Dim in a more intelligent way

[smichel17]

Motivation / Premise

There's two ways to dim the screen.

1. Turn down the backlight
2. Show a partially transparent black overlay (ie, use the filter).

Given the choice, I think I would always rather start with the backlight, and only engage the filter when the backlight reaches 0.

The problem

This is actually a hard problem to solve:

• What kind of control over the backlight would we want to give? A single slider for dim that first controls the backlight and then controls the filter once the backlight reaches zero? Separate sliders? Some type of conversion where after the user changes the brightness on their device (can we detect that?), we'll lower the brightness a bit and turn down the filter's dim?
• Backlights of different devices may behave in different ways, so we might not be able to do a simple conversion from dim to backlight
• Users can adjust the backlight in real time, independently of the filter. I don't know how valuable others may find this.
• We need to ask for an additional permission before we can adjust the backlight, but we'd want the app to behave consistently. How would we handle each case?

I am not planning on working on this any time soon, but I am interested in feedback. Would you find the proposal below acceptable? What do you find useful or not about Red Moon's current brightness/dim controls? Is there anything you wish Red Moon could do, or that you never want it to do?

Proposal

• Any time we darken the filter if the current brightness is not 0, lower it instead of darkening the filter.
• Any time we lighten the filter, if the filter dim level is already 0, raise the system brightness instead.

The problem with doing this is that if the user switches to a darker profile, turns up the brightness, and repeats that several times, we could reach a profile at maximum darkness without actually dimming the screen at all. So solve that, we need to:

• When we first start, save the current brightness level.
• Any time we change the filter, before doing the above, check if the brightness has changed (ie, by the user), and compensate both the filter levels and system brightness.

For example:

• Brightness starts at 50%
• Filter turns on at some dim level (equivalent to -30% brightness) -> we lower brightness to 20%
• User raises the brightness to 40%
• User changes the profile to a darker one (equivalent to -40% brightness)
• We dim the filter by the equivalent of 20% brightness, then lower the brightness by 10%

There's one final problem: unless the brightness is already at the minimum when the user turns it on, we'll never be able to reach the minimum. So, instead of raising/lowering a fixed amount, we need to scale it by whatever the initial brightness is.

• A profile at 50% dim means "halfway between the initial brightness and the minimum brightness".
• When the user adjusts the brightness, we also need to shift the saved "initial brightness".
  • Ex: the initial brightness is 50%. We lower it to 20%. The user then raises it to 60%.
  • 60% is halfway from 20% to 100%, so we change the "initial brightness" to 75% -- halfway from 50% to 100%.

Conclusion

I believe this implementation, while complex, will respect all the user's wishes.

• It will always lower the backlight before applying the filter
• If the user manually raises the brightness, it will not override their desire for a brighter backlight
• It will always be possible to reach the minimum brightness
• When turning off completely, the backlight will reflect any changes the user has made while the filter was active.

---

Note: I will keep this comment up to date, but comments below reflect my thoughts at the time, not now.

[mirh]

Also, why not hooking into KCAL, or using a driver like CF.lumen?

[smichel17]

See #20

[smichel17]

Currently thinking it might make sense to replace lower brightness with settings to control the system brightness. A couple ways we could do that:

1. An app-wide toggle for whether to control system brightness. If it's enabled, add per-filter:
   • A toggle to control whether automatic brightness is enabled
   • A slider to control the brightness level
2. Same as 1, but the toggle for controlling system brightness is per-filter.
3. Same as 2, but combine the two toggles into a list, ie Control brightness: [Off / Fixed / Auto]
   • If it's set to Off, the brightness slider disappears.

[smichel17]

Here's another one. It's more clever than the others. Maybe too clever.

• Add an app-wide toggle for whether to control the backlight
  • Allow toggling this from the notification
• Add a per-filter toggle to control whether automatic brightness is enabled
• Make the dim slider also control the system brightness.
  • If it's above halfway, it'll control the backlight brightness.
  • At halfway, when the backlight hits the minimum, it'll start to dim the screen using the filter.

