compositor: add .present event to struct wlr_surface_output

For the implementation of fifo-v1, we need to be able to track
the presentation of individual surface commits.
This is done already in `wlr_presentation_time`, but the way
that is implemented is suited only for use by clients through the
protocol interface (.feedback requests).

Here we use the `surface_output` structure, which is a low-level
structure that links wlr_surfaces with wlr_outputs.
Within this structure we listen to the surface's and the output's
.commit events. Through these 2 we link a surface commit to an output
commit. Then, a new struct wlr_surface_output_commit is created which
listens to the output's .present event.

For the interface to this functionality, 2 elements are introduced:
the new .present event in struct wlr_surface_output, which signals
listeners whether a particular pair of (surface_seq, output_seq) has
been presented or discarded, and the wlr_surface_textured_on_output()
function, used by the scene logic to inform the implementation that
the surface's buffer has been textured on a particular output.

Signed-off-by: Sergio Gómez <sergio.g.delreal@gmail.com>

include/wlr/types/wlr_compositor.h

@@ -118,14 +118,47 @@ struct wlr_surface_role {
 	void (*destroy)(struct wlr_surface *surface);
 };
 
+struct wlr_surface_output_event_present {
+	struct wlr_surface_output_commit *commit;
+	struct timespec when;
+};
+
+struct wlr_surface_output_commit {
+	struct wlr_surface_output *surface_output;
+
+	uint32_t surface_seq;
+	uint32_t output_seq;
+	bool committed_on_surface;
+	bool textured_on_output;
+	bool committed_on_output;
+	bool presented_on_output;
+
+	struct wl_list link; // wlr_surface_output.commits
+
+	struct {
+		struct wl_listener output_present;
+	} WLR_PRIVATE;
+};
+
 struct wlr_surface_output {
 	struct wlr_surface *surface;
 	struct wlr_output *output;
 
 	struct wl_list link; // wlr_surface.current_outputs
 
+	struct wlr_surface_output_commit current_commit;
+	struct wl_list commits; // wlr_surface_output_commit.link
+	struct {
+		/**
+		 * Signals that a surface commit has been presented or discarded on the output.
+		 */
+		struct wl_signal present;
+	} events;
+
 	struct {
 		struct wl_listener bind;
+		struct wl_listener output_commit;
+		struct wl_listener surface_commit;
 		struct wl_listener destroy;
 	} WLR_PRIVATE;
 };
@@ -399,6 +432,12 @@ void wlr_surface_send_enter(struct wlr_surface *surface,
 void wlr_surface_send_leave(struct wlr_surface *surface,
 		struct wlr_output *output);
 
+/**
+ * Mark the current surface's buffer as textured on the given output.
+ */
+void wlr_surface_textured_on_output(struct wlr_surface *surface,
+	struct wlr_output *output);
+
 /**
  * Complete the queued frame callbacks for this surface.
  *

types/scene/surface.c

@@ -141,6 +141,8 @@ static void handle_scene_buffer_output_sample(
 	} else {
 		wlr_presentation_surface_textured_on_output(surface->surface, output);
 	}
+
+	wlr_surface_textured_on_output(surface->surface, output);
 }
 
 static void handle_scene_buffer_frame_done(

types/wlr_compositor.c

@@ -1051,9 +1051,18 @@ struct wlr_surface *wlr_surface_surface_at(struct wlr_surface *surface,
 
 static void surface_output_destroy(struct wlr_surface_output *surface_output) {
 	wl_list_remove(&surface_output->bind.link);
+	wl_list_remove(&surface_output->output_commit.link);
+	wl_list_remove(&surface_output->surface_commit.link);
 	wl_list_remove(&surface_output->destroy.link);
 	wl_list_remove(&surface_output->link);
 
+	struct wlr_surface_output_commit *commit, *tmp;
+	wl_list_for_each_safe(commit, tmp, &surface_output->commits, link) {
+		wl_list_remove(&commit->link);
+		wl_list_remove(&commit->output_present.link);
+		free(commit);
+	}
+
 	free(surface_output);
 }
 
@@ -1069,6 +1078,87 @@ static void surface_handle_output_bind(struct wl_listener *listener,
 	}
 }
 
