Some suggestions for Chromecast integration
First of all, thank you for the hard work you have put into the browser. I switched from Chrome to Vivaldi recently and one of the things that I use a lot is to stream video from my laptop to the HD TV to free up my laptop to do other things whilst watching and listening to online content.
A few things that I have noticed since switching over is how different each browser works and some things are omitted that I would love to see added to Vivaldi, hopefully in the near future.
Whilst it is easy to invoke Chromecast through the right click menu, it would also be useful for a cast option to be available via the Vivaldi menu (which I have seen mentioned here elsewhere) - probably under the tools menu. The Cast pop-up also appears in the middle of the screen, not a showstopper but would be better suited at the top of the screen, as per Chrome.
One of the major differences between Chrome and Vivaldi is how full screen casting works. Chrome puts the video in a tab when you press the full screen button on a video player and casts the video within the tab, allowing you to use other tabs whilst the video plays in the casting tab. Vivaldi ignores this and puts the video full screen on the laptop, as if the tab wasn't casting at all. You can't use the computer and cast in full screen which defeats the purpose of casting on websites which don't natively support Chrome.
Something else I noted is that the tab mirroring will only update if you move the mouse on screen. Otherwise everything will freeze or at best, run at a very low framerate (1fps or less).
I know I could cast video via a tablet or phone but it defeats the purpose and convenience of casting content via a computer.
Regardless, many thanks and keep up the great work.