XQuartz: Detect FatalErrors on startup to prevent tight crash loops

If a FatalError occurs before the server finishes launching, it will
not have drained the launchd-owned DISPLAY socket, so launchd will
just relaunch it.  This can cause the server to crash in a tight loop
which will spam the user with CrashReporter windows that claim focus on
appearance.

This allows users stuck in this loop to "deal" with the problem without
popping up a crash report every 10 seconds.

Signed-off-by: Jeremy Huddleston <jeremyhu@apple.com>

hw/xquartz/X11Application.h

@@ -108,6 +108,9 @@ X11ApplicationCanEnterRandR(void);
 void
 X11ApplicationMain(int argc, char **argv, char **envp);
 
+void
+X11ApplicationFatalError(const char *f, va_list args) __printflike(1, 0);
+
 #define PREFS_APPSMENU              "apps_menu"
 #define PREFS_FAKEBUTTONS           "enable_fake_buttons"
 #define PREFS_KEYEQUIVS             "enable_key_equivalents"

hw/xquartz/X11Application.m

@@ -70,6 +70,7 @@ static dispatch_queue_t eventTranslationQueue;
 
 extern Bool noTestExtensions;
 extern Bool noRenderExtension;
+extern BOOL serverRunning;
 
 #if MAC_OS_X_VERSION_MIN_REQUIRED >= 1050
 static TISInputSourceRef last_key_layout;
@@ -1067,6 +1068,50 @@ NO] || XQuartzShieldingWindowLevel != 0)
     }
 }
 
+void
+X11ApplicationFatalError(const char *f, va_list args)
+{
+#ifdef HAVE_LIBDISPATCH
+    NSString *title, *msg;
+    char *error_msg;
+
+    /* This is called by FatalError() in the server thread just before
+     * we would abort.  If the server never got off the ground, We should
+     * inform the user of the error rather than letting the ever-so-friendly
+     * CrashReporter do it for us.
+     *
+     * This also has the benefit of forcing user interaction rather than
+     * allowing an infinite throttled-restart if the crash occurs before
+     * we can drain the launchd socket.
+     */
+
+    if (serverRunning) {
+        return;
+    }
+
+    title = NSLocalizedString(@"The application X11 could not be opened.",
+                              @"Dialog title when encountering a fatal error");
+    msg = NSLocalizedString(@"An error occurred while starting the X11 server: \"%s\"\n\nClick Quit to quit X11. Click Report to see more details or send a report to Apple.",
+                            @"Dialog when encountering a fatal error");
+
+    vasprintf(&error_msg, f, args);
+    msg = [NSString stringWithFormat:msg, error_msg];
+
+    /* We want the AppKit thread to actually service the alert or we will race [NSApp run] and create an
+     * 'NSInternalInconsistencyException', reason: 'NSApp with wrong _running count'
+     */
+    dispatch_sync(dispatch_get_main_queue(), ^{
+        if (NSAlertDefaultReturn == NSRunAlertPanel(title, msg, NSLocalizedString(@"Quit", @""),
+                                                    NSLocalizedString (@"Report...", @""), nil)) {
+            exit(EXIT_FAILURE);
+        }
+    });
+
+    /* fall back to caller to do the abort() in the DIX */
+#endif
+}
+
+
 static void
 check_xinitrc(void)
 {

hw/xquartz/darwin.c

@@ -78,6 +78,8 @@
 #include "quartzKeyboard.h"
 #include "quartz.h"
 
+#include "X11Application.h"
+
 aslclient aslc;
 
 void
@@ -636,7 +638,7 @@ InitOutput(ScreenInfo * pScreenInfo, int argc, char **argv)
 void
 OsVendorFatalError(const char *f, va_list args)
 {
-    ErrorF("   OsVendorFatalError\n");
+    X11ApplicationFatalError(f, args);
 }
 
 /*