[c][cpp] Port of commit f1e0f0f (#2807)

* [c][cpp] Port of commit f1e0f0f: Fixed animation not being mixed out in some cases. #2786

* [c][cpp] Format.

---------

Co-authored-by: Davide Tantillo <[email protected]>

spine-c/spine-c/src/spine/AnimationState.c

@@ -350,18 +350,16 @@ int /*boolean*/ _spAnimationState_updateMixingFrom(spAnimationState *self, spTra
 	from->animationLast = from->nextAnimationLast;
 	from->trackLast = from->nextTrackLast;
 
-	if (to->nextTrackLast != -1) {                           // The from entry was applied at least once.
-		int discard = to->mixTime == 0 && from->mixTime == 0;// Discard the from entry when neither have advanced yet.
-		if (to->mixTime >= to->mixDuration || discard) {
-			// Require totalAlpha == 0 to ensure mixing is complete or the transition is a single frame or discarded.
-			if (from->totalAlpha == 0 || to->mixDuration == 0 || discard) {
-				to->mixingFrom = from->mixingFrom;
-				if (from->mixingFrom) from->mixingFrom->mixingTo = to;
-				to->interruptAlpha = from->interruptAlpha;
-				_spEventQueue_end(internal->queue, from);
-			}
-			return finished;
+	// The from entry was applied at least once and the mix is complete.
+	if (to->nextTrackLast != -1 && to->mixTime >= to->mixDuration) {
+		// Mixing is complete for all entries before the from entry or the mix is instantaneous.
+		if (from->totalAlpha == 0 || to->mixDuration == 0) {
+			to->mixingFrom = from->mixingFrom;
+			if (from->mixingFrom) from->mixingFrom->mixingTo = to;
+			to->interruptAlpha = from->interruptAlpha;
+			_spEventQueue_end(internal->queue, from);
 		}
+		return finished;
 	}
 
 	from->trackTime += delta * from->timeScale;

spine-cpp/spine-cpp/src/spine/AnimationState.cpp

@@ -794,18 +794,16 @@ bool AnimationState::updateMixingFrom(TrackEntry *to, float delta) {
 	from->_animationLast = from->_nextAnimationLast;
 	from->_trackLast = from->_nextTrackLast;
 
-	if (to->_nextTrackLast != -1) {                             // The from entry was applied at least once.
-		bool discard = to->_mixTime == 0 && from->_mixTime == 0;// Discard the from entry when neither have advanced yet.
-		if (to->_mixTime >= to->_mixDuration || discard) {
-			// Require totalAlpha == 0 to ensure mixing is complete or the transition is a single frame or discarded.
-			if (from->_totalAlpha == 0 || to->_mixDuration == 0 || discard) {
-				to->_mixingFrom = from->_mixingFrom;
-				if (from->_mixingFrom) from->_mixingFrom->_mixingTo = to;
-				to->_interruptAlpha = from->_interruptAlpha;
-				_queue->end(from);
-			}
-			return finished;
+	// The from entry was applied at least once and the mix is complete.
+	if (to->_nextTrackLast != -1 && to->_mixTime >= to->_mixDuration) {
+		// Mixing is complete for all entries before the from entry or the mix is instantaneous.
+		if (from->_totalAlpha == 0 || to->_mixDuration == 0) {
+			to->_mixingFrom = from->_mixingFrom;
+			if (from->_mixingFrom) from->_mixingFrom->_mixingTo = to;
+			to->_interruptAlpha = from->_interruptAlpha;
+			_queue->end(from);
 		}
+		return finished;
 	}
 
 	from->_trackTime += delta * from->_timeScale;