Twenty Thirteen: responsive menu non-functional on Android phones

[tady]

The Twenty Thirteen theme proposes a responsive solution. This works great on browser screen resize and iPhone.

The fixed header that appears after scrolling past the main nav, does not appear on Android HTC Desire S. As this is required for responsive use of the site, this is a pretty large failing of the theme. Android older than version 4, does not support the css style "position:fixed".

Tested on HTC Desire S (Android 2.3.5) and Google Nexus 7 (Android 4.2.2), iPad 3 (iOS 6.1.1) and iPhone 4s (iOS 6.1.1).

Also wish to add that the YouTube example does not resize on same Android phone. I realise that developers will create their own themes that may accommodate these features better, but the bundled theme should at least work for all users.

The theme designer uses an Android ... hmm. :)

Thanks for the reports.

Samsung Galaxy S3 using Jelly Bean 4.1.1:

Stock browser: menu works fine. The fixed header that appears on scroll looks a bit funky though. The search icon floats left into the site title. Before scrolling and getting the fixed header, the search icon also floats left next to the menu toggle.

Chrome for Android: menu works fine. Fixed header looks rights until you tap the search icon, then it shifts into site title, but this has already been reported elsewhere.

On any mobile view, it would be nice if the menu toggle would appear in the fixed header when scrolling, making nav accessible at any scroll position. But certainly not necessary and not a bug.

In [23533] Twenty Thirteen: disable fixed navbar on small screens. Props obenland, fixes #23647.

Also closes #23526, #23535, and #23566