compositor: Add the fifo-v1 protocol

Add support for the fifo protocol, which allows an application to submit
a content update that can only be applied after the previous content
update has been active for a display refresh.

Signed-off-by: Derek Foreman <derek.foreman@collabora.com>

include/libweston/libweston.h

@@ -556,6 +556,9 @@ struct weston_output {
 
 	/** Needs to rebuild the paint node z ordered list */
 	bool paint_node_list_needs_rebuild;
+
+	/** fifo_v1 - list of surfaces to clear next repaint */
+	struct wl_list fifo_barrier_surfaces;
 };
 
 enum weston_pointer_motion_mask {
@@ -1796,6 +1799,10 @@ struct weston_surface_state {
 	 * color_management_surface_v1_interface.unset_image_description */
 	struct weston_color_profile *color_profile;
 	const struct weston_render_intent_info *render_intent;
+
+	/* wp_fifo_v1 */
+	bool fifo_barrier;
+	bool fifo_wait;
 };
 
 struct weston_surface_activation_data {
@@ -1975,6 +1982,11 @@ struct weston_surface {
 	 * calculations when considering this surface's visibility.
 	 */
 	uint32_t output_visibility_dirty_mask;
+
+	/** fifo_v1 */
+	struct weston_fifo *fifo;
+	bool fifo_barrier; /* Cleared after display */
+	struct wl_list fifo_barrier_link; /* output::fifo_barrier_surfaces */
 };
 
 struct weston_subsurface {

libweston/compositor.c

@@ -90,6 +90,7 @@
 #include "weston-trace.h"
 #include "renderer-vulkan/vulkan-renderer.h"
 
+#include <libweston/fifo.h>
 #include "weston-log-internal.h"
 
 /**
@@ -1006,6 +1007,8 @@ weston_surface_create(struct weston_compositor *compositor)
 	/* Also part of the CM&HDR protocol extension implementation. */
 	weston_surface_update_preferred_color_profile(surface);
 
+	wl_list_init(&surface->fifo_barrier_link);
+
 	return surface;
 }
 
@@ -2722,6 +2725,8 @@ weston_surface_unref(struct weston_surface *surface)
 	if (surface->cm_surface)
 		wl_resource_set_user_data(surface->cm_surface, NULL);
 
+	wl_list_remove(&surface->fifo_barrier_link);
+
 	free(surface);
 }
 
@@ -3652,6 +3657,13 @@ weston_output_latch(struct weston_output *output)
 	compositor->latched = true;
 
 	wl_signal_emit(&output->post_latch_signal, output);
+
+	/* We have now latched. It doesn't matter that the repaint
+	 * hasn't happened yet - it is inevitable. We can now clear
+	 * fifo barriers, but must not apply transactions again
+	 * until after the repaint.
+	 */
+	weston_fifo_output_clear_barriers(output);
 }
 
 static int
@@ -3819,8 +3831,9 @@ weston_output_check_repaint(struct weston_output *output, struct timespec *now)
 	    compositor->state == WESTON_COMPOSITOR_OFFSCREEN)
 		goto out;
 
-	/* We don't actually need to repaint this output; drop it from
-	 * repaint until something causes damage. */
+	if (weston_fifo_output_has_barriers(output))
+		output->repaint_needed = true;
+
 	if (!output->repaint_needed)
 		goto out;
 
@@ -7604,6 +7617,8 @@ weston_compositor_remove_output(struct weston_output *output)
 
 	weston_output_capture_info_destroy(&output->capture_info);
 
+	weston_fifo_output_clear_barriers(output);
+
 	compositor->output_id_pool &= ~(1u << output->id);
 	output->id = 0xffffffff; /* invalid */
 }
@@ -8040,6 +8055,8 @@ weston_output_init(struct weston_output *output,
 	output->gpu_track_id = 0;
 	output->paint_track_id = 0;
 	output->presentation_track_id = 0;
+
+	wl_list_init(&output->fifo_barrier_surfaces);
 }
 
 /** Adds weston_output object to pending output list.
@@ -9692,6 +9709,9 @@ weston_compositor_create(struct wl_display *display,
 			      ec, bind_tearing_controller))
 		goto fail;
 
+	if (fifo_setup(ec) != 0)
+		goto fail;
+
 	if (weston_input_init(ec) != 0)
 		goto fail;
 

