[Samsung Galaxy S 5 Unified Development] curiousrom:
Display Screen Curtain Black Screen - A Chinese Finger Trap!

[MENTION=9686420]Ilshatey[/MENTION] posted here in an other thread (thanks [MENTION=8031265]kurtn[/MENTION]):

Thanks for the reports guys! :good::cool:

It reminds me of Star Trek TNG - Data VS. Chinese Finger Trap :)

I can confirm that on my S5 G900M LineageOS 16.0 haggertk klte build 2019-01-09 if you enable > Display > Advanced > Advanced Display > Accessibility Mode > Screen Curtain the screen goes black immediately & there is no obvious way to return to the normal display.

Hopefully [MENTION=5795145]javelinanddart[/MENTION] (Paul Keith) who made the commits here for 15.1 ( [MENTION=2693412]haggertk[/MENTION] was one of the reviewers) & here for 16.0 that enabled Screen Curtain will either delete that option or enable a gesture & add a note below the option to explain how to disable it. (screenshot)

A LineageOS Gerrit search with topic:"advanced-display" (status open OR status:merged).

A warning was added to New S5 LineageOS 16.0 haggertk 2019-01-09 Build! - Report & Bugs.

The workarounds:

I simply used scrcpy via USB as described here: S5 16.0 Mirroring Workaround and I could see the S5's display & use a mouse to select Normal in Accessibility Mode et voila, the screen turned back on.

View attachment 4694166

Here is a short screen recording not affected by Screen Curtain & it's black screen on YouTube made with the LineageOS Recorder. The big white dots are taps with 3 fingers trying to disable Screen Curtain & turn the screen back on to no avail. At @ 0:57 a small white dot appears on the left side of the Status bar, that's when I connected the S5 to the computer & started scrcpy.

Reboot to TWRP recovery:

a- Connect the S5 to a computer which was previously authorized to connect to your phone's Android debugging enabled:

adb devices

adb reboot recovery

b- Turn off the S5 by using a long press of both Volume down + Power buttons & release them as soon as the screen goes black (much better than removing the battery!). If you are too slow & the Samsung boot logo appears keep on pressing until it loops back to a black screen again & release the buttons. Then boot normally to TWRP: volume up + Power + Home.

c- As seen in the attachment the Power off icon is 2cm left of the Power button in the S5 LOS 16.0 Power menu. If lucky even with the screen off you could turn off the S5 then boot in TWRP Recovery.

View attachment 4694167

Then TWRP > Advanced > File Manager > navigate to data/data/org.lineageos.settings.device/shared_prefs/org.lineageos.settings.device_preferences.xml and rename to org.lineageos.settings.device_preferences.xml.Old to disable it (screenshot) & reboot to System. Go to Accessibility Mode > & select anything EXCEPT Screen Curtain & a new ...preferences.xml file will be automatically created.

View attachment 4694565 View attachment 4694798

Or in TWRP & connected to a computer copy the attached org_lineageos_settings_device_preferences_2019-01-25_curiousrom.zip to sdcard, flash it in TWRP & reboot to system to restore the default > Accessibility Mode > Normal setting.

Report on S5 LineageOS 16.0 haggertk 2019-01-09 Build with Screen Curtain enabled:

The touch screen is enabled but you can't see what you are doing. The phone is working normally except for the screen off.

All the buttons are working including the capacitive buttons.

If you reboot the S5 using a long press of both Volume down + Power buttons & release them when the Samsung boot logo appears to force a reboot (much better than removing the battery!) you can see Home for a few seconds but then Screen Curtain kicks in & you are back to square 1.

The Samsung support page Accessibility Settings on Your Phone > Vision > if Voice Assistant is enabled then you can toggle on Dark screen (Samsung's name for the similar iOS' Screen Curtain) which says: "Double press the Power key to turn this function on or off". - This does NOT work on S5 LineageOS 16.0 @ the present.

iOS' Screen Curtain gesture: 3 taps made with 3 fingers to disable does NOT work as seen in the screen recording linked above. I tried fast tap, slow tap, fingers spread & together several other times not in the recording.

Thanks to your reports I took some precautions before trying Screen Curtain because I'm curious.

Full backup in TWRP.

Google site searches: site:xdaforums.com/ "Screen Curtain" returns horror stories with users restoring backups or doing clean installs.

site:reddit.com/r/LineageOS "Screen Curtain" returns only 1 result by 15.1 users @ the present but it's the most informative: LineageOS 15.1 - [SOLVED] Accidentally setting "Screen Curtain" (Black screen)

Backed up org.lineageos.settings.device_preferences.xml & made a TWRP flashable zip of the stock file using ZIPme.

I used the Lineage built-in screen Recorder after > Settings > Developer options > Show taps (Show visual feedback for taps) enabled to show where I was tapping before enabling Screen Curtain.

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Screen Curtain is a feature if you use it with a text-to-speech app like TalkBack (included in the Android Accessibility Suite) or adb or scrcpy for example.

I noticed in the app's description: "For Android 8.0 and above, the "Dim screen shortcut" has been removed."

From this 2013 Samsung Newsroom press release Galaxy Core Advance Extends Galaxy Experience to More Users with Enhanced Features: "...The device is also equipped with Screen Curtain that enables users to operate commands on a black screen to ensure privacy and saves battery life...".

Old article about Use Galaxy S5 with Screen Turned Off Marshmallow/Lollipop vs Kitkat

Hope this is helpful to somebody.

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