---

A simpler version is to do the same as the above, but not try to change the automatic (adaptive) backlight setting -- leave that for users to toggle manually. This would sacrifice some functionality, but might be worth it in simplicity and usefulness.

[mirh]

A toggle to control whether automatic brightness is enabled

If any, it should be natural to just stick to it if user had it enabled.
I mean.. Provided ALS curves are exposed to programs I guess? Ok wrong assumption. And I guess adaptive brightness introduced in L further complicates the situation.

...

In other news I found https://github.com/fython/Blackbulb

If it's above halfway, it'll control the backlight brightness.

I'd say 1/4 imo. Or at least because on my phone minimum brightness is already pretty low.

[smichel17]

If any, it should be natural to just stick to it if user had it enabled.

Right now, Lower brightness, if enabled, turns automatic* brightness off and sets the brightness level to 0. My point was, if we don't offer a way to turn off automatic brightness, we're losing functionality. Maybe we're okay with that, but any time you take away something that people might rely on, you need to think very hard about it, first. That's another reason why I'm often hesitant to add features/settings that I'm not sure we want to keep.

*ie, adaptive brightness. I use the names I do because that's what they're called in the code.

In other news I found https://github.com/fython/Blackbulb

Thank you for reminding me of this. I'd been meaning to look into how it's able to work without overlay permission (turns out, the filter is masquerading as a temporary notification).

I really like how simple their interface is, although they don't have separate controls for color/intensity/dim, profiles, a timer, or the ability to automatically pause in secure apps.

It looks like they proxy all their calls to the filtering service through a call to a tile receiver. Not sure why that is, but maybe related to #142.

I'd say 1/4 imo. Or at least because on my phone minimum brightness is already pretty low.

1/2 was just an example; If I end up going this route, I'll play around with it to see what value feels good.

[smichel17]

Stray thought: Would it make sense to combine this with the button backlight setting? It would be nice if that setting had some effect on all devices, as I don't really like a useless setting sitting around.

[smichel17]

I updated the top comment with a proposal.

[smichel17]

Copying the reply from @wavexx in #191 so I don't forget it:

I'm not sure all of this is needed. I agree that changing brightness
should dim/[un]dim before changing the backlight when going under 0.

Ideally "dim" just doubles the dynamic range of the brightness, so that
0-50% is from maximum to zero dim (keeping backlight to 0), and 50-100%
is zero backlight to 100% (keeping dim at 0).

If you could remap the system backlight control to this, then switching
filters would be trivial (the current brightness is absolute). I have no
experience with android development, so I cannot comment if that's
actually doable.

However, when I switch off the filter, just restore whatever brightness
was set before turning it on.

My specific use-case is super-simple: I just want darker, at night.
I just use "dim", with the timer.

I do agree that this would be ideal. Unfortunately, it is impossible to change the behavior of the system brightness control. I also don't know of any way for an app to be notified when the user changes the brightness, although we can periodically check what the brightness is and react accordingly -- this might have an impact on battery usage, but we can minimize that if Pause in excluded apps is enabled.

When I came up with the proposal, I was thinking, "What are the options with the controls we have? Which of those is the best?" This comment got me thinking, "What's the ideal? How close can we get to that?" It was a very useful change of mindset and has given me some new ideas -- thanks :)

[wavexx]

On Thu, Sep 28 2017, smichel17 wrote: I do agree that this would be ideal. Unfortunately, it is impossible to change the behavior of the system brightness control. I also don't know of any way for an app to be notified when the user changes the brightness, although we can periodically check what the brightness is and react accordingly -- this might have an impact on battery usage, but we can minimize that if `Pause in excluded apps` is enabled.

Could you get at least increase/decrease brightness events? (as opposed to sliding the brightness control, which I assume generates absolute values).

When I came up with the proposal, I was thinking, "What are the options with the controls we have? Which of those is the best?" This comment got me thinking, "What's the ideal? How close can we get to that?" It was a very useful change of mindset and has given me some new ideas -- thanks :)

But if you *did* include the backlight level in the filter settings, as opposed to just "lower to 0", it would be just a setting like the other. When changing the backlight, just update the preset value as well. I never had more than one filter, but if I had more in addition, I _wouldn't_ want the current brightness to influence my "dark reading" preset where I want the backlight to be always zero.

