;
+};
+

src/image_loader.hpp

@@ -27,6 +27,8 @@ struct ImageLoaderI {
 
 		// only positive values are valid
 		ImageResult crop(int32_t c_x, int32_t c_y, int32_t c_w, int32_t c_h) const;
+
+		// TODO: scale
 	};
 	virtual ImageResult loadFromMemoryRGBA(const uint8_t* data, uint64_t data_size) = 0;
 };

src/main.cpp

@@ -9,6 +9,7 @@
 #include "./chat_gui/theme.hpp"
 
 #include "./start_screen.hpp"
+#include "./content/sdl_video_frame_stream2.hpp"
 
 #include <memory>
 #include <iostream>
@@ -58,6 +59,26 @@ int main(int argc, char** argv) {
 		}
 	}
 
+	// optionally init audio and camera
+	if (SDL_Init(SDL_INIT_AUDIO) < 0) {
+		std::cerr << "SDL_Init AUDIO failed (" << SDL_GetError() << ")\n";
+	}
+	if (SDL_Init(SDL_INIT_CAMERA) < 0) {
+		std::cerr << "SDL_Init CAMERA failed (" << SDL_GetError() << ")\n";
+	} else { // HACK
+		SDLVideoCameraContent vcc;
+		auto* reader = vcc.aquireReader();
+		for (size_t i = 0; i < 200; i++) {
+			std::this_thread::sleep_for(std::chrono::milliseconds(50));
+			auto new_frame_opt = reader->getNext();
+			if (new_frame_opt.has_value()) {
+				std::cout << "video frame was " << new_frame_opt.value().surface->w << "x" << new_frame_opt.value().surface->h << " " << new_frame_opt.value().timestampNS << "ns\n";
+			}
+		}
+		vcc.releaseReader(reader);
+	}
+	std::cout << "after sdl video stuffery\n";
+
 	IMGUI_CHECKVERSION();
 	ImGui::CreateContext();