Add support for tearing-control-v1

References: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/3871

Adds option to allow tearing per output, as well as an option to force
enable or disable tearing for a specific application using a window
rule. Only works with fullscreen applications.

include/sway/commands.h

@@ -104,6 +104,7 @@ struct sway_container *container_find_resize_parent(struct sway_container *con,
 sway_cmd cmd_exec_validate;
 sway_cmd cmd_exec_process;
 
+sway_cmd cmd_allow_tearing;
 sway_cmd cmd_assign;
 sway_cmd cmd_bar;
 sway_cmd cmd_bindcode;
@@ -283,6 +284,7 @@ sway_cmd input_cmd_xkb_switch_layout;
 sway_cmd input_cmd_xkb_variant;
 
 sway_cmd output_cmd_adaptive_sync;
+sway_cmd output_cmd_allow_tearing;
 sway_cmd output_cmd_background;
 sway_cmd output_cmd_color_profile;
 sway_cmd output_cmd_disable;

include/sway/config.h

@@ -289,6 +289,7 @@ struct output_config {
 	enum render_bit_depth render_bit_depth;
 	bool set_color_transform;
 	struct wlr_color_transform *color_transform;
+	int allow_tearing;
 
 	char *background;
 	char *background_option;

include/sway/output.h

@@ -73,6 +73,7 @@ struct sway_output {
 	int max_render_time; // In milliseconds
 	struct wl_event_source *repaint_timer;
 	bool gamma_lut_changed;
+	bool allow_tearing;
 };
 
 struct sway_output_non_desktop {

include/sway/server.h

@@ -116,6 +116,10 @@ struct sway_server {
 
 	struct wl_listener request_set_cursor_shape;
 	
+	struct wlr_tearing_control_manager_v1 *tearing_control_v1;
+	struct wl_listener tearing_control_new_object;
+	struct wl_list tearing_controllers; // sway_tearing_controller::link
+
 	struct wl_list pending_launcher_ctxs; // launcher_ctx::link
 
 	// The timeout for transactions, after which a transaction is applied
@@ -182,4 +186,6 @@ void xdg_activation_v1_handle_new_token(struct wl_listener *listener,
 
 void set_rr_scheduling(void);
 
+void handle_new_tearing_hint(struct wl_listener *listener, void *data);
+
 #endif

include/sway/tree/view.h

@@ -4,6 +4,7 @@
 #include <wlr/config.h>
 #include <wlr/types/wlr_compositor.h>
 #include <wlr/types/wlr_scene.h>
+#include <wlr/types/wlr_tearing_control_v1.h>
 #include "sway/config.h"
 #if WLR_HAS_XWAYLAND
 #include <wlr/xwayland.h>
@@ -34,6 +35,12 @@ enum sway_view_prop {
 #endif
 };
 
+enum sway_view_tearing_mode {
+	TEARING_OVERRIDE_FALSE,
+	TEARING_OVERRIDE_TRUE,
+	TEARING_WINDOW_HINT,
+};
+
 struct sway_view_impl {
 	void (*get_constraints)(struct sway_view *view, double *min_width,
 			double *max_width, double *min_height, double *max_height);
@@ -111,6 +118,9 @@ struct sway_view {
 	int max_render_time; // In milliseconds
 
 	enum seat_config_shortcuts_inhibit shortcuts_inhibit;
+
+	enum sway_view_tearing_mode tearing_mode;
+	enum wp_tearing_control_v1_presentation_hint tearing_hint;
 };
 
 struct sway_xdg_shell_view {
@@ -335,4 +345,6 @@ void view_assign_ctx(struct sway_view *view, struct launcher_ctx *ctx);
 
 void view_send_frame_done(struct sway_view *view);
 
