Scala Swing GUI does not respond to pressed key - swing

Question

I want to write a Scala interface where I click on an image to draw coloured columns. I would also like to detect if the Enter key is pressed. Here is my tentative code:
def main = {
def top = new MainFrame {
title = "Reactive Swing App"
val label = new Label {
var matRaw, mat = new Mat
mat = Imgcodecs.imread("data/batch/14-ZoneDetection/01-noExtraCol/VISSAGE_115.jp2", Imgcodecs.CV_LOAD_IMAGE_COLOR) // images are stored as 8UC3
Image.printCaracColor("mat", mat)
var buf = toBufferedImage(mat)
icon = new ImageIcon(buf)
listenTo(mouse.clicks) // mouse.clicks is a member of Label, this is why the click position is relative to the label
listenTo(keys)
reactions += {
case MousePressed(_, point, _, _, _) => {
mat.submat(0, mat.rows, point.getX.toInt, point.getX.toInt + 1).setTo(new Scalar(0.0, 255.0, 0.0))
buf = toBufferedImage(mat)
icon = new ImageIcon(buf)
println("Click position, x: " + point.getX + ", y: " + point.getY)
}
}
reactions += {
case KeyPressed(_, Key.Enter, _, _) => {
println("Enter pressed")
}
}
}
contents = label
}
val frame = top
frame.resizable = false
frame.visible = true
}
The case MousePressed works properly and the a green column is properly added to the displayed image. However, the case KeyPressed does not work. Could you help me fix this ?

Answer 1

It works if the label is encapsulated in a panel. The label listens to the mouse and the panel to the keyboard.