I'd like to tag this post with '-webkit-overflow-scrolling' but I do not have enough reputation to create a new one. It seems to me adding -webkit-overflow-scrolling: touch creates a new stacking context for every descendent with a position set other then static regardless if z-index is set. After removing the -webkit-overflow-scrolling: touch it renders just as I expect. When the example is being tested on the iOS simulator, the 'sub-menu' is rendered behind the second row. Both Google Chrome and Safari on my laptop render the blue 'sub-menu' on top of the second row. IOS 6 seems to create a new stacking context for every descendent with position other than static regardless if z-index is set or not.ĭoes anyone know if this is normal expected behaviour, or is this a bug in the way -webkit-overflow-scrolling interferes with stacking order?īoth row elements have position relative, but no z-index. To the children of that element apply a translation in Z, and scale them back up to provide parallax motion without affecting their size on screen.To that same element apply a perspective value, and a perspective-origin set to top left, or 0 0.Set up a containing element to scroll with overflow-y: scroll (and probably overflow-x: hidden).# CSS in 3Dīoth Scott Kellum and Keith Clark have done significant work in the area of using CSS 3D to achieve parallax motion, and the technique they use is effectively this: Animista is a CSS animation library and a place where you can play with a collection of ready-made CSS animations and download only those you will use. If we want to deliver on the promise of parallax motion, we want something that can be applied as an accelerated property (which today means sticking to transforms and opacity), and which doesn’t rely on scroll events. Many solutions attempt to change background-position to provide the parallax look, which causes the browser to repaint the affected parts of the page on scroll, and that can be costly enough to significantly jank the animation. # Bad: updating background-positionĪnother situation we’d like to avoid is painting on every frame. ![]() If the main thread is busy with any other work, scroll events will not get delivered immediately, meaning the parallax effect will be lost. ![]() More recent versions do deliver scroll events during the animation, but, similarly to Chrome, on a "best-effort" basis. In older versions of Mobile Safari, scroll events were actually delivered at the end of the scroll, which made it impossible to make a JavaScript-based scroll effect. This important piece of information tells us why we need to avoid a JavaScript-based solution that moves elements based on scroll events: JavaScript doesn’t guarantee that parallaxing will keep in step with the page’s scroll position. In most browsers scroll events are delivered as "best-effort" and are not guaranteed to be delivered on every frame of the scroll animation! Feature: CSS property: -webkit-overflow-scrolling CSS property: -webkit-overflow-scrolling Usage of Global 0.56 Current aligned Usage relative Date relative Filtered Chrome 4 - 113 114 115 - 117 Edge 12 - 113 114 Safari 3.1 - 16.4 16.5 16. This applies, in our particular case, to scroll events. While that sounds simple, an important mechanism of modern browsers is their ability to work asynchronously. Value not found in DB Values auto Use 'regular' scrolling, where the content immediately ceases to scroll when you remove your finger from the touchscreen. The key requirement of parallaxing is that it should be scroll-coupled for every single change in the page’s scroll position, the parallaxing element's position should update. The -webkit-overflow-scrolling CSS property controls whether or not touch devices use momentum-based scrolling for the given element. To begin with, let’s take a look at two common ways of achieving a parallax effect, and in particular, why they are unsuitable for our purposes. If you want the drop-in solution, head over to the UI Element Samples GitHub repo and grab the Parallax helper JS! You can see a live demo of the parallax scroller in the GitHub repo. For Mobile Safari use position: sticky to ensure that the parallax effect gets propagated.auto Enable browser handling of all panning and zooming gestures. Use CSS 3D transforms to create a more accurate parallax effect. Syntax The touch-action property may be specified as either: any one of the keywords auto, none, manipulation, or one of the keywords pan-x, pan-left, pan-right, and/or one of the keywords pan-y, pan-up, pan-down, plus optionally the keyword pinch-zoom.Don’t use scroll events or background-position to create parallax animations.In this article, we’ll discuss a solution that is both performant and, just as importantly, works cross-browser. The problem, however, is that implementing parallaxing in a performant way can be challenging. When used judiciously, it can add depth and subtlety to a web app. Love it or hate it, parallaxing is here to stay.
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