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Screen Sharing

Screensharing in Wayland is done with the help of Portals. Portals were initially designed to allow applications sandboxes via Flatpak to access resources of the desktop, but have since gained popularity outside of the realm of Flatpaks. In our case, we can use the screen sharing portal to allow applications to access the contents of the Wayland compositor.

Note

Please be aware that you will only be able to share a single screen with this method, not individual windows.

Setup

Installation

First, we need to install xdg-desktop-portal-wlr. Unfortunately, Mir only has support for v0.5.0 of this software, so we will need to checkout the source at a particualr commit:

git clone https://github.com/emersion/xdg-desktop-portal-wlr
cd xdg-desktop-portal-wlr
git checkout 7c0f352  # This is release 0.5.0

Next, we can build the project: 

meson setup builddir --prefix=/usr
cd builddir
ninja -j4
sudo ninja install

Configuration

First, copy /usr/share/xdg-desktop-portal/portals/wlr.portal to /usr/share/xdg-desktop-portal/portals/mir.portal

Next, modify /usr/share/xdg-desktop-portal/portals/mir.portal:

[portal]
DBusName=org.freedesktop.impl.portal.desktop.wlr
Interfaces=org.freedesktop.impl.portal.Screenshot;org.freedesktop.impl.portal.ScreenCast;
-UseIn=wlroots;sway;Wayfire;river
+UseIn=mir

Finally, create a file at /etc/xdg/xdg-desktop-portal-wlr/config with: 

[screencast]
max_fps=30
chooser_type=simple
chooser_cmd=slurp -f %o -or

Note that you must have slurp installed on your machine.

Running

Build miracle with the systemd cmake flag: -DSYSTEMD_INTEGRATION=1. Next, add the following startup application to miracle:

# ~/.config/miracle-wm/config.yaml

startup_apps:
    - command: systemd-run --user /usr/libexec/xdg-desktop-portal --replace
      in_systemd_scope: true

This will make it so that your regular screensharing mechanism is disabled at runtime in favor of our new one.

Finally, restart your compositor and then open up obs-studio or Google Meet and see that you are able to share your screen.