rendition orientation not supported

[danielweck]

http://www.idpf.org/epub/fxl/#property-orientation

https://github.com/readium/readium-shared-js/blob/develop/js/models/spine_item.js#L50

[danielweck]

Firefox implements the screen API:
window.screen.lockOrientation('portrait')
https://developer.mozilla.org/en-US/docs/Web/API/Screen.lockOrientation

Demo: http://aurelio.audero.it/demo/screen-orientation-api-demo.html

[danielweck]

Clarification:

Readium currently does not support this:
http://www.idpf.org/epub/fxl/#property-orientation

...but supports this:
http://www.idpf.org/epub/fxl/#property-spread

In other words, Readium is currently not able to force a given hardware/physical device
rotation (landscape or portrait) when the authored metadata requires so, but Readium does adjust
single page vs. double synthetic spread depending on the viewport
aspect ratio (which obviously changes when a tablet device is
physically rotated), and respects the author intent specified in OPF metadata (unless of course the user settings override the default / auto behaviour).