How Can You Maintain Fixed Element Size on Touchscreen Zoom?

Maintain Element Size on Touchscreen Zoom

When fixed elements are displayed on a touchscreen device, zooming in or out can cause them to resize, creating an undesired behavior. This can disrupt site navigation or lead to overlapping content.

One approach to prevent this behavior is to dynamically adjust the element's scale using CSS3 transforms. By monitoring the scroll event, we can calculate the zoom factor and apply it to the element, keeping its size consistent.

For instance, the following code snippet calculates the zoom factor and applies it as a scale transformation:

el.style["transform"] = "scale(" + window.innerWidth/document.documentElement.clientWidth + ")";

However, this adjustment alone may not be sufficient. Fixed elements tend to behave differently on mobile Safari with zoomed pages. To compensate, we can place the scaled element absolutely within a 100% height parent element and adjust its position dynamically:

overlay.style.left = window.pageXOffset + 'px';
overlay.style.bottom = document.documentElement.clientHeight - (window.pageYOffset + window.innerHeight) + 'px';

By employing these techniques, we can effectively prevent fixed elements from resizing when zooming on touchscreen devices, ensuring they maintain their intended size and visibility.

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