Review Request 122505: Warn about brightness getting too low

Wed Feb 11 21:23:38 UTC 2015

> On Feb. 11, 2015, 12:50 a.m., Thomas Pfeiffer wrote:
> > Basic rule from design for safety: Don't use a warning if you can prevent the dangerous action completely.
> > In this case that means: Setting the brightness to zero should only be possible via keyboard, because that ensures recoverability.
> > 
> > Don't display any warning. Instead, when the slider reaches the minimum, display a hint saying "To prevent switching off the screen by accident, setting the brightness lower than [sensible value]% is only possible using the keyboard".
> > 
> > That way, it's not possible to maneuver yourself in an unrecoverable position but people who like to switch off their screen backlight can still do so using the keyboard. And we don't need to show a scary warning, but a helpful hint instead.
> 
> Emmanuel Pescosta wrote:
>     What about adding an option to "Adcanced Power Management Settings" that allows the user to change between safe/full screen brightness range (default: safe, minimum is 5% of the hw range)?
>     
>     [x] Use the full screen brightness range provided by your hardware (Warning: 0% may turn your screen off)
>     
>     So the warning in the widget can be avoided and the default behavior is the same as on most other operating systems (0% != screen off).
>     
>     My 2 cents ;)
> 
> Martin Klapetek wrote:
>     In my opinion, adding (yet another) option just complicates things more.
>     
>     > same as on most other operating systems (0% != screen off).
>     
>     I can't speak for Windows, but my OS X definitely turns screen off when you go to 0%.
> 
> Martin Klapetek wrote:
>     Oh now I can speak for Windows :) --> https://msdn.microsoft.com/en-us/library/windows/hardware/ff569755%28v=vs.85%29.aspx --> "Brightness levels are represented as single-byte values in the range from zero to 100 where zero is off and 100 is the maximum brightness that a laptop computer supports [...] however, a laptop computer is not required to support a level of zero.". So it's fully hardware/driver dependent, just like it is on Linux.
> 
> Emmanuel Pescosta wrote:
>     Just tested it on Windows: Turning off the screen by only using the brightness slider or the brightness buttons doesn't work, the dedicated screen on/off button is the only way to turn it off (http://goo.gl/3CLDGP Fn+F6)
> 
> Martin Klapetek wrote:
>     Yes, which matches what I said above about Windows. Some drivers on Linux also don't turn backlight off when you set 0%.
> 
> Emmanuel Pescosta wrote:
>     0% means backlight off on this notebook, but the user interface doesn't allow to turn it off on Windows (maybe they check if a screen off/on key is available?)
>     When I test it with Powerdevil, then the screen turns off when I drag the slider to 0%.
>     
>     So there is a difference between 0% on the UI and 0% on the hardware side on Windows.
> 
> Heiko Tietze wrote:
>     I'd like to suppport Thomas position be mentioning Android's behaviour: you switch off the backlight by hardware key but adjust the setting differently per slider. Two use cases, two ways of interaction.
>     
>     If we only could discuss all settings in such a depth... ;-)
> 
> Martin Klapetek wrote:
>     I really don't think you can compare laptops and (touch)phones. That's apples (but not only;) and oranges.
> 
> Thomas Pfeiffer wrote:
>     Martin: Does OS-X really allow to turn the screen off by pushing the brightness slider to zero? With the only way to turn it back on being via hardware keys? Even if they do, though, there is still a difference: Apple _knows_ for a fact that all devices (legally) running OS X have those hardware buttons. We can't be sure.
>     
>     Really, it's a simple logic: Don't allow the user to make a change that can't be reversed by the same means. Therefore, don't allow to switch off the screen via the slider. If a laptop has brightness keys, users can switch the screen off using those keys, and switch it back on using the same keys.
>     
>     And no, we don't need an expert setting to still allow sliding to off. I simply cannot believe that any user would be seriously pissed off because they need to use the keyboard to turn off their screen. It's not difficult.
>     
>     We can discuss that as long as you guys want, but I won't back down on basic usability principles.

> Martin: Does OS-X really allow to turn the screen off by pushing the brightness slider to zero? 

Yes. But as you say, this will *always* work (I'm not even sure if they have a slider at all).

> Really, it's a simple logic: Don't allow the user to make a change that can't be reversed by the same means. Therefore, don't allow to switch off the screen via the slider. 

Yes, I totally agree with that (I was also supporting this change all along).

> We can discuss that as long as you guys want, but I won't back down on basic usability principles.

I am with you on this. I just said "use a warning" and meant actually the hint you meant. My only problem was the suggestion to disallow turning backlight off by using the keys to set 0% (or disallow setting to 0% with keys).

- Martin

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On Feb. 9, 2015, 11:25 p.m., Kai Uwe Broulik wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/122505/
> -----------------------------------------------------------
> 
> (Updated Feb. 9, 2015, 11:25 p.m.)
> 
> 
> Review request for Plasma and KDE Usability.
> 
> 
> Repository: plasma-workspace
> 
> 
> Description
> -------
> 
> Some graphics drivers, notably Intel, turn off the backlight completely when brightness reached zero, which is also in the spec (0 = off, 1 = very dim) but imho that's unexpected. To prevent the user from accidentally turnign the screen off, especially when keyboard brightness controls don't work, which sadly still happens quite often, the slider breaks free from the user's drag (by becoming disable for two (perhaps 1 is enough?) seconds, so we also catch the mouse wheel case) and displays a warning (which stays there until screen brightness is dialed up again).
> 
> 
> Diffs
> -----
> 
>   applets/batterymonitor/package/contents/ui/BrightnessItem.qml 546ab58 
>   applets/batterymonitor/package/contents/ui/PopupDialog.qml a2acf31 
> 
> Diff: https://git.reviewboard.kde.org/r/122505/diff/
> 
> 
> Testing
> -------
> 
> Works pretty well, I just realized I forgot the mousewheel-on-trayicon case. Also, I'm open to wording suggestions since it sounds more like "we suck, sorry about that". (Note in the screenshot I used the mouse wheel, hence the displayed 4% rather than 5)
> 
> 
> File Attachments
> ----------------
> 
> Screenshot
>   https://git.reviewboard.kde.org/media/uploaded/files/2015/02/09/8b585088-e33e-4862-9c46-207d06f566f1__dimwarning.png
> 
> 
> Thanks,
> 
> Kai Uwe Broulik
> 
>

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