libweston/fifo.c

@@ -0,0 +1,270 @@
+/*
+ * Copyright 2025 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <assert.h>
+
+#include <libweston/libweston.h>
+#include <libweston/fifo.h>
+#include "libweston-internal.h"
+#include "shared/helpers.h"
+#include "shared/xalloc.h"
+
+struct weston_fifo {
+	struct weston_surface *surface;
+	struct wl_listener surface_destroy_listener;
+	uint64_t flow_id;
+};
+
+static void
+fifo_destructor(struct wl_resource *resource)
+{
+	struct weston_fifo *fifo = wl_resource_get_user_data(resource);
+
+	if (fifo->surface)
+		wl_list_remove(&fifo->surface_destroy_listener.link);
+
+	free(fifo);
+}
+
+static void
+fifo_set_barrier(struct wl_client *client, struct wl_resource *resource)
+{
+	struct weston_fifo *fifo = wl_resource_get_user_data(resource);
+	struct weston_surface *surface = fifo->surface;
+
+	if (!surface) {
+		wl_resource_post_error(resource,
+				       WP_FIFO_V1_ERROR_SURFACE_DESTROYED,
+				       "surface destroyed");
+		return;
+	}
+	surface->pending.fifo_barrier = true;
+}
+
+static void
+fifo_wait_barrier(struct wl_client *client, struct wl_resource *resource)
+{
+	struct weston_fifo *fifo = wl_resource_get_user_data(resource);
+	struct weston_surface *surface = fifo->surface;
+
+	if (!surface) {
+		wl_resource_post_error(resource,
+				       WP_FIFO_V1_ERROR_SURFACE_DESTROYED,
+				       "surface destroyed");
+		return;
+	}
+	surface->pending.fifo_wait = true;
+}
+
+static void
+fifo_destroy(struct wl_client *client, struct wl_resource *resource)
+{
+	struct weston_fifo *fifo = wl_resource_get_user_data(resource);
+	struct weston_surface *surface = fifo->surface;
+
+	wl_resource_destroy(resource);
+	if (!surface)
+		return;
+
+	surface->fifo = NULL;
+}
+
+static const struct wp_fifo_v1_interface weston_fifo_interface = {
+	.set_barrier = fifo_set_barrier,
+	.wait_barrier = fifo_wait_barrier,
+	.destroy = fifo_destroy,
+};
+
+static void
+fifo_manager_destroy(struct wl_client *client, struct wl_resource *resource)
+{
+	wl_resource_destroy(resource);
+}
+
+static void
+fifo_surface_destroy_cb(struct wl_listener *listener, void *data)
+{
+	struct weston_fifo *fifo =
+		container_of(listener,
+			struct weston_fifo, surface_destroy_listener);
+
+	fifo->surface = NULL;
+}
+
+static void
+fifo_manager_get_fifo(struct wl_client *client,
+		      struct wl_resource *fm_resource,
+		      uint32_t id,
+		      struct wl_resource *surface_resource)
+{
+	struct weston_fifo *fifo;
+	struct weston_surface *surface = wl_resource_get_user_data(surface_resource);
+	struct wl_resource *res;
+
+	if (surface->fifo) {
+		wl_resource_post_error(fm_resource,
+				       WP_FIFO_MANAGER_V1_ERROR_ALREADY_EXISTS,
+				       "Fifo resource already exists on surface");
+		return;
+	}
+
+	res = wl_resource_create(client, &wp_fifo_v1_interface,
+				 wl_resource_get_version(fm_resource), id);
+	fifo = xzalloc(sizeof *fifo);
+	fifo->surface = surface;
+	fifo->surface_destroy_listener.notify = fifo_surface_destroy_cb;
+	wl_signal_add(&surface->destroy_signal, &fifo->surface_destroy_listener);
+	wl_resource_set_implementation(res, &weston_fifo_interface, fifo,
+				       fifo_destructor);
+	surface->fifo = fifo;
+}
+
+static const struct wp_fifo_manager_v1_interface fifo_manager_interface_v1 = {
+	.destroy = fifo_manager_destroy,
+	.get_fifo = fifo_manager_get_fifo,
+};
+
+static void
+bind_fifo_manager(struct wl_client *client,
+		  void *data,
+		  uint32_t version,
+		  uint32_t id)
+{
+	struct wl_resource *resource;
+	struct weston_compositor *compositor = data;
+
+	resource = wl_resource_create(client,
+				      &wp_fifo_manager_v1_interface,
+				      version, id);
+	if (!resource) {
+		wl_client_post_no_memory(client);
+		return;
+	}
+
+	wl_resource_set_implementation(resource,
+				       &fifo_manager_interface_v1,
+				       compositor, NULL);
+}
+
+/** Advertise fifo protocol support
+ *
+ * Sets up fifo_v1 support so it is advertiszed to clients.
+ *
+ * \param compositor The compositor to init for.
+ * \return Zero on success, -1 on failure.
+ */
+int
+fifo_setup(struct weston_compositor *compositor)
+{
+        if (!wl_global_create(compositor->wl_display,
+                              &wp_fifo_manager_v1_interface,
+                              1, compositor,
+                              bind_fifo_manager))
+                return -1;
+
+        return 0;
+}
+
+static void
+weston_fifo_surface_clear_barrier(struct weston_surface *surface)
+{
+	surface->fifo_barrier = false;
+	wl_list_remove(&surface->fifo_barrier_link);
+	wl_list_init(&surface->fifo_barrier_link);
+}
+
+void
+weston_fifo_surface_set_barrier(struct weston_surface *surface)
+{
+	/* If nothing is waiting on barriers, we could set multiple times
+	 * before a repaint occurs.
+	 *
+	 * Theoretically, this surface could have a different primary
+	 * output than the last time a barrier was created, so let's
+	 * just blow away any old barrier (should one exist) before
+	 * setting the current one.
+	 */
+	weston_fifo_surface_clear_barrier(surface);
+
+	/* If the surface isn't associated with an output, we have no way
+	 * to clear a barrier - so just don't set one.
+	 */
+	if (!surface->output)
+		return;
+
+	surface->fifo_barrier = true;
+	wl_list_insert(&surface->output->fifo_barrier_surfaces,
+		       &surface->fifo_barrier_link);
+}
+
+void
+weston_fifo_output_clear_barriers(struct weston_output *output)
+{
+	struct weston_surface *surf, *tmp;
+
+	wl_list_for_each_safe(surf, tmp,
+			      &output->fifo_barrier_surfaces,
+			      fifo_barrier_link)
+		weston_fifo_surface_clear_barrier(surf);
+}
+
+bool
+weston_fifo_output_has_barriers(struct weston_output *output)
+{
+	return !wl_list_empty(&output->fifo_barrier_surfaces);
+}
+
+bool
+weston_fifo_surface_state_ready(struct weston_surface *surface,
+				struct weston_surface_state *state)
+{
+	struct weston_subsurface *sub = weston_surface_to_subsurface(surface);
+	bool e_sync = sub && sub->effectively_synchronized;
+
+	if (!state->fifo_wait)
+		return true;
+
+	/* The barrier is clear. */
+	if (!surface->fifo_barrier)
+		return true;
+
+	/* Effectively synchronized surfaces ignore fifo */
+	if (e_sync)
+		return true;
+
+	/* If there's no driving output, fifo will never clear,
+	 * so just ignore the condition.
+	 */
+	if (!surface->output)
+		return true;
+
+	/* Occluded surfaces ignore fifo */
+	if (!weston_surface_visibility_mask(surface))
+		return true;
+
+	return false;
+}

