DRM/KMS backebd

Signed-off-by: Slendi <slendi@socopon.com>
2026-01-30 16:28:58 +02:00 · 2026-01-12 16:38:28 +02:00
parent 402cdd43da
commit 9f2dab344d
4 changed files with 341 additions and 104 deletions
--- a/src/Application.cpp
+++ b/src/Application.cpp
@@ -405,6 +405,13 @@ namespace Lunar {

 Application::Application()
 {
+	auto const *display_env = getenv("DISPLAY");
+	auto const *wayland_env = getenv("WAYLAND_DISPLAY");
+	bool const has_display
+	    = (display_env && *display_env) || (wayland_env && *wayland_env);
+	m_backend = has_display ? Backend::SDL : Backend::KMS;
+
+	if (m_backend == Backend::SDL) {
 		if (!SDL_Init(SDL_INIT_VIDEO)) {
 			std::println(std::cerr, "Failed to initialize SDL.");
 			throw std::runtime_error("App init fail");
@@ -421,6 +428,12 @@ Application::Application()

 		m_window_focused
 		    = (SDL_GetWindowFlags(m_window) & SDL_WINDOW_INPUT_FOCUS) != 0;
+	} else {
+		m_logger.info("No display server detected; using KMS backend");
+		m_renderer = std::make_unique<VulkanRenderer>(
+		    VulkanRenderer::KmsSurfaceConfig {}, m_logger);
+		m_window_focused = true;
+	}
 	m_renderer->set_antialiasing_immediate(
 	    VulkanRenderer::AntiAliasingKind::MSAA_4X);

@@ -429,6 +442,7 @@ Application::Application()

 	init_input();

+	if (m_backend == Backend::SDL)
 		mouse_captured(true);

 	m_logger.info("App init done!");
@@ -452,14 +466,20 @@ Application::~Application()

 	shutdown_input();

+	if (m_backend == Backend::SDL) {
 		SDL_DestroyWindow(m_window);
 		SDL_Quit();
+	}

 	m_logger.info("App destroy done!");
 }

 auto Application::binary_directory() const -> std::filesystem::path
 {
+	if (m_backend != Backend::SDL) {
+		return std::filesystem::current_path();
+	}
+
 	auto const *base_path = SDL_GetBasePath();
 	if (!base_path) {
 		return std::filesystem::current_path();
@@ -533,15 +553,28 @@ auto Application::run() -> void

 {
 	SDL_Event e;
+	bool const use_sdl = (m_backend == Backend::SDL);
+	bool const use_imgui = use_sdl;

+	if (use_imgui) {
 		ImGuiIO &io = ImGui::GetIO();
 		io.IniFilename = nullptr;
+	}

 	uint64_t last { 0 };
 	float fps { 0.0f };
 	while (m_running) {
 		GZoneScopedN("Frame");
-		uint64_t now { SDL_GetTicks() };
+		uint64_t now { 0 };
+		if (use_sdl) {
+			now = SDL_GetTicks();
+		} else {
+			auto const now_tp = std::chrono::steady_clock::now();
+			now = static_cast<uint64_t>(
+			    std::chrono::duration_cast<std::chrono::milliseconds>(
+			        now_tp.time_since_epoch())
+			        .count());
+		}
 		uint64_t dt { now - last };
 		float dt_seconds { static_cast<float>(dt) / 1000.0f };
 		last = now;
@@ -554,6 +587,7 @@ auto Application::run() -> void
 			m_key_state_previous = m_key_state;
 			process_libinput_events();

+			if (use_sdl) {
 				while (SDL_PollEvent(&e)) {
 					bool forward_to_imgui { false };
 					if (e.type == SDL_EVENT_QUIT) {
@@ -594,10 +628,11 @@ auto Application::run() -> void
 						forward_to_imgui = true;
 					}

-				if (forward_to_imgui)
+					if (forward_to_imgui && use_imgui)
 						ImGui_ImplSDL3_ProcessEvent(&e);
 				}
 			}
+		}

 		bool const ctrl_down { is_key_down(KEY_LEFTCTRL)
 			|| is_key_down(KEY_RIGHTCTRL) };
@@ -687,7 +722,7 @@ auto Application::run() -> void
 			m_mouse_dy = 0.0;
 		}

