xwayland: Implement xwayland_shell_v1

Implements the xwayland_shell protocol which makes the surface
association happen via a shared serial, rather than sharing a wl_surface
resource ID across an X atom.

This solves a race that can happen if the wl_surface
associated with a WL_SURFACE_ID for a window was destroyed before the
update of the atom was processed by the compositor and another surface
(or other object) had taken its id due to recycling.

Closes: #1157

Signed-off-by: Joshua Ashton <joshua@froggi.es>
Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>

hw/xwayland/meson.build

@@ -47,6 +47,7 @@ viewporter_xml = join_paths(protodir, 'stable', 'viewporter', 'viewporter.xml')
 xdg_shell_xml = join_paths(protodir, 'stable', 'xdg-shell', 'xdg-shell.xml')
 drm_lease_xml = join_paths(protodir, 'staging', 'drm-lease', 'drm-lease-v1.xml')
 shortcuts_inhibit_xml = join_paths(protodir, 'unstable', 'keyboard-shortcuts-inhibit', 'keyboard-shortcuts-inhibit-unstable-v1.xml')
+xwayland_shell_xml = join_paths(protodir, 'staging', 'xwayland-shell', 'xwayland-shell-v1.xml')
 
 client_header = generator(scanner,
     output : '@BASENAME@-client-protocol.h',
@@ -74,6 +75,7 @@ srcs += client_header.process(viewporter_xml)
 srcs += client_header.process(xdg_shell_xml)
 srcs += client_header.process(drm_lease_xml)
 srcs += client_header.process(shortcuts_inhibit_xml)
+srcs += client_header.process(xwayland_shell_xml)
 srcs += code.process(relative_xml)
 srcs += code.process(pointer_xml)
 srcs += code.process(gestures_xml)
@@ -85,6 +87,7 @@ srcs += code.process(viewporter_xml)
 srcs += code.process(xdg_shell_xml)
 srcs += code.process(drm_lease_xml)
 srcs += code.process(shortcuts_inhibit_xml)
+srcs += code.process(xwayland_shell_xml)
 
 xwayland_glamor = []
 eglstream_srcs = []

hw/xwayland/xwayland-screen.c

@@ -59,6 +59,7 @@
 #include "xdg-output-unstable-v1-client-protocol.h"
 #include "viewporter-client-protocol.h"
 #include "xdg-shell-client-protocol.h"
+#include "xwayland-shell-v1-client-protocol.h"
 
 static DevPrivateKeyRec xwl_screen_private_key;
 static DevPrivateKeyRec xwl_client_private_key;
@@ -451,6 +452,10 @@ registry_global(void *data, struct wl_registry *registry, uint32_t id,
     else if (strcmp(interface, "wp_viewporter") == 0) {
         xwl_screen->viewporter = wl_registry_bind(registry, id, &wp_viewporter_interface, 1);
     }
+    else if (strcmp(interface, "xwayland_shell_v1") == 0 && xwl_screen->rootless) {
+        xwl_screen->xwayland_shell =
+            wl_registry_bind(registry, id, &xwayland_shell_v1_interface, 1);
+    }
 #ifdef XWL_HAS_GLAMOR
     else if (xwl_screen->glamor) {
         xwl_glamor_init_wl_registry(xwl_screen, registry, id, interface,

hw/xwayland/xwayland-screen.h

@@ -103,11 +103,13 @@ struct xwl_screen {
     struct zwp_linux_dmabuf_v1 *dmabuf;
     struct zxdg_output_manager_v1 *xdg_output_manager;
     struct wp_viewporter *viewporter;
+    struct xwayland_shell_v1 *xwayland_shell;
     struct xorg_list drm_lease_devices;
     struct xorg_list queued_drm_lease_devices;
     struct xorg_list drm_leases;
     struct xwl_output *fixed_output;
     struct xorg_list pending_wl_surface_destroy;
+    uint64_t surface_association_serial;
     uint32_t serial;
 
 #define XWL_FORMAT_ARGB8888 (1 << 0)

hw/xwayland/xwayland-window.c

@@ -45,6 +45,7 @@
 
 #include "viewporter-client-protocol.h"
 #include "xdg-shell-client-protocol.h"
+#include "xwayland-shell-v1-client-protocol.h"
 
 #define DELAYED_WL_SURFACE_DESTROY 1000 /* ms */
 
@@ -438,24 +439,30 @@ xwl_window_init_allow_commits(struct xwl_window *xwl_window)
         xwl_window_set_allow_commits(xwl_window, TRUE, "no property");
 }
 
-static void
+static uint32_t
-send_surface_id_event(struct xwl_window *xwl_window)
+serial_lo(uint64_t value)
+{
+    return value & 0xFFFFFFFFu;
+}
+
+static uint32_t
+serial_hi(uint64_t value)
+{
+    return value >> 32u;
+}
+
+static void
+send_window_client_message(struct xwl_window *xwl_window, Atom type_atom, uint64_t value)
 {
-    static const char atom_name[] = "WL_SURFACE_ID";
-    static Atom type_atom;
     DeviceIntPtr dev;
     xEvent e;
 
