offscreencanvas.getcontext.html

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This WPT test may be referenced by the following Test IDs:
- /html/canvas/offscreen/manual/the-offscreen-canvas/offscreencanvas.getcontext.html - WPT Dashboard Interop Dashboard

<!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-offscreencanvas-getcontext">

<script>

test(function() {

    var offscreenCanvas = new OffscreenCanvas(1, 1);

    assert_throws_js(TypeError, function() { offscreenCanvas.getContext('3d'); });

}, "Test that getContext with un-supported string throws a TypeError.");

test(function() {

    var offscreenCanvas1 = new OffscreenCanvas(1, 1);

    var ctx1 = offscreenCanvas1.getContext('2d');

    assert_true(ctx1 instanceof OffscreenCanvasRenderingContext2D);

    var offscreenCanvas2 = new OffscreenCanvas(1, 1);

    var ctx2 = offscreenCanvas2.getContext('webgl');

    assert_true(ctx2 instanceof WebGLRenderingContext);

    var offscreenCanvas3 = new OffscreenCanvas(1, 1);

    var ctx3 = offscreenCanvas3.getContext('webgl2');

    assert_true(ctx3 instanceof WebGL2RenderingContext);

}, "Test that getContext with supported string returns correct results");

test(function() {

    var offscreenCanvas1 = new OffscreenCanvas(1, 1);

    var ctx1 = offscreenCanvas1.getContext('2d');

    var ctx2 = offscreenCanvas1.getContext('webgl');

    assert_equals(ctx2, null);

    var offscreenCanvas2 = new OffscreenCanvas(1, 1);

    var ctx3 = offscreenCanvas2.getContext('webgl');

    var ctx4 = offscreenCanvas2.getContext('2d');

    assert_equals(ctx4, null);

}, "Test that getContext twice with different context type returns null the second time");

test(function() {

    var offscreenCanvas = new OffscreenCanvas(1, 2);

    var ctx = offscreenCanvas.getContext('2d');

    var dstCanvas = ctx.canvas;

    assert_equals(dstCanvas.width, 1);

    assert_equals(dstCanvas.height, 2);

}, "Test that 2dcontext.canvas should return the original OffscreenCanvas");

test(function() {

    var offscreenCanvas = new OffscreenCanvas(1, 2);

    var ctx = offscreenCanvas.getContext('webgl');

    var dstCanvas = ctx.canvas;

    assert_equals(dstCanvas.width, 1);

    assert_equals(dstCanvas.height, 2);

}, "Test that webglcontext.canvas should return the original OffscreenCanvas");

test(function() {

    var offscreenCanvas = new OffscreenCanvas(10, 10);

    var ctx = offscreenCanvas.getContext('2d', {alpha: false});

    ctx.fillStyle = 'rgba(0, 255, 0, 0.5)';

    ctx.fillRect(0, 0, 10, 10);

    _assertPixelApprox(offscreenCanvas, 5,5, 0,127,0,255, 2);

}, "Test that OffscreenCanvasRenderingContext2D with alpha disabled makes the OffscreenCanvas opaque");

test(function() {

    var offscreenCanvas = new OffscreenCanvas(10, 10);

    var ctx = offscreenCanvas.getContext('2d', {alpha: true});

    ctx.fillStyle = 'rgba(0, 255, 0, 0.5)';

    ctx.fillRect(0, 0, 10, 10);

    _assertPixelApprox(offscreenCanvas, 5,5, 0,255,0,127, 2);

}, "Test that OffscreenCanvasRenderingContext2D with alpha enabled preserves the alpha");

test(function() {

    var offscreenCanvas = new OffscreenCanvas(10, 10);

    var ctx = offscreenCanvas.getContext('2d');

    ctx.fillStyle = 'rgba(0, 255, 0, 0.5)';

    ctx.fillRect(0, 0, 10, 10);

    _assertPixelApprox(offscreenCanvas, 5,5, 0,255,0,127, 2);

}, "Test that 'alpha' context creation attribute is true by default");

</script>