plwm: The Complete Guide to the Prolog-Powered X11 Window Manager

What is plwm?

plwm is a dynamic tiling window manager for the X Window System, uniquely built using the Prolog programming language. This innovative approach redefines window management through logical programming paradigms, offering a fresh alternative to traditional C-based managers like dwm.

Core Features

• Logic Programming Framework: Define window rules using Prolog’s declarative syntax
• Dynamic Layout System: 12+ predefined layouts including stacks, grids, and master-slave configurations
• Lightweight Performance: 10-15MB memory usage with instant responsiveness
• Runtime Customization: Modify configurations without recompiling

Key Features Explained

1. Dynamic Layout Engine

plwm offers 12 ready-to-use layouts accessible via keyboard shortcuts:

Pro Tips:

• Super+H/L: Adjust master area width in 5% increments
• Super+I/D: Modify number of master windows
• Super+Space: Toggle window floating state

2. Workspace Management

Independent workspace systems per monitor (default: 9 workspaces):

% Custom workspace names
workspaces(['Dev', 'Web', 'Docs', 'Chat', 'Media', 'Term', 'Test', 'Temp', 'Misc']).

Advanced Operations:

• Dynamic workspace creation (Alt+C)
• Cross-monitor window transfer (Super+Shift+,/.)
• Hide empty workspaces (Super+Shift+Tab)

3. Rule-Based Automation

Define window rules using Prolog predicates:

rules([
  (_     , "Firefox" , _        -> "HDMI-1", 'Web' , fullscreen),
  ("GIMP", _         , _        -> _       , _     , [center, center, 0.8, 0.8]),
  (_     , "Alacritty", "cmus" -> _       , 'Media', managed)
]).

Installation & Configuration

System Requirements

• Xorg server
• SWI-Prolog 8.0+
• Development libraries: libx11, libxft, libxrandr

Ubuntu/Debian Setup:

sudo apt install xorg-dev swi-prolog
git clone https://github.com/Seeker04/plwm
cd plwm
make && sudo make install

First-Time Setup

1. Add to ~/.xinitrc:

   exec plwm
   

2. Launch with startx:

   echo "if [ -z \"\$DISPLAY\" ] && [ \"\$(tty)\" = \"/dev/tty1\" ]; then exec startx; fi" >> ~/.bash_profile
   

UI Customization Example

% Border and gap settings
border_width(2),
border_color_focused("#458588"),
outer_gaps(24),
inner_gaps(12),

% Animation parameters
animation_enabled(true),
animation_time(0.3),
animation_granularity(40),

Productivity Workflows

Window Navigation Mastery

Status Bar Integration

Sample polybar configuration:

[module/workspaces]
type = internal/plwm
format = <label-state>
label-active = %name%
label-occupied = ▘%name%

Script Automation

Control plwm via FIFO pipeline:

# Create temporary workspace
echo "create_workspace(temp), switch_workspace(temp)." > /tmp/plwm_fifo

# Batch workspace creation
seq 1 5 | xargs -I{} echo "create_workspace('{}')." > /tmp/plwm_fifo

Technical Deep Dive

Architectural Overview

1. Event Handling: Xlib-based event loop
2. Layout Engine: Prolog-powered geometry calculations
3. State Management: Dynamic database for window states

Performance Optimization

• Window state caching
• Batch geometry processing
• Recursion safety mechanisms

Comparative Analysis

Advanced Customization

Custom Layout Development

1. Add new predicate in layout.pl
2. Implement geometry logic
3. Bind to hotkey:

keymaps([
  super+shift+"Y" -> layout:set_layout(custom_layout)
]).

Event Hook Implementation

hooks([
  window_create_post -> (
    get_window_class(Class),
    (Class == "TelegramDesktop" -> move_to_workspace('Chat'))
]).

FAQ: Expert Answers

Q: Java applications display blank windows

Add to .xinitrc:

export _JAVA_AWT_WM_NONREPARENTING=1

Q: Debugging configuration errors

Validate configs with:

plwm --check -c ~/.config/plwm/config.pl

Q: Multi-monitor support details

• Super+,/. switches monitors
• Super+Shift+,/. moves windows across displays

Q: plwm vs i3/dwm?

• ✔️ Ideal for declarative configuration lovers
• ✔️ Excellent Prolog learning tool
• ❌ Not for Wayland users

Project Roadmap

Current (0.x) features:

• Core window management
• Multi-monitor support
• External bar integration

Planned for 1.0:

• Enhanced EWMH compliance
• Expanded test coverage
• Migration tools for dwm users

Final Thoughts

plwm revolutionizes window management by merging logical programming with practical workflow design. While requiring initial Prolog familiarity, it offers unparalleled customization depth for power users. For developers seeking full environment control or Prolog enthusiasts exploring real-world applications, plwm presents a compelling platform worth mastering.