DroidDeck/tools/desktop-kde/README.md

The desktop package (KDE Plasma)

The desktop the app installs into its Linux runtime the first time the desktop is opened: KDE Plasma set up as SteamOS's desktop mode, with Valve's Vapor theme, the Steam Deck wallpaper and launcher icon, Plasma's default bottom panel, and "Return to Gaming Mode" and Steam on the desktop.

• seeds.txt: the packages asked for. build.sh takes their closure over Arch Linux ARM's repositories (closure.py) and drops what the runtime already has.
• runtime-packages.txt: the runtime's own packages, name version from its pacman database (ls /var/lib/pacman/local in the rootfs). Refresh it when the runtime is rebuilt.
• overlay/: our files on top - system-wide KDE defaults in /etc/xdg, the Vapor theme and its layout script, the menu entries Steam and Return to Gaming Mode use.

pacman works on the desktop. pacman-db.py writes an install record for every package the desktop ships into /var/lib/pacman/local, and builds the droiddeck repository: Arch Linux ARM's core, extra and alarm databases as they were at build time, with the runtime's and the desktop's own packages at the installed versions. The release carries that database (droiddeck.db) and the packages mirror.txt names; everything else downloads from Arch Linux ARM as a CacheServer, so its 404s never disable a mirror. Installs therefore resolve against the desktop's exact Qt and KDE versions, and pacman -Syu only ever moves packages the user added.

• /usr/local/bin/pacman runs the real pacman with /usr/share/droiddeck/pacman/pacman.conf, first copying in the shipped database and dropping the runtime's records for packages the desktop replaced (prepare). As root it adds --needed to installs, so guides that reinstall something the desktop has just skip it.
• sudo, su and sudoedit run commands as root: the session is the app's own Android user, and libdroiddeck-root.so (root/root.c, preloaded by sudo) reports uid 0, accepts ownership changes and shows the runtime's 0700 directories as 0755. It grants nothing the user lacked.
• hooks/droiddeck-system.hook refuses to remove or replace any runtime or desktop package; droiddeck-remember.hook keeps the user's own packages in ~/.local/share/droiddeck/pacman/packages.txt, and restore (autostarted) reinstalls them after a runtime update and upgrades them after a desktop update. Hooks that need systemd, udev, kernel modules or an initramfs are masked.

.github/workflows/build-desktop-kde.yml builds it and, run with a new tag, publishes it as a release in Droid-Deck/DroidDeck-Components (tags with -rc are published as pre-releases for testing before an app build points at them). release.env pins the tag, sha256 and size the apk installs (DesktopCatalog.desktopEntry); a published tag is never replaced, so a changed package is a new tag and a release.env update.

At run time the desktop is started by tools/linuxfs/desktop/droiddeck-desktop (the app stages it at every session): Plasma's own startplasma-wayland, with KWin nested in the app's compositor through kwin_wayland_wrapper. The package's kwin-compositor marker selects OpenGL through Zink for KWin 6.8, which removed QPainter. Older packages retain their software compositor. KWin runs without Gallium's threaded context and without overlay layers. With the threaded context, KWin crashed uploading windows' shared-memory buffers by reading past their end, and the host shows only a single buffer. On Android the launcher explicitly selects the KGSL render node; the nested backend can use it when the host's dmabuf feedback cannot name a DRM device. Games and emulators from the menu go through droiddeck-gpu, and Steam goes back to the app as a Steam session.

kwin.env pins the KWin version shared by the build and packaging jobs. build-kwin.sh builds that version's Wayland executable and library on a native ARM64 runner, using a disposable Arch Linux ARM chroot with every build package signature-checked. It matches the current KWin package in Arch Linux ARM even when that repository trails KDE's latest release. The source tarball is pinned by SHA-256 from KDE's official source inventory; patches/0001-respect-nested-desktop-scale.patch lets Display Settings control the inner desktop scale independently of the outer window size. It keeps layer sizes, pointer/touch coordinates and the cursor in the same physical pixels. The behavior is enabled only with DROIDDECK_NESTED_SCALE, which the desktop script supplies. 0002-select-explicit-nested-render-node.patch lets that nested backend use one explicitly selected KWIN_RENDER_NODES device when host feedback cannot identify it. It does not guess between GPUs or change normal KWin device selection. 0003-forward-nested-scroll-source.patch passes the host's scroll source, wheel steps and scroll stops through the nested backend, which upstream leaves as a TODO. Two-finger touch scrolling then reaches apps as touchpad scrolling, and wheel steps stay whole clicks.

pins/mesa/desc keeps Mesa 26.2.4 and its actual package dependencies ahead of the rolling repository metadata. Mesa 26.2.5 crashes in Zink shader compilation on Thor with the selected Turnip driver. mesa.env points at immutable copies of the original 26.2.4 package and signature; both build jobs verify the Arch Linux ARM signature and pinned SHA-256 as for every other package.

The desktop workflow replaces the same-version kwin_wayland executable and libkwin.so; the rest comes from the signature-checked Arch packages. desktop-kde.kwin.txt records the source, patch, executable, library and build package hashes. Corresponding source is https://download.kde.org/stable/plasma/6.8.2/kwin-6.8.2.tar.xz plus the patch in this repository.

The inventories use .gzip rather than .gz: Android's asset packer expands .gz and strips its suffix. The shared local/CI runtime payload check verifies the exact APK names and bytes.

Desktop removal uses app/src/main/assets/desktop-removal/, generated by removal-manifests.py from the checksum-pinned LXQt r1, KDE r1/r2 and emulator r1 archives. KDE candidates are the files of the desktop applications/themes in seeds.txt (their source package hashes verified against desktop-kde.packages.txt) plus our overlay. Shared dependencies, fonts, Xwayland and Qt Wayland remain available to Steam, native apps and emulators. Regenerate the inventories and add the new version to versions.txt when publishing another desktop pin; unknown versions cannot be removed.

Removal checks file size and SHA-256, or the exact symlink target, before unlinking. Base-runtime pacman files and emulator bundle paths are protected even when they overlap an application. It never follows parent symlinks or recursively deletes directories. Home, added apps, custom files and modified package files stay. A pending marker disables the installed state and allows retry after interruption. Installing the desktop again repairs its package files and clears it. The old LXQt applications are cleaned after KDE installation and before the next guest launch on an already-upgraded runtime, protecting both KDE inventories as well as the runtime and emulators. Only files owned by lxqt-applications.txt's application packages are candidates; dependencies stay even when the old runtime's pacman database does not record them. In particular, gamescope still needs the old package's libseat. The source LXQt application archives are the versions in the published steamdeck-desktop-r1/desktop.packages.txt; verify their .sig files with gpgv --keyring tools/desktop-kde/archlinuxarm-builder.gpg and the Build System fingerprint used by build.sh. Put their filenames in selected.txt in the LXQt cache. sources.json records their SHA-256 values; file identities still come from the checksum-pinned published desktop.