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);
d8'>refs</a><a class='active' href='/guix/log/gnu/packages/djvu.scm'>log</a><a href='/guix/tree/gnu/packages/djvu.scm?id=fd2a3046a86a134bb81a8b6a8080908c7a967ed8'>tree</a><a href='/guix/commit/gnu/packages/djvu.scm?id=fd2a3046a86a134bb81a8b6a8080908c7a967ed8'>commit</a><a href='/guix/diff/gnu/packages/djvu.scm?id=fd2a3046a86a134bb81a8b6a8080908c7a967ed8'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/djvu.scm'>
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<div class='path'>path: <a href='/guix/log/?id=fd2a3046a86a134bb81a8b6a8080908c7a967ed8'>root</a>/<a href='/guix/log/gnu?id=fd2a3046a86a134bb81a8b6a8080908c7a967ed8'>gnu</a>/<a href='/guix/log/gnu/packages?id=fd2a3046a86a134bb81a8b6a8080908c7a967ed8'>packages</a>/<a href='/guix/log/gnu/packages/djvu.scm?id=fd2a3046a86a134bb81a8b6a8080908c7a967ed8'>djvu.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/djvu.scm?id=fd2a3046a86a134bb81a8b6a8080908c7a967ed8&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-06-10 04:37:22 +0200'>2020-06-10</span></td><td><a href='/guix/commit/gnu/packages/djvu.scm?id=e6c2a88f3d9717be183a0346766cd65d10a904f4'>gnu: djview: Update to 4.11.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/djvu.scm (djview): Update to 4.11.
[source]: Use GIT-FETCH and add a FILE-NAME.
[native-inputs]: Add autoconf, automake, and libtool.
[arguments]: Add a ‘make-files-writable’ phase.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-02-09 17:22:26 +0100'>2020-02-09</span></td><td><a href='/guix/commit/gnu/packages/djvu.scm?id=0d79e82acc28afdfc0881d0375ea168882a05312'>gnu: djview: Fix home-page.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/djvu.scm (djview)[home-page]: Point specifically to the project
home-page.
</span></span></td><td>Nicolas Goaziou</td></tr>
<tr><td><span title='2020-02-09 14:55:25 +0100'>2020-02-09</span></td><td><a href='/guix/commit/gnu/packages/djvu.scm?id=f8c2d32461d469f7133c7d79fe1b4eed5146aaf7'>gnu: djview: Fix executable's name in desktop file.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/djvu.scm (djview)[inputs]: Re-order inputs alphabetically.
[arguments]: Add a phase to fix executable's name in desktop file.
</span></span></td><td>Nicolas Goaziou</td></tr>
<tr><td><span title='2020-02-09 13:29:30 +0100'>2020-02-09</span></td><td><a href='/guix/commit/gnu/packages/djvu.scm?id=794ebb6b74e692e33d17552fe14b30bb9b7b771d'>gnu: Add djview.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/djvu.scm (djview): New variable.
</span></span></td><td>Nicolas Goaziou</td></tr>