Ubuntu Wiki

PC

We assume that any PC has a hardware brightness control, on either the keyboard or the display itself. And unlike sound volume, brightness does not need reassurance for troubleshooting purposes. Therefore, brightness should not have software UI as well; that would be redundant.

If you use a keyboard key to adjust brightness, a brightness notification bubble should appear.

Phone

The goal of the “Adjust automatically” setting is to maximize the average time you can use the device before feeling the need to adjust brightness manually. This is achieved by frequently adjusting the emitted brightness of the display based on the ambient brightness of the surroundings. So there is a function representing the emitted brightness desired at each level of ambient brightness detectable by the light sensor.

Because different hardware has different light sensors and displays, this function should be settable based on the hardware model.

Because users have different preferences, the function should also be user-adjustable. This should be achieved by altering the display brightness manually while “Adjust automatically” is checked. Therefore, the “Display brightness:” slider should be sensitive regardless of whether “Adjust automatically” is checked or unchecked.

If it is checked and you adjust the brightness manually, the function that determines the automatic brightness should be adjusted such that, in future, the current ambient light value would result in your just-chosen brightness being chosen automatically.

To achieve this, the function that generates emitted brightness E from the ambient brightness A should be a curve connecting from three to five coordinates of (A, E). Where A_min, A_max, E_min, and E_max are the minimum and maximum possible values:

• If you (or the default values for the handset model) set E_min at A_p > A_min, the function should include E = E_min for A_min ≤ A ≤ A_p.

  

• If you (or the default values for the handset model) set E_max at A_q < A_max, the function should include E = E_max for A_q ≤ A ≤ A_max.

  

• If you manually set a brightness (A_r, E_r) where any previously-set points exist with A ≤ A_r and E > E_r, those other points should be discarded from the curve, so that the screen does not brighten when surroundings dim.

• If you manually set a brightness (A_s, E_s) where any previously-set points exist with A ≥ A_s and E < E_s, those other points should be discarded from the curve, so that the screen does not dim when surroundings brighten.

  

• If you manually set a brightness such that the set of coordinates includes more than one for which A_min < A < A_max and E_min < E < E_max, all of them except the newest one should be discarded, so that the curve is not too complex.

• A new brightness curve should not be saved until you dismiss the brightness slider you are using (for example, by closing the indicator menu), so that a brief experiment does not obliterate a careful previous curve.