I want to know please if it is possible to build a cast app for google home which casts content from an app to Chromecast using Google home. For example, "Ok google, play XXXAudio/videoContent from XXXApp on the TV."
This means that I want to cast a content from XXXApp to Chromecast, but without using the phone to do that, but rather using Google home.
I have imagined doing that like : Google home retrieves the requested data from the XXXApp then casts the content, through the receiver, to Chromecast. The requested content is then displayed on the TV.
Any help or advice will be appreciated.
It depends exactly what you want your cast app to do.
If you want to be able to provide media just like someone like Spotify or a local streaming radio station does, you need to parter with Google. You'll then have access to a range of partner solution feed options.
If you have other cast apps that you want, or other things that you may want to cast to a tv (for example) - these aren't currently available. However, Smart Displays using the Assistant are coming shortly, and these may start to introduce capabilities that will also be available for cast devices.
One could probably do something that started the cast app from an existing supported device and then, once running, control it via an Action. But this isn't something directly available right now.