-		{
+		if (use_imgui) {
 			GZoneScopedN("ImGui");
 			ImGui_ImplSDL3_NewFrame();
 			ImGui_ImplVulkan_NewFrame();
@@ -909,6 +944,7 @@ auto Application::init_input() -> void
 		throw std::runtime_error("App init fail");
 	}

+	if (m_backend == Backend::SDL) {
 		int width {}, height {};
 		SDL_GetWindowSize(m_window, &width, &height);
 		float mouse_x {}, mouse_y {};
@@ -917,6 +953,10 @@ auto Application::init_input() -> void
 		m_mouse_y = mouse_y;
 		ImGui::GetIO().AddMousePosEvent(
 		    static_cast<float>(m_mouse_x), static_cast<float>(m_mouse_y));
+	} else {
+		m_mouse_x = 0.0;
+		m_mouse_y = 0.0;
+	}
 }

 auto Application::shutdown_input() -> void
@@ -973,7 +1013,8 @@ auto Application::handle_keyboard_event(libinput_event_keyboard *event) -> void
 		}
 	}

-	if (pressed && key == KEY_F11 && m_ctrl_pressed_count > 0) {
+	if (m_backend == Backend::SDL && pressed && key == KEY_F11
+	    && m_ctrl_pressed_count > 0) {
 		bool const new_show_imgui { !m_show_imgui };
 		m_show_imgui = new_show_imgui;
 		mouse_captured(!new_show_imgui);
@@ -1007,6 +1048,7 @@ auto Application::handle_keyboard_event(libinput_event_keyboard *event) -> void
 		}
 	}

+	if (m_backend == Backend::SDL) {
 		if (auto imgui_key { linux_key_to_imgui(key) }) {
 			if (m_show_imgui)
 				ImGui::GetIO().AddKeyEvent(*imgui_key, pressed);
@@ -1014,12 +1056,14 @@ auto Application::handle_keyboard_event(libinput_event_keyboard *event) -> void

 		if (m_show_imgui && pressed) {
 			bool const shift_pressed { is_key_down(KEY_LEFTSHIFT)
-			|| is_key_down(KEY_RIGHTSHIFT) || (key == KEY_LEFTSHIFT && pressed)
+				|| is_key_down(KEY_RIGHTSHIFT)
+				|| (key == KEY_LEFTSHIFT && pressed)
 				|| (key == KEY_RIGHTSHIFT && pressed) };

 			if (auto ch { linux_key_to_char(key, shift_pressed) })
 				ImGui::GetIO().AddInputCharacter(*ch);
 		}
+	}

 	if (key < m_key_state.size())
 		m_key_state[key] = pressed;
@@ -1039,6 +1083,11 @@ auto Application::clamp_mouse_to_window(int width, int height) -> void

 auto Application::mouse_captured(bool new_state) -> void
 {
+	if (m_backend != Backend::SDL) {
+		m_mouse_captured = false;
+		return;
+	}
+
 	if (!SDL_SetWindowRelativeMouseMode(m_window, new_state)) {
 		m_logger.err("Failed to capture mouse");
 		return;
--- a/src/Application.h
+++ b/src/Application.h
@@ -38,6 +38,11 @@ struct Application {
 	static auto the() -> Application &;

 private:
+	enum class Backend {
+		SDL,
+		KMS,
+	};
+
 	Application();
 	~Application();

@@ -50,6 +55,7 @@ private:
 	auto clamp_mouse_to_window(int width, int height) -> void;

 	SDL_Window *m_window { nullptr };
+	Backend m_backend { Backend::SDL };
 	Logger m_logger { "Lunar" };
 	std::unique_ptr<VulkanRenderer> m_renderer;
 	Skybox m_skybox;
--- a/src/VulkanRenderer.cpp
+++ b/src/VulkanRenderer.cpp
@@ -620,6 +620,9 @@ VulkanRenderer::VulkanRenderer(SDL_Window *window, Logger &logger)
 		throw std::runtime_error("VulkanRenderer requires a valid window");
 	}

+	m_use_kms = false;
+	m_imgui_enabled = true;
+
 	vk_init();
 	swapchain_init();
 	commands_init();
@@ -630,6 +633,22 @@ VulkanRenderer::VulkanRenderer(SDL_Window *window, Logger &logger)
 	imgui_init();
 }