+bool view_can_tear(struct sway_view *view);
+
 #endif

protocols/meson.build

@@ -14,6 +14,7 @@ protocols = [
 	wl_protocol_dir / 'unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml',
 	wl_protocol_dir / 'staging/content-type/content-type-v1.xml',
 	wl_protocol_dir / 'staging/cursor-shape/cursor-shape-v1.xml',
+	wl_protocol_dir / 'staging/tearing-control/tearing-control-v1.xml',
 	'wlr-layer-shell-unstable-v1.xml',
 	'idle.xml',
 	'wlr-output-power-management-unstable-v1.xml',

sway/commands.c

@@ -112,6 +112,7 @@ static const struct cmd_handler config_handlers[] = {
 
 /* Runtime-only commands. Keep alphabetized */
 static const struct cmd_handler command_handlers[] = {
+	{ "allow_tearing", cmd_allow_tearing },
 	{ "border", cmd_border },
 	{ "create_output", cmd_create_output },
 	{ "exit", cmd_exit },

sway/commands/allow_tearing.c

@@ -0,0 +1,24 @@
+#include <sway/commands.h>
+#include "sway/config.h"
+#include "sway/tree/view.h"
+#include "util.h"
+
+struct cmd_results *cmd_allow_tearing(int argc, char **argv) {
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, "allow_tearing", EXPECTED_AT_LEAST, 1))) {
+		return error;
+	}
+
+	struct sway_container *container = config->handler_context.container;
+	if (!container || !container->view) {
+		return cmd_results_new(CMD_INVALID, "Tearing can only be allowed on views");
+	}
+
+	bool wants_tearing = parse_boolean(argv[0], true);
+
+	struct sway_view *view = container->view;
+	view->tearing_mode = wants_tearing ? TEARING_OVERRIDE_TRUE :
+		TEARING_OVERRIDE_FALSE;
+
+	return cmd_results_new(CMD_SUCCESS, NULL);
+}

sway/commands/output.c

@@ -8,6 +8,7 @@
 // must be in order for the bsearch
 static const struct cmd_handler output_handlers[] = {
 	{ "adaptive_sync", output_cmd_adaptive_sync },
+	{ "allow_tearing", output_cmd_allow_tearing },
 	{ "background", output_cmd_background },
 	{ "bg", output_cmd_background },
 	{ "color_profile", output_cmd_color_profile },

sway/commands/output/allow_tearing.c

@@ -0,0 +1,23 @@
+#include "sway/commands.h"
+#include "sway/config.h"
+#include "util.h"
+
+struct cmd_results *output_cmd_allow_tearing(int argc, char **argv) {
+	if (!config->handler_context.output_config) {
+		return cmd_results_new(CMD_FAILURE, "Missing output config");
+	}
+	if (argc == 0) {
+		return cmd_results_new(CMD_INVALID, "Missing allow_tearing argument");
+	}
+
+	if (parse_boolean(argv[0],
+			(config->handler_context.output_config->allow_tearing == 1))) {
+		config->handler_context.output_config->allow_tearing = 1;
+	} else {
+		config->handler_context.output_config->allow_tearing = 0;
+	}
+
+	config->handler_context.leftovers.argc = argc - 1;
+	config->handler_context.leftovers.argv = argv + 1;
+	return NULL;
+}

sway/config/output.c

@@ -79,6 +79,7 @@ struct output_config *new_output_config(const char *name) {
 	oc->set_color_transform = false;
 	oc->color_transform = NULL;
 	oc->power = -1;
+	oc->allow_tearing = -1;
 	return oc;
 }
 
@@ -216,6 +217,9 @@ static void merge_output_config(struct output_config *dst, struct output_config
 	if (src->power != -1) {
 		dst->power = src->power;
 	}
+	if (src->allow_tearing != -1) {
+		dst->allow_tearing = src->allow_tearing;
+	}
 }
 
 void store_output_config(struct output_config *oc) {
@@ -258,11 +262,11 @@ void store_output_config(struct output_config *oc) {
 
 	sway_log(SWAY_DEBUG, "Config stored for output %s (enabled: %d) (%dx%d@%fHz "
 		"position %d,%d scale %f subpixel %s transform %d) (bg %s %s) (power %d) "
-		"(max render time: %d)",
+		"(max render time: %d) (allow tearing: %d)",
 		oc->name, oc->enabled, oc->width, oc->height, oc->refresh_rate,
 		oc->x, oc->y, oc->scale, sway_wl_output_subpixel_to_string(oc->subpixel),
 		oc->transform, oc->background, oc->background_option, oc->power,
-		oc->max_render_time);
+		oc->max_render_time, oc->allow_tearing);
 
