Milad Alizadeh
8d8a27c4c1
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.
186 lines
8.0 KiB
Markdown
186 lines
8.0 KiB
Markdown
# wl-pick
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A window switcher for wlroots compositors: a grid overlay of **live** window
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previews that looks like a rofi theme, and tells you which one you picked.
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It replaces a `wlthumbs | rofi` pipeline, and doubles as a screencast source
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picker for the desktop portal. The difference is that no thumbnails
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exist: each window is captured straight into a `wl_shm` buffer that is handed to
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its own `wl_subsurface`, and `wp_viewporter` tells the compositor which rectangle
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to scale it into. There is no image encoding, no scaler, and no full-resolution
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bitmap in this process — which is also why it appears in about 60 ms and holds
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~18 MB of RSS however many windows are open.
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```
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sway-tree 0.6ms window list + con_ids over sway IPC
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toplevels 0.2ms ext-foreign-toplevel-list handles
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constraints 1.5ms every capture session's buffer size, in one roundtrip
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capture 52.5ms 8 windows, all frames in flight at once
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labels 0.0ms shaped on a worker thread while the captures ran
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mapped 4.9ms layer surface + subsurfaces on screen
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```
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The capture phase is the compositor reading full-resolution window pixels out of
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the GPU. It is bandwidth-bound (~1.1 GB/s here) and unaffected by how large the
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thumbnails are — which also makes it a free window to do other work in. Loading
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a font and rasterising its first glyphs costs ~20ms, so labels are shaped on a
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worker thread started before the captures and joined after them, and cost
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nothing in wall clock.
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## Status
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Working: a labelled grid of live previews with keyboard navigation. Type-to-filter
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is the one thing the rofi version had that this doesn't — see the roadmap.
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## Usage
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```
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wl-pick [--format tsv|json|portal] [--live all|current|none] [--fps N]
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[--no-outputs] [--hide-labels] [--font FAMILY] [--font-size PX]
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[--timeout SECS] [--verbose]
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```
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- `--format tsv|json|portal` how to report the pick (default `tsv`)
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- `--live all|current|none` which tiles keep updating (default `all`; displays
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are always a single snapshot)
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- `--fps N` cap on live updates per tile per second (default 12)
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- `--no-outputs` windows only; displays are included as tiles by default
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- `--hide-labels` draws an icon-only grid
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- `--font FAMILY` label font family (default `Berkeley Mono`)
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- `--font-size PX` label size in logical px
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- `--timeout SECS` exits after a deadline, in case the keyboard grab ever traps
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you
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- `--verbose` phase timings, the tile list, and capture stats
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wl-pick is a chooser: the pick goes to stdout, nothing does if you cancel, and
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the exit status is 0 for a pick and 1 for a cancel. It never acts on the choice —
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it has no idea what you want to do with it. Focusing on sway looks like this:
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```sh
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#!/usr/bin/env bash
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# ~/.local/bin/winmenu, bound to $mod+Tab
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IFS=$'\t' read -r type id toplevel app title < <(wl-pick) || exit 0
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case $type in
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window) swaymsg "[con_id=$id] focus" ;;
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output) swaymsg "focus output $id" ;;
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esac
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```
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Windows only, as a one-liner:
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```sh
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swaymsg "[con_id=$(wl-pick --no-outputs | cut -f2)] focus"
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```
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Three formats, because the identifiers different consumers need differ:
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| `--format` | output |
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|---|---|
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| `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 |
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| `json` | the same record with every key always present, for `jq` |
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| `portal` | `Monitor: NAME` or `Window: TOPLEVEL_ID` |
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`portal` is exactly what xdg-desktop-portal-wlr's `simple` chooser reads, so
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wl-pick can be the picker for `getDisplayMedia` and friends — with live previews
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of both windows and displays:
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```ini
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[screencast]
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chooser_type=simple
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chooser_cmd=wl-pick --format portal
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```
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| key | |
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|---|---|
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| `→` `←` / `l` `h` / `Tab` `Shift+Tab` | next / previous tile |
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| `↓` `↑` / `j` `k` | move a row |
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| `Home` `End` | first / last |
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| `Enter` | pick |
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| `Escape` / `q` | cancel |
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Navigation reads raw evdev keycodes, so it is layout-independent — but it also
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means virtual-keyboard clients such as `wtype` (which invent their own keymap)
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cannot drive it. That goes away with xkb support, which filtering needs anyway.
