Building a Compositor for a Userbase of One

This describes RESONANCE, a custom Wayland compositor built to occupy a middle ground between floating and tiling window managers. Rather than letting windows pile up or forcing everything into a rigid grid, windows live on stacked "levels" (Basement, Ground, First, Second) that visually inset to convey depth; new windows map to Ground and are demoted upward if they overlap, promoted back down when space frees, and never force already-open windows to move. The compositor started from tinywl and grew into a full-featured system that handles multi-monitor layout, XWayland, layer-shell, server-side decorations, screen capture, pointer constraints, drag-and-drop, and an IPC port. Crucially, policy and placement live in a separate Python "brain" process communicating over a simple newline-delimited socket: the compositor reports events and accepts two commands (place and fullscreen), so window-decision logic can be edited and restarted mid-session without destabilizing the C compositor.

Key specifics include a persistent three-axis placement store (app_id → floor → per-window slots) with rules for when a geometry is recorded, monitor-aware replay, special handling for splashes and generic GTK dialogs, and fullscreen restoration semantics. A push-resize model prevents overlap by sliding at-most-one neighbor per axis with a 7 px gap and a 100 px minimum, recalculated live from committed frames; pushes do not chain and persist once applied. The separation of policy and execution, plus the spatial level model, yields a stable, readable workspace that avoids both chaotic stacking and intrusive automatic tiling.