Canvas disables smooth feature if renderTarget is not Canvas.Image

import QtQuick 2.0

Rectangle {
   width: 600; height: 500

   focus: true
   Keys.onReturnPressed: {
       print('repainting...')
       canvas.requestPaint()
   }

   Canvas {
     id: canvas
     width: parent.width
     height: parent.height

     smooth: true
     // renderTarget: Canvas.Image   // if this is set, rendered output is smooth

     onPaint: {
         var ctx = canvas.getContext('2d');

         ctx.beginPath();
         ctx.moveTo(75,25);
         ctx.quadraticCurveTo(25,25,25,62.5);
         ctx.quadraticCurveTo(25,100,50,100);
         ctx.quadraticCurveTo(50,120,30,125);
         ctx.quadraticCurveTo(60,120,65,100);
         ctx.quadraticCurveTo(125,100,125,62.5);
         ctx.quadraticCurveTo(125,25,75,25);
         ctx.lineWidth = 3
         ctx.closePath();
         ctx.strokeStyle = "steelblue";
         ctx.fillStyle = "yellow";
         ctx.fill();
         ctx.stroke();
         ctx.fillStyle="green";
         ctx.font = "Bold 15px";

         ctx.fillText("QML Rocks!", 35, 60);
     }
   }

}