| <!doctype html> |
| <script src="../../resources/js-test.js"></script> |
| <script src="../../resources/testharness.js"></script> |
| <script src="../../resources/testharnessreport.js"></script> |
| <script> |
| |
| async_test(t => { |
| assert_true(!!window.internals, 'This test requires window.internals.'); |
| |
| const canvas = new OffscreenCanvas(500, 500); |
| const ctx = canvas.getContext('2d'); |
| |
| canvas.oncontextlost = t.step_func(function() { |
| // Add calls are no-ops: `restore` and `endLayer` shouldn't throw despite |
| // not having matching `save` and `beginLayer` calls. |
| ctx.restore(); |
| ctx.endLayer(); |
| ctx.endLayer(); |
| ctx.beginLayer(); |
| }); |
| |
| canvas.oncontextrestored = t.step_func_done(function() { |
| // Canvas should be back to it's default state, with no layer opened. |
| ctx.beginLayer(); |
| ctx.endLayer(); |
| assert_throws_dom('INVALID_STATE_ERR', () => { |
| ctx.endLayer(); |
| }); |
| }); |
| |
| ctx.beginLayer(); |
| internals.forceLoseCanvasContext(ctx); |
| }, 'Test losing context while layers are opened.'); |
| |
| </script> |
