+ if (!display || !*display) {
+ localcopy = platform_get_x_display();
+ if (!localcopy || !*localcopy) {
+ sfree(localcopy);
+ localcopy = dupstr(":0"); /* plausible default for any platform */
+ }
+ } else
+ localcopy = dupstr(display);
+
+ /*
+ * Parse the display name.
+ *
+ * We expect this to have one of the following forms:
+ *
+ * - the standard X format which looks like
+ * [ [ protocol '/' ] host ] ':' displaynumber [ '.' screennumber ]
+ * (X11 also permits a double colon to indicate DECnet, but
+ * that's not our problem, thankfully!)
+ *
+ * - only seen in the wild on MacOS (so far): a pathname to a
+ * Unix-domain socket, which will typically and confusingly
+ * end in ":0", and which I'm currently distinguishing from
+ * the standard scheme by noting that it starts with '/'.
+ */
+ if (localcopy[0] == '/') {
+ disp->unixsocketpath = localcopy;
+ disp->unixdomain = TRUE;
+ disp->hostname = NULL;
+ disp->displaynum = -1;
+ disp->screennum = 0;
+ } else {
+ char *colon, *dot, *slash;
+ char *protocol, *hostname;
+
+ colon = strrchr(localcopy, ':');
+ if (!colon) {
+ sfree(disp);
+ sfree(localcopy);
+ return NULL; /* FIXME: report a specific error? */
+ }
+
+ *colon++ = '\0';
+ dot = strchr(colon, '.');
+ if (dot)
+ *dot++ = '\0';
+
+ disp->displaynum = atoi(colon);
+ if (dot)
+ disp->screennum = atoi(dot);
+ else
+ disp->screennum = 0;
+
+ protocol = NULL;
+ hostname = localcopy;
+ if (colon > localcopy) {
+ slash = strchr(localcopy, '/');
+ if (slash) {
+ *slash++ = '\0';
+ protocol = localcopy;
+ hostname = slash;
+ }
+ }
+
+ disp->hostname = *hostname ? dupstr(hostname) : NULL;
+
+ if (protocol)
+ disp->unixdomain = (!strcmp(protocol, "local") ||
+ !strcmp(protocol, "unix"));
+ else
+ disp->unixdomain = platform_uses_x11_unix_by_default;
+
+ if (!disp->hostname && !disp->unixdomain)
+ disp->hostname = dupstr("localhost");
+
+ disp->unixsocketpath = NULL;
+
+ sfree(localcopy);
+ }
+
+ /*
+ * Look up the display hostname, if we need to.
+ */
+ if (disp->unixdomain) {
+ disp->addr = platform_get_x11_unix_address(disp->unixsocketpath,
+ disp->displaynum);
+ if (disp->unixsocketpath)
+ disp->realhost = dupstr(disp->unixsocketpath);
+ else
+ disp->realhost = dupprintf("unix:%d", disp->displaynum);
+ disp->port = 0;
+ } else {
+ const char *err;
+
+ disp->port = 6000 + disp->displaynum;
+ disp->addr = name_lookup(disp->hostname, disp->port,
+ &disp->realhost, cfg, ADDRTYPE_UNSPEC);
+
+ if ((err = sk_addr_error(disp->addr)) != NULL) {
+ sk_addr_free(disp->addr);
+ sfree(disp->hostname);
+ sfree(disp->unixsocketpath);
+ return NULL; /* FIXME: report an error */
+ }
+ }
+
+ /*
+ * Invent the remote authorisation details.
+ */
+ if (authtype == X11_MIT) {
+ disp->remoteauthproto = X11_MIT;
+
+ /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
+ disp->remoteauthdata = snewn(16, unsigned char);
+ for (i = 0; i < 16; i++)
+ disp->remoteauthdata[i] = random_byte();
+ disp->remoteauthdatalen = 16;