With this Flatpak packaging of GameScope it's possible to run an existing Flatpak application through the GameScope compositor without needing to bundle GameScope with the application or make any change to the existing packaging of the application.
This extension was mainly created in preparation for me getting a HiDPI monitor.
I've been avoiding HiDPI displays like the plague, so I won't have to deal with problems in the so many apps that still
use outdated widget toolkits that don't support fractional scalling, but it does look like I would be forced to get such
display.
Hopefully, this extension will help scale these applications to fit HiDPI displays.
Another reason is sandboxing X11 applications from each other, while introducing less issues than Xpra or similar tools.
The Freedesktop runtime defines an extension mount point that bind-mounts any extension with the
org.freedesktop.Platform.VulkanLayer prefix onto a subdirectory of /usr/lib/extensions/vulkan.
This GameScope extension takes advantage of the above, and adds GameScope and it supporting files to the runtime under
/usr/lib/extensions/vulkan/GameScope.
Yes, this is a hack, as this specific extension mount point was likely not intended to be used with this kind of tool, and submission of this extension to Flathub might not be approved due to this fact, but that's good enough for my needs.
The extension definition doesn't include the add-ld-path key, and there's no extension key to append a directory to
PATH, so we will need to take care of both of these in a different way.
While it should be obvious, be aware that the extension's branch/version must match the runtime's one.
It should also be noted that this extension introduces a couple of shared libraries that will possibly conflict with those
provided by an application, if it does packages the same libraries.
This includes libevdev, libfontenc, libinput, libliftoff, libmtdev, libseat, libwlroots, libxcvt, libXfont2, libXRes.
There's an experimental static_libs branch
that avoids adding shared libraries, but I didn't confirmed that the static_libs branch doesn't introduce regressions.
My recommendation is to experiment first the default branch that includes shared libs, and only after this try the
static_libs branch.
If you found a reproducible regression when using the static_libs branch, then please file a bug report here.
First, build and install the extension. See Flatpak Builder's documentation for more details.
Next, run the application with gamescope as the given command, while setting the PATH and LD_LIBRARY_PATH
environment variables to include the directories of our GameScope extension.
Make sure to allow Wayland socket access, and append to the end gamescope's option and of course the application's
executable name.
Here it should be noted that the application's packaging might also set these variables manually, so if the application doesn't work as expected, then check its packaging.
For example, let's run ImHex through GameScope.
$ flatpak run \
--command=gamescope \
--env=LD_LIBRARY_PATH=/usr/lib/extensions/vulkan/GameScope/lib \
--env=PATH=/app/bin:/usr/bin:/usr/lib/extensions/vulkan/GameScope/bin \
--socket=wayland \
net.werwolv.ImHex \
-w 1920 -h 1080 -- \
imhexImHex is actually a good example, as this is an X11 application without Wayland support, so we can block X11 session access and see that it still runs correctly.
$ flatpak run \
--command=gamescope \
--env=LD_LIBRARY_PATH=/usr/lib/extensions/vulkan/GameScope/lib \
--env=PATH=/app/bin:/usr/bin:/usr/lib/extensions/vulkan/GameScope/bin \
--nosocket=x11 \
--socket=wayland \
net.werwolv.ImHex \
-w 1920 -h 1080 -- \
imhexGameScope is not perfect yet, and there are a couple of limitations to be aware of:
I don't plan to submit this, and in fact, I'm very much against it due to the current limitations of runtime extensions, and the existence of shared libraries in the extension.
If this GameScope extension is actually useful with existing Flatpak applications, then in my opinion GameScope should be added to the runtime, and an application that needs a newer version than the one provided by the runtime can bundle its own version.