It seems that Chrome forces hardware-accelerated transforms on text that is on top of a canvas element.
Can anyone help me understand this behavior? Ultimately, I'd like to scale text on top of a canvas element without having the text converted to a texture.
This fiddle shows the issue: http://jsfiddle.net/Gb6h4/1/
Here is the code:
// Get a reference to the canvas and its context
var $canvas = $("canvas");
var ctx = $canvas[0].getContext('2d');
// Make the canvas fullscreen
var width = $(window).width(),
height = $(window).height();
$canvas.attr({
width: width,
height: height
});
// In Chrome, modifying the canvas context in any way
// seems to force a hardware-accelerated transform
// on the text.
// (The text is scaled as a texture, becoming blurrier.)
// Uncomment the line below and compare the difference.
// ctx.fillStyle = "grey";
// Set up a simple zoom animation on our "Hello!" div
var $div = $(".transformed");
var scale = 1;
setInterval(function () {
scale += 0.005;
$div.css({
transform: "translate(0px, 0px) scale("+scale+")"
});
}, 16);
In the fiddle, by default, the text scales as expected (i.e., a non-accelerated CSS transform). However, after interaction with the canvas context, the text scales differently (as it would in an accelerated transform).