<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/html/canvas/resources/canvas-tests.js"></script>
<link rel="help" href="https://html.spec.whatwg.org/#dom-canvas-transfercontroltooffscreen">
<script>

test(function() {
    var placeholder = document.createElement('canvas');
    placeholder.width = 100;
    placeholder.height = 50;
    var offscreenCanvas = placeholder.transferControlToOffscreen();
    assert_equals(offscreenCanvas.width, 100);
    assert_equals(offscreenCanvas.height, 50);
}, "Test that an OffscreenCanvas generated by transferControlToOffscreen gets correct width and height");

test(function() {
    var placeholder = document.createElement('canvas');
    placeholder.width = 100;
    placeholder.height = 50;
    var offscreenCanvas = placeholder.transferControlToOffscreen();
    assert_throws_dom("InvalidStateError", function() { placeholder.getContext('2d'); });
}, "Test that calling getContext on a placeholder canvas that has already transferred its control throws an exception");

test(function() {
    var placeholder = document.createElement('canvas');
    placeholder.width = 100;
    placeholder.height = 50;
    var offscreenCanvas = placeholder.transferControlToOffscreen();
    assert_throws_dom("InvalidStateError", function() { placeholder.transferControlToOffscreen(); });
}, "Test that calling transferControlToOffscreen twice throws an exception");

</script>

