Why does the chromecast declare its client height and width to be 720p to the receiver app server?
I am trying to display non-video content and assumed I would be able to use the full 1080p resolution. The device reports to the TV that it is in 1080p 60hz but if you look at the on device developer tools it is only displaying my receiver app as 1280x720.
Is there a way to force the page to render at full resolution?
Chromecast devices have a different Graphics Window size than it's Video window - The Graphics window uses a 1280x720 resolution surface. The window.height and window.width properties are going to report 720 and 1280 respectively. However, Chromecast is capable of displaying video at up to 1080p resolution i.e. 1920x1080. Therefore applications should not use the screen size to select video content resolution.
While the UI layer of Chromecast currently only supports 1280x720, the Google Cast team recommends that developers do not hardcode this screen size as it might change in the future.
In a response to a similar question in the post below John Affaki wrote: "Right now, we have a limitation where the "UI" layer is at 720p even though video can run at 1080p. It's on our roadmap to revisit this, so I'm suggesting that you build your app in a way that will just work if this gets fixed."
https://plus.google.com/100147701757803136741/posts/JDhtJTw7jz5
It's possible this has changed at some point, but despite the pixel size being reported as 1280x720, it is actually rendering at the full resolution. Just like smartphone viewport scaling, except that I don't see a way to disable it.
So, even though it says 1280x720, trust that it is rendering at a higher resolution!
I have uploaded a test image on this question: Getting actual width of Chromecast receiver UI