 	// If the configuration was not merged into an existing configuration, add
 	// it to the list. Otherwise we're done with it and can free it.
@@ -574,6 +578,13 @@ static bool finalize_output_config(struct output_config *oc, struct sway_output
 		wlr_color_transform_unref(output->color_transform);
 		output->color_transform = oc->color_transform;
 	}
+	
+	if (oc && oc->allow_tearing >= 0) {
+		sway_log(SWAY_DEBUG, "Set %s allow tearing to %d", 
+			oc->name, oc->allow_tearing);
+		output->allow_tearing = oc->allow_tearing;
+	}
+
 	return true;
 }
 
@@ -594,6 +605,7 @@ static void default_output_config(struct output_config *oc,
 	oc->subpixel = output->detected_subpixel;
 	oc->transform = WL_OUTPUT_TRANSFORM_NORMAL;
 	oc->max_render_time = 0;
+	oc->allow_tearing = 0;
 }
 
 // find_output_config returns a merged output_config containing all stored

sway/desktop/output.c

@@ -232,6 +232,23 @@ static void output_configure_scene(struct sway_output *output,
 	}
 }
 
+static bool output_can_tear(struct sway_output *output) {
+	struct sway_workspace *workspace = output->current.active_workspace;
+	if (!workspace) {
+		return false;
+	}
+
+	struct sway_container *fullscreen_con = root->fullscreen_global;
+	if (!fullscreen_con) {
+		fullscreen_con = workspace->current.fullscreen;
+	}
+	if (fullscreen_con && fullscreen_con->view) {
+		return (output->allow_tearing && view_can_tear(fullscreen_con->view));
+	}
+
+	return false;
+}
+
 static int output_repaint_timer_handler(void *data) {
 	struct sway_output *output = data;
 
@@ -276,6 +293,17 @@ static int output_repaint_timer_handler(void *data) {
 		}
 	}
 	
+	if (output_can_tear(output)) {
+		pending.tearing_page_flip = true;
+		
+		if (!wlr_output_test_state(output->wlr_output, &pending)) {
+			sway_log(SWAY_DEBUG, "Output test failed on '%s', retrying without tearing page-flip",
+				output->wlr_output->name);
+				
+			pending.tearing_page_flip = false;
+		}
+	}
+
 	if (!wlr_output_commit_state(output->wlr_output, &pending)) {
 		sway_log(SWAY_ERROR, "Page-flip failed on output %s", output->wlr_output->name);
 	}

sway/desktop/tearing.c

@@ -0,0 +1,62 @@
+#include <wayland-server-core.h>
+#include <wlr/types/wlr_tearing_control_v1.h>
+#include "sway/server.h"
+#include "sway/tree/view.h"
+#include "sway/output.h"
+#include "log.h"
+
+struct sway_tearing_controller {
+	struct wlr_tearing_control_v1 *tearing_control;
+	struct wl_listener set_hint;
+	struct wl_listener destroy;
+
+	struct wl_list link; // sway_server::tearing_controllers
+};
+
+static void handle_tearing_controller_set_hint(struct wl_listener *listener,
+		void *data) {
+	struct sway_tearing_controller *controller =
+		wl_container_of(listener, controller, set_hint);
+	
+	struct sway_view *view = view_from_wlr_surface(
+		controller->tearing_control->surface);
+	if (view) {
+		view->tearing_hint = controller->tearing_control->current;
+	}
+}
+
+static void handle_tearing_controller_destroy(struct wl_listener *listener, 
+		void *data) {
+	struct sway_tearing_controller *controller = 
+		wl_container_of(listener, controller, destroy);
+	wl_list_remove(&controller->link);
+	free(controller);
+}
+
+void handle_new_tearing_hint(struct wl_listener *listener, 
+		void *data) {
+	struct sway_server *server = 
+		wl_container_of(listener, server, tearing_control_new_object);
+	struct wlr_tearing_control_v1 *tearing_control = data;
+	
+	enum wp_tearing_control_v1_presentation_hint hint = 
+		wlr_tearing_control_manager_v1_surface_hint_from_surface(
+			server->tearing_control_v1, tearing_control->surface);
+	sway_log(SWAY_DEBUG, "New presentation hint %d received for surface %p",
+		hint, tearing_control->surface);
+
+	struct sway_tearing_controller *controller = 
+		calloc(1, sizeof(struct sway_tearing_controller));
+	if (!controller) {
+		return;
+	}
+
+	controller->tearing_control = tearing_control;
+	controller->set_hint.notify = handle_tearing_controller_set_hint;
+	wl_signal_add(&tearing_control->events.set_hint, &controller->set_hint);
+	controller->destroy.notify = handle_tearing_controller_destroy;
+	wl_signal_add(&tearing_control->events.destroy, &controller->destroy);
+	wl_list_init(&controller->link);
+
+	wl_list_insert(&server->tearing_controllers, &controller->link);
+}

