transactions-v1: new protocol implementation

This implements the transactions-unstable-v1 protocol [1]. The protocol
allows clients to synchronize multiple surfaces together and ensure
their commits are applied atomically.

[1]: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/26

include/wlr/types/wlr_transactions_v1.h

@@ -0,0 +1,41 @@
+/*
+ * This an unstable interface of wlroots. No guarantees are made regarding the
+ * future consistency of this API.
+ */
+#ifndef WLR_USE_UNSTABLE
+#error "Add -DWLR_USE_UNSTABLE to enable unstable wlroots features"
+#endif
+
+#ifndef WLR_TYPES_WLR_TRANSACTIONS_V1_H
+#define WLR_TYPES_WLR_TRANSACTIONS_V1_H
+
+#include <wayland-server-core.h>
+
+struct wlr_transaction_v1_surface {
+	struct wlr_surface *surface;
+	struct wl_list link; // wlr_transactions_v1.surfaces
+	uint32_t cached_state_seq;
+
+	struct wl_listener surface_destroy;
+};
+
+struct wlr_transaction_v1 {
+	struct wl_resource *resource;
+
+	struct wl_list surfaces; // wlr_transaction_v1_surface.link
+};
+
+struct wlr_transaction_manager_v1 {
+	struct wl_global *global;
+
+	struct {
+		struct wl_signal destroy;
+	} events;
+
+	struct wl_listener display_destroy;
+};
+
+struct wlr_transaction_manager_v1 *wlr_transaction_manager_v1_create(
+	struct wl_display *display);
+
+#endif

protocol/meson.build

@@ -26,6 +26,7 @@ protocols = {
 	'relative-pointer-unstable-v1': wl_protocol_dir / 'unstable/relative-pointer/relative-pointer-unstable-v1.xml',
 	'tablet-unstable-v2': wl_protocol_dir / 'unstable/tablet/tablet-unstable-v2.xml',
 	'text-input-unstable-v3': wl_protocol_dir / 'unstable/text-input/text-input-unstable-v3.xml',
+	'transactions-unstable-v1': wl_protocol_dir / 'unstable/transactions/transactions-unstable-v1.xml',
 	'xdg-decoration-unstable-v1': wl_protocol_dir / 'unstable/xdg-decoration/xdg-decoration-unstable-v1.xml',
 	'xdg-foreign-unstable-v1': wl_protocol_dir / 'unstable/xdg-foreign/xdg-foreign-unstable-v1.xml',
 	'xdg-foreign-unstable-v2': wl_protocol_dir / 'unstable/xdg-foreign/xdg-foreign-unstable-v2.xml',

types/meson.build

@@ -59,6 +59,7 @@ wlr_files += files(
 	'wlr_tablet_tool.c',
 	'wlr_text_input_v3.c',
 	'wlr_touch.c',
+	'wlr_transactions_v1.c',
 	'wlr_viewporter.c',
 	'wlr_virtual_keyboard_v1.c',
 	'wlr_virtual_pointer_v1.c',

