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Circular Alt+Tab switcher showing windows as pie slices around the cursor

By Safwan Usaid Lubdhak / / 3 min read

A Circular Alt+Tab Switcher for KDE Plasma 6

qml kde linux open source project

The idea

Alt+Tab is a horizontal strip on almost every desktop. But a strip wastes the one piece of information you always have: where the cursor is. Circular Alt+Tab lays your windows out as pie slices around the cursor instead, so the target is always a short flick away. Hover to select, click to activate, middle-click to close. It works with the keyboard, the mouse, and the scroll wheel.

It’s a KWin window-switcher plugin for KDE Plasma 6, written in pure QML with no build step.

Key Takeaways

  • Windows are arranged as pie slices around the cursor, so the one you want is always a short flick away.
  • Live thumbnails, a multi-ring layout past 8 windows, and full Plasma theme integration, all in pure QML with no build step.
  • Hit-testing reads static ring geometry rather than animated positions, which is what keeps hover selection from jittering.

What it does

  • Pie-slice layout centered on the cursor, with live window thumbnails (icons for minimized windows).
  • Multi-ring layout when you have more than 8 windows. They distribute evenly across rings via a remainder algorithm, with the overflow pushed to the outer rings.
  • Semi-transparent background that adapts to your Plasma theme. Colors, captions, and the selection indicator all read from Kirigami theme variables, so reduced-motion and high-contrast modes are inherited for free rather than reimplemented.
Multi-ring layout with live thumbnails

How it works

The architecture is a small chain, TabBoxSwitcher → Window → Pie → Repeater → Piece, with rotation-based positioning and an OpacityMask for clipping each annular sector.

  • Hit-testing reads static ring geometry, not animated per-frame positions. This is the subtle one. If you hit-test against the scaled-up hovered piece, hovering becomes jittery as the geometry shifts under the cursor. Testing against the fixed ring layout eliminates that.
  • Single-window mode caps the slice at 180°. A full 360° circle for one window is degenerate and looks broken.
  • It leans on undocumented KWin APIs (model.activate(), KWin.Workspace.cursorPos, window enumeration), a deliberate, documented trade-off, since the polished interaction simply isn’t reachable through the public TabBox surface.

On an RTX 3070 with 30 simultaneous windows (4 rings), peak GPU SM utilization sat at 52% and KWin held under half a core, idle between interactions. No sustained load at realistic-to-extreme window counts.

Limitations

The README ships a frank limitations section, because that’s what I’d want to read before installing a compositor plugin. The undocumented APIs could break on a future Plasma point release; there’s no screen-reader support (the pie layout is inherently spatial and KWin’s overlay API exposes no accessibility hook to attach to); and multi-monitor is verified on one mixed-DPI setup, not all of them.

It started as a Plasma 6 port of an older switcher and has since been substantially reworked: multi-ring layout, live thumbnails, scroll support, and theme integration. Pure QML, GPLv3, installable from a release zip or a one-line script.

Skills & Deliverables:

  • QML / Qt Quick: rotation-based layout, OpacityMask sector clipping, and animation driven entirely by Kirigami theme units.
  • Desktop / compositor integration: a KWin TabBox plugin working across both Wayland and X11 sessions on Plasma 6.
  • Pragmatic engineering: hit-testing against static geometry to kill hover jitter, a remainder-based multi-ring distribution, and a documented stance on undocumented APIs.