-    if (type_atom == None)
-        type_atom = MakeAtom(atom_name, strlen(atom_name), TRUE);
-
     e.u.u.type = ClientMessage;
     e.u.u.detail = 32;
     e.u.clientMessage.window = xwl_window->window->drawable.id;
     e.u.clientMessage.u.l.type = type_atom;
-    e.u.clientMessage.u.l.longs0 =
+    e.u.clientMessage.u.l.longs0 = serial_lo(value);
-        wl_proxy_get_id((struct wl_proxy *) xwl_window->surface);
+    e.u.clientMessage.u.l.longs1 = serial_hi(value);
-    e.u.clientMessage.u.l.longs1 = 0;
     e.u.clientMessage.u.l.longs2 = 0;
     e.u.clientMessage.u.l.longs3 = 0;
     e.u.clientMessage.u.l.longs4 = 0;
@@ -465,6 +472,54 @@ send_surface_id_event(struct xwl_window *xwl_window)
                           &e, 1, SubstructureRedirectMask, NullGrab);
 }
 
+static void
+send_surface_id_event_serial(struct xwl_window *xwl_window)
+{
+    static const char atom_name[] = "WL_SURFACE_SERIAL";
+    static Atom type_atom;
+    uint64_t serial;
+
+    if (type_atom == None)
+        type_atom = MakeAtom(atom_name, strlen(atom_name), TRUE);
+
+    serial = ++xwl_window->xwl_screen->surface_association_serial;
+
+    send_window_client_message(xwl_window, type_atom, serial);
+    xwayland_surface_v1_set_serial(xwl_window->xwayland_surface,
+        serial_lo(serial), serial_hi(serial));
+    wl_surface_commit(xwl_window->surface);
+
+    /* Flush wayland display *after* commit in the new path. */
+    wl_display_flush(xwl_window->xwl_screen->display);
+}
+
+static void
+send_surface_id_event_legacy(struct xwl_window *xwl_window)
+{
+    static const char atom_name[] = "WL_SURFACE_ID";
+    static Atom type_atom;
+    uint32_t surface_id;
+
+    if (type_atom == None)
+        type_atom = MakeAtom(atom_name, strlen(atom_name), TRUE);
+
+    surface_id = wl_proxy_get_id((struct wl_proxy *) xwl_window->surface);
+
+    /* Flush wayland display *before* setting the atom in the legacy path */
+    wl_display_flush(xwl_window->xwl_screen->display);
+
+    send_window_client_message(xwl_window, type_atom, (uint64_t)surface_id);
+}
+
+static void
+send_surface_id_event(struct xwl_window *xwl_window)
+{
+    return xwl_window->xwayland_surface
+        ? send_surface_id_event_serial(xwl_window)
+        : send_surface_id_event_legacy(xwl_window);
+
+}
+
 static Bool
 xwl_window_set_fullscreen(struct xwl_window *xwl_window)
 {
@@ -772,11 +827,14 @@ ensure_surface_for_window(WindowPtr window)
         goto err;
     }
 
+    if (xwl_screen->xwayland_shell) {
+        xwl_window->xwayland_surface = xwayland_shell_v1_get_xwayland_surface(
+            xwl_screen->xwayland_shell, xwl_window->surface);
+    }
+
     if (!xwl_screen->rootless && !xwl_create_root_surface(xwl_window))
         goto err;
 
-    wl_display_flush(xwl_screen->display);
-
     send_surface_id_event(xwl_window);
 
     wl_surface_set_user_data(xwl_window->surface, xwl_window);
@@ -889,7 +947,7 @@ xwl_surface_destroy_callback(OsTimerPtr timer, CARD32 now, void *arg)
 }
 
 static void
-release_wl_surface_for_window(struct xwl_window *xwl_window)
+release_wl_surface_for_window_legacy_delay(struct xwl_window *xwl_window)
 {
     struct xwl_wl_surface *xwl_wl_surface;
 
@@ -916,6 +974,22 @@ release_wl_surface_for_window(struct xwl_window *xwl_window)
                  xwl_surface_destroy_callback, xwl_wl_surface);
 }
 
+static void
+release_wl_surface_for_window_shell(struct xwl_window *xwl_window)
+{
+    xwayland_surface_v1_destroy(xwl_window->xwayland_surface);
+    wl_surface_destroy(xwl_window->surface);
+}
+
+static void
+release_wl_surface_for_window(struct xwl_window *xwl_window)
+{
+    if (xwl_window->xwayland_surface)
+        release_wl_surface_for_window_shell(xwl_window);
+    else
+        release_wl_surface_for_window_legacy_delay(xwl_window);
+}
+
 Bool
 xwl_unrealize_window(WindowPtr window)
 {

hw/xwayland/xwayland-window.h

@@ -67,6 +67,7 @@ struct xwl_window {
 #ifdef XWL_HAS_LIBDECOR
     struct libdecor_frame *libdecor_frame;
 #endif
+    struct xwayland_surface_v1 *xwayland_surface;
 };
 
 struct xwl_window *xwl_window_get(WindowPtr window);

meson.build

@@ -64,7 +64,7 @@ libdrm_req = '>= 2.4.89'
 libselinux_req = '>= 2.0.86'
 xext_req = '>= 1.0.99.4'
 wayland_req = '>= 1.18.0'
-wayland_protocols_req = '>= 1.22'
+wayland_protocols_req = '>= 1.28'
 gbm_req = '>= 10.2'
 xf86dgaproto_req = '>= 2.0.99.1'