This patch fixes SLiM so it really waits for the X server to be ready
before attempting to connect to it.  Indeed, the X server notices that
its parent process has a handler for SIGUSR1, and consequently sends it
SIGUSR1 when it's ready to accept connections.

The problem was that SLiM doesn't pay attention to SIGUSR1.  So in practice,
if X starts slowly, then SLiM gets ECONNREFUSED a couple of time on
/tmp/.X11-unix/X0, then goes on trying to connect to localhost:6000,
where nobody answers; eventually, it times out and tries again on
/tmp/.X11-unix/X0, and finally it shows up on the screen.

Patch by L. Courtès.

--- slim-1.3.6/app.cpp	2014-02-05 15:27:20.000000000 +0100
+++ slim-1.3.6/app.cpp	2014-02-09 22:42:04.000000000 +0100
@@ -119,7 +119,9 @@ void CatchSignal(int sig) {
 	exit(ERR_EXIT);
 }
 
+static volatile int got_sigusr1 = 0;
 void User1Signal(int sig) {
+	got_sigusr1 = 1;
 	signal(sig, User1Signal);
 }
 
@@ -884,6 +886,7 @@ int App::WaitForServer() {
 	int	ncycles	 = 120;
 	int	cycles;
 
+	while (!got_sigusr1);
 	for(cycles = 0; cycles < ncycles; cycles++) {
 		if((Dpy = XOpenDisplay(DisplayName))) {
 			XSetIOErrorHandler(xioerror);
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<div class='path'>path: <a href='/guix/log/?id=83e6b0640acf933ef54a674dbbadf71f51e8cc14'>root</a>/<a href='/guix/log/gnu?id=83e6b0640acf933ef54a674dbbadf71f51e8cc14'>gnu</a>/<a href='/guix/log/gnu/packages?id=83e6b0640acf933ef54a674dbbadf71f51e8cc14'>packages</a>/<a href='/guix/log/gnu/packages/marst.scm?id=83e6b0640acf933ef54a674dbbadf71f51e8cc14'>marst.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/marst.scm?id=83e6b0640acf933ef54a674dbbadf71f51e8cc14&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-08-16 05:21:38 +0200'>2018-08-16</span></td><td><a href='/guix/commit/gnu/packages/marst.scm?id=70f57ae00525f6fc919f62aea647a33b29d28537'>gnu: Use ©.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/elixir.scm: Replace missing © with ©.
* gnu/packages/erlang.scm: Likewise.
* gnu/packages/marst.scm: Ditto.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2017-03-30 01:30:16 +0200'>2017-03-30</span></td><td><a href='/guix/commit/gnu/packages/marst.scm?id=6fd52309b8f52c9bb59fccffac53e029ce94b698'>gnu: Use HTTPS for almost all gnu.org HOME-PAGEs.</a><span class='msg-avail'>...<span class='msg-tooltip'>All HTTP gnu.org (and supported subdomain) HOME-PAGEs changed to HTTPS.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>