function createRoot(width, height) {
    var domRoot = document.createElement('div');

    // domRoot.onselectstart = returnFalse; // Avoid page selected
    domRoot.style.cssText = [
        'position:relative',
        // IOS13 safari probably has a compositing bug (z order of the canvas and the consequent
        // dom does not act as expected) when some of the parent dom has
        // `-webkit-overflow-scrolling: touch;` and the webpage is longer than one screen and
        // the canvas is not at the top part of the page.
        // Check `https://bugs.webkit.org/show_bug.cgi?id=203681` for more details. We remove
        // this `overflow:hidden` to avoid the bug.
        // 'overflow:hidden',
        'width:' + width + 'px',
        'height:' + height + 'px',
        'padding:0',
        'margin:0',
        'border-width:0'
    ].join(';') + ';';

    return domRoot;
}
zrender will do compositing when root is a canvas and have multiple zlevels.