Virtual outputs for screencasting

[axelkar]

I'm not sure if this exists in the GNOME screencast portal (I'm not running Niri yet), and if it does it could still be useful to be able to programmatically create these.

The dynamic screencast target is really useful but doesn't seem to support multiple dynamic targets and I use fullscreen monitors in some apps. There's still a problem when you want to cast something higher-resolution than a monitor of yours.
Would this work by putting them on another workspace and fullscreening them?

Note that I use gnome-network-displays as a replacement for connecting with HDMI.
Sway has swaymsg create_output

[YaLTeR]

I'm not sure if this exists in the GNOME screencast portal (I'm not running Niri yet), and if it does it could still be useful to be able to programmatically create these.

It exists in the portal but not in niri, and it's nontrivial to add.

There's still a problem when you want to cast something higher-resolution than a monitor of yours.

What is the problem with that?

[axelkar]

What is the problem with that?

Casting with different resolutions and aspect ratios.

I don't usually need extended displays for anything other than showing a single window, but having virtual outputs (i.e. dedicated workspaces) would be amazing.

Now I just remembered that GNOME's portal supports creating virtual outputs, while configuring the displays (resolution, HiDPI, etc.) with GNOME settings. Could you implement the API? Apparently it's the org.gnome.Mutter.ScreenCast.Session.RecordVirtual D-Bus method.
https://gitlab.gnome.org/GNOME/gnome-network-displays/-/merge_requests/167
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698

The GNOME RDP server also utilizes this.

[YaLTeR]

Casting with different resolutions and aspect ratios.

I don't usually need extended displays for anything other than showing a single window

You could make the window floating and resize it to arbitrary size though? For outputs, you can also use scale below 1 to get a higher resolution.

Could you implement the API?

As I said, it's nontrivial. It's not "just" "implementing the API", you need the whole infrastructure for driving virtual outputs.

[axelkar]

Thanks for the tips and I'm sorry I forgot that it's really nontrivial. My workflow doesn't currently require this but it's a good feature to have on a modern Wayland compositor.

Am I right in that Smithay doesn't provide nearly as much help compared to wlroots, which has X11 nesting, Wayland nesting, DRM/KMS and headless backends built-in?

[YaLTeR]

Yes, this part of Smithay is more of a "assemble your own"