scale fit mobile web content using viewport meta tag
I'm trying to figure out how to leverage the mobile viewport meta tag to automatically zoom the contents of a HTML page to fit into a web view.
Constraints:
- The HTML may or may not have fixed size elements (ex img has a fixed width of 640). In other words I don't want to force the content to be fluid and use %'s.
- I do not know the size of the webview, I just know its aspect ratio
For example, if I have a single image (640x100px) I want the image to zoom out if the webview is 300x250 (scale down to fit). On the other hand, if the webview is 1280x200 I want the image to zoom in and fill the webview (scale up to fit).
After reading the android docs and the iOS docs on viewports, it seems simple: since I know the width of my content (640) I just set the viewport width to 640 and let the webview decide if it needs to scale the content up or down to fit the webview.
If I put the following into my android/iPhone browser OR a 320x50 webview, the image does not zoom out to fit the width. I can scroll the image to the right and left..
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Test Viewport</title>
<meta name="viewport" content="width=640" />
<style type="text/css">
html, body {
margin: 0;
padding: 0;
vertical-align: top;
}
h1,h2,h3,h4,h5,h6,p,blockquote,pre,a,abbr,acronym,address,cite,code,del,dfn,em,img,q,s,samp,small,strike,strong,sub,sup,tt,var,dd,dl,dt,li,ol,ul,fieldset,form,label,legend,button,table,caption,tbody,tfoot,thead,tr,th,td
{
margin: 0;
padding: 0;
border: 0;
font-weight: normal;
font-style: normal;
font-size: 100%;
line-height: 1;
font-family: inherit;
vertical-align: top;
}
</style>
</head>
<body>
<img src="http://www.dmacktyres.com/img/head_car_tyres.jpg">
</body>
</html>
What am I doing wrong here? Does the viewport meta tag only zoom into content that is < the webview area?
Answer
In the head add this
//Include jQuery
<meta id="Viewport" name="viewport" content="initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no">
<script type="text/javascript">
$(function(){
if( /Android|webOS|iPhone|iPad|iPod|BlackBerry/i.test(navigator.userAgent) ) {
var ww = ( $(window).width() < window.screen.width ) ? $(window).width() : window.screen.width; //get proper width
var mw = 480; // min width of site
var ratio = ww / mw; //calculate ratio
if( ww < mw){ //smaller than minimum size
$('#Viewport').attr('content', 'initial-scale=' + ratio + ', maximum-scale=' + ratio + ', minimum-scale=' + ratio + ', user-scalable=yes, width=' + ww);
}else{ //regular size
$('#Viewport').attr('content', 'initial-scale=1.0, maximum-scale=2, minimum-scale=1.0, user-scalable=yes, width=' + ww);
}
}
});
</script>