screensaver: Add dynamic battery symbol to sleep screen message

[LostishCode]

I have enjoyed (possibly over) customizing my sleep screen message. However I kept getting confused between the book completed percentage and the battery percentage. At first I just tried adding the battery symbol, but when looking into it, it was simpler to just reference the function that returns the dynamic battery icon.

I added the battery symbol to the prompt as %B:

And examples of what it looks like (along with some other fun symbols I found along the way):

This was tested on a Kobo Clara 2E, but since it uses the same code that niluje wrote in frontend/ui/widget/touchmenu.lua for the touch menu icon, my guess is it will be device agnostic.

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This change is 

[Frenzie]

I was a bit too enthusiastic. You should also add a local batt_symbol = something up above where the same is done for batt_lvl.

[LostishCode]

I corrected the problem and the linter no longer throws errors. I also made a change so the icon acts the same as the footer as explained in the comment below. Though @NiLuJe said he had tentative concerns over the feature and I haven't heard back from him.

[NiLuJe]

I'm mildly wary of adding any kind of battery gauge in there... because it will be static. When the device is alseep, well, it's asleep.

As such, whatever will be shown on the message will be a snapshot taken at suspend time.

Which, granted, can be an interesting data point, but I fear may lead to confusion for a large section of users.

[LostishCode]

I can see how a static battery symbol can be confusing some of the time. For example, if you start charging, put the device to sleep, then unplug the charger, the symbol doesn't change. On my device I didn't like not-seeing the battery_percentage_filled level so added a work around using the battery_charging_percent glyphs from \u{E784} to \u{E78A} that add a lightning bolt next to the battery_percentage_filled icon. The problem is there are only 7 of those glyphs in symbols.ttf (as nerdfonts appears to have since added the remaining 4) making the battery percentages have to glom to the nearest value.

In the case of not-charging though, I think the dynamic symbol is helpful. We already have the displayed percentage from %b, and the icons are just reflecting that value.

If the glyph being replaced by the battery-charging symbol is too inconsistent, we should be able to tell powerd:getBatterySymbol() that the battery always isn't charging-or-charged which would would then always return only the battery_percentage_filled icons.

[deepakonwww]

@LostishCode Which font does have this book icon and the nice-looking square brackets? I tried with my available fonts but was not able to type these characters. Could you please help me by providing the details of this font? Thanks in advance.

[LostishCode]

@deepakonwww
The brackets are 【 】 which render here because they're normal unicode characters. The easiest way to add them is plug-in your device and edit the line ["screensaver_message"] = "your message here" in the file /path-to-your-device/.adds/koreader/settings.reader.lua. If you google "unicode brackets" you can find more examples of fancy brackets that should also all work.

[LostishCode]

I took another look at how battery symbols are handled other places and it appears aux_batt_lvl gets treated differently depending on where it is. In frontend/apps/reader/modules/readerfooter.lua batt_lvl is averaged when an aux battery is present, in frontend/ui/widget/touchmenu.lua it's shown as two separate icons, and here %b will show devices with an aux battery as having a max capacity of 200% (strange, but surprisingly accurate).

The sleep screen icon needs to be consistent with other icons presented to the user, that means either the touchmenu icon or the footer icon, and I believe the footer icon makes more sense. The touchmenu battery splits into two icons when an aux battery is added which I don't think works well for the sleep screen; given it's a user controlled symbol, people might format around it and having it occasionally act as 2 icons feels inconsistent. The footer icon is also more likely to be the last icon users saw before sleeping as it's unlikely someone had the menu open before sleeping.

Though, this specific issue only applies when an aux battery is used. For all other use cases the battery icon acts the same across all three locations.

Personally I feel when there is one icon representing both a main and auxiliary battery the battery should be show cumulatively rather than averaged, but that's a separate issue that ought to be handled in a different thread.

[NiLuJe]

The footer behavior was tweaked specifically because of the space constraints of that context, FWIW.

Note that the only device with an aux battery is the Sage with a PowerCover, and the PowerCover sucks really really really badly, so I wouldn't necessarily lose sleep over that ;).

That said, I do agree that the footer behavior is the one that makes more sense here.

(As for the average, that was necessary to be able to use the %-specific icons without jumping through extra hoops, IIRC)

[Frenzie]

@NiLuJe Good for you?

[NiLuJe]

Minor formatting nit, but as far as the feature goes, it's perfectly harmless ;).

Reviewed 1 of 1 files at r3, all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @Frenzie and @LostishCode)

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frontend/ui/screensaver.lua line 197 at r3 (raw file):

        if Device:hasAuxBattery() and powerd:isAuxBatteryConnected() then
            batt_lvl = powerd:getCapacity() + powerd:getAuxCapacity()
           batt_symbol = powerd:getBatterySymbol(powerd:isAuxCharged(), powerd:isAuxCharging(), batt_lvl / 2)

Indentation mishap here?

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frontend/ui/screensaver.lua line 200 at r3 (raw file):

        else
            batt_lvl = powerd:getCapacity()
           batt_symbol = powerd:getBatterySymbol(powerd:isCharged(), powerd:isCharging(), batt_lvl)

Ditto ;).

[NiLuJe]

Reviewed 1 of 1 files at r4, all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @Frenzie and @LostishCode)