LayoutTests/accessibility/accessibility-node-memory-management.html

<!DOCTYPE HTML>
<html>
<head>
<script src="../resources/accessibility-helper.js"></script>
<script src="../resources/js-test.js"></script>
</head>
<body>

<canvas id="canvas" tabindex="-1"></canvas>

<script>
var output = "This test makes sure that AccessibilityNodeObjects are properly detached when the node they point to is deleted.\n\n";


if (window.testRunner && window.accessibilityController) {
    window.jsTestIsAsync = true;

    var canvas = document.getElementById("canvas");
    // Create an ordinary button on the page, focus it and get its accessibility role.
    var button = document.createElement("button");
    document.body.appendChild(button);
    button.focus();

    var detachedRole = null;
    var buttonRole = null;
    var axCanvas = null;
    setTimeout(async function() {
        await waitFor(() => {
            axButton = accessibilityController.focusedElement;
            if (!axButton)
                return false;
            buttonRole = axButton.role;
            return buttonRole.toLowerCase().includes("button");
        });

        // Now remove the button from the tree and get the role of the detached accessibility object.
        document.body.removeChild(button);
        await waitFor(() => {
            detachedRole = axButton.role;
            return detachedRole !== buttonRole;
        });

        // This time create a button that's a child of a canvas element. It will be focusable but not rendered.
        // In particular, this will create an AccessibilityNodeObject rather than an AccessibilityRenderObject.
        button = document.createElement("button");
        canvas.appendChild(button);

        // Note: Focusing the button and using that to get its accessibility object creates an extra
        // reference to the button and it won't get deleted when we want it to. So instead we focus the
        // canvas and get its first child.
        canvas.focus();

        await waitFor(() => {
            axCanvas = accessibilityController.accessibleElementById("canvas");
            axButton = axCanvas?.childAtIndex(0);
            return axButton && axButton.role === buttonRole;
        });

        // Now delete the last reference to the button.
        canvas.removeChild(button);
        // Explicitly run garbage collection now. Since there are no more references to the button,
        // it will be destroyed.
        gc();

        // Ensure that the accessibility object is detached by checking its role.
        detachedCanvasButtonRole = axButton.role;
        output += await expectAsync("axButton.role", "detachedRole");

        debug(output);
        finishJSTest();
    }, 0);
}
</script>
</body>
</html>