Stage 9 — Floating Windows

What it is. The first stage of the daily-driver era: windows that shouldn’t tile, don’t. File pickers, “Save as…” dialogs, and fixed-size utility windows used to get force-tiled like any other toplevel — the single most disruptive behavior in day-to-day use of a pure tiler.

Deliverable (from KICKOFF.md): a file picker opens floating and centered instead of being tiled.

How it went

The key realization: tiled and floating aren’t two branches of the layout code — they’re two different protocol postures, and the difference shows up in the very first configure a client ever receives. A tiled window gets tiled states plus a binding size (Stage 8’s fix for browsers overriding their tile). A floating window gets the exact opposite: no tiled states and a 0×0 configure (“pick your own size”) — the client’s natural size is precisely what floating exists to preserve. That’s why float detection runs on the initial commit, not on map: by map time the first configure has long been answered.

A window floats when any of three signals match, checked in order:

1. It’s a dialog — the toplevel has a parent set (what xdg_toplevel.set_parent conveys; GTK file pickers, “Save as…” dialogs). This is the deliverable case, and it’s re-checked on map as a backstop for clients that set the parent late.
2. It declares a fixed size — committed min and max sizes that are equal and nonzero on both axes. Tiling a window that cannot resize only stretches or letterboxes it.
3. A config rule says so — float = <app_id> lines, matched case-insensitively (e.g. float = pavucontrol).

The first two keep the client’s natural size — that’s the point of floating them. Rule windows are different: they’re ordinary apps told to float, and an ordinary app’s “natural” size is whatever it last remembered — so they open at the configured default instead: float_size = 60% x 60% (percentages of the usable area; that’s also the built-in default).

On map the window is centered in the active output’s usable area at the natural size it just committed, in a new scene layer between the tiled windows and the layer-shell top layer — floating windows paint above tiles but never above bars (fullscreen keeps its own, higher layer). The spiral skips them entirely: refresh() and the initial-configure tile prediction now share one tiled_windows() filter, so the predicted tile count and the placed tile count can’t drift apart.

Two follow-on behaviors fell out of testing rather than planning:

• Oversized clients. A real GTK file picker remembered a size taller than the output, so naive centering pushed its header (and its Open button) off the top edge. The fix caps the size hint to the usable area and clamps the position into it — the hint is non-binding without tiled states, but the position clamp guarantees the top-left corner stays reachable no matter what size the client insists on.
• Keyboard moves. movewindow on a floating window has no tile to swap with, so it nudges the window 50 px in that direction instead, clamped to the usable area (the same clamp mouse moves use).

Mod+V (togglefloating) flips the focused window between the postures: tiled → floating resizes to the float_size default, centered (keeping the tile’s size looked arbitrary in practice — whatever the spiral last assigned); floating → tiled restores the tiled states so refresh()’s sizes bind again.

The stage closed with pointer grabs: Mod+left-drag moves a floating window, Mod+right-drag resizes it (bottom-right-corner semantics, 50 px minimum). A grab is a mode the cursor enters — from press to release the seat never hears about the pointer, so the client under the cursor sees neither the button nor the motion; the release is swallowed along with the press it belongs to. The shim keeps owning the cursor event handlers and asks Rust “is this yours?” at the two decision points (button, motion) — the same policy/glue split as keybindings. All grab state lives in Rust: mode, window, and the cursor-position/window-rect pair captured at grab start (motion applies deltas against the start state, never the previous event, so rounding can’t accumulate). One safety detail found by thinking rather than crashing: a client closing mid-drag must clear the grab, or the next motion event dereferences a freed window.

Verified nested with logs and screenshots: a tiled kitty, a GTK app whose file chooser (parent set) mapped floating and centered with its header visible, and a float = rule floating an ordinary terminal by app id.

Status

Done. The gate — a file picker opens floating and centered — is verified, and the full interaction set is in: automatic detection, config rules, float_size, the toggle, keyboard nudges, and mouse move/resize.