Can I change the viewport meta tag in mobile safari on the fly?
JavascriptMobile SafariViewportJavascript Problem Overview
I have an AJAX app built for mobile Safari browser that needs to display different types of content.
For some content, I need user-scalable=1 and for other ones, I need user-scalable=0.
Is there a way to modify the value of the content attribute without refreshing the page?
<meta name="viewport" content="width=device-width; initial-scale=1.0; maximum-scale=1.0; user-scalable=0;" />
Javascript Solutions
Solution 1 - Javascript
I realize this is a little old, but, yes it can be done. Some javascript to get you started:
viewport = document.querySelector("meta[name=viewport]");
viewport.setAttribute('content', 'width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0');
Just change the parts you need and Mobile Safari will respect the new settings.
Update:
If you don't already have the meta viewport tag in the source, you can append it directly with something like this:
var metaTag=document.createElement('meta');
metaTag.name = "viewport"
metaTag.content = "width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0"
document.getElementsByTagName('head')[0].appendChild(metaTag);
Or if you're using jQuery:
$('head').append('<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">');
Solution 2 - Javascript
in your <head>
<meta id="viewport"
name="viewport"
content="width=1024, height=768, initial-scale=0, minimum-scale=0.25" />
somewhere in your javascript
document.getElementById("viewport").setAttribute("content",
"initial-scale=0.5; maximum-scale=1.0; user-scalable=0;");
... but good luck with tweaking it for your device, fiddling for hours... and i'm still not there!
Solution 3 - Javascript
This has been answered for the most part, but I will expand...
Step 1
My goal was to enable zoom at certain times, and disable it at others.
// enable pinch zoom
var $viewport = $('head meta[name="viewport"]');
$viewport.attr('content', 'width=device-width, initial-scale=1, maximum-scale=4');
// ...later...
// disable pinch zoom
$viewport.attr('content', 'width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no');
Step 2
The viewport tag would update, but pinch zoom was still active!! I had to find a way to get the page to pick up the changes...
It's a hack solution, but toggling the opacity of body did the trick. I'm sure there are other ways to accomplish this, but here's what worked for me.
// after updating viewport tag, force the page to pick up changes
document.body.style.opacity = .9999;
setTimeout(function(){
document.body.style.opacity = 1;
}, 1);
Step 3
My problem was mostly solved at this point, but not quite. I needed to know the current zoom level of the page so I could resize some elements to fit on the page (think of map markers).
// check zoom level during user interaction, or on animation frame
var currentZoom = $document.width() / window.innerWidth;
I hope this helps somebody. I spent several hours banging my mouse before finding a solution.