[manifest] orientation member

TLDR; orientation is hard. We've temporarily removed it from the spec. We have two proposals below.  


Orientation of an application is dependent on the media features of the display. For example an application might need to be launched in landscape on phones (in order to have sufficient display width), but prefer to be in portrait on tablets.

When analyzing applications across various runtimes, we've found evidence that such applications are common (e.g., basically any application on the iPhone that has an iPad counterpart will be designed to constrain to a particular orientation based on the device being used: LinkedIn, Flipboard, GoodReads, etc. will all go from portrait-primary on the iPhone to allowing "any" orientation on the iPad. A more extreme example is BBC iPlayer - which supports portrait-primary on the iPhone, but both landscape orientations on iPad. The same can be seen on Android devices. Unlike native apps, Web Apps should not target devices/OS's - they have to be device neutral. 

In order to address the use cases, we currently have two proposals. 

Option 1: Provide a list of orientation sets in the manifest. The user agent uses the first one with a matching media query. The order in which the orientations are listed by a developer does not imply a preference for setting the orientation - it is always left up to the user agent to pick the best orientation given, for example, how the user is holding the device. In the example below, no orientation is given for widths of 721px or above, so the default is used: allowing all orientations supported by the device.

{
    "orientations": [{
        "media": "max-width: 320px",
        "supported": ["portrait-primary", "landscape"]
    }, {
        "media": "max-width: 720px",
        "supported": ["landscape"]
    }]
}

In this example, a device with a screen width of 320px or below would start either "portrait-primary" or "landscape" with the abilty to be "flipped" depending on how the user is holding the device (and OS permitting). A device with a screen width of 321px through 720px would request to be launched in landscape (leaving it up to the UA to pick either landscape-primary or landscape-secondary, while allowing "flippability"), and a device with a screen width of 721px and above would start in any orientation chosen by the UA (ideally, one that matches how the user is holding the device).

Option 2: The second proposal is to remove orientation from the manifest and use CSS @viewport instead. This would mean:

<head>
    <style>
        /*set it by default to portrait primary for small screens */
        @media (max-width: 320px) {
            @viewport {
                orientation: portrait-primary, landscape;
            }
        }
        /*Tablet, switch to landscape only*/
        @media (max-width: 720px) {
            @viewport {
                orientation: landscape;
            }
        }
        
        /* similarly on screens with a width of 721px or more, all orientations are allowed */
    </style>
</head>
        
Problem with using @viewport at the moment is that the specification is progressing a bit  slowly and no one has implemented the "orientation" descriptor. It also lacks definitions for "-primary" and "-secondary" contraints, which are important for various applications, and doesn't currently allow providing multiple allowed orientations - hopefully the CSS Device Adaption spec can align with the Screen Orientation spec.

Received on Friday, 29 November 2013 15:40:11 UTC