FR: Screensaver option for e-Ink android devices

[elvvis]

• KOReader version: 2019.12
• Device: Tolino Epos 2

Issue

Is it possible to implement the screensaver option for e-Ink android reader?

[pazos]

Nope

[elvvis]

@pazos:
Why is that not possible?
I suppose on Android 4.4 the wallpaper is located at:
/data/system/users/0/wallpaper
Replace the 0 with the user id (take a look in /data/system/users).

By the way, the tolino reading app can save the book cover as screensaver.
Can't you introduce a whitelist for android devices that support this?

[pazos]

Why is that not possible?

Because on android KOReader is just another application and applications do not mess with low-level system stuff like lockscreens and power routines. They normally can't unless the device is rooted.

I suppose on Android 4.4 the wallpaper is located at:
/data/system/users/0/wallpaper
Replace the 0 with the user id (take a look in /data/system/users).

That's a specific configuration on a specific device. /data is not accesible on non rooted devices

By the way, the tolino reading app can save the book cover as screensaver.
Can't you introduce a whitelist for android devices that support this?

No, I can't. I don't have any android e-ink device. I do help with development using emulators and a tablet. I'm willing to put effort to help users to add support for e-ink refreshes and other things, but I cannot do it myself.

You probably can hack a way to display a screensaver that works for your Tolino, but that's up to you, as a contributor. I wouldn't bother with that issue but I'm not you 😄

[elvvis]

@pazos Ok, thank you for your answer. I'll take a look at the code, maybe there is a way.

[pazos]

@elvvis: you are welcome.

I would suggest to work on a barebones app implementation that just displays a image from a file when the power button is pressed (and clear that image when the device is resumed if the system doesn't do that for you).

If you manage to do that (i.e overwritting the image that tolino fw uses as a screensaver) from an app we can port it to https://github.com/koreader/android-luajit-launcher and tweak the screensaver to work on supported android devices.

[pazos]

@elvvis: see https://www.mobileread.com/forums/showthread.php?t=332401 for a workaround