sway-mirror

Fast zero-copy screen mirroring for Sway/wlroots compositors.

Features

• Zero-copy rendering - Uses DMA-BUF for efficient GPU-to-GPU frame transfer
• Multi-output support - Mirror to one or all other outputs simultaneously
• Workspace management - Automatically moves workspaces to source output and restores on exit
• Scaling modes - Fit, fill, stretch, or center content on target displays
• Cursor capture - Optionally include the cursor in the mirrored output
• Clean shutdown - Stop via --stop flag or Ctrl+C

Requirements

• Sway or wlroots-based compositor
• zwlr_export_dmabuf_manager_v1 protocol support
• zwlr_layer_shell_v1 protocol support
• EGL/OpenGL ES support

Works with both discrete GPUs and integrated graphics (Intel, AMD APU).

Build Dependencies

Install the required development libraries before building:

# Debian/Ubuntu
sudo apt install libwayland-dev

# Fedora/RHEL
sudo dnf install wayland-devel

# Arch Linux
sudo pacman -S wayland

Installation

# Build
cargo build --release

# Install to ~/.local/bin (user)
cp target/release/sway-mirror ~/.local/bin/

# Or install system-wide
sudo cp target/release/sway-mirror /usr/local/bin/

Usage

# List available outputs
sway-mirror --list

# Mirror eDP-1 to all other outputs
sway-mirror eDP-1

# Mirror eDP-1 to specific output only
sway-mirror eDP-1 -t DP-7

# Mirror to multiple specific outputs
sway-mirror eDP-1 -t DP-7 -t DP-8

# Use fill scaling (crops to fill target)
sway-mirror eDP-1 -s fill

# Don't move workspaces
sway-mirror eDP-1 -w false

# Stop a running instance
sway-mirror --stop

Options

Option	Description
SOURCE	Source output to mirror (e.g., eDP-1, DP-7)
-t, --to <OUTPUT>	Target output(s). If not specified, mirrors to all other outputs
-l, --list	List available outputs and exit
-s, --scale <MODE>	Scaling mode: fit (default), fill, stretch, center
-w, --workspaces	Move all workspaces to source while mirroring (default: true)
--cursor	Include cursor in mirror (default: true)
--stop	Stop a running sway-mirror instance

Scaling Modes

• fit - Preserve aspect ratio, fit within target (letterbox/pillarbox if needed)
• fill - Preserve aspect ratio, fill target completely (crops edges)
• stretch - Stretch to fill target, ignoring aspect ratio
• center - Display at 1:1 pixel ratio, centered (no scaling)

How It Works

1. Captures frames from the source output using zwlr_export_dmabuf_manager_v1
2. Imports the DMA-BUF as an EGL image (zero-copy GPU texture)
3. Renders to layer-shell overlay surfaces on target outputs
4. Workspaces are moved to the source output so all content is visible in the mirror

License

MIT