wl-mirror - a simple Wayland output mirror client

wl-mirror attempts to provide a solution to sway's lack of output mirroring by mirroring an output onto a client surface.

Features

• Mirror an output onto a resizable window
• Mirror an output onto another output by fullscreening the window
• Reacts to changes in output scale (including fractional scaling)
• Preserves aspect ratio
• Corrects for flipped or rotated outputs
• Supports custom flips or rotations
• Supports mirroring custom regions of outputs
• Supports receiving additional options on stdin for changing the mirrored screen or region on the fly (works best when used with pipectl)

Usage

usage: wl-mirror [options] <output>

options:
  -h,   --help                  show this help
  -V,   --version               print version
  -v,   --verbose               enable debug logging
        --no-verbose            disable debug logging (default)
  -c,   --show-cursor           show the cursor on the mirrored screen (default)
        --no-show-cursor        don't show the cursor on the mirrored screen
  -i,   --invert-colors         invert colors in the mirrored screen
        --no-invert-colors      don't invert colors in the mirrored screen (default)
  -f,   --freeze                freeze the current image on the screen
        --unfreeze              resume the screen capture after a freeze
        --toggle-freeze         toggle freeze state of screen capture
  -F,   --fullscreen            display wl-mirror as fullscreen
        --no-fullscreen         display wl-mirror as a window (default)
        --fullscreen-output O   set fullscreen target output to output O, implies --fullscreen
        --no-fullscreen-output  unset fullscreen target output, implies --no-fullscreen (default)
  -s f, --scaling fit           scale to fit (default)
  -s c, --scaling cover         scale to cover, cropping if needed
  -s e, --scaling exact         only scale to exact multiples of the output size
  -s l, --scaling linear        use linear scaling (default)
  -s n, --scaling nearest       use nearest neighbor scaling
  -b B  --backend B             use a specific backend for capturing the screen
  -t T, --transform T           apply custom transform T
  -r R, --region R              capture custom region R
        --no-region             capture the entire output (default)
  -S,   --stream                accept a stream of additional options on stdin
        --title N               specify a custom title N for the mirror window

backends:
  - auto        automatically try the backends in order and use the first that works (default)
  - dmabuf      use the wlr-export-dmabuf-unstable-v1 protocol to capture outputs
  - screencopy  use the wlr-screencopy-unstable-v1 protocol to capture outputs

transforms:
  transforms are specified as a dash-separated list of flips followed by a rotation
  flips are applied before rotations
  - normal                         no transformation
  - flipX, flipY                   flip the X or Y coordinate
  - 0cw,  90cw,  180cw,  270cw     apply a clockwise rotation
  - 0ccw, 90ccw, 180ccw, 270ccw    apply a counter-clockwise rotation
  the following transformation options are provided for compatibility with sway output transforms
  - flipped                        flip the X coordinate
  - 0,    90,    180,    270       apply a clockwise rotation

regions:
  regions are specified in the format used by the slurp utility
  - '<x>,<y> <width>x<height> [output]'
  on start, the region is translated into output coordinates
  when the output moves, the captured region moves with it
  when a region is specified, the <output> argument is optional

stream mode:
  in stream mode, wl-mirror interprets lines on stdin as additional command line options
  - arguments can be quoted with single or double quotes, but every argument must be fully
    quoted or fully unquoted
  - unquoted arguments are split on whitespace
  - no escape sequences are implemented

title placeholders:
  the title string supports the following placeholders:
  - {width}, {height}:               size of the mirrored area
  - {x}, {y}:                        offsets on the screen
  - {target_width}, {target_height}
    {target_output}:                 info about the mirrored device
  a few perhaps useful examples:
    --title='Wayland Mirror Output {target_output}'
    --title='{target_output}:{width}x{height}+{x}+{y}'
    --title='resize set {width} {height} move position {x} {y}'

The scripts/ folder contains examples on how wl-mirror can be used.

• wl-present is a small script to demonstrate the use of the -S option to interactively present on Sway.
  This script is especially useful when binding the wl-present subcommands to keyboard shortcuts. See example below.
• release.sh Generates a release tar ball for the currently checked out commit if there's a release tag on it.