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## Live previews
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Capture sessions stay open, so a tile can be refreshed. Three things keep that
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from being expensive:
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- **It is damage-driven.** After a session's first frame the compositor only
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produces another once the window content changes, so a request left
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outstanding on an idle window costs nothing. Measured over 4s with one
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animating window out of ten: `52,52,1,1,1,1,1,1,13,1` frames — the static
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windows delivered exactly their first frame and nothing more.
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- **Frame callbacks are the clock.** Re-captures are driven by the overlay's own
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`wl_surface.frame` callbacks, so they stop when it isn't being presented, and
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`--fps` throttles per tile on top of that (12 fps measured as 12.1).
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- **Two buffers per window, alternating.** A capture must not write into a buffer
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the compositor is reading, so each window gets two and `wl_buffer.release`
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decides which is free. Note that release is the entire contract: with `wl_shm`
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the compositor copies the pixels out at commit and hands the buffer straight
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back, so the slot on screen is usually free too — waiting for it to stop being
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displayed instead deadlocks after two frames.
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The cost is memory and bandwidth: two full-resolution buffers per window (138 MB
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of shm for eight windows and a display here, against 83 MB with `--live none`)
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and a readback per refreshed frame. `--live current` refreshes only the selected tile,
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which is much cheaper and still reads as alive.
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## Look
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Colours, font metrics and grid geometry come from the rofi theme this replaces
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(gruvbox dark, a yellow selection filling the element padding, `ceil(sqrt(n))`
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columns capped at 4, 16:9 tiles, `title · app` centred underneath) and live in
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`src/theme.rs`, which is the one place to change them. They are not
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configurable at runtime beyond the font flags.
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The font is looked up by family name. Your own font directories are scanned
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first because they are small; the full system scan (~37ms) happens only if the
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family isn't found there, and an unknown family then falls back to whatever
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cosmic-text picks rather than failing. Long titles are ellipsised to the cell.
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## Requirements
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A wlroots compositor advertising `ext-image-copy-capture-v1`,
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`ext-image-capture-source-v1` (with the foreign-toplevel source manager),
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`ext-foreign-toplevel-list-v1`, `wlr-layer-shell-unstable-v1` and
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`wp_viewporter` — sway 1.11+, and in principle Hyprland, labwc and jay, though
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only sway is tested. sway is also the source of truth for the window list, over
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its IPC socket, which is the one thing that would need replacing to run
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elsewhere (`ext-foreign-toplevel-list-v1` already reports app id and title).
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Known upstream issue: holding per-toplevel capture sessions open makes windows
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blurry on **fractionally scaled** outputs
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([sway#9113](https://github.com/swaywm/sway/issues/9113)). Integer scales are
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unaffected. It matters more once previews are live.
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## Roadmap
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- type-to-filter with fzf-quality fuzzy matching (and the xkb keyboard input it
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needs, which would also let virtual-keyboard clients drive the overlay)
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- dmabuf capture, so the pixels never leave the GPU at all — and live previews
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stop costing a readback per frame
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## Source layout
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```
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main.rs orchestration: list, capture, map, report the pick
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cli.rs flags, defaults, and the help text that documents them
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sway.rs the window list and display names, over sway's IPC socket
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target.rs what a tile stands for, and the three output formats
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app.rs the Wayland client state every event dispatches into
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capture.rs capture sessions, their buffers, and the live clock
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overlay.rs the layer surface, the drawing, and the keyboard
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theme.rs colours, grid geometry, aspect fitting
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text.rs label shaping on a worker thread
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shm.rs memfd allocation and the ARGB painter
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```
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## Building
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```
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cargo build --release
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cargo test # grid geometry, ellipsising, output formats, glyph output
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```
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