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Milad Alizadeh 8d8a27c4c1 Split the client into modules, and clear out what iteration left behind

main.rs had grown to 1290 lines holding everything: the CLI, the client
state, the capture engine, the drawing, the input handling and twelve
Dispatch impls. It is now orchestration only, and the concerns live where
you would look for them — cli, app, capture, overlay — with the module
docs saying what each owns. No behaviour changed; the code moved.

Iterating in response to review left residue, now gone:

- Tile::handle was only ever written. Dropping a wayland-rs proxy does
  not destroy the object, so nothing needed it held.
- Tile::failed likewise: an earlier captures_settled() read it, and
  `settled` is what everything waits on now.
- A blanket #[allow(dead_code)] on Tile hid both of those. Fields are
  pub(crate) rather than pub so the lint keeps working.
- Tile's doc comment had drifted onto the Format enum during a patch.
- Three consecutive `if args.verbose` blocks became describe() and
  report(), and the loose ticks/releases/starved/pool_bytes counters
  became one Stats. `releases` went: frames already imply it.
- quit + quit_why + activate became one Ending enum and picked, so
  "closed by the compositor" is a state rather than a string.
- App::new took seven positional arguments, two of them bare integers in
  a row; the four that always travel together are now Settings.
- sway::scale and the display listing each called get_outputs; one call
  does both.
- scaled(rect, n) became Rect::scaled(n), and Format lives with Target
  where render() dispatches on it.

README had drifted too: the usage line still advertised --print, which
no longer exists, and omitted --format and --no-outputs. Its flag list is
now checked against --help, the memory figures are re-measured, and there
is a source layout for anyone arriving cold.

2026-08-23 19:17:04 +01:00

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wl-pick

A window switcher for wlroots compositors: a grid overlay of live window previews that looks like a rofi theme, and tells you which one you picked.

It replaces a wlthumbs | rofi pipeline, and doubles as a screencast source picker for the desktop portal. The difference is that no thumbnails exist: each window is captured straight into a wl_shm buffer that is handed to its own wl_subsurface, and wp_viewporter tells the compositor which rectangle to scale it into. There is no image encoding, no scaler, and no full-resolution bitmap in this process — which is also why it appears in about 60 ms and holds ~18 MB of RSS however many windows are open.

sway-tree       0.6ms     window list + con_ids over sway IPC
toplevels       0.2ms     ext-foreign-toplevel-list handles
constraints     1.5ms     every capture session's buffer size, in one roundtrip
capture        52.5ms     8 windows, all frames in flight at once
labels          0.0ms     shaped on a worker thread while the captures ran
mapped          4.9ms     layer surface + subsurfaces on screen

The capture phase is the compositor reading full-resolution window pixels out of the GPU. It is bandwidth-bound (~1.1 GB/s here) and unaffected by how large the thumbnails are — which also makes it a free window to do other work in. Loading a font and rasterising its first glyphs costs ~20ms, so labels are shaped on a worker thread started before the captures and joined after them, and cost nothing in wall clock.

Status

Working: a labelled grid of live previews with keyboard navigation. Type-to-filter is the one thing the rofi version had that this doesn't — see the roadmap.

Usage

wl-pick [--format tsv|json|portal] [--live all|current|none] [--fps N]
        [--no-outputs] [--hide-labels] [--font FAMILY] [--font-size PX]
        [--timeout SECS] [--verbose]

--format tsv|json|portal how to report the pick (default tsv)
--live all|current|none which tiles keep updating (default all; displays are always a single snapshot)
--fps N cap on live updates per tile per second (default 12)
--no-outputs windows only; displays are included as tiles by default
--hide-labels draws an icon-only grid
--font FAMILY label font family (default Berkeley Mono)
--font-size PX label size in logical px
--timeout SECS exits after a deadline, in case the keyboard grab ever traps you
--verbose phase timings, the tile list, and capture stats

wl-pick is a chooser: the pick goes to stdout, nothing does if you cancel, and the exit status is 0 for a pick and 1 for a cancel. It never acts on the choice — it has no idea what you want to do with it. Focusing on sway looks like this:

#!/usr/bin/env bash
# ~/.local/bin/winmenu, bound to $mod+Tab
IFS=$'\t' read -r type id toplevel app title < <(wl-pick) || exit 0
case $type in
    window) swaymsg "[con_id=$id] focus" ;;
    output) swaymsg "focus output $id" ;;
esac

Windows only, as a one-liner:

swaymsg "[con_id=$(wl-pick --no-outputs | cut -f2)] focus"

