Mango Displays

Per-output resolution, refresh rate and scale for MangoWC, applied from the bar, plus mirroring one output onto another. Every control applies as you pick it: the plugin writes mango monitorrule= lines and reloads the compositor, so the change lands and survives a reboot in one step.

Plugin

Field	Value
ID	prponkshe/mango-displays
Entries	Bar widget: bar; panel: panel; services: watcher, mirror

Requirements

• mmsg, MangoWC's IPC client. Everything that changes state goes through it, and the watcher reads mmsg watch all-monitors. The plugin is MangoWC-only.
• wlr-randr, read once per panel open for the mode list and the make/model/serial the rules match on. It never sets anything.
• wdisplays. Arrangement is out of scope, so right-clicking the bar tile hands off to it.
• wl-mirror, needed only for the Mirror card. See Mirroring.

Usage

Add the Mango Displays widget to a bar in Settings → Bar, or by hand:

[widget.display]
type = "prponkshe/mango-displays:bar"

Left-click the tile to open the panel, right-click to open wdisplays. The panel also opens over IPC:

noctalia msg panel-toggle prponkshe/mango-displays:panel

The panel carries three cards for the selected output - Monitor (picker plus an on/off toggle), Mode (resolution and refresh rate) and Scale - and a Mirror card for the layout as a whole. There is no Apply button: picking a value writes the rules and reloads mango straight away, and the last thing that happened is reported along the bottom of the panel. With auto_save on, a change made anywhere else (a drag in wdisplays, a monitor unplugged) is written by the watcher without the panel being open.

Settings

Setting	Type	Default	Description
auto_save	bool	true	Let the watcher write monitorrule= lines when the layout changes on its own, such as a drag in wdisplays. With this off, only the panel writes.
monitor_rules_path	string	~/.config/mango/monitors.conf	The mango config the rules are written into. It has to be a file mango sources.
glyph	glyph	device-desktop	Bar tile icon.

IPC

The mirror service takes start, stop and toggle, so a compositor keybind can raise a mirror without opening the panel. start and toggle accept an optional "<source> <destination>" payload; without one they copy the built-in panel onto the first other lit output, which is the right guess on a laptop and the only guess available on a desktop.

noctalia msg plugin prponkshe/mango-displays:mirror all toggle
noctalia msg plugin prponkshe/mango-displays:mirror all start "DP-1 eDP-1"
noctalia msg plugin prponkshe/mango-displays:mirror all stop

Notes

Why wlr-randr is still a dependency

Everything that changes state goes through mango: mmsg dispatch to apply, enable and disable, mmsg watch all-monitors for events. Two things mango cannot answer:

• Which modes a display supports. mmsg get all-monitors reports no refresh rate at all, not even the current one, and /sys/class/drm/*/modes lists resolutions without them - the eight identical 1920x1080 lines on a 144 Hz panel are its eight refresh rates, indistinguishable.
• make, model and serial, which the rules match on so a monitor keeps its settings across a reboot or a different port. Mango's own docs say to use wlr-randr for these.

So wlr-randr --json is read once per panel open, purely to describe the hardware. It is never used to set anything.

Turning monitors off

The Monitor card carries an on/off toggle that runs mmsg dispatch enable_monitor / disable_monitor straight away. The last enabled monitor cannot be switched off - its toggle locks and the label reads "Last output" - so there is always somewhere to draw.

Disabled monitors stay in the picker (otherwise there would be no way back on) and are drawn with the device-desktop-off glyph; the mode and scale controls go inert while a monitor is off.

Mirroring

Mango cannot clone an output through monitorrule or an IPC dispatch, so the Mirror card starts wl-mirror. The card picks both ends: From lists every lit output and To lists the rest, so a desktop with no eDP-1 can mirror whichever way round it likes. The pair defaults to the built-in panel copied onto the first other output, and goes inert while a mirror is running, because that pair is what wl-mirror was launched with.

Mango honours a fullscreen request but ignores the output the client asks for, so --fullscreen-output alone leaves the mirror on whichever monitor had focus

• pointed at the laptop that is a feedback tunnel, not a mirror. The service finds the client by its unique window title and moves it with mmsg dispatch tagmon, then returns focus with focusmon so the mirror does not swallow the keyboard.

Scaling is fit, so a 16:10 panel on a 16:9 projector is letterboxed rather than cropped. The mirror service owns the process and stops it when either output disconnects, the plugin reloads, or Noctalia exits. A private marker in the plugin data directory controls normal shutdown; process errors stay in memory and are shown through Noctalia.

A keybind can drive the mirror without the panel; see IPC.

Never a dark session

save() refuses to write a config in which every monitor is disabled, because that state cannot be undone from the machine itself.

If the service ever sees nothing lit - the last enabled monitor unplugged while the others were off - it turns one back on. It picks whichever monitor was lit most recently, falling back to the first connected one. Nothing here is keyed to a connector name: a desktop has no eDP-1 to fall back to.

The watcher

The compositor is the event source: mmsg watch all-monitors emits a line whenever anything about a monitor changes, and service.luau holds that stream open with noctalia.runStream. It also fires on focus and tag changes, so a line means "look again", not "the layout moved" - an in-process noctalia.outputs() signature decides that, and a change has to hold for 1.2 seconds before anything is written.

A 30 second tick stays armed behind the stream as a backstop, and becomes the only trigger if mmsg is missing. runStream reports that the process spawned rather than that it works, so mmsg is probed once before the tick goes quiet.

Writing is skipped when the rendered rules already match the file, which stops the reload_config it triggers from coming back round as another change. Set auto_save to false to leave writing to the panel alone.

Known limitation

Mango matches rules per monitor, not per combination, so position is a property of the display rather than of the set that is plugged in. Two setups that want the same monitor in different places cannot both be expressed: the most recent one wins. Resolution, refresh, scale and enabled state do not have this problem.

Layout

Panel size is manifest-declared and cannot change at runtime, so the header and the status line are pinned and the card stack sits in a ui.scroll, whatever the monitor count and mode count do to its height. Every size in the tree is logical px that the host scales with the surface, so a 4K output at 2x renders the panel at the same apparent size as a 1080p one.

Caveats

• plugin_api = 22 for require, so it needs Noctalia 5.0.0-beta.8 or newer.
• Right-click is wired in widget.luau rather than a manifest [widget.actions] block, which 5.0.0-beta.8 parses but does not apply.
• Scale here is the Wayland output scale, so it drives every client on that monitor including the Noctalia bar. Noctalia's own [accessibility] ui_scale and [bar.*] scale are separate multipliers on top and are left alone.