Abort animation start if the properties are already being animated

framer/Animation.coffee

@@ -98,11 +98,16 @@ class exports.Animation extends EventEmitter
 			@_stateB[k] = v if @_stateA[k] != v
 
 		if _.isEqual(@_stateA, @_stateB)
-			console.warn "Nothing to animate"
-			return
+			console.warn "Animation: nothing to animate, all properties are equal to what it is now"
+			return false
 
 		# See if another animation targeting the same layer is animating the same properties
-
+		for runningAnimation in @_target.animations()
+			for key in _.keys(runningAnimation._stateA)
+				if @_stateA.hasOwnProperty(key)
+					console.warn "Animation: property #{key} is already being animated for this 
+						layer by another animation, so we bail"
+					return false
 
 		if @options.debug
 			console.log "Animation.start"
@@ -124,6 +129,8 @@ class exports.Animation extends EventEmitter
 		else
 			@_start()
 
+		return true
+
 	stop: (emit=true)->
 		@options.layer._context._animationList = _.without(
 			@options.layer._context._animationList, @)

test/tests/LayerAnimationTest.coffee

@@ -103,6 +103,25 @@ describe "LayerAnimation", ->
 				layer.x.should.be.within(10, 40)
 				done()
 
+		it "should not start animating the same property", ->
+
+			layer = new Layer()
+
+			animationA = new Animation
+				layer: layer
+				properties: {x:50}
+				curve: "linear"
+				time: 0.5
+
+			animationB = new Animation
+				layer: layer
+				properties: {x:50}
+				curve: "linear"
+				time: 0.5
+
+			animationA.start().should.equal true
+			animationB.start().should.equal false
+
 	describe "Context", ->
 
 		it "should list running animations", ->