surface-dial-overlay

A Wayland overlay for the Microsoft Surface Dial. It listens for dial events broadcast over D-Bus and renders a Windows Fluent-style visual indicator on screen.

How it works

Surface Dial (evdev)
       │
  dialmenu daemon
       │  D-Bus signals (com.dialmenu.Daemon)
       ▼
surface-dial-overlay
       │  tiny-skia rendering
       ▼
  wlr-layer-shell overlay

The daemon (a separate project) handles raw evdev input and re-broadcasts events as D-Bus signals. This overlay subscribes to those signals and draws a centred, transparent overlay on your Wayland desktop that auto-hides after a configurable period of inactivity.

Visual styles

Four styles are available, selected in the config file.

dial (default) — Windows Fluent experience

Matches the Windows Surface Dial interaction model:

Gesture	Visual
Rotate (button up)	Dark Fluent disc + glowing accent-blue arc. A white tip dot marks the current position on the arc.
Press & hold	Radial menu appears — sections arranged around a dark disc with a Fluent centre hub and subtle outer ring.
Rotate while held	Selection advances through sections (wraps around). An accent-colour dot tracks the selected section.
Release	Menu closes immediately.

fill

A dark background disc with a coloured wedge that grows from 12 o'clock as you rotate. Pressing shows a filled press circle.

arc

Ring stroke with a coloured arc that traces the rotation amount.

pie_menu

Circle always split into sections while rotating. Rotation changes selection continuously without requiring a button press.

Configuration

Config file location:

~/.config/surface-dial-overlay/config.toml

Missing keys fall back to defaults. The file does not need to exist.

Full example

# Style: "dial" (default), "fill", "arc", "pie_menu"
style = "dial"

# Hide the overlay this many milliseconds after the last event.
timeout_ms = 2000

# Overlay size in pixels.
size = 240

[colors]
# All colours: [red, green, blue, alpha]  (0–255)
cw         = [0, 120, 212, 240]    # accent blue — arc indicator
ccw        = [0, 120, 212, 240]    # same for dial style
press      = [0, 120, 212, 255]    # confirmation dot
background = [28, 28, 28, 230]     # Fluent dark surface

[pie_menu]
# Section labels — also used by the "dial" radial menu.
# Maximum ~7 items recommended.
sections = ["Volume", "Scroll", "Zoom", "Undo"]

# Highlight colour for the selected section.
selected_color   = [255, 255, 255, 215]

# Colour for unselected sections.
unselected_color = [255, 255, 255, 32]

# Gap between sections in degrees.
gap_degrees = 3.0

# Raw rotation delta to advance one section. Lower = more sensitive.
selection_step = 5.0

Requirements

• A Wayland compositor with wlr-layer-shell support (Sway, Hyprland, KDE Plasma, GNOME 45+, etc.)
• The dialmenu daemon running and broadcasting on the session D-Bus

If the compositor does not support wlr-layer-shell the overlay falls back to a standard XDG window.

D-Bus interface

Property	Value
Service	com.dialmenu.Daemon
Object path	/com/dialmenu/Daemon
Interface	com.dialmenu.Daemon

Signals consumed:

Signal	Arguments	Meaning
DialRotated	delta: i32	One step of rotation
DialPressed	—	Button pressed
DialReleased	—	Button released

Building

cargo build --release

Running

cargo run --release

Enable debug logging:

RUST_LOG=debug cargo run --release

Project structure

src/
├── main.rs      # Entry point: Wayland init, calloop event loop, D-Bus thread
├── config.rs    # TOML config loading, style/colour/menu types
├── dbus.rs      # zbus proxy and async signal listener
└── overlay.rs   # Wayland surface, SCTK delegates, style-dispatched rendering

Threading model

• Main thread — calloop event loop dispatching Wayland protocol events and D-Bus channel messages; 100 ms heartbeat for visibility timeout
• D-Bus thread — single-threaded tokio runtime running the async zbus signal listener; forwards events through a calloop::channel to the main thread

Arc rendering

Circular arcs are approximated using cubic Bézier curves, split into at most 90° segments. The control-point distance factor is:

k = (4/3) · tan(α/4)

where α is the sweep angle of one segment. This gives a maximum radial error of ~0.06% of the radius — indistinguishable from a true circle at any overlay size.