+VulkanRenderer::VulkanRenderer(KmsSurfaceConfig /*config*/, Logger &logger)
+    : gl(*this)
+    , m_logger(logger)
+{
+	m_use_kms = true;
+	m_imgui_enabled = false;
+
+	vk_init();
+	swapchain_init();
+	commands_init();
+	sync_init();
+	descriptors_init();
+	pipelines_init();
+	default_data_init();
+}
+
 VulkanRenderer::~VulkanRenderer()
 {
 	m_device.waitIdle();
@@ -671,8 +690,12 @@ VulkanRenderer::~VulkanRenderer()
 	}

 	if (m_vk.surface) {
-		SDL_Vulkan_DestroySurface(
-		    m_vkb.instance, static_cast<VkSurfaceKHR>(m_vk.surface), nullptr);
+		if (m_use_kms) {
+			m_instance.destroySurfaceKHR(m_vk.surface);
+		} else {
+			SDL_Vulkan_DestroySurface(m_vkb.instance,
+			    static_cast<VkSurfaceKHR>(m_vk.surface), nullptr);
+		}
 		m_vk.surface = nullptr;
 	}

@@ -847,6 +870,107 @@ auto VulkanRenderer::immediate_submit(
 	}
 }

+auto VulkanRenderer::setup_kms_surface() -> void
+{
+	auto const devices = m_instance.enumeratePhysicalDevices();
+	if (devices.empty()) {
+		m_logger.err("No Vulkan physical devices available for KMS");
+		throw std::runtime_error("App init fail");
+	}
+
+	for (auto const &device : devices) {
+		auto const displays = device.getDisplayPropertiesKHR();
+		if (displays.empty()) {
+			continue;
+		}
+
+		for (auto const &display_props : displays) {
+			auto const modes
+			    = device.getDisplayModePropertiesKHR(display_props.display);
+			if (modes.empty()) {
+				continue;
+			}
+
+			auto const best_mode_it = std::max_element(modes.begin(),
+			    modes.end(), [](auto const &lhs, auto const &rhs) {
+				    auto const lhs_extent = lhs.parameters.visibleRegion;
+				    auto const rhs_extent = rhs.parameters.visibleRegion;
+				    auto const lhs_area
+				        = static_cast<uint64_t>(lhs_extent.width)
+				        * static_cast<uint64_t>(lhs_extent.height);
+				    auto const rhs_area
+				        = static_cast<uint64_t>(rhs_extent.width)
+				        * static_cast<uint64_t>(rhs_extent.height);
+				    if (lhs_area == rhs_area) {
+					    return lhs.parameters.refreshRate
+					        < rhs.parameters.refreshRate;
+				    }
+				    return lhs_area < rhs_area;
+			    });
+
+			auto const planes = device.getDisplayPlanePropertiesKHR();
+			std::optional<uint32_t> plane_index;
+			uint32_t plane_stack_index { 0 };
+			for (uint32_t i = 0; i < planes.size(); ++i) {
+				auto const supported_displays
+				    = device.getDisplayPlaneSupportedDisplaysKHR(i);
+				if (std::find(supported_displays.begin(),
+				        supported_displays.end(), display_props.display)
+				    != supported_displays.end()) {
+					plane_index = i;
+					plane_stack_index = planes[i].currentStackIndex;
+					break;
+				}
+			}
+			if (!plane_index) {
+				continue;
+			}
+
+			auto const extent = best_mode_it->parameters.visibleRegion;
+			KmsState state {};
+			state.display = display_props.display;
+			state.mode = best_mode_it->displayMode;
+			state.extent = extent;
+			state.plane_index = *plane_index;
+			state.plane_stack_index = plane_stack_index;
+			if (display_props.displayName) {
+				state.display_name = display_props.displayName;
+			}
+
+			m_kms_state = state;
+			m_kms_extent = extent;
+			m_kms_physical_device = device;
+			m_kms_physical_device_set = true;
+
+			m_logger.info("Using KMS display {} ({}x{} @ {} mHz)",
+			    state.display_name.empty() ? "unnamed" : state.display_name,
+			    extent.width, extent.height,
+			    best_mode_it->parameters.refreshRate);
+			break;
+		}
+
+		if (m_kms_state) {
+			break;
+		}
+	}
+
+	if (!m_kms_state) {
+		m_logger.err("No suitable KMS display found");
+		throw std::runtime_error("App init fail");
+	}
+
+	vk::DisplaySurfaceCreateInfoKHR surface_info {};
+	surface_info.displayMode = m_kms_state->mode;
+	surface_info.planeIndex = m_kms_state->plane_index;
+	surface_info.planeStackIndex = m_kms_state->plane_stack_index;
+	surface_info.transform = vk::SurfaceTransformFlagBitsKHR::eIdentity;
+	surface_info.alphaMode = vk::DisplayPlaneAlphaFlagBitsKHR::eOpaque;
+	surface_info.globalAlpha = 1.0f;
+	surface_info.imageExtent = m_kms_state->extent;
+
+	m_vk.surface = m_instance.createDisplayPlaneSurfaceKHR(surface_info);
+}
+
 auto VulkanRenderer::vk_init() -> void
 {
 	VULKAN_HPP_DEFAULT_DISPATCHER.init(vkGetInstanceProcAddr);
@@ -884,6 +1008,9 @@ auto VulkanRenderer::vk_init() -> void

