Milad Alizadeh
dbfc06519a
A switcher to replace a wlthumbs + rofi pipeline, with the same look (gruvbox, ceil(sqrt(n)) columns capped at 4, 16:9 tiles, a yellow selection filling the element padding) but no thumbnails anywhere. Each window is captured straight into a wl_shm buffer that is handed to its own wl_subsurface, with wp_viewporter giving the compositor the rectangle to scale it into. So there is no PNG encode, no scaler, no full-resolution bitmap in this process, and the capture buffers are never even mapped here — the compositor writes those pages and samples them again for display. Opens in ~65ms for 8 windows (55ms of which is the compositor reading pixels back out of the GPU) and holds ~9MB of RSS. All capture sessions are opened before a single roundtrip and every frame goes in flight together, the same batching wlthumbs uses, because the readback is bandwidth-bound rather than latency-bound. sway remains the source of truth: the window list, the con_ids and the focusing all come from its IPC socket, joined to the Wayland side by foreign_toplevel_identifier. Navigation reads raw evdev keycodes so it is layout-independent, which does mean virtual-keyboard clients that invent their own keymap can't drive it; that resolves when filtering brings xkb. Labels, type-to-filter and live previews are next.
94 lines
3.4 KiB
Markdown
94 lines
3.4 KiB
Markdown
# wlgrid
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A window switcher for wlroots compositors: a thumbnail grid overlay that looks
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like a rofi theme, and focuses the window you pick.
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It replaces a `wlthumbs | rofi` pipeline. 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 holds ~9 MB of RSS and appears in
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about 60 ms.
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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 55.0ms 8 windows, all frames in flight at once
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mapped 4.2ms 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.
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## Status
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Working, and usable as a switcher today: a static grid with keyboard navigation.
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Labels, filtering and live previews are next — see the roadmap.
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## Usage
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```
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wlgrid [--print] [--verbose] [--timeout SECS]
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```
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- `--print` writes the selected sway `con_id` to stdout instead of focusing it
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- `--verbose` prints phase timings and how many windows were captured
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- `--timeout SECS` exits after a deadline (an escape hatch: the overlay takes an
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exclusive keyboard grab)
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Bind it in sway:
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```
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bindsym $mod+Tab exec wlgrid
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```
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| key | |
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|---|---|
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| `→` `←` / `Tab` `Shift+Tab` | next / previous window |
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| `↑` `↓` | move a row |
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| `Home` `End` | first / last |
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| `Enter` | focus the selection |
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| `Escape` / `q` | cancel, leaving focus alone |
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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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## 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) and live in `src/theme.rs`. They will move to a
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config file so they can't drift from the `.rasi`.
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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 and
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for focusing, over its IPC socket.
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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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- **M2** labels: real text via cosmic-text, `--hide-labels` for an icon-only grid
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- **M3** type-to-filter with fzf-quality fuzzy matching (and xkb keyboard input)
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- **M4** live previews: keep the capture sessions open and re-capture on a rate
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limit, `--live all|current|none`
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- **M5** dmabuf capture, so the pixels never leave the GPU at all
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## Building
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```
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cargo build --release
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cargo test # grid geometry
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```
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