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Rust and Pantheon upstreams: what we pull, what we patch, how to update

This machine runs a custom stack: elementary OS 9 Early Access on Ubuntu 26.04 "resolute", Asahi kernels, a patched Gala, a private libmutter, and a growing Rust layer. Every piece below comes from an upstream we must pull from to stay current. Keep this file updated whenever a pin moves. Background: RUST-IN-THE-STACK.md (what is Rust today and why) and PANTHEON-CRASH-2026-10-18.md (why we patch mutter).

Strategy (decided 2026-10-18)

  • Stay on upstream Vala for Pantheon apps. Gala, Wingpanel, Dock and Granite stay upstream Vala code. No Vala-to-Rust translator exists; writing one would mean maintaining a compiler, and generated Rust would mirror GObject's shared mutable references inside unsafe, losing Rust's benefit.
  • New code in Rust, talking to Vala libraries through GObject Introspection (GIR). Vala libraries can export GIR; gtk-rs generates safe Rust bindings from it.
  • Rewrite in Rust only with evidence (a crash, a measured cost). The compositor qualifies (mutter is C and crashed); see codex/rust-mutter-pantheon.

Upstream inventory

Component Upstream Pinned / installed Our changes Where
mutter (libmutter) Ubuntu source mutter on Launchpad; GNOME mutter Ubuntu 50.1-0ubuntu2.4 Upstream commit c18af474 (null surface in cursor path), private libmutter-18.so.0 for the patched Gala only install-gala-mutter-fix.sh, patches/mutter-surface-actor-null-cursor.patch, test-gala-mutter-fix.sh
Gala elementary/gala f0791434ac40a50f2aec64700a47b3bb04145752 (gala 8.6.2+r3174) Screen/window corners, panel offset (protocol v2), dock work area, screenshot patches install-gala-screen-corners.sh, patches/gala-*.patch
Wingpanel elementary/wingpanel Installed io.elementary.wingpanel 8.0.4+r814 (elementary daily); patch made against e737de88bc02 Export Wingpanel-9.gir + typelib (not installed yet) patches/wingpanel-export-gir.patch
Granite elementary/granite libgranite-7 7.8.1 (ships Granite-7.0.gir) None system package
granite-rs davidmhewitt/granite-rs (crates.io granite-rs, granite-rs-sys) granite-rs 3.3.0, granite-rs-sys 0.9.0 None; consumers must enable gtk4 v4_10+ (see below) rust/granite-smoke, rust/mseries-updates (Software Updates app)
gtk4-rs / glib gtk-rs/gtk4-rs, gtk-rs/gtk-rs-core gtk4 0.11.5 (feature v4_20), glib 0.22.10; system GTK 4.22.4 None rust/Cargo.lock
pangocairo, rayon, libc crates gtk-rs-core (pangocairo 0.22, same release train as glib/gtk4), rayon, libc rust/Cargo.lock None rust/mseries-diskspace (Disk Space app); keep pangocairo on the same minor as glib/pango when bumping gtk-rs
Smithay Smithay/smithay (smallvil example as base) 023b78b1c5a05ca512767cacc07efca55fae8be4 Pantheon desktop-shell v2 in a nested compositor rust/pantheon-compositor on codex/rust-mutter-pantheon (Codex)
Pantheon desktop-shell protocol XML from elementary/gala f0791434 v2 with our set_offset set_offset extension gala-panel-offset.patch; copy in the compositor branch
Vala GNOME/vala system valac None n/a

Upstream Rust branches checked 2026-10-18: none in GNOME/vala, GNOME/mutter (only wip/nielsdg/uncrustify, a C formatter), elementary/gala, granite, wingpanel or dock.

Update procedures

mutter (after every Ubuntu mutter update)

The mseries-gala launcher stops using the private libmutter as soon as the system libmutter-18-0 version changes (it logs patched libmutter is for …). Then:

  1. Check whether Ubuntu's new version already contains c18af474: search the Launchpad changelog for "Handle destroyed surfaces when updating cursor" or check src/compositor/meta-surface-actor-wayland.c for the if (surface) guard. If it does, run bash mseries/install-gala-mutter-fix.sh --uninstall and drop the patch.
  2. Otherwise run bash mseries/install-gala-mutter-fix.sh (downloads the matching Ubuntu source, verifies the .dsc checksums, applies the patch, builds with debian/rules flags), then bash mseries/test-gala-mutter-fix.sh.
  3. If Ubuntu adds build dependencies, the meson step fails with the missing program; add it to need=().

