Refine OpenXR backend formatting

AGENTS.md

@@ -0,0 +1,3 @@
+Coding conventions:
+- Use `clang-format` on all C and C++ sources before committing.
+- In `CMakeLists.txt`, indent with four spaces. Tabs may be used for C++ files as per .clang-format.

CMakeLists.txt

@@ -28,27 +28,28 @@ pkg_check_modules(X11 REQUIRED x11)
 pkg_check_modules(wayland REQUIRED wayland-server wayland-protocols)
 
 include_directories(
-	${wayland_INCLUDE_DIRS}
-	${X11_INCLUDE_DIRS}
-	${GLM_INCLUDE_DIRS}
-	${Wlroots_INCLUDE_DIRS}
+    ${wayland_INCLUDE_DIRS}
+    ${X11_INCLUDE_DIRS}
+    ${GLM_INCLUDE_DIRS}
+    ${Wlroots_INCLUDE_DIRS}
 )
 
 set(SOURCES
-	src/wlr/backend.cpp
-	src/wlr/output.cpp
+    src/wlr/backend.cpp
+    src/wlr/output.cpp
+    src/wlr/openxr_gl.cpp
 
-	src/compositor.cpp
-	src/main.cpp
+    src/compositor.cpp
+    src/main.cpp
 )
 
 add_executable(${PROJECT_NAME} ${SOURCES})
 
 target_link_libraries(${PROJECT_NAME}
-	OpenGL::GL
-	openxr_loader
-	${wayland_LIBRARIES}
-	${X11_LIBRARIES}
-	${GLM_LIBRARIES}
-	${Wlroots_LIBRARIES}
+    OpenGL::GL
+    openxr_loader
+    ${wayland_LIBRARIES}
+    ${X11_LIBRARIES}
+    ${GLM_LIBRARIES}
+    ${Wlroots_LIBRARIES}
 )

src/wlr/backend.cpp

@@ -1,60 +1,20 @@
-#include <stdlib.h>
+#include "openxr_gl.h"
 
 extern "C" {
 #include <wayland-server-core.h>
-#include <wlr/backend/interface.h>
-#include <wlr/util/log.h>
 }
 
-struct my_backend {
-	struct wlr_backend base;
-	// TODO: any backend‐specific fields
-};
-
 extern "C" {
 
-static bool backend_start(struct wlr_backend* backend)
-{
-	(void)backend;
-	// TODO: start event loops, create outputs, inputs, etc.
-	return true;
-}
-
-static void backend_destroy(struct wlr_backend* backend)
-{
-	(void)backend;
-	// TODO: destroy outputs, free everything
-}
-
-static int backend_get_drm_fd(struct wlr_backend* backend)
-{
-	(void)backend;
-	// TODO: return drm FD or -1
-	return -1;
-}
-
-static const struct wlr_backend_impl backend_impl = {
-	.start = backend_start,
-	.destroy = backend_destroy,
-	.get_drm_fd = backend_get_drm_fd,
-};
-
 struct wlr_backend* wlr_my_backend_create(
     struct wl_event_loop* loop, char const* name)
 {
-	(void)loop;
 	(void)name;
-	struct my_backend* b = (struct my_backend*)calloc(1, sizeof(*b));
-	if (!b) {
-		return NULL;
-	}
-	wlr_backend_init(&b->base, &backend_impl);
-	// TODO: store loop/name, setup
-	return &b->base;
+	return wlr_openxr_backend_create(nullptr, loop);
 }
 
 bool wlr_backend_is_mybackend(struct wlr_backend* backend)
 {
-	return backend->impl == &backend_impl;
+	return wlr_backend_is_openxr(backend);
 }
 }

