update-client-feature-table

name	update-client-feature-table
description	Refresh the alternative-client comparison tables in docs/Usage/Clients.md (features, and project size / build cost) from the client repos they describe (go-xpra, rust-xpra, xpra-html5, vispra). Use when asked to update, refresh or check those tables, or when told to "look at the updates to ~/projects/<client>" and reflect them in the docs.

update-client-feature-table

docs/Usage/Clients.md compares the xpra client implementations, feature by feature and project by project. It describes other repositories, so it goes stale on their commits, not on this one's — a refresh means reading those repos and rewriting only the entries that actually moved.

The shape of the section

Nothing here is one wide table: prose in a six-column grid forced a horizontal scrollbar. There are four layers, and a change usually has to land in more than one:

1. ## Client implementations — identity only: link, maintainer, license. No languages here; they belong to the size table below, which says more about them.
2. ## Project size and build — one row per client: languages, source size, binary size, build time. Measured, not estimated — see Measuring the size table.
3. The feature matrix — one narrow | Feature | xpra | html5 | vispra | rust | go | table carrying only markers, so it fits on screen. No prose, ever; a qualifier here re-widens the table.
4. A ### section per client — one intro sentence carrying what has no matrix row (maturity, platforms, any server requirement) followed by a two-column | Feature | Notes | table with the detail the markers cannot carry.

Feature names must match between the matrix and the per-client tables. The name is the text before the (: a matrix row reading Picture encodings (rgb/jpeg/png/webp/avif) pairs with a Picture encodings notes row. A per-client table only lists the rows it has something to add; a row the matrix already says everything about is left to the matrix alone — since the counted rows below carry the per-option detail, a note that just re-lists the same options is noise and comes out.

Above the legend sits the line that dates the whole section:

This comparison should be correct as of **YYYY-MM-DD HH:MM ±ZZZZ**, the last time it was checked
against each client's repository.

It records when the repos were read, which is the only honest claim this doc can make about clients it does not control — a refresh that finds nothing still moves it forward.

Markers

Legend: 🟢 supported · 🟠 partial, platform-limited or degraded · 🔴 absent

🟠 is for a feature that is really there but really incomplete: desktop notifications that are only written to the log, a transport that works on one of three backends, h264 on Windows and nowhere else. "Works everywhere, with fewer options than the native client" is 🟢, and the options it lacks belong in its notes row.

Graded rows carry one marker: the feature is one thing and it either works, half-works or is missing.

Counted rows name a fixed menu of options in the Feature cell and carry one marker per option, in that order, so the cells can be read down the column as well as across:

Row	Options, in order
Transports (tcp/ssl/ssh/ws/quic)	ws covers wss; quic covers WebTransport
Transport security (tls/ssh/aes)	TLS trust, an ssh tunnel, xpra's own AES layer
Packet encoding (rencodeplus/yaml)
Compression in (lz4/zstd/brotli)	what the client can decompress
Compression out (lz4/zstd/brotli)	what it compresses before sending
Picture encodings (rgb/jpeg/png/webp/avif)	scroll and void are not encodings, leave them to the notes
Video encodings (h264/vp8/vp9/av1)	hevc and the rest go in the notes
Speaker audio (opus/vorbis/mp3/flac/aac)

Rules for a counted row, all of them about keeping the table on screen:

• At most five options, and the Feature cell under 40 characters. A sixth option that only the native client has is a note, not a column of four 🔴.
• Every client gets the same number of markers, in the same order — an option no one implements is a row of 🔴 in every column and is better dropped from the list entirely.
• Adding an option to a row means editing all five cells. Do not leave a short cell behind.
• A parenthesis in a Feature cell means "counted", so a graded row must not carry one: the mmap row is Shared memory, with the word mmap in its notes, not Shared memory (mmap).

