This ruined the illusion that the vertical menus were attached to the horizontal menu, and instead appeared to be floating above the entire page. Putting the effect there made the menus stand out nicely with respect to the page content beneath, however, the shadow poked above the top of the element and extended into the horizontal menu. I was happily adding box-shadow to all sorts of elements ( tastefully of course!) until I got to the drop-down menu system. With the imminent release of Opera 10.5, Internet Explorer will be the only mainstream browser that doesn't support the property in any form.īy definition, IE will just ignore the property, so adding it will give users of other browsers a richer experience, while not harming the experience of IE users. The real difference is in their performance.I've been redesigning the company website for the past couple months and have found myself taking a liking to the box-shadow CSS3 property. Let’s look at it alongside a regular shadow animation. ![]() Let’s create a simple box-shadow animation, starting with some HTML: Īnd here’s some CSS for the initial and the final shadow. A typical shadow animation will involve a change in one or more of these values: box-shadow : These four values are the shadow’s horizontal position (x-offset), vertical position (y-offset), spread, and blur radius respectively. Just because it looks good on your computer doesn’t mean it’s the same everywhere else.Ī box-shadow has four values and a color. But you have to consider users with slower PCs and unreliable internet connections. The video below shows what you should see.Īs a developer, you may not have any issue running shadow animations because you have a fast computer. Please note that paint flashing may not work in CodePen demos, so you’ll want to try this with a live preview from a text editor. You can also do the same experiment with layout: just uncheck Paint flashing and select Layout Shift Regions. ![]() You’ll find that every element with a shadow flashes green when you hover over it, or when you refresh the page. ![]() Every time there’s a painting event, the screen will flash green: Check More tools and select Rendering.įor this example, Paint flashing is selected. First, open up the inspector tool (Chrome is pictured below), and click on the three dots on the top right corner of the tab. With your browser’s inspector tool, you can observe this process in real time. Compositing is the least tasking process out of all three. This will mean fewer style recalculations, and smoother animations. CSS properties like opacity and transform affect just the element they’re applied to. In compositing, only parts of the page change. Simply put, if the animated property affects other elements, it will change the layout of the page, causing recalculations - which uses a lot of system resources.Ĭompositing. The CSS properties that cause this include padding, margin, border. A good example would be a sidebar pushing other elements out of the way when expanding. Some animations change the structure of a page, which can lead to many style recalculations. According to Mozilla, the ideal CSS animation should run at 60fps. Basically, it creates a new shadow at every frame of the animation. In painting, the browser fills in the pixels with color, and box-shadow is one of the CSS properties that triggers this event. These events are painting, layout, and compositing. There are three main processes, or events, that are triggered during box shadow animation (or any form of animation, for that matter). Three Main CSS Box Shadow Animation Eventsīecause of what’s happening behind the scenes, CSS box-shadow animation can be resource heavy.
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