Design & ideas

0xin is a dynamic tiling window manager for Wayland, written in Rust on wlroots. This chapter documents its design decisions — how the layout, configuration, and workspace model work and why — and the ideas planned next. It is updated as decisions are made.

Layout

Tiled windows sit in an explicit split tree (layout::Node: Leaf or Split { vertical, ratio, first, second }), one per workspace, shaped like the dwindle spiral described in Stage 5 by default but with a persisted ratio per split — Stage 10’s addition. Mod+Ctrl+hjkl (resizewindow) adjusts the ratio of whichever split borders the focused window in that direction; every other window’s ratio is untouched, including across opening and closing unrelated windows.

Windows themselves stay unaware of the tree: which window is tiled-position i is still decided purely by Workspace.windows’ order (now filtered to non-floating, non-fullscreen ones), exactly as before. The tree only adds the one thing a plain Vec had no room for — a number that survives between refresh() calls. Directional navigation (spatial_neighbor) still uses Stage 5’s geometric heuristic rather than the tree’s actual adjacency, so the corner-touch ambiguity documented there is unchanged.

Configuration

Three rules, applied throughout src/config.rs:

1. Nothing is fatal. A line that doesn’t parse warns on stderr and is skipped. A missing config file means defaults. A config with zero bind lines still has every default binding. 0xin always starts.
2. User config merges, never replaces. A bind line overrides exactly that key combination; every unmentioned default stays active. A two-line config is a two-line diff, not a fork of the whole keymap.
3. Explicit over implicit. Monitor placement is literal pixel coordinates per named connector (monitor = eDP-1, 0x0) — no relative keywords, no DPI auto-scale heuristics. The config states what happens; nothing else does.

Workspaces and outputs

Nine workspaces, with one invariant: a workspace is never visible on two outputs at once. Switching to a workspace already shown on another monitor swaps the two monitors’ workspaces instead of duplicating it. New windows open on the monitor the cursor is on (focus-follows-monitor). The model stays predictable regardless of how many outputs are attached.

Floating windows

Windows that shouldn’t tile, don’t: dialogs (a toplevel with a parent set — file pickers, “Save as…”), windows that declare a fixed size, and anything matched by a float = <app_id> config rule open floating instead — centered, painted above the tiled layer. Dialogs and fixed-size windows keep their own natural size (that’s the point of floating them); rule windows and the manual float toggle use the configured default size (float_size, a percentage of the screen’s usable area). Everything else tiles; floating is the exception, decided per window, never a mode the whole workspace switches into. Floating windows move and resize with Mod+drag (left moves, right resizes) or keyboard nudges. The details are in the Stage 9 chapter.

Decorations

0xin always claims server-side decoration and draws nothing in its place: every window is a bare, borderless rectangle. In a tiler the layout itself conveys what title bars and borders would — window position and focus are already visible from the arrangement.

Planned ideas

Under consideration, not committed:

• Runtime control — a socket/IPC for querying and scripting the compositor without keybindings.
• Exact tree-based directional navigation — now that the split tree exists, spatial_neighbor could use its real adjacency instead of Stage 5’s geometric heuristic, fully resolving the corner-touch case. Not pursued in Stage 10 since it wasn’t needed for the resize deliverable.

When one of these lands, it moves out of this list and into a stage chapter.