text: #include <assert.h>
  #include <stdlib.h>
  #include <wlr/interfaces/wlr_input_device.h>
  #include <wlr/interfaces/wlr_output.h>
  #include <wlr/util/log.h>
  #include "backend/headless.h"
  #include "util/signal.h"
  
  struct wlr_headless_backend *headless_backend_from_backend(
  		struct wlr_backend *wlr_backend) {
  	assert(wlr_backend_is_headless(wlr_backend));
  	return (struct wlr_headless_backend *)wlr_backend;
  }
  
  static bool backend_start(struct wlr_backend *wlr_backend) {
  	struct wlr_headless_backend *backend =
  		headless_backend_from_backend(wlr_backend);
  	wlr_log(WLR_INFO, "Starting headless backend");
  
  	struct wlr_headless_output *output;
  	wl_list_for_each(output, &backend->outputs, link) {
  		wl_event_source_timer_update(output->frame_timer, output->frame_delay);
  		wlr_output_update_enabled(&output->wlr_output, true);
  		wlr_signal_emit_safe(&backend->backend.events.new_output,
  			&output->wlr_output);
  	}
  
  	struct wlr_headless_input_device *input_device;
  	wl_list_for_each(input_device, &backend->input_devices, link) {
  		wlr_signal_emit_safe(&backend->backend.events.new_input,
  			&input_device->wlr_input_device);
  	}
  
  	backend->started = true;
  	return true;
  }
  
  static void backend_destroy(struct wlr_backend *wlr_backend) {
  	struct wlr_headless_backend *backend =
  		headless_backend_from_backend(wlr_backend);
  	if (!wlr_backend) {
  		return;
  	}
  
  	wl_list_remove(&backend->display_destroy.link);
  
  	struct wlr_headless_output *output, *output_tmp;
  	wl_list_for_each_safe(output, output_tmp, &backend->outputs, link) {
  		wlr_output_destroy(&output->wlr_output);
  	}
  
  	struct wlr_headless_input_device *input_device, *input_device_tmp;
  	wl_list_for_each_safe(input_device, input_device_tmp,
  			&backend->input_devices, link) {
  		wlr_input_device_destroy(&input_device->wlr_input_device);
  	}
  
  	wlr_backend_finish(wlr_backend);
  
  	free(backend);
  }
  
  static uint32_t get_buffer_caps(struct wlr_backend *wlr_backend) {
  	return WLR_BUFFER_CAP_DATA_PTR
  		| WLR_BUFFER_CAP_DMABUF
  		| WLR_BUFFER_CAP_SHM;
  }
  
  static const struct wlr_backend_impl backend_impl = {
  	.start = backend_start,
  	.destroy = backend_destroy,
  	.get_buffer_caps = get_buffer_caps,
  };
  
  static void handle_display_destroy(struct wl_listener *listener, void *data) {
  	struct wlr_headless_backend *backend =
  		wl_container_of(listener, backend, display_destroy);
  	backend_destroy(&backend->backend);
  }
  
  struct wlr_backend *wlr_headless_backend_create(struct wl_display *display) {
  	wlr_log(WLR_INFO, "Creating headless backend");
  
  	struct wlr_headless_backend *backend =
  		calloc(1, sizeof(struct wlr_headless_backend));
  	if (!backend) {
  		wlr_log(WLR_ERROR, "Failed to allocate wlr_headless_backend");
  		return NULL;
  	}
  
  	wlr_backend_init(&backend->backend, &backend_impl);
  
  	backend->display = display;
  	wl_list_init(&backend->outputs);
  	wl_list_init(&backend->input_devices);
  
  	backend->display_destroy.notify = handle_display_destroy;
  	wl_display_add_destroy_listener(display, &backend->display_destroy);
  
  	return &backend->backend;
  }
  
  bool wlr_backend_is_headless(struct wlr_backend *backend) {
  	return backend->impl == &backend_impl;
  }
  