libweston/fifo.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2025 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#pragma once
+
+#include "config.h"
+
+#include "fifo-v1-server-protocol.h"
+
+int
+fifo_setup(struct weston_compositor *compositor);
+
+void
+weston_fifo_surface_set_barrier(struct weston_surface *surface);
+
+void
+weston_fifo_output_clear_barriers(struct weston_output *output);
+
+bool
+weston_fifo_output_has_barriers(struct weston_output *output);
+
+bool
+weston_fifo_surface_state_ready(struct weston_surface *surface,
+                                struct weston_surface_state *state);

libweston/meson.build

@@ -25,6 +25,7 @@ srcs_libweston = [
 	'content-protection.c',
 	'data-device.c',
 	'drm-formats.c',
+	'fifo.c',
 	'id-number-allocator.c',
 	'input.c',
 	'linux-dmabuf.c',
@@ -47,6 +48,8 @@ srcs_libweston = [
 	'weston-direct-display.c',
 	color_management_v1_protocol_c,
 	color_management_v1_server_protocol_h,
+	fifo_v1_protocol_c,
+	fifo_v1_server_protocol_h,
 	linux_dmabuf_unstable_v1_protocol_c,
 	linux_dmabuf_unstable_v1_server_protocol_h,
 	linux_explicit_synchronization_unstable_v1_protocol_c,

libweston/surface-state.c

@@ -29,6 +29,7 @@
 #include "config.h"
 
 #include <libweston/libweston.h>
+#include <libweston/fifo.h>
 #include "libweston-internal.h"
 
 #include "backend.h"
@@ -151,6 +152,9 @@ weston_surface_state_init(struct weston_surface *surface,
 
 	state->color_profile = NULL;
 	state->render_intent = NULL;
+
+	state->fifo_barrier = false;
+	state->fifo_wait = false;
 }
 
 void
@@ -480,6 +484,10 @@ weston_surface_apply_state(struct weston_surface *surface,
 	surface->is_unmapping = false;
 	surface->is_mapping = false;
 
+	if (state->fifo_barrier)
+		weston_fifo_surface_set_barrier(surface);
+	state->fifo_barrier = false;
+
 	if (weston_surface_status_invalidates_visibility(status))
 		surface->output_visibility_dirty_mask |= surface->output_mask;
 
@@ -523,6 +531,9 @@ weston_surface_schedule_repaint(struct weston_surface *surface,
 	struct weston_output *output;
 	uint32_t visible_mask;
 
+	if (surface->output && surface->fifo_barrier)
+		weston_output_schedule_repaint(surface->output);
+
 	if (status == WESTON_SURFACE_CLEAN)
 		return;
 
@@ -628,6 +639,11 @@ weston_surface_state_merge_from(struct weston_surface_state *dst,
 			    &src->feedback_list);
 	wl_list_init(&src->feedback_list);
 
+	dst->fifo_barrier = src->fifo_barrier;
+	src->fifo_barrier = false;
+	dst->fifo_wait = src->fifo_wait;
+	src->fifo_wait = false;
+
 	dst->status |= src->status;
 	src->status = WESTON_SURFACE_CLEAN;
 }
@@ -748,6 +764,9 @@ static bool
 weston_surface_state_ready(struct weston_surface *surface,
 			   struct weston_surface_state *state)
 {
+	if (!weston_fifo_surface_state_ready(surface, state))
+		return false;
+
 	return true;
 }
 

