Paneru

A sliding, tiling window manager for MacOS.

About

Paneru is a MacOS window manager that arranges windows on an infinite strip, extending to the right. A core principle is that opening a new window will never cause existing windows to resize, maintaining your layout stability.

Each monitor operates with its own independent window strip, ensuring that windows remain confined to their respective displays and do not “overflow” onto adjacent monitors.

Why Paneru?

• Optimal for Large Displays: Standard tiling window managers can be suboptimal for large displays, often resulting in either huge maximized windows or numerous tiny, unusable windows. Paneru addresses this by providing a more flexible and practical arrangement.
• Improved Small Display Usability: On smaller displays (like laptops), traditional tiling can make windows too small to be productive, forcing users to constantly maximize. Paneru’s sliding strip approach aims to provide a better experience without this compromise.
• Niri-like Behavior on MacOS: Inspired by the user experience of Niri, Paneru aims to bring a similar scrollable tiling workflow to MacOS.
• Focus follows mouse on MacOS: Very useful for people who would like to avoid an extra click.
• Sliding windows with touchpad: Using a touchpad is quite natural for navigation of the window pane.
• Learning Opportunity: This project serves as a hands-on opportunity to delve into the MacOS API and Objective-C, as well as to deepen understanding and practice Rust programming.

Inspiration

The fundamental architecture and window management techniques are heavily inspired by Yabai, another excellent MacOS window manager. Studying its source code has provided invaluable insights into managing windows on MacOS, particularly regarding undocumented functions.

The innovative concept of managing windows on a sliding strip is directly inspired by Niri and PaperWM.spoon.

Installation

Paneru is currently in a basic, working state.

Building

Paneru is built using Rust’s cargo.

$ cargo build --target release
$ cp target/release/paneru ~/bin/

Configuration

To configure Paneru, create a configuration file named .paneru in your home directory (~/.paneru). You can use the following example configuration as a starting point:

# syntax=toml
#
# Example configuration for Paneru.
#
[options]
# Enables focus follows mouse
focus_follows_mouse = true

[bindings]
# Moves the focus between windows.
window_focus_west = "cmd - h"
window_focus_east = "cmd - l"
window_focus_north = "cmd - k"
window_focus_south = "cmd - j"

# Swaps windows in chosen direction.
window_swap_west = "alt - h"
window_swap_east = "alt - l"

# Jump to the left-most or right-most windows.
window_focus_first = "cmd + shift - h"
window_focus_last = "cmd + shift - l"

# Move the current window into the left-most or right-most positions.
window_swap_first = "alt + shift - h"
window_swap_last = "alt + shift - l"

# Centers the current window on screen.
window_center = "alt - c"

# Shuffles between predefined window sizes: 25%, 33%, 50%, 66% and 75%.
window_resize = "alt - r"

# Toggles the window for management. If unmanaged, the window will be "floating".
window_manage = "ctrl + alt - t"

# Stacks and unstacks a window into the left column. Each window gets a 1/N of the height.
window_stack = "alt - ]"
window_unstack = "alt + shift - ]"

# Quits the window manager.
quit = "ctrl + alt - q"

Live Reloading: Configuration changes made to your ~/.paneru file are automatically reloaded while Paneru is running. This is extremely useful for tweaking keyboard bindings and other settings without restarting the application. The settings can be changed while Paneru is running - they will be automatically reloaded.

Running

Start the main binary without any parameters:

$ cargo run paneru

You can change the default info log level to more verbose levels (debug, trace) with:

$ RUST_LOG=debug cargo run paneru

Future Enhancements

• More commands for manipulating windows: fullscreen, finegrained size adjustments, etc.
• Scriptability. A nice feature would be to use Lua for configuration and simple scripting, like triggering and positioning specific windows or applications.

Architecture Overview

The overall architecture is layered, with a platform interaction layer at the base. This bottom layer, primarily within platform.rs, interfaces directly with the MacOS operating system via Objective-C and Core Graphics APIs. It runs the main RunLoop in the main thread, receiving OS-level events and acting as the bridge between the operating system and the application’s logic. Events captured by this layer, such as window events, application state changes, and mouse events, are then pushed into a multiple-producer single-consumer (MPSC) queue.

Higher layers of the application consume events from this queue. These layers include the WindowManager, ProcessManager, and various event handlers. The WindowManager is responsible for tracking and manipulating window states, while the ProcessManager handles the lifecycle of applications. Event handlers in modules like events.rs interpret the raw events and orchestrate the appropriate responses within the application. This design promotes a decoupled architecture, allowing modules to operate independently while reacting to system-level changes.

Tile Scrollably Elsewhere

Here are some other projects which implement a similar workflow:

• Niri: a scrollable tiling Wayland compositor.
• PaperWM: scrollable tiling on top of GNOME Shell.
• karousel: scrollable tiling on top of KDE.
• papersway: scrollable tiling on top of sway/i3.
• hyprscroller and hyprslidr: scrollable tiling on top of Hyprland.
• PaperWM.spoon: scrollable tiling on top of MacOS.