NSProgress: Add cancellation logic

Author: hmelder

Source/NSProgress.m

@@ -71,6 +71,7 @@
 #import "Foundation/NSThread.h"
 #import "Foundation/NSKeyValueObserving.h"
 #import "GNUstepBase/NSObject+GNUstepBase.h"
+#import "GSFastEnumeration.h"
 
 #define	GSInternal NSProgressInternal
 #include "GSInternal.h"
@@ -453,10 +454,20 @@ - (BOOL) cancelled
 
 - (void) cancel
 {
+  GS_MUTEX_LOCK(_lock);
   [self willChangeValueForKey: @"cancelled"];
   CALL_BLOCK_NO_ARGS(internal->_cancellationHandler);
   internal->_cancelled = YES;
   [self didChangeValueForKey: @"cancelled"];
+
+  // Cancel all child progresses
+  FOR_IN(NSProgress*, child, _children)
+    {
+      [child cancel];
+    }
+  END_FOR_IN(children)
+
+  GS_MUTEX_UNLOCK(_lock);
 }
 
 - (void) setCancellationHandler: (GSProgressCancellationHandler) handler