tests/fifo-test.c

@@ -0,0 +1,691 @@
+/*
+ * Copyright © 2025 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+
+#include "libweston-internal.h"
+#include "weston-test-client-helper.h"
+#include "weston-test-fixture-compositor.h"
+#include "weston-test-assert.h"
+#include "presentation-time-client-protocol.h"
+#include "shared/xalloc.h"
+
+static int feedback_count;
+
+struct feedback {
+	struct client *client;
+	struct wp_presentation_feedback *obj;
+	bool expect_present;
+};
+
+enum fifo_barrier_status {
+	FIFO_BARRIER_INACTIVE = 0,
+	FIFO_BARRIER_ACTIVE,
+};
+
+enum rearm_breakpoint {
+	REARM_BREAKPOINT_NO = 0,
+	REARM_BREAKPOINT_YES,
+};
+
+static enum test_result_code
+fixture_setup(struct weston_test_harness *harness)
+{
+	struct compositor_setup setup;
+
+	compositor_setup_defaults(&setup);
+	setup.renderer = WESTON_RENDERER_PIXMAN;
+	setup.width = 320;
+	setup.height = 240;
+	setup.shell = SHELL_TEST_DESKTOP;
+	setup.logging_scopes = "log,test-harness-plugin";
+	setup.refresh = HIGHEST_OUTPUT_REFRESH;
+
+	return weston_test_harness_execute_as_client(harness, &setup);
+}
+DECLARE_FIXTURE_SETUP(fixture_setup);
+
+static struct buffer *
+surface_commit_color(struct client *client, struct wl_surface *surface,
+		     pixman_color_t *color, int width, int height)
+{
+	struct buffer *buf;
+
+	buf = create_shm_buffer_a8r8g8b8(client, width, height);
+	fill_image_with_color(buf->image, color);
+	wl_surface_attach(surface, buf->proxy, 0, 0);
+	wl_surface_damage_buffer(surface, 0, 0, width, height);
+	wl_surface_commit(surface);
+
+	return buf;
+}
+
+/* Ensure we can only have one fifo object for a surface */
+TEST(get_two_fifos)
+{
+	struct client *client;
+	struct wp_fifo_v1 *fifo1, *fifo2;
+
+	client = create_client_and_test_surface(100, 50, 100, 100);
+	test_assert_ptr_not_null(client);
+
+	fifo1 = wp_fifo_manager_v1_get_fifo(client->fifo_manager, client->surface->wl_surface);
+	fifo2 = wp_fifo_manager_v1_get_fifo(client->fifo_manager, client->surface->wl_surface);
+	expect_protocol_error(client, &wp_fifo_manager_v1_interface,
+			      WP_FIFO_MANAGER_V1_ERROR_ALREADY_EXISTS);
+	wp_fifo_v1_destroy(fifo2);
+	wp_fifo_v1_destroy(fifo1);
+	client_destroy(client);
+
+	return RESULT_OK;
+}
+
+/* Ensure we can get a second fifo for a surface if we destroy the first. */
+TEST(get_two_fifos_safely)
+{
+	struct client *client;
+	struct wp_fifo_v1 *fifo;
+
+	client = create_client_and_test_surface(100, 50, 100, 100);
+	test_assert_ptr_not_null(client);
+
+	fifo = wp_fifo_manager_v1_get_fifo(client->fifo_manager, client->surface->wl_surface);
+	wp_fifo_v1_destroy(fifo);
+	fifo = wp_fifo_manager_v1_get_fifo(client->fifo_manager, client->surface->wl_surface);
+	wp_fifo_v1_destroy(fifo);
+	client_roundtrip(client);
+	client_destroy(client);
+
+	return RESULT_OK;
+}
+
+/* Ensure the appropriate error occurs for using a fifo object associated
+ * with a destroyed surface.
+ */
+TEST(use_fifo_on_destroyed_surface)
+{
+	struct client *client;
+	struct wp_fifo_v1 *fifo;
+
+	client = create_client_and_test_surface(100, 50, 100, 100);
+	test_assert_ptr_not_null(client);
+
+	fifo = wp_fifo_manager_v1_get_fifo(client->fifo_manager, client->surface->wl_surface);
+	surface_destroy(client->surface);
+	client->surface = NULL;
+	wp_fifo_v1_set_barrier(fifo);
+	expect_protocol_error(client, &wp_fifo_v1_interface,
+			      WP_FIFO_V1_ERROR_SURFACE_DESTROYED);
+	wp_fifo_v1_destroy(fifo);
+	client_destroy(client);
+
+	return RESULT_OK;
+}
+
+/* Ensure the compositor doesn't explode if we delete a surface with
+ * active barriers
+ */
+TEST(fifo_delete_surface_with_barriers)
+{
+	struct client *client;
+	struct buffer *buf;
+	struct wp_fifo_v1 *fifo;
+	pixman_color_t red;
+	int i;
+
+	color_rgb888(&red, 255, 0, 0);
+
+	client = create_client_and_test_surface(100, 50, 100, 100);
+	test_assert_ptr_not_null(client);
+
+	fifo = wp_fifo_manager_v1_get_fifo(client->fifo_manager, client->surface->wl_surface);
+	wp_fifo_v1_set_barrier(fifo);
+	buf = surface_commit_color(client, client->surface->wl_surface, &red, 100, 100);
+
+	/* Load up some future transactions */
+	for (i = 0; i < 10; i++) {
+		wp_fifo_v1_set_barrier(fifo);
+		wp_fifo_v1_wait_barrier(fifo);
