client: Fix shell unstable version check

Use a static assert to catch mismatch between implementation and
interface version.  Fix window.c to not use XDG_SHELL_VERSION_CURRENT,
which will fail to catch version mismatches.  The implementation version
must updated manually when the implementation is updated to use the new
interface.
diff --git a/clients/simple-egl.c b/clients/simple-egl.c
index 63b3aa1..ca1c2aa 100644
--- a/clients/simple-egl.c
+++ b/clients/simple-egl.c
@@ -717,6 +717,12 @@
 	xdg_shell_ping,
 };
 
+#define XDG_VERSION 2 /* The version of xdg-shell that we implement */
+#ifdef static_assert
+static_assert(XDG_VERSION == XDG_SHELL_VERSION_CURRENT,
+	      "Interface version doesn't match implementation version");
+#endif
+
 static void
 registry_handle_global(void *data, struct wl_registry *registry,
 		       uint32_t name, const char *interface, uint32_t version)
@@ -731,7 +737,7 @@
 		d->shell = wl_registry_bind(registry, name,
 					    &xdg_shell_interface, 1);
 		xdg_shell_add_listener(d->shell, &xdg_shell_listener, d);
-		xdg_shell_use_unstable_version(d->shell, 1);
+		xdg_shell_use_unstable_version(d->shell, XDG_VERSION);
 	} else if (strcmp(interface, "wl_seat") == 0) {
 		d->seat = wl_registry_bind(registry, name,
 					   &wl_seat_interface, 1);
diff --git a/clients/simple-shm.c b/clients/simple-shm.c
index 820e8a2..2dbe7cb 100644
--- a/clients/simple-shm.c
+++ b/clients/simple-shm.c
@@ -331,6 +331,12 @@
 	xdg_shell_ping,
 };
 
+#define XDG_VERSION 2 /* The version of xdg-shell that we implement */
+#ifdef static_assert
+static_assert(XDG_VERSION == XDG_SHELL_VERSION_CURRENT,
+	      "Interface version doesn't match implementation version");
+#endif
+
 static void
 registry_handle_global(void *data, struct wl_registry *registry,
 		       uint32_t id, const char *interface, uint32_t version)
@@ -344,7 +350,7 @@
 	} else if (strcmp(interface, "xdg_shell") == 0) {
 		d->shell = wl_registry_bind(registry,
 					    id, &xdg_shell_interface, 1);
-		xdg_shell_use_unstable_version(d->shell, 1);
+		xdg_shell_use_unstable_version(d->shell, XDG_VERSION);
 		xdg_shell_add_listener(d->shell, &xdg_shell_listener, d);
 	} else if (strcmp(interface, "wl_shm") == 0) {
 		d->shm = wl_registry_bind(registry,
diff --git a/clients/window.c b/clients/window.c
index 93aa368..400b16c 100644
--- a/clients/window.c
+++ b/clients/window.c
@@ -5019,6 +5019,12 @@
 	xdg_shell_ping,
 };
 
+#define XDG_VERSION 2 /* The version of xdg-shell that we implement */
+#ifdef static_assert
+static_assert(XDG_VERSION == XDG_SHELL_VERSION_CURRENT,
+	      "Interface version doesn't match implementation version");
+#endif
+
 static void
 registry_handle_global(void *data, struct wl_registry *registry, uint32_t id,
 		       const char *interface, uint32_t version)
@@ -5050,7 +5056,7 @@
 	} else if (strcmp(interface, "xdg_shell") == 0) {
 		d->xdg_shell = wl_registry_bind(registry, id,
 						&xdg_shell_interface, 1);
-		xdg_shell_use_unstable_version(d->xdg_shell, XDG_SHELL_VERSION_CURRENT);
+		xdg_shell_use_unstable_version(d->xdg_shell, XDG_VERSION);
 		xdg_shell_add_listener(d->xdg_shell, &xdg_shell_listener, d);
 	} else if (strcmp(interface, "text_cursor_position") == 0) {
 		d->text_cursor_position =
diff --git a/desktop-shell/shell.c b/desktop-shell/shell.c
index 2a82a1d..8c8e4eb 100644
--- a/desktop-shell/shell.c
+++ b/desktop-shell/shell.c
@@ -3635,7 +3635,7 @@
 		return 0;
 	}
 
-#define XDG_SERVER_VERSION 1
+#define XDG_SERVER_VERSION 2
 
 	static_assert(XDG_SERVER_VERSION == XDG_SHELL_VERSION_CURRENT,
 		      "shell implementation doesn't match protocol version");
diff --git a/protocol/xdg-shell.xml b/protocol/xdg-shell.xml
index d122ff5..ef755b7 100644
--- a/protocol/xdg-shell.xml
+++ b/protocol/xdg-shell.xml
@@ -43,7 +43,7 @@
 	Use this enum to check the protocol version, and it will be updated
 	automatically.
       </description>
-      <entry name="current" value="1" summary="Always the latest version"/>
+      <entry name="current" value="2" summary="Always the latest version"/>
     </enum>