Skip Preferences close work during app terminate

PreferencesController.handleWillClose: runs read_config_file,
machine reselection, scaler hotswap, [machineRomsController
setContent:nil], and [machineRoms release] alongside removing its
NSWindowWillCloseNotification observer. When [NSApp terminate:]
cascade-closes the windows with Preferences still open, the
WillClose notification fires the handler and one of those teardowns
reaches into NSWindow's notification observer table while it is
still being walked. _platform_strcmp segfaults inside
__CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__.

Latent in the runModal era: the modal session blocked Cmd+Q
delivery, so the user could not quit with Preferences open.
Removing runModal reaches this path.

Register a class-target observer for
NSApplicationWillTerminateNotification (which fires before the
close cascade), set a file-static flag, and short-circuit
handleWillClose: when it is set. Settings have already been
persisted to NSUserDefaults via the binding chain by the time the
user clicks Quit, so the work being skipped is the apply-back
path: meaningless at exit and dangerous when invoked from inside
the terminate cascade.

Author: morozov

fusepb/controllers/PreferencesController.m

@@ -60,6 +60,32 @@
 
 @implementation PreferencesController
 
+/* Set on NSApplicationWillTerminateNotification so handleWillClose:
+   can skip the settings-apply / KVO-teardown work when the close is
+   part of [NSApp terminate:]'s cascade. Touching NSArrayController
+   content or driving graphics hotswaps from inside that cascade
+   reaches the notification observer table while NSWindow is still
+   walking it, producing the strcmp crash in
+   __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__. The work
+   skipped here only matters when the emulator continues running
+   after the window closes; at quit time the settings have already
+   been persisted to NSUserDefaults via the binding chain. */
+static BOOL appTerminating = NO;
+
++ (void)load
+{
+  [[NSNotificationCenter defaultCenter]
+    addObserver:self
+       selector:@selector(handleAppWillTerminate:)
+           name:NSApplicationWillTerminateNotification
+         object:nil];
+}
+
++ (void)handleAppWillTerminate:(NSNotification *)note
+{
+  appTerminating = YES;
+}
+
 +(void) initialize
 {
   ScalerNameToIdTransformer *sNToITransformer;
@@ -225,6 +251,8 @@ - (void)handleWillClose:(NSNotification *)note
 {
   [[NSNotificationCenter defaultCenter] removeObserver:self];
 
+  if( appTerminating ) return;
+
   int old_bilinear = settings_current.bilinear_filter;
   int old_joy1_number = settings_current.joy1_number;
   int old_joy2_number = settings_current.joy2_number;