Thursday, December 17, 2015

More Responsive WebKit Tapping on iOS

Wenson Hsieh:

We know that responsive tapping is really important to web developers — so much so that many are willing to employ JavaScript frameworks to avoid the delay using touch handlers. Instead of waiting for WebKit to fire a click after a delay, these libraries prevent the default behavior of the touchend event and call click() immediately so that the element is clicked the moment the user stops touching the element. While this may make a link feel fast, it can also reduce responsiveness in other ways, including page load time and scrolling. To address this, we baked fast tapping optimizations into WebKit so well-scaled mobile web pages will be able to achieve responsive tapping out of the box without the drawbacks of third-party frameworks.

On web pages optimized for mobile viewports, elements such as links and form controls are scaled to fit well on smaller screens. As such, double tapping on these elements increases the page scale by only a small amount. Since double tapping provides little value on these web pages, we’ve implemented a mechanism for removing the delay for single taps by disabling double tap gestures.

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