src/wlr/openxr_gl.cpp

@@ -0,0 +1,208 @@
+#include "openxr_gl.h"
+
+extern "C" {
+#include <wayland-server-core.h>
+#include <wlr/backend/interface.h>
+#include <wlr/interfaces/wlr_output.h>
+#include <wlr/util/log.h>
+}
+
+#include <cstring>
+#include <memory>
+
+#include <GL/glx.h>
+#include <X11/Xlib.h>
+#include <openxr/openxr.h>
+#include <openxr/openxr_platform.h>
+
+static void output_destroy(struct wlr_output* wlr_output) { (void)wlr_output; }
+
+static bool output_test(
+    struct wlr_output* wlr_output, const struct wlr_output_state* state)
+{
+	(void)wlr_output;
+	(void)state;
+	return true;
+}
+
+static bool output_commit(
+    struct wlr_output* wlr_output, const struct wlr_output_state* state)
+{
+	(void)wlr_output;
+	(void)state;
+	return true;
+}
+
+static const struct wlr_drm_format_set* output_get_primary_formats(
+    struct wlr_output* wlr_output, uint32_t buffer_caps)
+{
+	(void)wlr_output;
+	(void)buffer_caps;
+	return NULL;
+}
+
+static const struct wlr_output_impl output_impl = {
+	.destroy = output_destroy,
+	.test = output_test,
+	.commit = output_commit,
+	.get_primary_formats = output_get_primary_formats,
+};
+
+#include <GL/glx.h>
+#include <X11/Xlib.h>
+#include <cstring>
+#include <memory>
+#include <openxr/openxr.h>
+#include <openxr/openxr_platform.h>
+
+struct openxr_backend {
+	wlr_backend base;
+	wl_display* display;
+	XrInstance instance {};
+	XrSession session {};
+	bool started = false;
+	struct wlr_output* output = nullptr;
+};
+
+static bool backend_start(wlr_backend* backend)
+{
+	auto* xr = reinterpret_cast<openxr_backend*>(backend);
+	if (xr->started)
+		return true;
+
+	XrApplicationInfo ai {};
+	std::strncpy(
+	    ai.applicationName, "LunarWM", XR_MAX_APPLICATION_NAME_SIZE - 1);
+	ai.applicationVersion = 1;
+	std::strncpy(ai.engineName, "LunarWM", XR_MAX_ENGINE_NAME_SIZE - 1);
+	ai.engineVersion = 1;
+	ai.apiVersion = XR_CURRENT_API_VERSION;
+
+	char const* exts[] = {
+		XR_EXT_DEBUG_UTILS_EXTENSION_NAME,
+		XR_KHR_OPENGL_ENABLE_EXTENSION_NAME,
+	};
+
+	XrInstanceCreateInfo ic { XR_TYPE_INSTANCE_CREATE_INFO };
+	ic.applicationInfo = ai;
+	ic.enabledExtensionCount = sizeof(exts) / sizeof(exts[0]);
+	ic.enabledExtensionNames = exts;
+
+	if (xrCreateInstance(&ic, &xr->instance) != XR_SUCCESS) {
+		wlr_log(WLR_ERROR, "Failed to create OpenXR instance");
+		return false;
+	}
+
+	XrSystemGetInfo sgi { XR_TYPE_SYSTEM_GET_INFO };
+	sgi.formFactor = XR_FORM_FACTOR_HEAD_MOUNTED_DISPLAY;
+	XrSystemId system_id;
+	if (xrGetSystem(xr->instance, &sgi, &system_id) != XR_SUCCESS) {
+		wlr_log(WLR_ERROR, "xrGetSystem failed");
+		return false;
+	}
+
+	PFN_xrGetOpenGLGraphicsRequirementsKHR get_reqs;
+	xrGetInstanceProcAddr(xr->instance, "xrGetOpenGLGraphicsRequirementsKHR",
+	    reinterpret_cast<PFN_xrVoidFunction*>(&get_reqs));
+	XrGraphicsRequirementsOpenGLKHR gl_reqs {
+		XR_TYPE_GRAPHICS_REQUIREMENTS_OPENGL_KHR
+	};
+	get_reqs(xr->instance, system_id, &gl_reqs);
+
+	Display* dpy = XOpenDisplay(nullptr);
+	if (!dpy) {
+		wlr_log(WLR_ERROR, "Failed to open X display");
