Layer functioning in roImageCanvas

Hi All,

I am trying to make custom UI by using roImageCanvas. but I am not able to understand the exact behaviour of layers.
What is the exact meaning of clear() interface in roImageCanvas?

for better understanding of my problem I am giving my sample code below.

function main()
	mainCanvas = createObject("roImageCanvas")
	mainCanvas.setlayer(0, {color:"#FF0000"})
	mainCanvas.show()
	
	canvas	= createObject("roImageCanvas")
	port = createObject("romessagePort")
	canvas.setMessagePort(port)
	
	canvas.show()
	yPosition = 0
	showDataOnCanvas(yPosition, canvas)
	
	while true
		msg = wait(0, port)
		if(type(msg) = "roImageCanvasEvent")
			if(msg.IsRemoteKeyPressed())
				index =  msg.GetIndex()
				if(index = 0)
					mainCanvas.close()
					canvas.close()
				else if(index = 2)
					yPosition = yPosition - 100
					showDataOnCanvas(yPosition, canvas)
				else if(index = 3)
					yPosition = yPosition + 100
					showDataOnCanvas(yPosition, canvas)
				end if
				
			else if(msg.isScreenClosed())
				print "comes into screen closed"
				exit while
			end if
		end if
	end while
end function


function showDataOnCanvas(yPos, canvas)
	list = []	
	canvas.AllowUpdates(false)
	canvas.ClearLayer(0)
	list.push({
		color:"#33FFFFFF", 
		compossionMode:"Source_Over"
		TargetRect:{x:0, y:0, w:1280, h:720}
		})
	list.push({
		color: "#FF0000",
		TargetRect: {x:100, y:yPos, w:300,h:100}
		})
	list.push({
		text: yPos.toStr(),
		textattrs: {color:"#000000"}, 
		TargetRect: {x:100, y:yPos, w:300,h:100}
		})
	canvas.setlayer(0, list)
	canvas.AllowUpdates(true)
end function

In this code I am create a red canvas first.
On above of this screen I made an another canvas with low opacity. On that canvas I am trying to make a box of red color and updating that canvas on click on up and down keys.

I am not able to understand the working of clear() interface.

As you can see In showDataOnCanvas(yPos, canvas) method, I am clearing the layer and drawing new data on that but its showing me the previous data also.

Can anyone explain? why is this behaving like that? Or I am missing something?


Thanks in advance.