surface: Make send_enter store entered outputs

wlr_surface_send_enter now stores outputs that have been entered.
Combined with a new 'bind' event on wlr_output, this allows us to delay
enter events as necessary until the respective wl_output global has been
bound.

Closes: https://github.com/swaywm/wlroots/issues/2466

include/wlr/types/wlr_output.h

@@ -166,6 +166,8 @@ struct wlr_output {
 		struct wl_signal commit; // wlr_output_event_commit
 		// Emitted right after the buffer has been presented to the user
 		struct wl_signal present; // wlr_output_event_present
+		// Emitted after a client bound the wl_output global
+		struct wl_signal bind; // wlr_output_event_bind
 		struct wl_signal enable;
 		struct wl_signal mode;
 		struct wl_signal scale;
@@ -233,6 +235,11 @@ struct wlr_output_event_present {
 	uint32_t flags; // enum wlr_output_present_flag
 };
 
+struct wlr_output_event_bind {
+	struct wlr_output *output;
+	struct wl_resource *resource;
+};
+
 struct wlr_surface;
 
 /**

include/wlr/types/wlr_surface.h

@@ -67,6 +67,15 @@ struct wlr_surface_role {
 	void (*precommit)(struct wlr_surface *surface);
 };
 
+struct wlr_surface_output {
+	struct wlr_surface *surface;
+	struct wlr_output *output;
+
+	struct wl_list link; // wlr_surface::current_outputs
+	struct wl_listener bind;
+	struct wl_listener destroy;
+};
+
 struct wlr_surface {
 	struct wl_resource *resource;
 	struct wlr_renderer *renderer;
@@ -126,6 +135,8 @@ struct wlr_surface {
 	// wlr_subsurface::parent_pending_link
 	struct wl_list subsurface_pending_list;
 
+	struct wl_list current_outputs; // wlr_surface_output::link
+
 	struct wl_listener renderer_destroy;
 
 	void *data;

types/wlr_output.c

@@ -93,6 +93,13 @@ static void output_bind(struct wl_client *wl_client, void *data,
 	send_current_mode(resource);
 	send_scale(resource);
 	send_done(resource);
+
+	struct wlr_output_event_bind evt = {
+		.output = output,
+		.resource = resource,
+	};
+
+	wlr_signal_emit_safe(&output->events.bind, &evt);
 }
 
 void wlr_output_create_global(struct wlr_output *output) {
@@ -333,6 +340,7 @@ void wlr_output_init(struct wlr_output *output, struct wlr_backend *backend,
 	wl_signal_init(&output->events.precommit);
 	wl_signal_init(&output->events.commit);
 	wl_signal_init(&output->events.present);
+	wl_signal_init(&output->events.bind);
 	wl_signal_init(&output->events.enable);
 	wl_signal_init(&output->events.mode);
 	wl_signal_init(&output->events.scale);

types/wlr_surface.c

@@ -616,9 +616,16 @@ static void subsurface_destroy(struct wlr_subsurface *subsurface) {
 	free(subsurface);
 }
 
+static void surface_output_destroy(struct wlr_surface_output *surface_output);
+
 static void surface_handle_resource_destroy(struct wl_resource *resource) {
+	struct wlr_surface_output *surface_output, *tmp;
 	struct wlr_surface *surface = wlr_surface_from_resource(resource);
 
+	wl_list_for_each_safe(surface_output, tmp, &surface->current_outputs, link) {
+		surface_output_destroy(surface_output);
+	}
+
 	wlr_signal_emit_safe(&surface->events.destroy, surface);
 
 	wl_list_remove(wl_resource_get_link(surface->resource));
@@ -676,6 +683,7 @@ struct wlr_surface *wlr_surface_create(struct wl_client *client,
 	wl_signal_init(&surface->events.new_subsurface);
 	wl_list_init(&surface->subsurfaces);
 	wl_list_init(&surface->subsurface_pending_list);
+	wl_list_init(&surface->current_outputs);
 	pixman_region32_init(&surface->buffer_damage);
 	pixman_region32_init(&surface->opaque_region);
 	pixman_region32_init(&surface->input_region);
@@ -1091,10 +1099,59 @@ struct wlr_surface *wlr_surface_surface_at(struct wlr_surface *surface,
 	return NULL;
 }
 
+static void surface_output_destroy(struct wlr_surface_output *surface_output) {
+	wl_list_remove(&surface_output->bind.link);
+	wl_list_remove(&surface_output->destroy.link);
+	wl_list_remove(&surface_output->link);
+
+	free(surface_output);
+}
+
+static void surface_handle_output_bind(struct wl_listener *listener,
+		void *data) {
+	struct wlr_output_event_bind *evt = data;
+	struct wlr_surface_output *surface_output =
+		wl_container_of(listener, surface_output, bind);
+	struct wl_client *client = wl_resource_get_client(
+			surface_output->surface->resource);
+	if (client == wl_resource_get_client(evt->resource)) {
+		wl_surface_send_enter(surface_output->surface->resource, evt->resource);
+	}
+}
+
+static void surface_handle_output_destroy(struct wl_listener *listener,
+		void *data) {
+	struct wlr_surface_output *surface_output =
+		wl_container_of(listener, surface_output, destroy);
+	surface_output_destroy(surface_output);
+}
+
 void wlr_surface_send_enter(struct wlr_surface *surface,
 		struct wlr_output *output) {
 	struct wl_client *client = wl_resource_get_client(surface->resource);
+	struct wlr_surface_output *surface_output;
 	struct wl_resource *resource;
+
+	wl_list_for_each(surface_output, &surface->current_outputs, link) {
+		if (surface_output->output == output) {
+			return;
+		}
+	}
+
+	surface_output = calloc(1, sizeof(struct wlr_surface_output));
+	if (surface_output == NULL) {
+		return;
+	}
+	surface_output->bind.notify = surface_handle_output_bind;
+	surface_output->destroy.notify = surface_handle_output_destroy;
+
+	wl_signal_add(&output->events.bind, &surface_output->bind);
+	wl_signal_add(&output->events.destroy, &surface_output->destroy);
+
+	surface_output->surface = surface;
+	surface_output->output = output;
+	wl_list_insert(&surface->current_outputs, &surface_output->link);
+
 	wl_resource_for_each(resource, &output->resources) {
 		if (client == wl_resource_get_client(resource)) {
 			wl_surface_send_enter(surface->resource, resource);
@@ -1105,12 +1162,21 @@ void wlr_surface_send_enter(struct wlr_surface *surface,
 void wlr_surface_send_leave(struct wlr_surface *surface,
 		struct wlr_output *output) {
 	struct wl_client *client = wl_resource_get_client(surface->resource);
+	struct wlr_surface_output *surface_output, *tmp;
 	struct wl_resource *resource;
+
+	wl_list_for_each_safe(surface_output, tmp,
+			&surface->current_outputs, link) {
+		if (surface_output->output == output) {
+			surface_output_destroy(surface_output);
 			wl_resource_for_each(resource, &output->resources) {
 				if (client == wl_resource_get_client(resource)) {
 					wl_surface_send_leave(surface->resource, resource);
 				}
 			}
+			break;
+		}
+	}
 }
 
 void wlr_surface_send_frame_done(struct wlr_surface *surface,