 		        return VK_FALSE;
 	        });
+	if (m_use_kms) {
+		instance_builder.enable_extension(VK_KHR_DISPLAY_EXTENSION_NAME);
+	}
 #ifndef NDEBUG
 	instance_builder.request_validation_layers();
 #endif
@@ -898,6 +1025,9 @@ auto VulkanRenderer::vk_init() -> void
 	m_instance = vk::Instance { m_vkb.instance.instance };
 	VULKAN_HPP_DEFAULT_DISPATCHER.init(m_instance);

+	if (m_use_kms) {
+		setup_kms_surface();
+	} else {
 		VkSurfaceKHR raw_surface {};
 		if (!SDL_Vulkan_CreateSurface(
 		        m_window, m_vkb.instance, nullptr, &raw_surface)) {
@@ -905,6 +1035,7 @@ auto VulkanRenderer::vk_init() -> void
 			throw std::runtime_error("App init fail");
 		}
 		m_vk.surface = vk::SurfaceKHR { raw_surface };
+	}

 	vkb::PhysicalDeviceSelector phys_device_selector { m_vkb.instance };
 	VkPhysicalDeviceVulkan13Features features_13 {};
@@ -946,6 +1077,10 @@ auto VulkanRenderer::vk_init() -> void

 	m_logger.info("Chosen Vulkan physical device: {}",
 	    m_vkb.phys_dev.properties.deviceName);
+	if (m_use_kms && m_kms_physical_device_set
+	    && m_physical_device != m_kms_physical_device) {
+		m_logger.warn("KMS display is not on the selected physical device");
+	}

 	auto const props = m_physical_device.getProperties();
 	m_vk.supported_framebuffer_samples
@@ -974,6 +1109,13 @@ auto VulkanRenderer::vk_init() -> void
 	}
 	m_vk.graphics_queue_family = queue_family_ret.value();
 	m_vk.graphics_queue = m_device.getQueue(m_vk.graphics_queue_family, 0);
+	if (m_use_kms) {
+		if (!m_physical_device.getSurfaceSupportKHR(
+		        m_vk.graphics_queue_family, m_vk.surface)) {
+			m_logger.err("Selected device does not support KMS surface");
+			throw std::runtime_error("App init fail");
+		}
+	}

 	VmaAllocatorCreateInfo allocator_ci {};
 	allocator_ci.physicalDevice = m_vkb.phys_dev.physical_device;
@@ -985,12 +1127,21 @@ auto VulkanRenderer::vk_init() -> void

 auto VulkanRenderer::swapchain_init() -> void
 {
-	int w, h;
+	uint32_t width { 0 };
+	uint32_t height { 0 };
+	if (m_use_kms) {
+		width = m_kms_extent.width;
+		height = m_kms_extent.height;
+	} else {
+		int w {}, h {};
 		SDL_GetWindowSize(m_window, &w, &h);
-	create_swapchain(static_cast<uint32_t>(w), static_cast<uint32_t>(h));
-	create_draw_image(static_cast<uint32_t>(w), static_cast<uint32_t>(h));
-	create_msaa_color_image(static_cast<uint32_t>(w), static_cast<uint32_t>(h));
-	create_depth_image(static_cast<uint32_t>(w), static_cast<uint32_t>(h));
+		width = static_cast<uint32_t>(w);
+		height = static_cast<uint32_t>(h);
+	}
+	create_swapchain(width, height);
+	create_draw_image(width, height);
+	create_msaa_color_image(width, height);
+	create_depth_image(width, height);
 }