+		wl_surface_commit(client->surface->wl_surface);
+	}
+
+	/* Steal and destroy the surface */
+	wl_surface_destroy(client->surface->wl_surface);
+	client->surface->wl_surface = NULL;
+
+	client_roundtrip(client);
+
+	wp_fifo_v1_destroy(fifo);
+	buffer_destroy(buf);
+	client_destroy(client);
+
+	return RESULT_OK;
+}
+
+static void
+check_fifo_status(struct client *client,
+		  struct wet_testsuite_data *suite_data,
+		  enum fifo_barrier_status expected,
+		  enum rearm_breakpoint rearm)
+{
+	bool expected_fifo_barrier = expected == FIFO_BARRIER_ACTIVE;
+
+	RUN_INSIDE_BREAKPOINT(client, suite_data) {
+		struct weston_surface *surface;
+		struct wl_resource *surface_res;
+
+		test_assert_enum(breakpoint->template_->breakpoint,
+				 WESTON_TEST_BREAKPOINT_POST_LATCH);
+		surface_res = wl_client_get_object(suite_data->wl_client,
+						   wl_proxy_get_id((struct wl_proxy *)client->surface->wl_surface));
+		surface = wl_resource_get_user_data(surface_res);
+
+		test_assert_int_eq(surface->fifo_barrier, expected_fifo_barrier);
+		if (rearm == REARM_BREAKPOINT_YES)
+			REARM_BREAKPOINT(breakpoint);
+	}
+}
+
+/* Make sure N barriers provokes N redraws */
+TEST(fifo_many_barriers)
+{
+	struct wet_testsuite_data *suite_data = TEST_GET_SUITE_DATA();
+	struct client *client;
+	struct buffer *buf, *buf2;
+	struct wp_fifo_v1 *fifo;
+	pixman_color_t red;
+	int i;
+
+	color_rgb888(&red, 255, 0, 0);
+
+	client = create_client_and_test_surface(100, 50, 100, 100);
+	test_assert_ptr_not_null(client);
+
+	client_push_breakpoint(client, suite_data,
+			       WESTON_TEST_BREAKPOINT_POST_LATCH,
+			       (struct wl_proxy *) client->output->wl_output);
+
+	fifo = wp_fifo_manager_v1_get_fifo(client->fifo_manager, client->surface->wl_surface);
+	wp_fifo_v1_set_barrier(fifo);
+	buf = surface_commit_color(client, client->surface->wl_surface, &red, 100, 100);
+	/* Check that a string of commits with fifo set result in that
+	 * number of repaints.
+	 */
+	for (i = 0; i < 10; i++) {
+		wp_fifo_v1_set_barrier(fifo);
+		wp_fifo_v1_wait_barrier(fifo);
+		wl_surface_commit(client->surface->wl_surface);
+	}
+	client_roundtrip(client);
+
+	for (i = 0; i < 11; i++)
+		check_fifo_status(client, suite_data, FIFO_BARRIER_ACTIVE, REARM_BREAKPOINT_YES);
+
+	/* A new commit with a visible change will cause a repaint now, and we can
+	 * check for clear fifo status after.
+	 */
+	buf2 = surface_commit_color(client, client->surface->wl_surface, &red, 100, 100);
+	wl_surface_commit(client->surface->wl_surface);
+	client_roundtrip(client);
+	check_fifo_status(client, suite_data, FIFO_BARRIER_INACTIVE, REARM_BREAKPOINT_NO);
+
+	wp_fifo_v1_destroy(fifo);
+	buffer_destroy(buf2);
+	buffer_destroy(buf);
+	client_destroy(client);
+
+	return RESULT_OK;
+}
+
+static void
+feedback_sync_output(void *data,
+		     struct wp_presentation_feedback *presentation_feedback,
+		     struct wl_output *output)
+{
+	/* do nothing */
+}
+
+static void
+feedback_presented(void *data,
+		   struct wp_presentation_feedback *presentation_feedback,
+		   uint32_t tv_sec_hi,
+		   uint32_t tv_sec_lo,
+		   uint32_t tv_nsec,
+		   uint32_t refresh_nsec,
+		   uint32_t seq_hi,
+		   uint32_t seq_lo,
+		   uint32_t flags)
+{
+	struct feedback *fb = data;
+
+	test_assert_true(fb->expect_present);
+
+	wp_presentation_feedback_destroy(fb->obj);
+	free(fb);
+	feedback_count--;
+}
+
+static void
+feedback_discarded(void *data,
+		   struct wp_presentation_feedback *presentation_feedback)
+{
+	struct feedback *fb = data;
+
+	test_assert_false(fb->expect_present);
+
+	wp_presentation_feedback_destroy(fb->obj);
+	free(fb);
+	feedback_count--;
+}
+
+static const struct wp_presentation_feedback_listener feedback_listener = {
+	feedback_sync_output,
+	feedback_presented,
+	feedback_discarded
+};
+
+static void
+feedback_create(struct client *client,
+		struct wl_surface *surface,
+		struct wp_presentation *pres,
+		bool expect_present)
+{
+	struct feedback *fb;
+
+	fb = xzalloc(sizeof *fb);
+	fb->client = client;
+	fb->obj = wp_presentation_feedback(pres, surface);
+	wp_presentation_feedback_add_listener(fb->obj, &feedback_listener, fb);
+	fb->expect_present = expect_present;
+	feedback_count++;
+}
+
+/* Make sure fifo is ignored on occluded surfaces.