sway/ipc-json.c

@@ -399,6 +399,8 @@ static void ipc_json_describe_enabled_output(struct sway_output *output,
 	}
 
 	json_object_object_add(object, "max_render_time", json_object_new_int(output->max_render_time));
+
+	json_object_object_add(object, "allow_tearing", json_object_new_boolean(output->allow_tearing));
 }
 
 json_object *ipc_json_describe_disabled_output(struct sway_output *output) {
@@ -593,6 +595,8 @@ static void ipc_json_describe_view(struct sway_container *c, json_object *object
 
 	json_object_object_add(object, "max_render_time", json_object_new_int(c->view->max_render_time));
 
+	json_object_object_add(object, "allow_tearing", json_object_new_boolean(view_can_tear(c->view)));
+
 	json_object_object_add(object, "shell", json_object_new_string(view_get_shell(c->view)));
 
 	json_object_object_add(object, "inhibit_idle",

sway/meson.build

@@ -18,6 +18,7 @@ sway_sources = files(
 	'desktop/idle_inhibit_v1.c',
 	'desktop/layer_shell.c',
 	'desktop/output.c',
+	'desktop/tearing.c',
 	'desktop/transaction.c',
 	'desktop/xdg_shell.c',
 	'desktop/launcher.c',
@@ -41,6 +42,7 @@ sway_sources = files(
 	'config/seat.c',
 	'config/input.c',
 
+	'commands/allow_tearing.c',
 	'commands/assign.c',
 	'commands/bar.c',
 	'commands/bind.c',
@@ -188,6 +190,7 @@ sway_sources = files(
 	'commands/input/xkb_variant.c',
 
 	'commands/output/adaptive_sync.c',
+	'commands/output/allow_tearing.c',
 	'commands/output/background.c',
 	'commands/output/disable.c',
 	'commands/output/dpms.c',

sway/server.c

@@ -372,6 +372,13 @@ bool server_init(struct sway_server *server) {
 		wlr_content_type_manager_v1_create(server->wl_display, 1);
 	wlr_fractional_scale_manager_v1_create(server->wl_display, 1);
 	
+	server->tearing_control_v1 = 
+		wlr_tearing_control_manager_v1_create(server->wl_display, 1);
+	server->tearing_control_new_object.notify = handle_new_tearing_hint;
+	wl_signal_add(&server->tearing_control_v1->events.new_object,
+		&server->tearing_control_new_object);
+	wl_list_init(&server->tearing_controllers);
+
 	struct wlr_xdg_foreign_registry *foreign_registry =
 		wlr_xdg_foreign_registry_create(server->wl_display);
 	wlr_xdg_foreign_v1_create(server->wl_display, foreign_registry);

sway/sway-output.5.scd

@@ -190,6 +190,26 @@ must be separated by one space. For example:
 	may have no effect or produce unexpected output when used together with future
 	HDR support features.
 
