How do I reset the scale/zoom of a web app on an orientation change on the iPhone?

How do I reset the scale/zoom of a web app on an orientation change on the iPhone?

When I start my app in portrait mode, it works fine. Then I rotate into landscape and it’s scaled up. To get it to scale correctly for the landscape mode I have to double tap on something twice, first to zoom all the way in (the normal double tap behavior) and again to zoom all the way out (again, the normal double tap behavior). When it zooms out, it zooms out to the correct NEW scale for landscape mode.
Switching back to portrait seems to work more consistently; that is, it handles the zoom so that the scale is correct when the orientation changes back to portrait.
I am trying to figure out if this is a bug? or if this is something that can be fixed with JavaScript?
With the viewport meta content, I am setting the initial-scale to 1.0 and I am NOT setting minimum or maximum scale (nor do I want to). I am setting the width to device-width.
Any ideas? I know a lot of people would be grateful to have a solution as it seems to be a persistent problem.

Solutions/Answers:

Solution 1:

Jeremy Keith (@adactio) has a good solution for this on his blog Orientation and scale

Keep the Markup scalable by not setting a maximum-scale in markup.

<meta name="viewport" content="width=device-width, initial-scale=1">

Then disable scalability with javascript on load until gesturestart when you allow scalability again with this script:

if (navigator.userAgent.match(/iPhone/i) || navigator.userAgent.match(/iPad/i)) {
    var viewportmeta = document.querySelector('meta[name="viewport"]');
    if (viewportmeta) {
        viewportmeta.content = 'width=device-width, minimum-scale=1.0, maximum-scale=1.0, initial-scale=1.0';
        document.body.addEventListener('gesturestart', function () {
            viewportmeta.content = 'width=device-width, minimum-scale=0.25, maximum-scale=1.6';
        }, false);
    }
}

Update 22-12-2014:
On an iPad 1 this doesnt work, it fails on the eventlistener. I’ve found that removing .body fixes that:

document.addEventListener('gesturestart', function() { /* */ });

Solution 2:

Scott Jehl came up with a fantastic solution that uses the accelerometer to anticipate orientation changes. This solution is very responsive and does not interfere with zoom gestures.

https://github.com/scottjehl/iOS-Orientationchange-Fix

How it works: This fix works by listening to the device’s
accelerometer to predict when an orientation change is about to occur.
When it deems an orientation change imminent, the script disables user
zooming, allowing the orientation change to occur properly, with
zooming disabled. The script restores zoom again once the device is
either oriented close to upright, or after its orientation has
changed. This way, user zooming is never disabled while the page is in
use.

Minified source:

/*! A fix for the iOS orientationchange zoom bug. Script by @scottjehl, rebound by @wilto.MIT License.*/(function(m){if(!(/iPhone|iPad|iPod/.test(navigator.platform)&&navigator.userAgent.indexOf("AppleWebKit")>-1)){return}var l=m.document;if(!l.querySelector){return}var n=l.querySelector("meta[name=viewport]"),a=n&&n.getAttribute("content"),k=a+",maximum-scale=1",d=a+",maximum-scale=10",g=true,j,i,h,c;if(!n){return}function f(){n.setAttribute("content",d);g=true}function b(){n.setAttribute("content",k);g=false}function e(o){c=o.accelerationIncludingGravity;j=Math.abs(c.x);i=Math.abs(c.y);h=Math.abs(c.z);if(!m.orientation&&(j>7||((h>6&&i<8||h<8&&i>6)&&j>5))){if(g){b()}}else{if(!g){f()}}}m.addEventListener("orientationchange",f,false);m.addEventListener("devicemotion",e,false)})(this);

Solution 3:

I had the same problem, and setting the maximum-scale=1.0 worked for me.

Edit:
As mentioned in the comments this does disable user zoom except when the content exceeds the width-resolution. As mentioned, this might not be wise. It might also be desired in some cases.

The viewport code:

    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0;">

Solution 4:

If you have the width set in the viewport :

<meta name = "viewport" content = "width=device-width; initial-scale=1.0;
 maximum-scale=1.0;" />

And then change the orientation it will randomly zoom in sometimes (especially if you are dragging on the screen) to fix this don’t set a width here I used :

<meta id="viewport" name="viewport" content="initial-scale=1.0; user-scalable=0;
minimum-scale=1.0; maximum-scale=1.0" />

This fixes the zoom whatever happens then you can use either window.onorientationchange event or if you want it to be platform independant (handy for testing) the window.innerWidth method.

Solution 5:

MobileSafari supports the orientationchange event on the window object. Unfortunately there doesn’t seem to be a way to directly control the zoom via JavaScript. Perhaps you could dynamically write/change the meta tag which controls the viewport — but I doubt that would work, it only affects the initial state of the page. Perhaps you could use this event to actually resize your content using CSS. Good luck!

Solution 6:

I created a working demo of a landscape/portrait layout but the zoom must be disabled for it to work without JavaScript:

http://matthewjamestaylor.com/blog/ipad-layout-with-landscape-portrait-modes