Handle case where a subclass/something shuts the label down between animations [Common]

Author: cbpowell

Sources/ObjC/MarqueeLabel.m

@@ -576,22 +576,38 @@ - (void)scrollAwayWithInterval:(NSTimeInterval)interval delayAmount:(NSTimeInter
 
     __weak __typeof__(self) weakSelf = self;
     self.scrollCompletionBlock = ^(BOOL finished) {
-        if (!finished || !weakSelf) {
-            // Do not continue into the next loop
+        if (!weakSelf) {
             return;
         }
+        
         // Call returned home method
         [weakSelf labelReturnedToHome:YES];
+        
         // Check to ensure that:
-        // 1) We don't double fire if an animation already exists
-        // 2) The instance is still attached to a window - this completion block is called for
+        // 1) The instance is still attached to a window - this completion block is called for
         //    many reasons, including if the animation is removed due to the view being removed
         //    from the UIWindow (typically when the view controller is no longer the "top" view)
-        if (self.window && ![weakSelf.subLabel.layer animationForKey:@"position"]) {
-            // Begin again, if conditions met
-            if (weakSelf.labelShouldScroll && !weakSelf.tapToScroll && !weakSelf.holdScrolling) {
-                [weakSelf scrollAwayWithInterval:interval delayAmount:delayAmount shouldReturn:shouldReturn];
-            }
+        if (!weakSelf.window) {
+            return;
+        }
+        // 2) We don't double fire if an animation already exists
+        if ([weakSelf.subLabel.layer animationForKey:@"position"]) {
+            return;
+        }
+        // 3) We don't not start automatically if the animation was unexpectedly interrupted
+        if (!finished) {
+            // Do not continue into the next loop
+            return;
+        }
+        // 4) A completion block still exists for the NEXT loop. A notable case here is if
+        // returnLabelToHome was called during a subclass's labelReturnToHome function
+        if (!weakSelf.scrollCompletionBlock) {
+            return;
+        }
+        
+        // Begin again, if conditions met
+        if (weakSelf.labelShouldScroll && !weakSelf.tapToScroll && !weakSelf.holdScrolling) {
+            [weakSelf scrollAwayWithInterval:interval delayAmount:delayAmount shouldReturn:shouldReturn];
         }
     };
 

Sources/Swift/MarqueeLabel.swift

@@ -840,11 +840,6 @@ open class MarqueeLabel: UILabel, CAAnimationDelegate {
         #endif
 
         scrollCompletionBlock = { [weak self] (finished: Bool) -> () in
-            guard finished else {
-                // Do not continue into the next loop
-                return
-            }
-            
             guard (self != nil) else {
                 return
             }
@@ -853,17 +848,27 @@ open class MarqueeLabel: UILabel, CAAnimationDelegate {
             self!.labelReturnedToHome(true)
 
             // Check to ensure that:
-            // 1) We don't double fire if an animation already exists
-            // 2) The instance is still attached to a window - this completion block is called for
+            
+            // 1) The instance is still attached to a window - this completion block is called for
             //    many reasons, including if the animation is removed due to the view being removed
             //    from the UIWindow (typically when the view controller is no longer the "top" view)
             guard self!.window != nil else {
                 return
             }
-            
+            // 2) We don't double fire if an animation already exists
             guard self!.sublabel.layer.animation(forKey: "position") == nil else {
                 return
             }
+            // 3) We don't not start automatically if the animation was unexpectedly interrupted
+            guard finished else {
+                // Do not continue into the next loop
+                return
+            }
+            // 4) A completion block still exists for the NEXT loop. A notable case here is if
+            // returnLabelToHome() was called during a subclass's labelReturnToHome() function
+            guard (self!.scrollCompletionBlock != nil) else {
+                return
+            }
 
             // Begin again, if conditions met
             if (self!.labelShouldScroll() && !self!.tapToScroll && !self!.holdScrolling) {