Better exit handling of updateLayer; clean builds for a 10.9 target o…

…n macOS 10.13, 10.14. 10.15, 11, 12, 13, 14, 15; all tests pass on these, except 10.15 and 15 (due to stderr issue)

macosx/tkMacOSXColor.c

@@ -641,13 +641,15 @@ TkpGetColor(
 	    NSAppearance *windowAppearance;
 	    /* See comments in tkMacOSXDraw.c */
 	    if (@available(macOS 12.0, *)) {
+#if MAC_OS_X_VERSION_MAX_ALLOWED > 120000
 		NSAppearance *current = NSAppearance.currentDrawingAppearance;
 		NSAppearance *effective = view.effectiveAppearance;
 		if( current != effective) {
 		    // printf("Appearances are out of sync!\n");
 		    // Deprecations be damned!
 		    NSAppearance.currentAppearance = effective;
 		}
+#endif
 	    }
 	    if (@available(macOS 10.14, *)) {
 		if (view) {

macosx/tkMacOSXDraw.c

@@ -1280,13 +1280,15 @@ TkMacOSXSetupDrawingContext(
 	 */
 
 	if (@available(macOS 12.0, *)) {
+#if MAC_OS_X_VERSION_MAX_ALLOWED > 120000
 	    NSAppearance *current = NSAppearance.currentDrawingAppearance;
 	    NSAppearance *effective = view.effectiveAppearance;
 	    if( current != effective) {
 		// printf("Appearances are out of sync!\n");
 		// Deprecations be damned!
 		NSAppearance.currentAppearance = effective;
 	    }
+#endif
 	} else {
 	    /*
 	     *It is not clear if this is a problem before macos 12.0, but

macosx/tkMacOSXInit.c

@@ -43,6 +43,7 @@ static Tcl_ObjCmdProc TkMacOSVersionObjCmd;
 @synthesize poolLock = _poolLock;
 @synthesize macOSVersion = _macOSVersion;
 @synthesize tkLiveResizeEnded = _tkLiveResizeEnded;
+@synthesize tkWillExit = _tkWillExit;
 @synthesize tkPointerWindow = _tkPointerWindow;
 - (void) setTkPointerWindow: (TkWindow *)winPtr
 {
@@ -136,6 +137,7 @@ static Tcl_ObjCmdProc TkMacOSVersionObjCmd;
 
 - (BOOL)applicationSupportsSecureRestorableState:(NSApplication *)app
 {
+    (void) app;
     return YES;
 }
 
@@ -405,17 +407,13 @@ TCL_NORETURN void TkpExitProc(
     /*
      * At this point it is too late to be looking up the Tk window associated
      * to any NSWindows, but it can happen.  This makes sure the answer is None
-     * if such a query is attempted.
-     * It is also too late to be updating the backing layer of a window.  All
-     * tkLayerBitmapContext properties are set to nil so that updateLayer will
-     * return immediately.
+     * if such a query is attempted.  It is also too late to be running any
+     * event loops, as happens in updateLayer.  Set the tkWillExit flag to
+     * prevent this.
      */
 
+    [NSApp setTkWillExit:YES];
     for (TKWindow *w in [NSApp orderedWindows]) {
-	TKContentView *view = (TKContentView *) [w contentView];
-	if ([view respondsToSelector: @selector (tkLayerBitmapContext)]) {
-	    [view setTkLayerBitmapContext: nil];
-	}
 	if ([w respondsToSelector: @selector (tkWindow)]) {
 	    [w setTkWindow: None];
 	}

macosx/tkMacOSXPrivate.h

@@ -321,6 +321,7 @@ VISIBILITY_HIDDEN
 @property int poolLock;
 @property int macOSVersion;
 @property Bool tkLiveResizeEnded;
+@property Bool tkWillExit;
 
 /*
  * Persistent state variables used by processMouseEvent.

macosx/tkMacOSXWindowEvent.c

@@ -960,7 +960,7 @@ ExposeRestrictProc(
 }
 - (void) updateLayer {
     CGContextRef context = self.tkLayerBitmapContext;
-    if (context) {
+    if (context && ![NSApp tkWillExit]) {
 	/*
 	 * Create a CGImage by copying (probably using copy-on-write) the
 	 * bitmap data of the CGBitmapContext that we have been using for