test/x11comp: Fix contention between X11 and Xvfb on Mac OS X

 - Abandon use of -displayfd.
 - Have x11comp itself look for an unused X11 display number instead.

1 files changed, 31 insertions, 25 deletions

diff --git a/test/x11comp.c b/test/x11comp.c
index 71928a6..bf5bbe7 100644
--- a/test/x11comp.c
+++ b/test/x11comp.c
@@ -39,23 +39,24 @@ main(void)
     struct xkb_keymap *keymap;
     xcb_connection_t *conn;
     int32_t device_id;
-    int pipefds[2];
     int ret, status;
-    char displayfd[128], display[128];
+    char display[512];
     char *xkb_path;
     char *original, *dump;
     char *envp[] = { NULL };
-    char *xvfb_argv[] = { "Xvfb", "-displayfd", displayfd, NULL };
+    char *xvfb_argv[] = { "Xvfb", display, NULL };
     pid_t xvfb_pid;
     char *xkbcomp_argv[] = { "xkbcomp", "-I", NULL /* xkb_path */, display,
                              NULL };
     pid_t xkbcomp_pid;
 
+    char *xhost;
+    int xdpy_current;
+    int xdpy_candidate;
+
     /*
      * What all of this mess does is:
-     * 1. Launch Xvfb on the next available DISPLAY. Xvfb reports the
-     *    display number to an fd passed with -displayfd once it's
-     *    initialized. We pass a pipe there to read it.
+     * 1. Launch Xvfb on available DISPLAY.
      * 2. Make an xcb connection to this display.
      * 3. Launch xkbcomp to change the keymap of the new display (doing
      *    this programmatically is major work [which we may yet do some
@@ -65,30 +66,35 @@ main(void)
      * 6. Kill the server & clean up.
      */
 
-    ret = pipe(pipefds);
-    assert(ret == 0);
-
-    ret = snprintf(displayfd, sizeof(displayfd), "%d", pipefds[1]);
-    assert(ret >= 0 && ret < sizeof(displayfd));
-
-    ret = posix_spawnp(&xvfb_pid, "Xvfb", NULL, NULL, xvfb_argv, envp);
+    ret = xcb_parse_display(NULL, &xhost, &xdpy_current, NULL);
+    assert(ret != 0);
+    /*
+     * IANA assigns TCP port numbers from 6000 through 6063 to X11
+     * clients.  In addition, the current XCB implementaion shows
+     * that, when an X11 client tries to establish a TCP connetion,
+     * the port number needed is specified by adding 6000 to a given
+     * display number.  So, one of reasonable ranges of xdpy_candidate
+     * is [0, 63].
+     */
+    for (xdpy_candidate = 63; xdpy_candidate >= 0; xdpy_candidate--) {
+        char *buf;
+
+        if (xdpy_candidate == xdpy_current) {
+            continue;
+        }
+        snprintf(display, sizeof(display), "%s:%d", xhost, xdpy_candidate);
+        ret = posix_spawnp(&xvfb_pid, "Xvfb", NULL, NULL, xvfb_argv, envp);
+        if (ret == 0) {
+            break;
+        }
+    }
     if (ret != 0) {
         ret = SKIP_TEST;
         goto err_ctx;
     }
 
-    close(pipefds[1]);
-
-    display[0] = ':';
-    ret = read(pipefds[0], display + 1, sizeof(display) - 1);
-    if (ret <= 0 || 1 + ret >= sizeof(display) - 1) {
-        ret = SKIP_TEST;
-        goto err_xvfd;
-    }
-    if (display[ret] == '\n')
-        display[ret] = '\0';
-    display[1 + ret] = '\0';
-    close(pipefds[0]);
+    /* Wait for Xvfb fully waking up to accept a connection from a client. */
+    sleep(1);
 
     conn = xcb_connect(display, NULL);
     if (xcb_connection_has_error(conn)) {