[smichel17]

Could you get at least increase/decrease brightness events? (as opposed to sliding the brightness control, which I assume generates absolute values).

Nope, there's no interface at all for apps to interact with the backlight brightness that I'm aware of, aside from getting and setting the backlight values (which is done the same way you'd change any other system setting, like toggling the wifi).

But if you did include the backlight level in the filter settings, as opposed to just "lower to 0", it would be just a setting like the other. When changing the backlight, just update the preset value as well.

If possible I'd like to integrate backlight controls without increasing the number of settings. At its core, Red Moon has a pretty simple function and its design should reflect that. There are ways to do what you want without adding settings, though (for example, making the Lower backlight option multiple choice and/or combining it with Hardware button backlight).

I never had more than one filter, but if I had more in addition, I wouldn't want the current brightness to influence my "dark reading" preset where I want the backlight to be always zero.

Noted. I think the current proposal is better than any previous version, but not good enough to build, yet.

[mirh]

Nope, there's no interface at all for apps to interact with the backlight brightness that I'm aware of

That sounds something the kernel would care\handle
https://github.com/torvalds/linux/blob/master/include/linux/backlight.h any new idea?

[smichel17]

I haven't read 100% of the android documentation so it's possible there's a callback I missed somewhere, but it seems unlikely.

It's probably possible with root -- almost anything is. However, such things are typically undocumented and might be a ton of work to implement.

[wavexx]

On Fri, Sep 29 2017, mirh wrote: That sounds something the kernel would care/handle https://github.com/torvalds/linux/blob/master/include/linux/backlight.h any idea?

Under vanilla linux, yes. Unified leds and backlight control is available on KMS drivers (and some others) via /proc/. Events (user and system driven) are also emitted via ACPI. However, this might tell very little on what android actually does/has under the hood.

[mirh]

ARM certainly gives no fucks to ACPI...
Though something else in the kernel might or might not be exposed

Again, I guess this is yet another time one of those "perfect with root - horrible pretension to be even working without" situations

[AdamNiederer]

Nope, there's no interface at all for apps to interact with the backlight brightness that I'm aware of

I know Lux manages to do it; the system brightness slider is entirely disabled when Lux is enabled, and one can control the system brightness and overlay opacity from the notification or the slider within the app. It targets android 5, but it's worked on 4.x in the past as well. Maybe that'll help narrow down the search or give a reversal target.

I'm pretty sure the core mechanism of action doesn't require any additional permissions, either. It asks for usage access for some unrelated features.

[mirh]

I'm not sure what you actually meant with "entirely disabled" (always stuck on the same setting, is not technically "disabled"), but yes there is this stupid thing since the first version of android.

It's not what dev was talking about, if you just proceeded reading the reminder of the following sentence.
Could instead this or this be of any help?

[smichel17]

This issue has gotten long enough that I think it's pretty unfocused.

I'm traveling this week but when I get back, I'll close this and make a new issue with a summary of the parts here that are still relevant, with some screenshots to clarify the problems.

[smichel17]

Copying @decadent's comment from #21 so I don't lose it when I go to summarize this issue

I have to disagree that this can be trusted to the system's automatic brightness control. I don't know about the situation in stock Android or custom ROMs, but phone vendors' brightness algorithms are rather deficient in all phones that I've used. There are already several apps to correct this, e.g. Lux and CF.lumen, and a slew of 'dark filters' to lower the brightness below the minimum. Bundling both brightness and red filter control in one app makes all the sense.

Moreover, ambient brightness measurements can help the functionality of the red filter. E.g. if I step into a mall at night, strong red filter isn't of much use to me under the fluorescent lights: I have to disable it to see the screen.

However, I don't know about the power usage and optimization factors here. Since the system already measures the brightness anyway, I would hope that there's an event-subscription API instead of polling, or that measurements of the app instead of those of the system wouldn't make much difference. And the feature could be optional, to satisfy the power-conscious users.