Minimal working headless output

backend/headless/backend.c

@@ -26,6 +26,9 @@ static void backend_destroy(struct wlr_backend *wlr_backend) {
 	}
 
 	wl_list_remove(&backend->display_destroy.link);
+
+	// TODO: destroy outputs
+
 	wlr_egl_finish(&backend->egl);
 	free(backend);
 }
@@ -61,6 +64,12 @@ static bool egl_get_config(EGLDisplay disp, EGLConfig *out) {
 
 	static const EGLint attribs[] = {
 		EGL_SURFACE_TYPE, EGL_PBUFFER_BIT,
+		EGL_BUFFER_SIZE, 32,
+		EGL_ALPHA_SIZE, 0,
+		EGL_BLUE_SIZE, 8,
+		EGL_GREEN_SIZE, 8,
+		EGL_RED_SIZE, 8,
+		EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
 		EGL_NONE,
 	};
 
@@ -146,6 +155,7 @@ struct wlr_backend *wlr_headless_backend_create(struct wl_display *display) {
 	}
 	wlr_backend_init(&backend->backend, &backend_impl);
 	backend->display = display;
+	wl_list_init(&backend->outputs);
 
 	egl_init(&backend->egl);
 

backend/headless/output.c

@@ -6,6 +6,27 @@
 #include <wlr/util/log.h>
 #include "backend/headless.h"
 
+static void output_transform(struct wlr_output *wlr_output,
+		enum wl_output_transform transform) {
+	struct wlr_headless_backend_output *output =
+		(struct wlr_headless_backend_output *)wlr_output;
+	output->wlr_output.transform = transform;
+}
+
+static void output_make_current(struct wlr_output *wlr_output) {
+	struct wlr_headless_backend_output *output =
+		(struct wlr_headless_backend_output *)wlr_output;
+	if (!eglMakeCurrent(output->backend->egl.display,
+		output->egl_surface, output->egl_surface,
+		output->backend->egl.context)) {
+		wlr_log(L_ERROR, "eglMakeCurrent failed: %s", egl_error());
+	}
+}
+
+static void output_swap_buffers(struct wlr_output *wlr_output) {
+	// No-op
+}
+
 static void output_destroy(struct wlr_output *wlr_output) {
 	struct wlr_headless_backend_output *output =
 		(struct wlr_headless_backend_output *)wlr_output;
@@ -19,13 +40,20 @@ static void output_destroy(struct wlr_output *wlr_output) {
 }
 
 static const struct wlr_output_impl output_impl = {
-	//.set_custom_mode = wlr_wl_output_set_custom_mode,
+	//.set_custom_mode = output_set_custom_mode,
-	//.transform = wlr_wl_output_transform,
+	.transform = output_transform,
 	.destroy = output_destroy,
-	//.make_current = wlr_wl_output_make_current,
+	.make_current = output_make_current,
-	//.swap_buffers = wlr_wl_output_swap_buffers,
+	.swap_buffers = output_swap_buffers,
 };
 
+static int signal_frame(void *data) {
+	struct wlr_headless_backend_output *output = data;
+	wl_signal_emit(&output->wlr_output.events.frame, &output->wlr_output);
+	wl_event_source_timer_update(output->frame_timer, 16);
+	return 0;
+}
+
 static EGLSurface egl_create_surface(struct wlr_egl *egl, unsigned int width,
 		unsigned int height) {
 	EGLint attribs[] = {EGL_WIDTH, width, EGL_HEIGHT, height, EGL_NONE};
@@ -49,10 +77,15 @@ struct wlr_output *wlr_headless_add_output(struct wlr_backend *wlr_backend,
 		wlr_log(L_ERROR, "Failed to allocate wlr_headless_backend_output");
 		return NULL;
 	}
+	output->backend = backend;
 	wlr_output_init(&output->wlr_output, &backend->backend, &output_impl);
 	struct wlr_output *wlr_output = &output->wlr_output;
 
 	output->egl_surface = egl_create_surface(&backend->egl, width, height);
+	if (output->egl_surface == EGL_NO_SURFACE) {
+		// TODO: cleanup
+		return NULL;
+	}
 
 	wlr_output_update_size(wlr_output, width, height);
 
@@ -67,14 +100,13 @@ struct wlr_output *wlr_headless_add_output(struct wlr_backend *wlr_backend,
 	glClearColor(1.0, 1.0, 1.0, 1.0);
 	glClear(GL_COLOR_BUFFER_BIT);
 
-	if (!eglSwapBuffers(output->backend->egl.display, output->egl_surface)) {
+	struct wl_event_loop *ev = wl_display_get_event_loop(backend->display);
-		wlr_log(L_ERROR, "eglSwapBuffers failed: %s", egl_error());
+	output->frame_timer = wl_event_loop_add_timer(ev, signal_frame, output);
-		goto error;
-	}
 
 	wl_list_insert(&backend->outputs, &output->link);
 	wlr_output_create_global(wlr_output, backend->display);
 	wl_signal_emit(&backend->backend.events.output_add, wlr_output);
+	wl_event_source_timer_update(output->frame_timer, 16);
 	return wlr_output;
 
 error:

include/backend/headless.h

@@ -20,6 +20,7 @@ struct wlr_headless_backend_output {
 	struct wl_list link;
 
 	void *egl_surface;
+	struct wl_event_source *frame_timer;
 };
 
 #endif