RemotePlayback

True when media elements expose a remote object. Chromium and Safari implement it; note that the presence of the API says nothing about whether any device is on the network - that is what WatchAvailability answers.

@inject Bit.Butil.RemotePlayback remotePlayback

var isSupported = await remotePlayback.IsSupported();

The callback fires immediately with the current answer and again whenever it changes, so a cast button can be hidden until there is somewhere to cast to. Watching costs battery - the browser keeps scanning the network - so dispose the subscription when the UI it feeds goes away.

var subscription = await remotePlayback.WatchAvailability(mediaElement, available =>
{
    showCastButton = available;
    StateHasChanged();
});

// later - or when the component is disposed
await subscription!.DisposeAsync();

Prompt opens the browser's own device picker and needs a user gesture. A true from it means the picker was answered, not that playback has started - the state subscription is what reports the connection being made, and the disconnect that happens when the user stops the cast from the TV.

await remotePlayback.SubscribeStateChange(mediaElement, state =>
{
    // Connecting -> Connected, and Disconnected when the user ends it from the device
    Console.WriteLine(state);
});

// from a click handler:
var prompted = await remotePlayback.Prompt(mediaElement);

var state = await remotePlayback.GetState(mediaElement);

Sets the element's disableRemotePlayback property, which removes the cast affordance the browser draws inside its own controls. Worth doing for media that must not leave the device - a DRM stream whose licence forbids it, or a local preview.

await remotePlayback.SetDisabled(mediaElement, true);   // no cast button on this element
await remotePlayback.SetDisabled(mediaElement, false);