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scale fit mobile web content using viewport meta tag

Asked 2012-01-04T23:11:57.377
39

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
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1 Answer

8

For Android there is the addition of target-density tag.

target-densitydpi=device-dpi

So, the code would look like

<meta name="viewport" content="width=device-width, target-densitydpi=device-dpi, initial-scale=0, maximum-scale=1, user-scalable=yes" />

Please note, that I believe this addition is only for Android (but since you have answers, I felt this was a good extra) but this should work for most mobile devices.

answered 2013-07-22T14:13:37.043

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