This is taken from Gerda OS. You just need to replace 3 files from the js folder of system app with those from Gerda OS.
This is what you get at the end.
Slider full open + power button = minimize app (If you exit an app by pressing Back-button, now the app closes completely)
Slider partial open + power button = screenshot
Slider full closed + power button = normal power button function
Slider full open + hold power button = task manager
Download js.zip from below link and extract.
https://drive.google.com/file/d/1GOatLqWvmze1Drc_ILWOVAc6lfY1YAda/view?usp=sharing
You will get 3 files :-
task_manager.js
hardware_buttons.js
app_window_manager.js
Steps:
1. Get copy of system folder
adb pull /system/b2g/webapps/system.gaiamobile.org
(if you edited system folder before, you need this command :
adb pull /data/local/webapps/system.gaiamobile.org
)
2.Now open system.gaiamobile.org/application.zip/js/
Now drag the downloaded js files to the opened js folder one by one.
Now close the zip
3.
Push the app and its folder on the data partition, exactly in/data/local/webapps
using a temporary root access
adb push system.gaiamobile.org /data/local/webapps
4.Get the webapps.json file:
adb pull /data/local/webapps/webapps.json
And change the value of the system.gaiamobile.org app
5.After this change push the webapps.json file in its place and reboot the phone:
adb push webapps.json /data/local/webapps/
adb reboot
Note :-
Do not press Back-button in task manager. To go back, press Power-button. If you accidentally pressed Back-button don't
worry. Just hold Power-button, it will again open task manager, then press power-button.