Sway Keybindings Example

The following keybindings shortcuts can be used in your sway config.

mode "present" {
    # command starts mirroring
    bindsym m mode "default"; exec wl-present mirror
    # these commands modify an already running mirroring window
    bindsym o mode "default"; exec wl-present set-output
    bindsym r mode "default"; exec wl-present set-region
    bindsym Shift+r mode "default"; exec wl-present unset-region
    bindsym s mode "default"; exec wl-present set-scaling
    bindsym f mode "default"; exec wl-present toggle-freeze
    bindsym c mode "default"; exec wl-present custom

    # return to default mode
    bindsym Return mode "default"
    bindsym Escape mode "default"
}
bindsym $mod+p mode "present"

This requires wl-mirror, the wl-present script, pipectl (optional), slurp, and one of wofi, wmenu, rofi, or dmenu.

Note that wl-present only allows one instance by default, but multiple instances can be used at the same time using the --name option or WL_PRESENT_PIPE_NAME environment variable.

Kanshi Configuration Example

The following kanshi profile will launch wl-mirror in fullscreen on an external output mirroring your internal output when switched to with kanshictl switch mirror-hdmi or when selected automatically.

profile mirror-hdmi {
    output eDP-1 enable mode 1920x1080 position 0,0
    output HDMI-A-1 enable mode 1920x1080 position 1920,0
    exec wl-present mirror eDP-1 --fullscreen-output HDMI-A-1 --fullscreen

    # alternatively, for wl-mirror < 0.16.4
    # exec wl-present mirror eDP-1 & sleep .5; wl-present fullscreen-output HDMI-A-1; wl-present fullscreen
}

Installation

wl-mirror is already packaged in many distros and can be installed via the package manager:

Supported Wayland Compositors

wl-mirror should work on all Wayland compositors based on wlroots, such as sway or hyprland.

wl-mirror currently does not work on KDE and Gnome, due to wl-mirror not supporting the XDG Desktop Portal screen sharing protocol. This is being worked on (see issues #16 and #17).

Dependencies

• CMake
• pkg-config
• libwayland-client
• libwayland-egl
• libEGL
• libGLESv2
• epoll-shim (on systems that do not have epoll, e.g. FreeBSD)
• libdecor (see WITH_LIBDECOR)
• wayland-scanner
• scdoc (for manual pages, see INSTALL_DOCUMENTATION)

Script Dependencies

• pipectl (optional for scripts/wl-present)
• slurp (scripts/wl-present)
• wofi, wmenu, rofi or dmenu (scripts/wl-present)

Building

• Install Dependencies
• Clone Submodules (git submodule update --init)
• Run cmake -B build
• Run cmake --build build

CMake Options

• INSTALL_EXAMPLE_SCRIPTS: also install example scripts (default OFF)
• INSTALL_DOCUMENTATION: also build and install manual pages (default OFF)
• WITH_LIBDECOR: build with libdecor for window decoration (default OFF)
• FORCE_WAYLAND_SCANNER_PATH: always use the provided path for wayland-scanner, do not use pkg-config (default empty)
• FORCE_SYSTEM_WL_PROTOCOLS: always use system-installed wayland-protocols, do not use submodules (default OFF)
• FORCE_SYSTEM_WLR_PROTOCOLS: always use system-installed wlr-protocols, do not use submodules (default OFF)
• WL_PROTOCOL_DIR: directory where system-installed wayland-protocols are located (default /usr/share/wayland-protocols)
• WLR_PROTOCOL_DIR: directory where system-installed wlr-protocols are located (default /usr/share/wlr-protocols)

Files

• src/main.c: main entrypoint
• src/options.c: CLI and stream option parsing
• src/wayland.c: Wayland and xdg_surface boilerplate
• src/egl.c: EGL boilerplate
• src/mirror.c: output mirroring code
• src/mirror-dmabuf.c: wlr-export-dmabuf-unstable-v1 backend code
• src/mirror-screencopy.c: wlr-screencopy-unstable-v1 backend code
• src/transform.c: matrix transformation code
• src/event.c: event loop
• src/stream.c: asynchronous option stream input

License

This project is licensed under the GNU GPL version 3.0 or later (SPDX GPL-3.0-or-later). The full license text can also be found in the LICENSE file.