backend/wayland: maintain a list of displays

backend/wayland/backend.c

@@ -236,6 +236,34 @@ static const struct zwp_linux_dmabuf_feedback_v1_listener
 	.tranche_flags = linux_dmabuf_feedback_v1_handle_tranche_flags,
 };
 
+static void wlr_output_handle_scale(void *data,
+		struct wl_output *wl_output, int32_t factor) {
+	struct wlr_wl_remote_output *output = data;
+	output->scale = factor;
+}
+
+static void wlr_output_handle_geometry(void *data, struct wl_output *wl_output,
+		int32_t x, int32_t y, int32_t phys_width, int32_t phys_height,
+		int32_t subpixel, const char *make, const char *model, int32_t transform) {
+	// This is intentionally left blank
+}
+
+static void wlr_output_handle_mode(void *data, struct wl_output *wl_output,
+		uint32_t flags, int32_t width, int32_t height, int32_t refresh) {
+	// This is intentionally left blank
+}
+
+static void wlr_output_handle_done(void *data, struct wl_output *wl_output) {
+	// This is intentionally left blank
+}
+
+static const struct wl_output_listener output_listener = {
+	.scale = wlr_output_handle_scale,
+	.geometry = wlr_output_handle_geometry,
+	.mode = wlr_output_handle_mode,
+	.done = wlr_output_handle_done
+};
+
 static bool device_has_name(const drmDevice *device, const char *name) {
 	for (size_t i = 0; i < DRM_NODE_MAX; i++) {
 		if (!(device->available_nodes & (1 << i))) {
@@ -393,6 +421,24 @@ static void registry_global(void *data, struct wl_registry *registry,
 	} else if (strcmp(iface, xdg_activation_v1_interface.name) == 0) {
 		wl->activation_v1 = wl_registry_bind(registry, name,
 			&xdg_activation_v1_interface, 1);
+	} else if (strcmp(iface, wl_output_interface.name) == 0) {
+		struct wlr_wl_remote_output *output = calloc(1, sizeof(*output));
+		if (!output) {
+			return;
+		}
+
+		struct wl_output *wl_output = wl_registry_bind(registry, name, &wl_output_interface, 2);
+		if (!wl_output) {
+			free(output);
+			return;
+		}
+
+		output->output = wl_output;
+		output->scale = 1;
+		output->name = name;
+
+		wl_list_insert(&wl->remote_outputs, &output->link);
+		wl_output_add_listener(wl_output, &output_listener, output);
 	}
 }
 
@@ -407,6 +453,15 @@ static void registry_global_remove(void *data, struct wl_registry *registry,
 			break;
 		}
 	}
+
+	struct wlr_wl_remote_output *output;
+	wl_list_for_each(output, &wl->remote_outputs, link) {
+		if (output->name == name) {
+			wl_list_remove(&output->link);
+			free(output);
+			break;
+		}
+	}
 }
 
 static const struct wl_registry_listener registry_listener = {
@@ -466,6 +521,13 @@ static void backend_destroy(struct wlr_backend *backend) {
 		destroy_wl_buffer(buffer);
 	}
 
+	struct wlr_wl_remote_output *remote_output, *tmp_remote_output;
+	wl_list_for_each_safe(remote_output, tmp_remote_output,
+			&wl->remote_outputs, link) {
+		wl_output_release(remote_output->output);
+		free(remote_output);
+	}
+
 	wlr_backend_finish(backend);
 
 	wl_list_remove(&wl->local_display_destroy.link);
@@ -560,6 +622,7 @@ struct wlr_backend *wlr_wl_backend_create(struct wl_display *display,
 	wl_list_init(&wl->outputs);
 	wl_list_init(&wl->seats);
 	wl_list_init(&wl->buffers);
+	wl_list_init(&wl->remote_outputs);
 	wl->presentation_clock = CLOCK_MONOTONIC;
 
 	wl->remote_display = wl_display_connect(remote);

include/backend/wayland.h

@@ -47,9 +47,21 @@ struct wlr_wl_backend {
 	struct wlr_drm_format_set linux_dmabuf_v1_formats;
 	struct wl_drm *legacy_drm;
 	struct xdg_activation_v1 *activation_v1;
+	struct wl_list remote_outputs; // wlr_wl_remote_output.link
 	char *drm_render_name;
 };
 
+struct wlr_wl_remote_output {
+	struct wl_output *output;
+	uint32_t scale;
+
+	// we use this to identify the output in the
+	// global registry so that we can remove it later
+	uint32_t name;
+
+	struct wl_list link; // wlr_wl_backend.remote_outputs
+};
+
 struct wlr_wl_buffer {
 	struct wlr_buffer *buffer;
 	struct wl_buffer *wl_buffer;