When UI is centered (page) the background design is not stretched

[mackonsti]

Hello and many warm thanks for your great plugin/extension.

Running Firefox 58.0.2 64bit on MacOS and v0.5 of your extension.

Upon loading our HbbTV site(s), when I select in Preferences to center the HbbTV page in the UI, regardless of light or dark theme, the background image is not stretched (zebra-like) but stays only on top-left corner, rest of screen is grayish.

In the sample URLs you have (e.g. ARTE) this doesn't occur. What header do you expect in index.xhtml for example? How can I force the page to be HbbTV-interactive (per your comment on top of Preferences) to see if the background zebra-image is stretched?

Thanks!