+static void commit_handle_output_present(struct wl_listener *listener,
+		void *data) {
+	struct wlr_surface_output_commit *commit =
+		wl_container_of(listener, commit, output_present);
+	struct wlr_surface_output *surface_output = commit->surface_output;
+
+	struct wlr_output_event_present *output_event = data;
+	assert(commit->output_seq >= output_event->commit_seq);
+
+	if (commit->output_seq > output_event->commit_seq) {
+		return;
+	}
+
+	struct wlr_surface_output_event_present surface_output_event_present = {0};
+	surface_output_event_present.commit = commit;
+	surface_output_event_present.when = output_event->when;
+	commit->presented_on_output = output_event->presented;
+	wl_signal_emit_mutable(&surface_output->events.present, &surface_output_event_present);
+
+	wl_list_remove(&commit->link);
+	wl_list_remove(&commit->output_present.link);
+	free(commit);
+}
+
+static void surface_handle_output_commit(struct wl_listener *listener,
+		void *data) {
+	struct wlr_surface_output *surface_output =
+		wl_container_of(listener, surface_output, output_commit);
+	if (!surface_output->current_commit.textured_on_output) {
+		return;
+	}
+
+	struct wlr_surface_output_commit *commit = calloc(1, sizeof(*commit));
+	*commit = surface_output->current_commit;
+	commit->committed_on_output = true;
+	commit->output_present.notify = commit_handle_output_present;
+	wl_signal_add(&surface_output->output->events.present, &commit->output_present);
+	wl_list_insert(&surface_output->commits, &commit->link);
+
+	// reset current commit
+	surface_output->current_commit = (struct wlr_surface_output_commit){0};
+}
+
+void wlr_surface_textured_on_output(struct wlr_surface *surface,
+		struct wlr_output *output) {
+	struct wlr_surface_output *surface_output;
+	wl_list_for_each(surface_output, &surface->current_outputs, link) {
+		if (surface_output->output == output) {
+			break;
+		}
+	}
+	assert(surface_output->output == output);
+
+	if (!surface_output->current_commit.committed_on_surface) {
+		return;
+	}
+
+	surface_output->current_commit.textured_on_output = true;
+	surface_output->current_commit.output_seq = surface_output->output->commit_seq+1;
+}
+
+static void surface_handle_surface_commit(struct wl_listener *listener,
+		void *data) {
+	struct wlr_surface_output *surface_output =
+		wl_container_of(listener, surface_output, surface_commit);
+	if (wl_list_empty(&surface_output->events.present.listener_list)) {
+		return;
+	}
+
+	struct wlr_surface_output_commit *current_commit = &surface_output->current_commit;
+	// if a surface commit is replaced by another one before it is latched onto the output,
+	// it won't be presented.
+	if (current_commit->committed_on_surface) {
+		struct wlr_surface_output_event_present event_present = { .commit = current_commit };
+		wl_signal_emit_mutable(&surface_output->events.present, &event_present);
+	}
+	current_commit->surface_output = surface_output;
+	current_commit->committed_on_surface = true;
+	current_commit->surface_seq = surface_output->surface->current.seq;
+}
+
 static void surface_handle_output_destroy(struct wl_listener *listener,
 		void *data) {
 	struct wlr_surface_output *surface_output =
@@ -1093,10 +1183,17 @@ void wlr_surface_send_enter(struct wlr_surface *surface,
 		return;
 	}
 	surface_output->bind.notify = surface_handle_output_bind;
+	surface_output->output_commit.notify = surface_handle_output_commit;
+	surface_output->surface_commit.notify = surface_handle_surface_commit;
 	surface_output->destroy.notify = surface_handle_output_destroy;
 
 	wl_signal_add(&output->events.bind, &surface_output->bind);
+	wl_signal_add(&output->events.commit, &surface_output->output_commit);
 	wl_signal_add(&output->events.destroy, &surface_output->destroy);
+	wl_signal_add(&surface->events.commit, &surface_output->surface_commit);
+
+	wl_signal_init(&surface_output->events.present);
+	wl_list_init(&surface_output->commits);
 
 	surface_output->surface = surface;
 	surface_output->output = output;