+ * This is a "may" in the spec, so this isn't necessarily rigorous,
+ * but a strong effort.
+ */
+TEST(fifo_on_occluded_surface)
+{
+	struct wl_subcompositor *subco;
+	struct wl_surface *oc_surf;
+	struct wl_region *opaque_region;
+	struct wl_subsurface *oc_subsurf;
+	struct client *client;
+	struct buffer *buf_main, *buf_main_small, *buf_sub;
+	struct wp_fifo_v1 *fifo;
+	struct wp_presentation *pres;
+	pixman_color_t red, green, blue;
+	int i;
+	bool match;
+
+	color_rgb888(&red, 255, 0, 0);
+	color_rgb888(&green, 0, 255, 0);
+	color_rgb888(&blue, 0, 0, 255);
+
+	client = create_client_and_test_surface(10, 10, 100, 100);
+	test_assert_ptr_not_null(client);
+
+	pres = client_get_presentation(client);
+
+	/* move the pointer clearly away from our screenshooting area */
+	weston_test_move_pointer(client->test->weston_test, 0, 1, 0, 2, 30);
+
+	subco = client_get_subcompositor(client);
+	oc_surf = wl_compositor_create_surface(client->wl_compositor);
+	oc_subsurf = wl_subcompositor_get_subsurface(subco, oc_surf,
+						     client->surface->wl_surface);
+	buf_main = surface_commit_color(client, client->surface->wl_surface, &red, 100, 100);
+	buf_sub = surface_commit_color(client, oc_surf, &green, 50, 50);
+	wl_subsurface_set_position(oc_subsurf, 0, 0);
+	wl_subsurface_place_above(oc_subsurf, client->surface->wl_surface);
+	wl_subsurface_set_desync(oc_subsurf);
+
+	/* Tell the compositor our subsurface is opaque so it knows it should
+	 * occlude the parent later
+	 */
+	opaque_region = wl_compositor_create_region(client->wl_compositor);
+	wl_region_add(opaque_region, 0, 0, 50, 50);
+	wl_surface_set_opaque_region(oc_surf, opaque_region);
+	wl_region_destroy(opaque_region);
+	wl_surface_commit(oc_surf);
+
+	/* Let's take a shot to make sure the smaller red parent surface is above the
+	 * large green subsurface at this point.
+	 */
+	match = verify_screen_content(client, "fifo_occlude_start", 0, NULL,
+				      0, NULL, NO_DECORATIONS);
+	test_assert_true(match);
+
+	fifo = wp_fifo_manager_v1_get_fifo(client->fifo_manager, client->surface->wl_surface);
+	wp_fifo_v1_set_barrier(fifo);
+	wl_surface_commit(client->surface->wl_surface);
+
+	feedback_count = 0;
+	for (i = 0; i < 10; i++) {
+		wp_fifo_v1_set_barrier(fifo);
+		wp_fifo_v1_wait_barrier(fifo);
+		feedback_create(client, client->surface->wl_surface, pres, true);
+		wl_surface_commit(client->surface->wl_surface);
+	}
+
+	/* Commit a buffer on the main surface that is smaller than the opaque subsurface
+	 * that is above it. This will cause the main surface to become occluded.
+	 */
+	wp_fifo_v1_wait_barrier(fifo);
+	buf_main_small = surface_commit_color(client, client->surface->wl_surface, &red, 25, 25);
+	wl_surface_commit(client->surface->wl_surface);
+
+	/* These waits shouldn't happen, so all the feedback should be discarded */
+	for (i = 0; i < 10; i++) {
+		wp_fifo_v1_set_barrier(fifo);
+		wp_fifo_v1_wait_barrier(fifo);
+		feedback_create(client, client->surface->wl_surface, pres, false);
+		wl_surface_commit(client->surface->wl_surface);
+	}
+
+	/* Kick that last feedback out as discarded */
+	wp_fifo_v1_wait_barrier(fifo);
+	wl_surface_commit(client->surface->wl_surface);
+
+	/* Destroy the fifo early so we can be sure destroying a fifo proxy
+	 * doesn't change existing content updates.
+	 */
+	wp_fifo_v1_destroy(fifo);
+	client_roundtrip(client);
+
+	while (feedback_count)
+		test_assert_int_ge(wl_display_dispatch(client->wl_display), 0);
+
+	/* And let's make sure what we're seeing is just the subsurface */
+	match = verify_screen_content(client, "fifo_occlude_restack", 0, NULL,
+				      0, NULL, NO_DECORATIONS);
+	test_assert_true(match);
+
+	wp_presentation_destroy(pres);
+	wl_subcompositor_destroy(subco);
+	wl_subsurface_destroy(oc_subsurf);
+	wl_surface_destroy(oc_surf);
+	buffer_destroy(buf_main);
+	buffer_destroy(buf_main_small);
+	buffer_destroy(buf_sub);
+	client_destroy(client);
+
+	return RESULT_OK;
+}
+
+static int
+count_barriers(struct client *client,
+	       struct wl_surface *wlsurface,
+	       struct wet_testsuite_data *suite_data)
+{
+	int barrier_count = 0;
+	bool barrier;
+
+	do {
+		RUN_INSIDE_BREAKPOINT(client, suite_data) {