+*output* <name> allow_tearing yes|no
+	Allows or disallows screen tearing as a result of immediate page flips,
+	and an immediate presentation mode from a client. The default is that no
+	screen tearing is allowed.
+
+	With immediate page flips, frames from the client are presented as soon
+	as possible instead of synchronizing with the monitor's vblank interval 
+	(VSync). 
+	
+	It is recommended to set *max_render_time* to *off*. In that case a page flip
+	happens as soon as a client updates. Otherwise, tearing will only happen if
+	rendering takes longer than the configured milliseconds before the next
+	display refresh.
+
+	To adjust whether tearing is allowed for specific applications, see
+	*allow_tearing* in *sway*(5). Note that tearing will only be enabled
+	when it's allowed for both the output and the application.
+
+	This setting only has effect when a window is fullscreen on the output.
+
 # SEE ALSO
 
 *sway*(5) *sway-input*(5)

sway/sway.5.scd

@@ -215,6 +215,20 @@ set|plus|minus|toggle <amount>
 	effect on the output the window is currently on. See *sway-output*(5) for
 	further details.
 
+*allow_tearing* yes|no
+	Allows or disallows screen tearing as a result of immediate page flips
+	for a fullscreen application.
+
+	When this option is not set, the tearing hints provided by the application
+	determine whether tearing is allowed. When _yes_ is specified,
+	the application allows tearing regardless of the tearing hints.
+	When _no_ is specified, tearing will never be allowed on the application,
+	regardless of the tearing hints.
+
+	This setting only has an effect if tearing is allowed on the output through
+	the per-output *allow_tearing* setting. See *sway-output*(5) 
+	for further details.
+
 *move* left|right|up|down [<px> px]
 	Moves the focused container in the direction specified. The optional _px_
 	argument specifies how many pixels to move the container. If unspecified,

sway/tree/view.c

@@ -58,6 +58,7 @@ bool view_init(struct sway_view *view, enum sway_view_type type,
 	view->executed_criteria = create_list();
 	view->allow_request_urgent = true;
 	view->shortcuts_inhibit = SHORTCUTS_INHIBIT_DEFAULT;
+	view->tearing_mode = TEARING_WINDOW_HINT;
 	wl_signal_init(&view->events.unmap);
 	return true;
 }
@@ -1260,6 +1261,19 @@ bool view_is_transient_for(struct sway_view *child,
 		child->impl->is_transient_for(child, ancestor);
 }
 
+bool view_can_tear(struct sway_view *view) {
+	switch (view->tearing_mode) {
+	case TEARING_OVERRIDE_FALSE:
+		return false;
+	case TEARING_OVERRIDE_TRUE:
+		return true;
+	case TEARING_WINDOW_HINT:
+		return view->tearing_hint == 
+			WP_TEARING_CONTROL_V1_PRESENTATION_HINT_ASYNC;
+	}
+	return false;
+}
+
 static void send_frame_done_iterator(struct wlr_scene_buffer *scene_buffer,
 		int x, int y, void *data) {
 	struct timespec *when = data;

swaymsg/main.c

@@ -193,7 +193,7 @@ static void pretty_print_output(json_object *o) {
 	json_object_object_get_ex(o, "current_workspace", &ws);
 	json_object_object_get_ex(o, "non_desktop", &non_desktop);
 	json_object *make, *model, *serial, *scale, *scale_filter, *subpixel,
-		*transform, *max_render_time, *adaptive_sync_status;
+		*transform, *max_render_time, *adaptive_sync_status, *allow_tearing;
 	json_object_object_get_ex(o, "make", &make);
 	json_object_object_get_ex(o, "model", &model);
 	json_object_object_get_ex(o, "serial", &serial);
@@ -203,6 +203,7 @@ static void pretty_print_output(json_object *o) {
 	json_object_object_get_ex(o, "transform", &transform);
 	json_object_object_get_ex(o, "max_render_time", &max_render_time);
 	json_object_object_get_ex(o, "adaptive_sync_status", &adaptive_sync_status);
+	json_object_object_get_ex(o, "allow_tearing", &allow_tearing);
 	json_object *x, *y;
 	json_object_object_get_ex(rect, "x", &x);
 	json_object_object_get_ex(rect, "y", &y);
@@ -256,6 +257,9 @@ static void pretty_print_output(json_object *o) {
 
 		printf("  Adaptive sync: %s\n",
 			json_object_get_string(adaptive_sync_status));
+
+		printf("  Allow tearing: %s\n",
+			json_object_get_boolean(allow_tearing) ? "yes" : "no");
 	} else {
 		printf(
 			"Output %s '%s %s %s' (disabled)\n",