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Agent skill

Gui Debug

by natsukium in natsukium/dotfiles

Verify a rendering or window-chrome change in a GUI app unattended on Linux/Wayland under the niri compositor — enumerate windows and read output scale via niri msg --json, capture a specific window…

CC0-1.0Auto-check passed

Install Gui Debug

skills CLI
$ npx skills add natsukium/dotfiles --skill gui-debug -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install natsukium/dotfiles gui-debug --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/natsukium/dotfiles.git skills-src && mkdir -p .claude/skills && cp -r skills-src/modules/features/coding-agents/common/skills-linux/gui-debug .claude/skills/gui-debug && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
gui-debug
GitHub stars
106
Token cost
~1.1k tokens
SKILL.md length
446 words
Files
1
Skills in repo
10
Repo updated
First seen
Licence
CC0-1.0

At a glance

Verify a rendering or window-chrome change in a GUI app unattended on Linux/Wayland under the niri compositor — enumerate windows and read output scale via niri msg --json, capture a specific window…

  • Layout/glyph/color/HiDPI rendering bugs where a screenshot
  • SKILL.md covers Find the window and the output…, Capture a specific window, Pixel probe — exact RGBA and Process hygiene, plus 1 more section
  • Calls jq, magick and nix
  • Pixel value is the ground truth

What it does

Gui Debug is an agent skill from natsukium/dotfiles. Verify a rendering or window-chrome change in a GUI app unattended on Linux/Wayland under the niri compositor — enumerate windows and read output scale via niri msg --json, capture a specific window to a file with niri msg action screenshot-window --id, and probe exact pixel RGBA with ImageMagick. Use for layout/glyph/color/HiDPI rendering bugs where a screenshot or pixel value is the ground truth.

Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It works with Linux. The repository describes itself as: Nix dotfiles for NixOS, Darwin and WSL. The licence is CC0-1.0.

When your agent uses it

  • Layout/glyph/color/HiDPI rendering bugs where a screenshot
  • Pixel value is the ground truth

Example prompts

  • “/gui-debug”

What it can do on your machine

Read from SKILL.md and the folder at commit 1457bd1. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • jq
    • magick
    • nix

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Gui Debug loads about 1.1k tokens when it runs. Until then it costs about 103 tokens; SKILL.md has 446 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~103
When it runs · the whole SKILL.md, loaded when a task matches
~1.1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from natsukium/dotfiles at commit 1457bd1, republished under its CC0-1.0 licence (© natsukium). 446 words, ~1,090 tokens.

Download SKILL.mdSave it as .claude/skills/gui-debug/SKILL.md (or your agent's skills folder).
name
gui-debug
description
Verify a rendering or window-chrome change in a GUI app unattended on Linux/Wayland under the niri compositor — enumerate windows and read output scale via niri msg --json, capture a specific window to a file with niri msg action screenshot-window --id, and probe exact pixel RGBA with ImageMagick. Use for layout/glyph/color/HiDPI rendering bugs where a screenshot or pixel value is the ground truth.

Wayland (niri) GUI debugging

Verify a rendering change by launching the app, finding its window through the compositor, capturing that window to a file, and probing pixels. On Wayland there is no cross-client "capture window N" API — capture goes through the compositor, and under niri that is the niri msg IPC, which can target a window by id directly. No external screenshot tool is needed.

niri msg action arguments evolve between versions — niri msg action screenshot-window --help shows the flags your running niri actually accepts.

ImageMagick (magick) and jq may not be on PATH. On Nix, run them ad-hoc without installing: nix run nixpkgs#imagemagick -- magick ..., nix run nixpkgs#jq -- ....

Find the window and the output scale

sh
# windows: id, title, app_id, pid, focus, and logical window_size
niri msg --json windows | jq '.[] | {id, app_id, title, is_focused, size: .layout.window_size}'

# outputs: logical size/position and scale per monitor
niri msg --json outputs | jq 'to_entries[] | {output: .key, logical: .value.logical}'
  • layout.window_size is in logical pixels; the screenshot PNG is in physical pixels — physical = logical × scale. A logical 960×600 window on a scale: 2.0 output captures as 1920×1200. Do this math before claiming a size regression.
  • Use the window list to confirm the app actually mapped a window (and to grab its id) before capturing — a crash leaves an empty list, a clearer signal than a black frame.