+			struct weston_surface *surface;
+			struct wl_resource *surface_res;
+
+			test_assert_enum(breakpoint->template_->breakpoint,
+					 WESTON_TEST_BREAKPOINT_POST_LATCH);
+			surface_res = wl_client_get_object(suite_data->wl_client,
+							   wl_proxy_get_id((struct wl_proxy *)wlsurface));
+			surface = wl_resource_get_user_data(surface_res);
+
+			barrier = surface->fifo_barrier;
+			if (barrier) {
+				barrier_count++;
+				REARM_BREAKPOINT(breakpoint);
+			}
+		}
+	} while (barrier);
+	return barrier_count;
+}
+
+static int
+get_surface_width(struct client *client,
+		  struct wl_surface *wlsurface,
+		  struct wet_testsuite_data *suite_data,
+		  bool rearm)
+{
+	int width;
+
+	RUN_INSIDE_BREAKPOINT(client, suite_data) {
+		struct weston_surface *surface;
+		struct wl_resource *surface_res;
+
+		test_assert_enum(breakpoint->template_->breakpoint,
+				 WESTON_TEST_BREAKPOINT_POST_LATCH);
+		surface_res = wl_client_get_object(suite_data->wl_client,
+						   wl_proxy_get_id((struct wl_proxy *)wlsurface));
+		surface = wl_resource_get_user_data(surface_res);
+
+		width = surface->width;
+		if (rearm)
+			REARM_BREAKPOINT(breakpoint);
+	}
+	return width;
+}
+
+/* Make sure fifo is ignored on synchronous subsurfaces, but works on desync */
+TEST(fifo_on_subsurface)
+{
+	struct wet_testsuite_data *suite_data = TEST_GET_SUITE_DATA();
+	struct wl_subcompositor *subco;
+	struct wl_surface *surf;
+	struct wl_subsurface *subsurf;
+	struct client *client;
+	struct buffer *buf_main, *buf_sub, *buf_sub_2;
+	struct buffer *buf[10];
+	struct wp_fifo_v1 *fifo;
+	pixman_color_t red, green, blue;
+	bool match;
+	int i;
+
+	color_rgb888(&red, 255, 0, 0);
+	color_rgb888(&green, 0, 255, 0);
+	color_rgb888(&blue, 0, 0, 255);
+
+	client = create_client_and_test_surface(100, 50, 100, 100);
+	test_assert_ptr_not_null(client);
+
+	subco = client_get_subcompositor(client);
+	surf = wl_compositor_create_surface(client->wl_compositor);
+
+	subsurf = wl_subcompositor_get_subsurface(subco, surf,
+						  client->surface->wl_surface);
+	buf_main = surface_commit_color(client, client->surface->wl_surface, &red, 150, 150);
+	weston_test_move_surface(client->test->weston_test, client->surface->wl_surface, 50, 50);
+	buf_sub = surface_commit_color(client, surf, &green, 200, 200);
+	wl_subsurface_set_position(subsurf, -25, -25);
+	wl_subsurface_place_below(subsurf, client->surface->wl_surface);
+
+	/* surf is implicitly in synchronized mode */
+	wl_surface_commit(surf);
+	wl_surface_commit(client->surface->wl_surface);
+
+	fifo = wp_fifo_manager_v1_get_fifo(client->fifo_manager, surf);
+
+	match = verify_screen_content(client, "fifo_subsurface_start", 0,
+				      NULL, 0, NULL, NO_DECORATIONS);
+	test_assert_true(match);
+
+	client_push_breakpoint(client, suite_data,
+			       WESTON_TEST_BREAKPOINT_POST_LATCH,
+			       (struct wl_proxy *) client->output->wl_output);
+
+	/* Since the surface is synchronized, weston will push all of these
+	 * into the suburface cache. And also because it's synchronized,
+	 * the fifo_wait won't wait.
+	 */
+	for (i = 0; i < 20; i++) {
+		if (i < 19)
+			wp_fifo_v1_set_barrier(fifo);
+		wp_fifo_v1_wait_barrier(fifo);
+		wl_surface_commit(surf);
+	}
+	wl_surface_commit(client->surface->wl_surface);
+
+	/* Change the surface width so we have something to look for. */
+	buf_sub_2 = surface_commit_color(client, surf, &green, 201, 201);
+	wl_surface_commit(surf);
+	wl_surface_commit(client->surface->wl_surface);
+
+	/* This effectively serializes with the compositor, breaking at the first
+	 * latch. If our width is updated at the first latch, then the sync
+	 * subsurface commits were properly consumed.
+	 */
+	test_assert_int_eq(get_surface_width(client, surf, suite_data, false), 201);
+
+	client_push_breakpoint(client, suite_data,
+			       WESTON_TEST_BREAKPOINT_POST_LATCH,
+			       (struct wl_proxy *) client->output->wl_output);
+
+	/* Let's make sure desynchronized surfaces work properly too */
+	wl_subsurface_set_desync(subsurf);
+	for (i = 0; i < 10; i++) {
+		/* Skip the last barrier so we're assured a redraw with no
+		 * barrier set to give count_barriers a terminal case */
+		if (i < 9)
+			wp_fifo_v1_set_barrier(fifo);
