Android viewport setting “user-scalable=no” breaks width / zoom level of viewport

Question

I am working on a web app which has a width of 640px.

In the document head I set

Answer 1

I wanted mobile to always show a website 640px wide because of a design that would break otherwise. (a design I did not make..) Thereby I wanted to disable zooming for mobile users. What worked for me me is the following:

- UPDATED 2013-10-31

First of all, there is no way you can do this without Javascript. You will have to check the user agent string. Therefore I created a mobile-viewport.js and included the script just before the closing tag:

function writeViewPort() {
    var ua = navigator.userAgent;
    var viewportChanged = false;
    var scale = 0;

    if (ua.indexOf("Android") >= 0 && ua.indexOf("AppleWebKit") >= 0) {
        var webkitVersion = parseFloat(ua.slice(ua.indexOf("AppleWebKit") + 12));
        // targets android browser, not chrome browser (http://jimbergman.net/webkit-version-in-android-version/)
        if (webkitVersion < 535) {
            viewportChanged = true;
            scale = getScaleWithScreenwidth();
            document.write('');
        }
    }

    if (ua.indexOf("Firefox") >= 0) {
        viewportChanged = true;
        scale = (getScaleWithScreenwidth() / 2);
        document.write('');
    }

    if (!viewportChanged) {
        document.write('');
    }

    if (ua.indexOf("IEMobile") >= 0) {
        document.write('');
    }

    document.write('');
}

function getScaleWithScreenwidth() {
    var viewportWidth = 640;
    var screenWidth = window.innerWidth;
    return (screenWidth / viewportWidth);
}

writeViewPort();

The script checks if the visitor has an android (not chrome) or firefox browser. The android browser does not support the combination of width=640 and user-scalable=false, and the firefox browser does have a double screen width for some strange reason. If the visitor has a windows phone IE browser MobileOptimized is set.