 auto VulkanRenderer::commands_init() -> void
@@ -1404,10 +1555,14 @@ auto VulkanRenderer::render(std::function<void(GL &)> const &record) -> void
 	    m_vk.swapchain, 1'000'000'000, frame.swapchain_semaphore.get(), {});
 	if (acquire_result.result == vk::Result::eErrorOutOfDateKHR
 	    || acquire_result.result == vk::Result::eSuboptimalKHR) {
+		if (m_use_kms) {
+			recreate_swapchain(m_kms_extent.width, m_kms_extent.height);
+		} else {
 			int width {}, height {};
 			SDL_GetWindowSize(m_window, &width, &height);
 			recreate_swapchain(
 			    static_cast<uint32_t>(width), static_cast<uint32_t>(height));
+		}
 		return;
 	}
 	VK_CHECK(m_logger, acquire_result.result);
@@ -1463,7 +1618,10 @@ auto VulkanRenderer::render(std::function<void(GL &)> const &record) -> void
 	    vk::ImageLayout::eTransferDstOptimal,
 	    vk::ImageLayout::eColorAttachmentOptimal);

-	draw_imgui(cmd, m_vk.swapchain_image_views.at(swapchain_image_idx).get());
+	if (m_imgui_enabled) {
+		draw_imgui(
+		    cmd, m_vk.swapchain_image_views.at(swapchain_image_idx).get());
+	}

 	vkutil::transition_image(cmd, m_vk.swapchain_images.at(swapchain_image_idx),
 	    vk::ImageLayout::eColorAttachmentOptimal,
@@ -1577,10 +1735,14 @@ auto VulkanRenderer::render(std::function<void(GL &)> const &record) -> void
 	auto const present_result = m_vk.graphics_queue.presentKHR(present_info);
 	if (present_result == vk::Result::eErrorOutOfDateKHR
 	    || present_result == vk::Result::eSuboptimalKHR) {
+		if (m_use_kms) {
+			recreate_swapchain(m_kms_extent.width, m_kms_extent.height);
+		} else {
 			int width {}, height {};
 			SDL_GetWindowSize(m_window, &width, &height);
 			recreate_swapchain(
 			    static_cast<uint32_t>(width), static_cast<uint32_t>(height));
+		}
 		return;
 	}
 	VK_CHECK(m_logger, present_result);
--- a/src/VulkanRenderer.h
+++ b/src/VulkanRenderer.h
@@ -7,6 +7,7 @@
 #include <mutex>
 #include <optional>
 #include <span>
+#include <string>
 #include <variant>
 #include <vector>

@@ -130,7 +131,10 @@ struct VulkanRenderer {
 		MSAA_8X,
 	};

+	struct KmsSurfaceConfig { };
+
 	VulkanRenderer(SDL_Window *window, Logger &logger);
+	VulkanRenderer(KmsSurfaceConfig config, Logger &logger);
 	~VulkanRenderer();

 	auto render(std::function<void(GL &)> const &record = {}) -> void;
@@ -232,6 +236,7 @@ private:

 	auto vk_init() -> void;
 	auto swapchain_init() -> void;
+	auto setup_kms_surface() -> void;
 	auto commands_init() -> void;
 	auto sync_init() -> void;
 	auto descriptors_init() -> void;
@@ -359,10 +364,25 @@ private:
 		vk::UniqueSampler default_sampler_nearest;
 	} m_vk;

+	struct KmsState {
+		vk::DisplayKHR display {};
+		vk::DisplayModeKHR mode {};
+		vk::Extent2D extent {};
+		uint32_t plane_index { 0 };
+		uint32_t plane_stack_index { 0 };
+		std::string display_name {};
+	};
+
 	SDL_Window *m_window { nullptr };
 	Logger &m_logger;
 	std::mutex m_command_mutex;
 	std::vector<RenderCommand> m_pending_render_commands;
+	bool m_use_kms { false };
+	bool m_imgui_enabled { true };
+	std::optional<KmsState> m_kms_state {};
+	vk::PhysicalDevice m_kms_physical_device {};
+	vk::Extent2D m_kms_extent {};
+	bool m_kms_physical_device_set { false };
 };

 } // namespace Lunar