+		wp_fifo_v1_wait_barrier(fifo);
+		/* Commit a new buffer so there's scene damage. */
+		buf[i] = surface_commit_color(client, surf, &red, 100, 100);
+	}
+	test_assert_int_eq(count_barriers(client, surf, suite_data), 9);
+
+	wp_fifo_v1_destroy(fifo);
+	wl_subcompositor_destroy(subco);
+	wl_subsurface_destroy(subsurf);
+	wl_surface_destroy(surf);
+	buffer_destroy(buf_main);
+	buffer_destroy(buf_sub_2);
+	buffer_destroy(buf_sub);
+	for (i = 0; i < 10; i++)
+		buffer_destroy(buf[i]);
+	client_destroy(client);
+
+	return RESULT_OK;
+}
+
+/* Make sure that surface state changes that can change occlusion status are
+ * properly noticed before a redraw.
+ */
+TEST(fifo_when_occlusion_changes)
+{
+	struct wet_testsuite_data *suite_data = TEST_GET_SUITE_DATA();
+	struct wl_subcompositor *subco;
+	struct wl_surface *surf;
+	struct wl_subsurface *subsurf;
+	struct wl_region *opaque_region;
+	struct client *client;
+	struct buffer *buf_main[3], *buf_sub;
+	struct wp_fifo_v1 *fifo;
+	pixman_color_t red, green, blue;
+	int i, width;
+	bool match;
+
+	color_rgb888(&red, 255, 0, 0);
+	color_rgb888(&green, 0, 255, 0);
+	color_rgb888(&blue, 0, 0, 255);
+
+	client = create_client_and_test_surface(100, 50, 100, 100);
+	test_assert_ptr_not_null(client);
+
+	subco = client_get_subcompositor(client);
+	surf = wl_compositor_create_surface(client->wl_compositor);
+
+	subsurf = wl_subcompositor_get_subsurface(subco, surf,
+						  client->surface->wl_surface);
+	buf_main[0] = surface_commit_color(client, client->surface->wl_surface, &red, 150, 150);
+	weston_test_move_surface(client->test->weston_test, client->surface->wl_surface, 50, 50);
+	buf_sub = surface_commit_color(client, surf, &green, 200, 200);
+	wl_subsurface_set_position(subsurf, -25, -25);
+	/* Make the subsurface opaque and above the parent */
+	opaque_region = wl_compositor_create_region(client->wl_compositor);
+	wl_region_add(opaque_region, 0, 0, 200, 200);
+	wl_surface_set_opaque_region(surf, opaque_region);
+	wl_region_destroy(opaque_region);
+	wl_subsurface_place_above(subsurf, client->surface->wl_surface);
+
+	/* surf is implicitly in synchronized mode */
+	wl_surface_commit(surf);
+	wl_surface_commit(client->surface->wl_surface);
+
+	fifo = wp_fifo_manager_v1_get_fifo(client->fifo_manager,
+					   client->surface->wl_surface);
+
+	/* Wait for a render before we start queuing up fifo requests */
+	match = verify_screen_content(client, "occlusion_change_start", 0,
+				      NULL, 0, NULL, NO_DECORATIONS);
+	test_assert_true(match);
+
+	client_push_breakpoint(client, suite_data,
+			       WESTON_TEST_BREAKPOINT_POST_LATCH,
+			       (struct wl_proxy *) client->output->wl_output);
+
+	/* fifo operations should do nothing, as the surface is occluded. */
+	for (i = 0; i < 30; i++) {
+		wp_fifo_v1_set_barrier(fifo);
+		wp_fifo_v1_wait_barrier(fifo);
+		wl_surface_commit(client->surface->wl_surface);
+	}
+
+	/* Bigger buffer, the surface will no longer be fully occluded */
+	wp_fifo_v1_set_barrier(fifo);
+	wp_fifo_v1_wait_barrier(fifo);
+	buf_main[1] = surface_commit_color(client, client->surface->wl_surface, &red, 200, 200);
+
+	/* Another buffer - if visibility is improperly tracked, we'll only
+	 * see this one and not the previous.
+	 */
+	wp_fifo_v1_set_barrier(fifo);
+	wp_fifo_v1_wait_barrier(fifo);
+	buf_main[2] = surface_commit_color(client, client->surface->wl_surface, &red, 210, 210);
+	client_roundtrip(client);
+
+	width = get_surface_width(client, client->surface->wl_surface,
+				  suite_data, true);
+	test_assert_int_eq(width, 200);
+
+	width = get_surface_width(client, client->surface->wl_surface,
+				  suite_data, false);
+	test_assert_int_eq(width, 210);
+
+	wp_fifo_v1_destroy(fifo);
+	wl_subcompositor_destroy(subco);
+	wl_subsurface_destroy(subsurf);
+	wl_surface_destroy(surf);
+	for (i = 0; i < 3; i++)
+		buffer_destroy(buf_main[i]);
+	buffer_destroy(buf_sub);
+	client_destroy(client);
+
+	return RESULT_OK;
+}

tests/meson.build

@@ -156,6 +156,7 @@ tests = [
 	{	'name': 'drm-smoke', 'run_exclusive': true },
 	{	'name': 'drm-writeback-screenshot', 'run_exclusive': true },
 	{	'name': 'event', },
+	{	'name': 'fifo', },
 	{	'name': 'idalloc', },
 	{
 		'name': 'keyboard',