Function render_indicators 

async fn render_indicators(
    driver: &mut Driver<SpiTransport<Spi<'static, Async, Master>, Output<'static>, Output<'static>, 2>, 2>,
    state: BacklightState,
) -> Result<(), SpiTransportError<<Spi<'static, Async, Master> as ErrorType>::Error>>

Writes only the two indicator LEDs according to state.

Used when only indicator state has changed and the background is already correct, avoiding a full redraw.

Errors

Returns Err if any bus transaction fails. See [BacklightDriver::flush].