Capture a specific window

screenshot-window takes a window --id (no need to focus it) and a --path (must be absolute); it writes the PNG there and also copies to the clipboard.

sh
WID=$(niri msg --json windows | jq '.[] | select(.app_id=="MyApp") | .id')
niri msg action screenshot-window --id "$WID" --path /tmp/win.png
# focused output instead of a single window:
niri msg action screenshot-screen --path /tmp/screen.png
  • --id targets the window even when it isn't focused. If you need it focused for some other reason (e.g. it only renders when active), niri msg action focus-window --id "$WID" first.
  • The pointer is excluded from screenshot-window by default (--show-pointer to include); screenshot-screen includes it by default (--show-pointer false to drop).
  • The capture is the window's composited contents — it cannot by itself prove a window's own per-pixel alpha (that's a macOS screencapture -l strength, not Wayland's). Test transparency by compositing over a known solid backdrop and reading the blended result, or via the app's own rendering logs.
Show full SKILL.md (136 more words)Show less

Pixel probe — exact RGBA

sh
# single pixel at (x,y), as "srgba(r,g,b,a)"
magick /tmp/win.png -format '%[pixel:p{120,80}]' info:

# dimensions + a few sample points
magick /tmp/win.png -format 'w=%w h=%h\n' info:

# average a region (coarse "is this the colour I expect" check)
magick /tmp/win.png -crop 20x20+100+100 +repage -resize 1x1 -format '%[pixel:p{0,0}]' info:
  • Sample in physical pixels (the capture's own coordinates), not logical — account for the output scale from niri msg outputs.

Process hygiene

  • pkill -x myapp — match the exact process name. Never pkill -f path/to/MyApp, which also matches helper/renderer processes whose argv contains that path and can kill unrelated user sessions.
  • Comparing against an older build: use a separate build dir / git worktree so the two binaries don't clobber each other's artifacts.

When niri's own capture won't do

If you need a raw framebuffer grab outside niri's path (e.g. capturing a layer-shell surface niri won't target, or a whole output region), grim works: nix run nixpkgs#grim -- -o <output> /tmp/out.png. slurp, satty, and swappy are interactive — they block on a human, so don't use them in unattended runs; compute regions from niri msg geometry instead.

© natsukium, CC0-1.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in modules/features/coding-agents/common/skills-linux/gui-debug of natsukium/dotfiles.

Open the folder on GitHubat commit 1457bd1

Compare with similar skills

Gui Debug next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Gui Debug compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Gui Debug this skillnatsukium/dotfiles106—~1.1kAutomated safety check: PassCC0-1.0
Configuring Horizoncoollabsio/coolify63k4 repos~898Automated safety check: PassMIT
Engine Whats Newflutter/flutter179k—~978Automated safety check: PassBSD-3-Clause
Openclaw Live Updateropenclaw/openclaw392k—~3.7kAutomated safety check: PassMIT
Upgrade Browserflutter/flutter179k—~1.1kAutomated safety check: PassBSD-3-Clause
K8s Security PoliciesCybereason-Public/owLSM28012 repos~2kAutomated safety check: PassGPL-2.0

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Works with

Questions about Gui Debug

What does Gui Debug do?

Verify a rendering or window-chrome change in a GUI app unattended on Linux/Wayland under the niri compositor — enumerate windows and read output scale via niri msg --json, capture a specific window…. Gui Debug is an agent skill from natsukium/dotfiles. Verify a rendering or window-chrome change in a GUI app unattended on Linux/Wayland under the niri compositor — enumerate windows and read output scale via niri msg --json, capture a specific window to a file with niri msg action screenshot-window --id, and probe exact pixel RGBA with ImageMagick.

When should I use Gui Debug?

Gui Debug fits situations like: layout/glyph/color/HiDPI rendering bugs where a screenshot; pixel value is the ground truth.

How do I install Gui Debug in Claude Code?

Run `npx skills add natsukium/dotfiles --skill gui-debug -a claude-code`. Or copy the skill folder (modules/features/coding-agents/common/skills-linux/gui-debug in natsukium/dotfiles) into .claude/skills/gui-debug in your project. Claude Code loads it when a task matches its description.

How do I install Gui Debug in Codex?

Run `npx skills add natsukium/dotfiles --skill gui-debug -a codex`. Or copy the skill folder (modules/features/coding-agents/common/skills-linux/gui-debug in natsukium/dotfiles) into .agents/skills/gui-debug in your project. Codex loads it when a task matches its description.

Can I use Gui Debug in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add natsukium/dotfiles --skill gui-debug -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/gui-debug, .gemini/skills/gui-debug, .github/skills/gui-debug and .opencode/skills/gui-debug in your project.

What does Gui Debug need to run?

Going by SKILL.md and its folder, Gui Debug needs the command-line tools its instructions call (jq, magick and nix).

Does Gui Debug access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Gui Debug safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Gui Debug use?

Gui Debug is published under the CC0-1.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Gui Debug use?

About 1.1k tokens (SKILL.md is roughly 4.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Gui Debug?

Skills that share tags, products or a category with Gui Debug: Configuring Horizon (coollabsio/coolify, 63k stars), Engine Whats New (flutter/flutter, 179k stars), Openclaw Live Updater (openclaw/openclaw, 392k stars) and Upgrade Browser (flutter/flutter, 179k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Gui Debug?

natsukium (a GitHub user) maintains it in natsukium/dotfiles, which has 106 GitHub stars. The repository holds 10 skills in this directory. The repository was last updated on October 7, 2026.

Source: natsukium/dotfiles on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.