# Compositor

Sway is the **temporary** Wayland compositor while Nebula Desktop is developed. Configuration lives in `sway/nebula-sway.conf`.

Sway currently provides:

- Wayland compositor
- floating-first application window management
- temporary title bars and borders on normal application windows
- XWayland
- input and the pointer cursor
- output handling

Nebula provides the visible shell (Qt Quick/QML via LayerShellQt) and logical window management through `WindowService` (`core/windows`). The Sway config must not enable a Sway bar.

A custom Nebula compositor is a later milestone. Do not treat this Sway setup as the final architecture. QML must not call `swaymsg`; the Sway IPC backend is the only Sway-specific code, and it is isolated so it can be replaced.

```text
Ubuntu/Linux
 ↓
Wayland
 ↓
Sway                 now
Nebula compositor    later
 ↓
Nebula Shell
Qt Quick/QML
```

## Floating-first session

Ordinary application windows open as floating windows, sized to about **70% of the current workspace** (the usable output area below the 40px Nebula top bar) and centred. Sway workspace geometry already excludes the top-bar exclusive zone, so placement stays on-screen at any resolution.

Rules match only normal application views:

- Wayland: `shell="xdg_shell"` (`app_id`)
- XWayland: `shell="xwayland"` (`class`)

Layer-shell surfaces (Nebula desktop, top bar, launcher, overlays) are a different shell and are not matched. They stay on BACKGROUND / TOP / OVERLAY.

Sway draws a restrained title bar and border on those application windows so they can be identified, dragged, and resized with the mouse. This is **temporary**. Custom Nebula decorations, CSD, and wrapping Wayland clients inside QML are out of scope.

## Development session

From the NebulaOS repository root:

```bash
sway -c compositor/sway/nebula-sway.conf
```

Recommended on the Ubuntu VMware VM (repo-root `cd`, cursor environment, software cursors):

```bash
sh compositor/sway/dev/run-sway-vm.sh
```

Sway then autostarts Nebula Desktop through `scripts/run-nebula-vm.sh`.

Skip shell autostart:

```bash
NEBULA_SHELL_AUTOSTART=0 sh compositor/sway/dev/run-sway-vm.sh
```

### Output / resolution

The development config uses scale `1` and does not pin a resolution. Sway uses the output's preferred mode, which follows the current display size (including VMware Autofit Guest). Window sizes use workspace-relative percentages, not hard-coded pixel dimensions.

```bash
swaymsg -t get_outputs
swaymsg output <name> scale 1
```

### Cursor

```text
seat * xcursor_theme Adwaita 24
XCURSOR_THEME=Adwaita
XCURSOR_SIZE=24
```

Requires `adwaita-icon-theme`. A Nebula-branded cursor theme is a later task.

`WLR_NO_HARDWARE_CURSORS=1` is VMware-specific and is set by `run-sway-vm.sh`, not by production session files.

### Emergency / development shortcuts

Normal launching, focusing, and closing is done from the Nebula GUI. These remain compositor fallbacks:

| Shortcut | Action |
|----------|--------|
| Super+Enter | open Foot |
| Super+Left Mouse | move the floating window under the pointer |
| Super+Right Mouse | resize the floating window under the pointer |
| Super+Left | snap to left half of the usable area |
| Super+Right | snap to right half of the usable area |
| Super+Up | maximise to the usable area (below the top bar) |
| Super+Down | restore to the default ~70% centred size |
| Super+Shift+Q | close the focused window |
| Super+Shift+E | exit Sway |
| Super+Shift+C | reload Sway config |

Title-bar drag and border resize should be the normal mouse path. Super+mouse is an emergency convenience.

### Rendering

`scripts/run-nebula-vm.sh` sets `QT_QUICK_BACKEND=software` for the VMware guest GPU. Production `nebula-shell` must not set that variable.