Rewrite host GPU abstraction

- Don't have to repeat the same thing for 4 renderers.
 - Add native Metal renderer.

src/util/vulkan_loader.h

@@ -0,0 +1,100 @@
+// SPDX-FileCopyrightText: 2019-2023 Connor McLaughlin <stenzek@gmail.com>
+// SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)
+
+#pragma once
+
+#define VK_NO_PROTOTYPES
+
+#ifdef _WIN32
+#define VK_USE_PLATFORM_WIN32_KHR
+
+// vulkan.h pulls in windows.h on Windows, so we need to include our replacement header first
+#include "common/windows_headers.h"
+#elif defined(__APPLE__)
+#define VK_USE_PLATFORM_METAL_EXT
+#elif defined(__ANDROID__)
+#define VK_USE_PLATFORM_ANDROID_KHR
+#else
+#ifdef USE_X11
+#define VK_USE_PLATFORM_XLIB_KHR
+#endif
+
+#ifdef USE_WAYLAND
+#define VK_USE_PLATFORM_WAYLAND_KHR
+#endif
+#endif
+
+#include "vulkan/vulkan.h"
+
+#if defined(USE_X11)
+
+// This breaks a bunch of our code. They shouldn't be #defines in the first place.
+#ifdef None
+#undef None
+#endif
+#ifdef Always
+#undef Always
+#endif
+#ifdef Status
+#undef Status
+#endif
+#ifdef CursorShape
+#undef CursorShape
+#endif
+#ifdef KeyPress
+#undef KeyPress
+#endif
+#ifdef KeyRelease
+#undef KeyRelease
+#endif
+#ifdef FocusIn
+#undef FocusIn
+#endif
+#ifdef FocusOut
+#undef FocusOut
+#endif
+#ifdef FontChange
+#undef FontChange
+#endif
+#ifdef Expose
+#undef Expose
+#endif
+#ifdef Unsorted
+#undef Unsorted
+#endif
+#ifdef Bool
+#undef Bool
+#endif
+
+#endif
+
+#include "vulkan_entry_points.h"
+
+// We include vk_mem_alloc globally, so we don't accidentally include it before the vulkan header somewhere.
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+#pragma clang diagnostic ignored "-Wunused-variable"
+#elif defined(_MSC_VER)
+#pragma warning(push, 0)
+#endif
+
+#define VMA_STATIC_VULKAN_FUNCTIONS 1
+#define VMA_DYNAMIC_VULKAN_FUNCTIONS 0
+#define VMA_STATS_STRING_ENABLED 0
+#include "vulkan/vk_mem_alloc.h"
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#elif defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+
+namespace Vulkan {
+bool IsVulkanLibraryLoaded();
+bool LoadVulkanLibrary();
+bool LoadVulkanInstanceFunctions(VkInstance instance);
+bool LoadVulkanDeviceFunctions(VkDevice device);
+void UnloadVulkanLibrary();
+void ResetVulkanLibraryFunctionPointers();
+} // namespace Vulkan