+		return false;
+	}
+	int screen = DefaultScreen(dpy);
+	static int vis_attrs[] = { GLX_X_RENDERABLE, True, GLX_DRAWABLE_TYPE,
+		GLX_WINDOW_BIT, GLX_RENDER_TYPE, GLX_RGBA_BIT, GLX_X_VISUAL_TYPE,
+		GLX_TRUE_COLOR, GLX_RED_SIZE, 8, GLX_GREEN_SIZE, 8, GLX_BLUE_SIZE, 8,
+		GLX_DEPTH_SIZE, 24, GLX_DOUBLEBUFFER, True, None };
+	int fbcount;
+	GLXFBConfig* fbcs = glXChooseFBConfig(dpy, screen, vis_attrs, &fbcount);
+	if (!fbcs || !fbcount) {
+		wlr_log(WLR_ERROR, "No GLXFBConfig found");
+		return false;
+	}
+	GLXFBConfig fbc = fbcs[0];
+	XFree(fbcs);
+
+	XVisualInfo* vi = glXGetVisualFromFBConfig(dpy, fbc);
+	Window root = RootWindow(dpy, screen);
+	XSetWindowAttributes swa;
+	swa.colormap = XCreateColormap(dpy, root, vi->visual, AllocNone);
+	swa.event_mask = ExposureMask;
+	Window win = XCreateWindow(dpy, root, 0, 0, 16, 16, 0, vi->depth,
+	    InputOutput, vi->visual, CWColormap | CWEventMask, &swa);
+	GLXContext ctx
+	    = glXCreateNewContext(dpy, fbc, GLX_RGBA_TYPE, nullptr, True);
+	glXMakeContextCurrent(dpy, win, win, ctx);
+
+	XrGraphicsBindingOpenGLXlibKHR bind {
+		XR_TYPE_GRAPHICS_BINDING_OPENGL_XLIB_KHR
+	};
+	bind.xDisplay = dpy;
+	bind.visualid = vi->visualid;
+	bind.glxFBConfig = fbc;
+	bind.glxDrawable = win;
+	bind.glxContext = ctx;
+
+	XrSessionCreateInfo sci { XR_TYPE_SESSION_CREATE_INFO };
+	sci.next = &bind;
+	sci.systemId = system_id;
+	if (xrCreateSession(xr->instance, &sci, &xr->session) != XR_SUCCESS) {
+		wlr_log(WLR_ERROR, "xrCreateSession failed");
+		return false;
+	}
+
+	xr->output = static_cast<wlr_output*>(calloc(1, sizeof(wlr_output)));
+	if (xr->output) {
+		wlr_output_init(xr->output, &xr->base, &output_impl, "OpenXR");
+		wlr_output_create_global(xr->output);
+	}
+
+	xr->started = true;
+	wlr_log(WLR_INFO, "OpenXR backend started");
+	return true;
+}
+
+static void backend_destroy(wlr_backend* backend)
+{
+	auto* xr = reinterpret_cast<openxr_backend*>(backend);
+	if (xr->session) {
+		xrDestroySession(xr->session);
+	}
+	if (xr->instance) {
+		xrDestroyInstance(xr->instance);
+	}
+	free(xr);
+}
+
+static int backend_get_drm_fd(wlr_backend* backend)
+{
+	(void)backend;
+	return -1;
+}
+
+static wlr_backend_impl const backend_impl = {
+	.start = backend_start,
+	.destroy = backend_destroy,
+	.get_drm_fd = backend_get_drm_fd,
+};
+
+wlr_backend* wlr_openxr_backend_create(wl_display* display, wl_event_loop* loop)
+{
+	(void)loop;
+	auto* b = static_cast<openxr_backend*>(calloc(1, sizeof(*b)));
+	if (!b)
+		return nullptr;
+	b->display = display;
+	wlr_backend_init(&b->base, &backend_impl);
+	return &b->base;
+}
+
+bool wlr_backend_is_openxr(wlr_backend* backend)
+{
+	return backend->impl == &backend_impl;
+}

src/wlr/openxr_gl.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct wlr_backend;
+struct wl_display;
+struct wl_event_loop;
+
+struct wlr_backend* wlr_openxr_backend_create(
+    struct wl_display* display, struct wl_event_loop* loop);
+
+bool wlr_backend_is_openxr(struct wlr_backend* backend);
+
+#ifdef __cplusplus
+}
+#endif