Hi, if you're the author of
https://github.com/koreader/koreader/issues/11319 please move questions there
Also, please do not trust random user patches unless they're github tickets with the tag "user patch available".
The best way to write your own patches is to read the source and understand specific parts of its behaviour to be able to change what you want to change.
In this case there're already a few places where we set a viewport in android devices:
https://github.com/koreader/koreader...oid/device.lua
Use them as an inspiration.