fix(linux): position tray windows against the real work area

[fan711]

Description

A window attached to the system tray is laid over the taskbar. positionWindow clamps against Screen.Size, and Screen.WorkArea is no help because on the GTK4 backend it is the whole monitor: gdk_monitor_get_workarea was removed in GTK4 and Wayland has no protocol for it, so there is currently nothing that reports the space panels and docks leave free.

The window manager still publishes _NET_WORKAREA on the X11 root window, so that is read instead. A Wayland session keeps the property current through XWayland, and the process already has libX11 mapped there because GTK links both backends, so the existing dlsym-from-RTLD_DEFAULT approach used elsewhere in linux_cgo.c reaches it without adding a link dependency. Where there is no X display at all, the caller keeps the full monitor it uses today.

Only the first desktop's rectangle is read — a per-desktop work area is a concept no other platform here has.

No issue filed; found while building a tray-based app.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• WEP (proposal only; no implementation)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

A tray app with AttachWindow(window).WindowOffset(4), on a monitor with the Plasma panel at the bottom. Before, the window's lower edge ran under the panel; after, it sits above it.

The property being read is the one the panel actually publishes:

$ xrandr | grep -w connected
eDP-1 connected primary 1680x1050+0+0 ...
$ xprop -root _NET_WORKAREA
_NET_WORKAREA(CARDINAL) = 0, 0, 1680, 1006

— the 44px difference is the panel, and that is the height the window is now clamped to.

Scope of what I actually exercised: KDE Plasma 6 on Wayland, panel at the bottom, single active output. I have not tested this under X11, GNOME/Mutter, a top or side panel, or a multi-monitor layout with panels on different outputs — the last is the case I would most want a second pair of eyes on, since _NET_WORKAREA is a single global rectangle while positionWindow is otherwise per-screen. On a multi-monitor setup where the panel is not on the screen the tray window opens on, this will clamp to the wrong rectangle, so it may need to intersect with currentScreen rather than replace it outright. Happy to take direction there.

• Windows
• macOS
• Linux

Debian 13 (trixie), KDE Plasma 6 on Wayland.

Test Configuration

GTK 4.18.6, WebKitGTK 2.52.3, Go 1.25.0.

Checklist:

• (v2 only) I have updated website/src/pages/changelog.mdx with details of this PR (v3 changelog entries are added automatically)
• My code follows the general coding style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

I kept this scoped to positionWindow rather than making Screen.WorkArea itself report the real area, since that is a wider behaviour change and I did not want to presume — but it may well be the better place for it, and I am happy to move it if you prefer. v3/UNRELEASED_CHANGELOG.md is updated under Fixed, per CONTRIBUTING.md; drop that commit if v3 entries are generated automatically.

Summary by CodeRabbit

• Bug Fixes
  • Improved Linux system tray positioning to account for panels, docks, and other reserved desktop areas.
  • Added a fallback to full-screen dimensions when the usable desktop area cannot be detected.

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Walkthrough

The change adds Linux X11 work-area retrieval and exposes it to Go. System tray positioning clips the work area to the active monitor and falls back to monitor geometry when the work area is unavailable or does not overlap.

Changes

Linux tray positioning

Layer / File(s)	Summary
X11 work-area retrieval v3/pkg/application/linux_cgo.c, v3/pkg/application/linux_cgo.h, v3/pkg/application/linux_cgo.go	The CGO layer resolves X11 functions, reads validated _NET_WORKAREA data, and exposes the result through screenWorkArea.
Tray positioning integration v3/pkg/application/systemtray_linux.go, v3/UNRELEASED_CHANGELOG.md	positionWindow intersects the work area with the active monitor. It retains monitor geometry when the intersection is empty. The changelog records the fix.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: 🔵 Low · up to f0bee

The fix keeps tray windows above panels, but on some multi-monitor layouts it may use the desktop-wide work area instead of the window’s monitor-specific bounds, allowing the window to be positioned or clamped incorrectly. The PR is mergeable with explicit owner awareness or follow-up for multi-monitor behavior.

Sequence Diagram(s)

sequenceDiagram
  participant TrayWindow
  participant positionWindow
  participant screenWorkArea
  participant X11
  TrayWindow->>positionWindow: request positioning
  positionWindow->>screenWorkArea: retrieve work-area geometry
  screenWorkArea->>X11: read _NET_WORKAREA
  X11-->>screenWorkArea: return desktop bounds
  screenWorkArea-->>positionWindow: return geometry and availability
  positionWindow-->>TrayWindow: apply clipped or monitor geometry

Loading

Poem

A rabbit checks the desktop line,
Finds room where panels shine.
The tray hops clear of taskbar bars,
With fallback bounds beneath the stars.
X11 guides each careful glide.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the Linux tray window positioning fix.
Description check	✅ Passed	The description explains the problem, implementation, testing scope, configuration, limitations, and checklist status in sufficient detail.
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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Inline comments:
In `@v3/pkg/application/systemtray_linux.go`:
- Around line 264-265: Update the screenWorkArea handling so its desktop-wide
work area is intersected with currentScreen before assigning screenX, screenY,
screenWidth, and screenHeight. Only apply the intersection when it has positive
dimensions; otherwise preserve the existing currentScreen geometry.

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• v3/pkg/application/systemtray_linux.go

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