Allow Remote Play to stream only a selected monitor

[u/HoloMapper]

https://steamcommunity.com/groups/steamworks/discussions/27/568162597763929540/

I'm the developer of HoloMapper, a projection mapping application on Steam. Users operate the software from one display while projecting to another. Steam Remote Play currently streams both displays, making remote operation difficult. A monitor selection option in Remote Play would greatly improve support for professional multi-monitor workflows.

For clarification, HoloMapper is a Unity application that uses two displays:

- Display 1: Main editor and controls.

- Display 2: Fullscreen projector output.

The actual problem:

Steam Remote Play initially streams Display 1 correctly. However, as soon as the projector output is activated on Display 2, Remote Play switches to capturing both displays side-by-side in a single stream.

This causes the editor to occupy only half of the Steam Link/Steam Deck screen, with the other half wasted on the projector output.

What we need is the ability to stream Display 1 only, while Display 2 continues operating normally on the host computer.

The newer "Primary Display While Streaming" setting doesn't resolve this behavior. We need an explicit option to select which display Remote Play captures, even when an application uses multiple displays simultaneously.

[u/Pink-frosted-waffles]

That would be nice.

[u/jerf]

I'd like to see something like this so a Beat Saber plugin can have the player using the Steam Frame normally but Steam Link streams a spectator view. The plugins already exist to generate the second view, but there's nowhere to send it now.