Yeay, I think
found the problem for all the graphical glitches (like when scrolling in the App drawer, the screen 'tears') or when pulling the notification bar up and down very fast (it'll 'tear').
The vSync is off
This is just a basic description of vSync:
Say your screen refreshes at 60Hz - vSync on will attempt to display 30fps to avoid tearing. 30 goes into 60 twice evenly... get it?
vSync off will display as many fps as possible. So rather than holding back and displaying 30fps it will allow 35fps. This will cause tearing because 35 does not go into 60 evenly.
So we have to enable vSync to avoid this..
Edit: The LG Optimus One kernel developer did it like this:
pinfo->lcd.vsync_enable = TRUE;
pinfo->lcd.hw_vsync_mode = TRUE;
Samsung Galaxy S4 i9505 Black Mist
Stock, unrooted I9505XXUEMJ7 (4.3) ROM & Kernel
Signature updated on: November 5th