Re: Screen Shade/curtain?

Didier Colle

On 17/12/2017 21:04, Lino Morales wrote:
Trust me it does not extend the battery of any i device.
This statement is based on what?

1) It is my experience it does extend the time you can do on a battery charge as I mentioned previously.
2) I just checked the battery usage on my android smartphone: 31% went to the screen, which is the winner. As it is a phone, the screen is relatively small: roughly speaking 4x the size of a laptop screen --> the powr usage of a laptop screen would thus be 4x higher.
3) Given my electrical engineering background, it makes perfectly sense to me the backlight of a screen is one of the most power hungry components in a laptop/tablet/smartphone.
4) Together with my father I repaired a couple of years ago the powr supply of the backlight (switching power supply transforming the 5Volt into something like 400Volt)of an external LCD monitor: everything in this monitor consists of minituraized SMD components, except this part that is built with large discrete components, indicating the backlight is not at all low power (otherwise they would not opt for such costly approach).
4) The backlight of a screen is one of the few components that is constantly consuming power (at the rate of the duty cycle, representing the dim level), while other periphery have a more intermittent power profile (you are not constantly transmitting data with your wireless interfaces, speakers are not constantly driven, most of the time the cpu is underutilized letting it switch down the clock frequency is mobile devices to save energy, etc).

Now the purpose of screen shade is say you are in a work inviroment and you don't want people looking over your shoulder. Makes since.

On 12/17/2017 2:53 PM, Sarah k Alawami wrote:
Actually if you look on the screen brightness thing on ios or android it does bring the brightness all the way down to 0 so yes it does in effect shut off the display. I've seen my batery actually be extended this way.

On Dec 17, 2017, at 6:36 AM, Didier Colle <> wrote:

Hi all,

I am not sure what this functionality is exactly about.

When it is about switching off / dimming the monitor, I do not understand why it would not save on battery....

The backlight of a monitor in a laptop, tablet, smartphone, ... whatever is one of the main power sinks in such systems.

On a laptop, you can often (this may vary between laptops) use Fn+f7 for switching between different display modes (signal send only to laptop monitor, signal send to external monitor only or signal send to both) or Fn+F5 to dim the backlight and Fn+F6 to light it up.When I am on battery power for a long time, I dim the backlight with Fn+f5 to save battery.

Thus you don't need a NVDA add-on for that, although such add-on may be useful to read the status of the screen (to which monitor is the signal send, on what level is the backlight). I have no clue whether windows has access to such info, let alone it provides an api to request that info (it might be the case that on some laptops this is a pure BIOS feature completely transparent to windows).

Once again, I am not sure what this functionality is supposed to be exactly, and thus I may be speaking about something completely different.

Kind regards,


On 17/12/2017 9:24, Brian's Mail list account via Groups.Io wrote:
 From what I know about Windows and indeed most screenreaders, this function is just for privacy, ie its not going to save any battery.
If that is what you want then I'd have thought it was possible to do it, kind of like a screensaver that never actually loses focus but then you need to be able to tell nvda that you want it to use the invisible window not the visible one.

In the  issues tracker there is a thread on this.
Also the ultimate way |of doing this on a desktop is called the monitor off switch..... ahem.

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----- Original Message ----- From: "Kevin Chao" <>
To: <>
Sent: Saturday, December 16, 2017 11:30 PM
Subject: [nvda] Screen Shade/curtain?


VoiceOver has had screen curtain feature for a long while and JAWS recently
got screen shade.

Does NVDA have a similar feature via an add-on or natively?

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