Three formats, because the identifiers different consumers need differ:

`--format`	output
`tsv` (default)	`TYPE⇥ID⇥TOPLEVEL_ID⇥APP⇥TITLE` — `ID` is the sway `con_id`, or the output name for a display; `TOPLEVEL_ID` is the ext-foreign-toplevel-list-v1 identifier that `grim -T` and the portal capture by
`json`	the same record with every key always present, for `jq`
`portal`	`Monitor: NAME` or `Window: TOPLEVEL_ID`

portal is exactly what xdg-desktop-portal-wlr's simple chooser reads, so wl-pick can be the picker for getDisplayMedia and friends — with live previews of both windows and displays:

[screencast]
chooser_type=simple
chooser_cmd=wl-pick --format portal

key
`→` `←` / `l` `h` / `Tab` `Shift+Tab`	next / previous tile
`↓` `↑` / `j` `k`	move a row
`Home` `End`	first / last
`Enter`	pick
`Escape` / `q`	cancel

Navigation reads raw evdev keycodes, so it is layout-independent — but it also means virtual-keyboard clients such as wtype (which invent their own keymap) cannot drive it. That goes away with xkb support, which filtering needs anyway.

Live previews

Capture sessions stay open, so a tile can be refreshed. Three things keep that from being expensive:

It is damage-driven. After a session's first frame the compositor only produces another once the window content changes, so a request left outstanding on an idle window costs nothing. Measured over 4s with one animating window out of ten: 52,52,1,1,1,1,1,1,13,1 frames — the static windows delivered exactly their first frame and nothing more.
Frame callbacks are the clock. Re-captures are driven by the overlay's own wl_surface.frame callbacks, so they stop when it isn't being presented, and --fps throttles per tile on top of that (12 fps measured as 12.1).
Two buffers per window, alternating. A capture must not write into a buffer the compositor is reading, so each window gets two and wl_buffer.release decides which is free. Note that release is the entire contract: with wl_shm the compositor copies the pixels out at commit and hands the buffer straight back, so the slot on screen is usually free too — waiting for it to stop being displayed instead deadlocks after two frames.

The cost is memory and bandwidth: two full-resolution buffers per window (138 MB of shm for eight windows and a display here, against 83 MB with --live none) and a readback per refreshed frame. --live current refreshes only the selected tile, which is much cheaper and still reads as alive.

Look

Colours, font metrics and grid geometry come from the rofi theme this replaces (gruvbox dark, a yellow selection filling the element padding, ceil(sqrt(n)) columns capped at 4, 16:9 tiles, title · app centred underneath) and live in src/theme.rs, which is the one place to change them. They are not configurable at runtime beyond the font flags.

The font is looked up by family name. Your own font directories are scanned first because they are small; the full system scan (~37ms) happens only if the family isn't found there, and an unknown family then falls back to whatever cosmic-text picks rather than failing. Long titles are ellipsised to the cell.

Requirements

A wlroots compositor advertising ext-image-copy-capture-v1, ext-image-capture-source-v1 (with the foreign-toplevel source manager), ext-foreign-toplevel-list-v1, wlr-layer-shell-unstable-v1 and wp_viewporter — sway 1.11+, and in principle Hyprland, labwc and jay, though only sway is tested. sway is also the source of truth for the window list, over its IPC socket, which is the one thing that would need replacing to run elsewhere (ext-foreign-toplevel-list-v1 already reports app id and title).

Known upstream issue: holding per-toplevel capture sessions open makes windows blurry on fractionally scaled outputs (sway#9113). Integer scales are unaffected. It matters more once previews are live.

Roadmap

type-to-filter with fzf-quality fuzzy matching (and the xkb keyboard input it needs, which would also let virtual-keyboard clients drive the overlay)
dmabuf capture, so the pixels never leave the GPU at all — and live previews stop costing a readback per frame

Source layout

main.rs     orchestration: list, capture, map, report the pick
cli.rs      flags, defaults, and the help text that documents them
sway.rs     the window list and display names, over sway's IPC socket
target.rs   what a tile stands for, and the three output formats
app.rs      the Wayland client state every event dispatches into
capture.rs  capture sessions, their buffers, and the live clock
overlay.rs  the layer surface, the drawing, and the keyboard
theme.rs    colours, grid geometry, aspect fitting
text.rs     label shaping on a worker thread
shm.rs      memfd allocation and the ARGB painter

Building

cargo build --release
cargo test          # grid geometry, ellipsising, output formats, glyph output

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