Worth re-running after any edit to the matrix — it catches a cell that lost a marker, which is invisible in the rendered table:

python3 - <<'EOF'
import re
rows = [[c.strip() for c in ln.strip().strip("|").split("|")]
        for ln in open("docs/Usage/Clients.md") if ln.startswith("| ") and not set(ln.strip()) <= set("|-: ")]
for r in rows:
    if r[1:] and all(set(c) <= set("🟢🟠🔴") and c for c in r[1:]):
        want = len(r[0].split("(")[1].rstrip(")").split("/")) if "(" in r[0] else 1
        if any(len(c) != want for c in r[1:]):
            print(f"{r[0]}: want {want} markers, got {[len(c) for c in r[1:]]}")
EOF

The repos behind each client

Client	Local clone	Upstream
Native xpra client	this repo	Xpra-org/xpra
xpra-html5	~/projects/xpra-html5	Xpra-org/xpra-html5
vispra	~/projects/vispra	MajidNajafi/vispra (third party)
Rust client	~/projects/rust-xpra	Xpra-org/rust-xpra
Go client	~/projects/go-xpra	Xpra-org/go-xpra

~/projects/kotlin-xpra (Android, Kotlin/Compose) is a sibling client that has no column yet — worth raising when it comes up, but adding it is a bigger edit than a refresh.

Method

1. Find what changed. The "correct as of" line above the legend is the cut-off: git log --format='%h %ad %s' --date=iso --since='<that datetime>' in each client repo gives the candidate changes. Compare timestamps, not dates — several rounds of this can land in one day. The README and CHANGELOG of each client are the best summary of its current state: read them whole, not just the diff, since a feature can regress or be re-scoped without a commit that says so.
2. Verify against the code, not the prose. A README describes intent; the hello capabilities describe what the server will actually send. Anything not advertised in the hello is never sent, so an unadvertised feature is absent no matter what else the repo says:
   • go-xpra: client/hello.go (one buildHello, commented with the server-side references)
   • rust-xpra: src/client/client.rs
   • xpra-html5: Client.js, init_encodings() and _get_network_caps()
   • vispra: src/core/protocol/
   • Counted rows need this most: a codec named in a const list is not the same as one offered in the hello, and a helper with no caller (vispra's lz4Compress, reached only from its own test) is not an implemented option.
   • Backend coverage differs within a client — check for a per-backend file (x11/cursor.go, wayland/cursor.go, win32/cursor.go) before writing 🟢 rather than 🟠.
3. Re-measure the size table whenever a client's tree or packaging moved — see below. Nothing in it can be reasoned out from a diff.
4. Edit both layers, then re-align. Hand-edit the matrix markers and the client's notes row, then run the bundled script, which pads every column of every | Feature table and regenerates the separator rows (keeping the matrix's :---: centering):

   python3 .claude/skills/update-client-feature-table/retable.py docs/Usage/Clients.md
   

   It also fails on a row whose cell count drifted from the header — usually an unescaped |. The identity and size tables have their own header, so re-align those with --prefix '| Client ' — which also matches the | Client tray / menu body rows, and only skips them because the script requires a |---| separator on the line below a header. Do not remove that check: without it the script turns those rows into separators and eats the row underneath.
5. Update the prose too when a client moves enough to contradict it: the paragraph under "Client implementations" and each client's intro sentence are edited separately from the tables.
6. Stamp it. Set the "correct as of" line to date '+%Y-%m-%d %H:%M %z' taken at the start of the pass — every time, including a pass that changed nothing, since "checked and unchanged" is exactly what the line is there to say.

Measuring the size table

Every number in it is measured on the machine doing the refresh, and the table says so. Round hard — these are orders of magnitude, not benchmarks — and never carry a stale number forward because the measurement is inconvenient.

Source size: tracked files only, in each project's own languages, with vendored third-party sources excluded and the project's own tests included. git ls-files is what keeps build output, node_modules and untracked scratch files out of the count:

count() { git -C ~/projects/$1 ls-files -- "${@:2}" | wc -l
          git -C ~/projects/$1 ls-files -- "${@:2}" | xargs wc -l | tail -1; }
count xpra       '*.py' '*.pyx' '*.pxd' '*.c' '*.h' '*.cu'
count xpra-html5 '*.js' '*.css' '*.html' ':!:html5/js/lib/*'   # jquery, simple-keyboard, aurora
count vispra     '*.ts' '*.tsx' '*.css' ':!:src/vendor/*'      # its npm deps are not in the tree
count rust-xpra  '*.rs'
count go-xpra    '*.go'

The two browser clients vendor differently — html5 commits its libraries, vispra pulls them from npm — so the html5 row names the excluded weight (about 70 kloc) rather than pretending the trees are comparable.

