# `Emerge.Config.Backlight`
[🔗](https://github.com/emerge-elixir/emerge/blob/v0.5.1/lib/emerge/config/backlight.ex#L1)

The panel backlight managed by a DRM output. Set this record as
`Emerge.Config.DRM.backlight`; it does not apply to desktop windows.

```elixir
%Emerge.Config{
  output: %Emerge.Config.DRM{
    backlight: %Emerge.Config.Backlight{
      device: "/sys/class/backlight/panel",
      brightness: 0.5
    }
  },
  renderer: %Emerge.Config.Renderer{api: :opengl}
}
```

Replace the example device path with your panel's actual backlight path.

## Fields

- `device` — `:auto` (default), an absolute sysfs backlight path, or `nil` to
  leave brightness unmanaged. Automatic selection requires a clear association
  with the chosen connector. No associated backlight is acceptable unless you
  request brightness; an ambiguous association is an error.
- `brightness` — a number from `0` to `1`, rounded to the device's supported
  levels. `0.5` requests half its numeric range, not a perceptual brightness curve.
  The default `nil` uses the original requested brightness. Returning to `nil`
  restores that original value, including after renderer recovery.

Brightness `0` is **not** display-off. Set `DRM.display` to `:off` to blank the
display. A brightness change while off is used when the display turns on again.
Requesting brightness with `device: nil` is invalid.

## Changing settings

Brightness can change through `config` with explicit OpenGL, Vulkan or raster
(CPU or GPU-upload presentation).
Changing `device` requires a new viewport. Avoid writing the same backlight
from another process while Emerge manages it. Stopping a managed display leaves
its backlight dark.

# `device`

```elixir
@type device() :: :auto | nil | String.t()
```

Automatic association, no management, or an absolute sysfs backlight device path.

# `normalized_t`

```elixir
@type normalized_t() :: t()
```

Canonical form after nested keyword records have been expanded.

# `options`

```elixir
@type options() :: [device: device(), brightness: number() | nil]
```

Typed keyword shorthand accepted in this record's parent field.

# `t`

```elixir
@type t() :: %Emerge.Config.Backlight{brightness: number() | nil, device: device()}
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*