types/wlr_transactions_v1.c

@@ -0,0 +1,156 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <wlr/types/wlr_surface.h>
+#include <wlr/types/wlr_transactions_v1.h>
+#include "transactions-unstable-v1-protocol.h"
+
+#define TRANSACTION_MANAGER_V1_VERSION 1
+
+static const struct zwp_transaction_v1_interface transaction_impl;
+
+static struct wlr_transaction_v1 *transaction_from_resource(
+		struct wl_resource *resource) {
+	assert(wl_resource_instance_of(resource,
+		&zwp_transaction_v1_interface, &transaction_impl));
+	return wl_resource_get_user_data(resource);
+}
+
+static void transaction_surface_destroy(
+		struct wlr_transaction_v1_surface *transaction_surface) {
+	if (transaction_surface == NULL) {
+		return;
+	}
+
+	wl_list_remove(&transaction_surface->surface_destroy.link);
+	wl_list_remove(&transaction_surface->link);
+	free(transaction_surface);
+}
+
+static void transaction_handle_resource_destroy(struct wl_resource *resource) {
+	struct wlr_transaction_v1 *transaction =
+		transaction_from_resource(resource);
+
+	struct wlr_transaction_v1_surface *transaction_surface, *tmp;
+	wl_list_for_each_safe(transaction_surface, tmp, &transaction->surfaces, link) {
+		wlr_surface_unlock_cached(transaction_surface->surface,
+			transaction_surface->cached_state_seq);
+		transaction_surface_destroy(transaction_surface);
+	}
+
+	free(transaction);
+}
+
+static void transaction_surface_handle_surface_destroy(
+		struct wl_listener *listener, void *data) {
+	struct wlr_transaction_v1_surface *transaction_surface =
+		wl_container_of(listener, transaction_surface, surface_destroy);
+	transaction_surface_destroy(transaction_surface);
+}
+
+static void transaction_handle_add_surface(struct wl_client *client,
+		struct wl_resource *transaction_resource,
+		struct wl_resource *surface_resource) {
+	struct wlr_transaction_v1 *transaction =
+		transaction_from_resource(transaction_resource);
+	struct wlr_surface *surface = wlr_surface_from_resource(surface_resource);
+
+	struct wlr_transaction_v1_surface *transaction_surface =
+		calloc(1, sizeof(*transaction_surface));
+	if (transaction_surface == NULL) {
+		wl_resource_post_no_memory(transaction_resource);
+		return;
+	}
+
+	transaction_surface->surface = surface;
+	transaction_surface->cached_state_seq = wlr_surface_lock_pending(surface);
+
+	transaction_surface->surface_destroy.notify = transaction_surface_handle_surface_destroy;
+	wl_signal_add(&surface->events.destroy, &transaction_surface->surface_destroy);
+
+	wl_list_insert(&transaction->surfaces, &transaction_surface->link);
+}
+
+static void transaction_handle_commit(struct wl_client *client,
+		struct wl_resource *transaction_resource) {
+	// The resource destroy handler will release surface locks
+	wl_resource_destroy(transaction_resource);
+}
+
+static const struct zwp_transaction_v1_interface transaction_impl = {
+	.add_surface = transaction_handle_add_surface,
+	.commit = transaction_handle_commit,
+};
+
+static void manager_handle_create_transaction(struct wl_client *client,
+		struct wl_resource *manager_resource, uint32_t id) {
+	struct wlr_transaction_v1 *transaction = calloc(1, sizeof(*transaction));
+	if (transaction == NULL) {
+		wl_resource_post_no_memory(manager_resource);
+		return;
+	}
+
+	wl_list_init(&transaction->surfaces);
+
+	uint32_t version = wl_resource_get_version(manager_resource);
+	transaction->resource = wl_resource_create(client,
+		&zwp_transaction_v1_interface, version, id);
+	if (transaction->resource == NULL) {
+		wl_resource_post_no_memory(manager_resource);
+		free(transaction);
+		return;
+	}
+	wl_resource_set_implementation(transaction->resource, &transaction_impl,
+		transaction, transaction_handle_resource_destroy);
+}
+
+static void manager_handle_destroy(struct wl_client *client,
+		struct wl_resource *manager_resource) {
+	wl_resource_destroy(manager_resource);
+}
+
+static const struct zwp_transaction_manager_v1_interface manager_impl = {
+	.destroy = manager_handle_destroy,
+	.create_transaction = manager_handle_create_transaction,
+};
+
+static void manager_bind(struct wl_client *client, void *data,
+		uint32_t version, uint32_t id) {
+	struct wlr_transaction_manager_v1 *manager = data;
+
+	struct wl_resource *resource = wl_resource_create(client,
+		&zwp_transaction_manager_v1_interface, version, id);
+	if (resource == NULL) {
+		wl_client_post_no_memory(client);
+		return;
+	}
+	wl_resource_set_implementation(resource, &manager_impl, manager, NULL);
+}
+
+static void handle_display_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_transaction_manager_v1 *manager =
+		wl_container_of(listener, manager, display_destroy);
+	wl_global_destroy(manager->global);
+	wl_list_remove(&manager->display_destroy.link);
+	free(manager);
+}
+
+struct wlr_transaction_manager_v1 *wlr_transaction_manager_v1_create(
+		struct wl_display *display) {
+	struct wlr_transaction_manager_v1 *manager = calloc(1, sizeof(*manager));
+	if (manager == NULL) {
+		return NULL;
+	}
+
+	manager->global = wl_global_create(display,
+		&zwp_transaction_manager_v1_interface, TRANSACTION_MANAGER_V1_VERSION,
+		manager, manager_bind);
+	if (manager->global == NULL) {
+		free(manager);
+		return NULL;
+	}
+
+	manager->display_destroy.notify = handle_display_destroy;
+	wl_display_add_destroy_listener(display, &manager->display_destroy);
+
+	return manager;
+}