Binary size: from the published artefacts in ~/projects/repos, not from a local build, since that is what a user actually downloads. The column is a range, and the point of the range is that a distribution package leans on the distribution's Python, GTK and codecs while a Windows or macOS installer carries all of it:

ls -l ~/projects/repos/stable/Fedora/*/x86_64/xpra-{common,client,client-gtk3,codecs}-*.rpm
ls -l ~/projects/repos/stable/MSWindows/x86_64/Xpra-x86_64_Setup_*.exe
ls -l ~/projects/repos/stable/MacOS/*/Xpra-*.dmg ~/projects/repos/stable/MacOS/*/Xpra-*.pkg
find ~/projects/repos/beta -name 'rust-xpra*' -o -name 'go-xpra*' | grep -v SRPMS   # the two native clients
find ~/projects/repos -name 'xpra-html5*' \( -name '*.deb' -o -name '*.rpm' \)

For the native xpra client, sum the client subpackages (xpra-common dominates, plus xpra, xpra-client, xpra-client-gtk3, xpra-codecs) rather than the whole set — the server packages are not what this page compares. For the browser clients, the size that matters is what is served: the built tree, with the pre-compressed .br/.gz twins excluded, since a browser fetches one of each file, not three.

Build time: wall-clock, from cold, on this machine, with the CPU named in the doc so the numbers mean something. Always build into the scratch directory — never into the user's own build/, target/ or GOCACHE, and never cargo clean their tree:

cd ~/projects/xpra       && time python3 setup.py build --build-base=$SCRATCH/xpra-build --without-nvidia
cd ~/projects/rust-xpra  && time CARGO_TARGET_DIR=$SCRATCH/rust-target cargo build --release
cd ~/projects/go-xpra    && time GOCACHE=$SCRATCH/gocache go build -o $SCRATCH/go-xpra ./cmd/go-xpra
cd ~/projects/vispra     && time npm run build
cd ~/projects/xpra-html5 && time python3 ./setup.py install $SCRATCH/html5-install

Two caveats worth carrying into the doc rather than hiding: xpra's Linux build reuses the .c files Cython already generated in the tree, so a first-ever build is longer than the measured one; and the Windows and macOS builds are the ones that take over ten minutes, which no Linux measurement will show. The browser clients need their dependencies installed already (npm ci time is not build time).

Rules that keep the comparison honest

• Committed state only. These clients are developed in parallel with this doc, so their working trees often hold the next feature (git status --short). Documenting uncommitted work publishes a claim about a repo that does not have it yet. Leave it out, and say in the reply what was left out and why, so the user can ask for it once it lands.
• The legend means what it says. A feature that works on one of three backends is 🟠 with the limit named, never 🟢.
• Grade the client's code, not the platform's answer. A client that asks through the mechanism its platform provides has implemented the feature, even where the compositor, window manager or OS is free to decline - go-xpra sending window icons through xdg-toplevel-icon-v1 is 🟢, with whose call it is named in the notes. 🟠 is for the client itself doing less: rust-xpra is 🟠 on the same row because winit never sends an icon on Wayland at all.
• Name the limit, not just the feature. "PNG icons; on Wayland through xdg-toplevel-icon-v1, which the compositor is free to ignore" is the useful note; "Icons" is not. The per-client READMEs have a "what it does not do" / "known limitations" section written for exactly this.
• Do not upgrade an intro sentence out of enthusiasm. "Proof of concept - the README says it is not yet usable" stays until that README says otherwise.
• A new feature needs a matrix row with a cell for every client, including a 🔴 for the ones that lack it — then a notes row only under the clients that have something to qualify.
• A number nobody measured is not a number. If an artefact is missing from ~/projects/repos (no Windows build of a client, say), leave that platform out of its cell and say so, rather than scaling a Linux figure.

Committing

Commit straight to master (this repo's convention). Subject line names the columns that moved, e.g. update the client feature table for the rust and go clients, with the body listing what each client gained. Docs-only, so the pre-commit hooks have nothing to lint.