Is there a way to change styles found in a shadow element? Specifically, extend/overwrite some properties found in a css class? I am using a chrome-extension called Beanote which hasn't been updated since April(2017) and there's a pesky bug I'd like to fix. I found that one line of css patches it up enough for me, but I am at a loss at applying it without going inside of the shadow element itself and directly editing those styles in the dev tools.
I'm looking for a way for this:
/*global css rule*/ .the-class-name { property-name: my-value; }
to overwrite this:
/* style tag inside the shadow-root */ .the-class-name { property-name: bad-value; }
Most of the resources I've found online with queries involving shadow-root override style
or edit shadow-root styling
had something to do with :host
which, if its meant for this, doesn't work for my needs or deprecated functionality like ::shadow
.
Work with Shadow DOM elements using RemoteWebDriver To access these Shadow DOM elements, we need to use the JavascriptExecutor executeScript() function. If you look at the DOM structure, every element that includes Shadow DOM also has a shadowRoot property that describes the underlying elements.
To override the CSS properties of a class using another class, we can use the ! important directive. In CSS, ! important means “this is important”, and the property:value pair that has this directive is always applied even if the other element has higher specificity.
The :host selector allows to select the shadow host (the element containing the shadow tree).
Because of the isolation of styles, which is a feature of Shadow DOM, you cannot define a global CSS rule that will be applied in the Shadow DOM scope.
It could be possible with CSS variables but they should be implemented explicitly in the shadowed component (which is not the case with this 3rd party library).
A workaround is to inject the line of style in the shadow DOM directly.
//host is the element that holds the shadow root: var style = document.createElement( 'style' ) style.innerHTML = '.the-class-name { property-name: my-value; }' host.shadowRoot.appendChild( style )
NB: it will work only if the Shadow DOM mode
is set to 'open'
.
2019 update for Chrome 73+ and Opera 60+
Now it is possible to instantiate a CSSStyleSheet object directly and to affect it to a Shadow DOM or a document:
var sheet = new CSSStyleSheet sheet.replaceSync( `.color { color: pink }`) host.shadowRoot.adoptedStyleSheets = [ sheet ]
Ionic V4 select down icon color change example
document.querySelector('#my-select').shadowRoot.querySelector('.select-icon-inner').setAttribute('style', 'opacity:1'); ionViewDidEnter() { document.querySelector('#my-select').shadowRoot.querySelector('.select-icon-inner').setAttribute('style', 'opacity:1'); }
If you want overwrite the default generated shadowRoot style then have to call js function after page loaded fully.
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