Gala

install-gala-screen-corners.sh pins commit=. To move: pick the elementary/gala commit matching the installed gala package, update commit=, re-apply each patches/gala-*.patch (git apply --check first), rebuild, run window-snapping/test-nested.sh and test-gala-mutter-fix.sh. Pantheon must be logged out and in to pick it up.

Wingpanel GIR

  1. Clone elementary/wingpanel at the commit matching the installed io.elementary.wingpanel (elementary daily rNNN numbers do not equal git rev-list --count; match by date or ask the packaging repo).
  2. git apply mseries/patches/wingpanel-export-gir.patch, meson setup build, ninja -C build lib/Wingpanel-9.typelib.
  3. Check: GI_TYPELIB_PATH=build/lib LD_LIBRARY_PATH=build/lib python3 -c "import gi; gi.require_version('Wingpanel','9'); from gi.repository import Wingpanel". Verified 2026-10-18: GIR has Indicator, KeybindingHelper, PopoverMenuItem; typelib loads.
  4. Not yet installed system-wide or proposed upstream. Proposing it upstream is an outward action: owner decides. With it upstream, Rust indicators need no fork.

granite-rs and gtk4-rs

  • granite-rs 3.3 does not turn on any gtk4 version feature, but gtk4-rs 0.11 puts gtk::Accessible behind v4_10. Every crate using granite-rs here must set gtk4 = { version = "0.11", features = ["v4_20"] } and granite-rs features ["v7_8", "gtk_v4_20"], or granite-rs fails with cannot find type Accessible in crate gtk. Worth reporting upstream (owner decides).
  • granite::prelude::* together with gtk::prelude::* makes Box::append ambiguous; import the specific Granite traits instead (for example granite::prelude::PlaceholderExt).
  • To update (the crate now lives in techmore/mseries-sdk-apps, rust/granite-smoke): bump versions in its Cargo.toml, cargo update, then CARGO_TARGET_DIR=<scratch> cargo build -p granite-smoke and run it under dbus-run-session -- env -u WAYLAND_DISPLAY GDK_BACKEND=x11 GSETTINGS_BACKEND=memory xvfb-run -a <scratch>/debug/granite-smoke. Expect PASS: Granite widgets built from Rust …. Match granite-rs v7_N to the installed Granite minor version.

Smithay compositor

Owned by Codex on codex/rust-mutter-pantheon; its README keeps the pin and says to review any Smithay upgrade explicitly. Do not commit to that branch from another agent.

Repository caveats

  • rust/target/ (build output, about 377 files) is committed on main. Build with CARGO_TARGET_DIR outside the repo so those files do not churn; removing them from git is a separate cleanup.
  • Packages installed on the owner's machine for the mutter build (2026-10-18): libei-dev libsysprof-6-dev sysprof libcanberra-gtk3-dev libpam0g-dev libumockdev-dev python3-argcomplete python3-docutils patchelf.

Testing a Rust session end to end: the login entry

Nested and headless runs only prove pieces. To test the whole thing, the Rust compositor needs its own opt-in login session: a /usr/share/wayland-sessions/pantheon-rust.desktop entry next to Pantheon and Ubuntu in the LightDM session menu. It would start the compositor on DRM/KMS, then the unmodified Vala Wingpanel, Dock and settings daemon. Rules for that step:

  • Never the default or autologin session; Pantheon (pantheon-wayland) stays the default and rollback.
  • A failure must return to the greeter, not a black screen (same OnFailure idea as Gala's unit).
  • Prerequisites from the compositor branch: DRM/KMS backend, libinput, output configuration, lock screen.
  • Acceptance follows pantheon-rust-compositor/EXPERIENCE-REQUIREMENTS.md (login, apps, panel/dock, monitor changes, snapping, lock/unlock, crash recovery) on the M1 Pro, with the owner present.
  • Consumers: rust/granite-smoke (compile check) and rust/mseries-updates (updates-app: header labels, placeholder with an action button, toast). Both carry the same gtk4 v4_20 / granite-rs v7_8, gtk_v4_20 feature lines; update them together. Ubuntu 26.04's own libgranite-7-dev is 7.8.0, which is enough for v7_8, so CI needs no PPA for it.
  • granite-rs 3.3 surprises met while writing the app: granite::HeaderLabel has no set_label (set the label property); PlaceholderExt::append_button takes a gio::Icon (not a gtk::Image) and returns the gtk::Button (it has no action-activated signal binding); a gtk::Expander's collapsed child is not reachable by walking first_child(), so tests expand it first.
  • Dark scheme in a test: Granite's stylesheet follows gtk-application-prefer-dark-theme (deprecated since GTK 4.20 but still honoured); gtk-interface-color-scheme did not switch it on 4.22.4.