Huawei tried contributing its proprietary take on a one-handed smartphone mode to the Android Open Source Project (AOSP) but was denied, newly uncovered commits reveal. In late 2016, one software engineer from the Chinese original equipment manufacturer uploaded a number of commits meant to implement one-handed mode in Android, with the code itself presumably being the work of a larger number of developers. The commits were denied by Google's reviewers on the basis of various code conflicts as they would prevent manual app installation by virtue of the fact that the system doesn't allow for such actions when one app is permitted to draw over other active ones. Likewise, the code was making approving permission requests and sideloading apps impossible in certain scenarios, one reviewer noted.
The original Huawei-made commits were modified by the LineageOS team and made their way to LineageOS 14.1 in an entirely stable capacity and without resulting in any kind of conflicts. The developers behind the open-source Android distribution and spiritual successor to CyanogenMod apparently managed to fix the previously submitted code and compile it into a working OS build, with the end result being extremely similar to the one-handed mode seen on Huawei's devices running the company's EMUI software suite. LineageOS refers to the feature as a "Single Hand Mode" and hasn't uploaded it to AOSP, though the adaptation should theoretically work in vanilla Android with little optimizations. The implementation itself is set to activate one-handed mode on any device running LineageOS 14.1 whenever the user swipes right or left over the on-screen Home button. Depending on which direction is chosen, the downsized screen will end up in the bottom left or right corner of the display panel and act as most other one-handed modes. The default shortcut for activating the mode can be customized in the "Buttons" menu of the system Settings app, with the feature hence being even more versatile than Huawei's original solution.
Vanilla Android still doesn't have a native solution for one-handed phone use and it's currently unclear whether such a feature is a priority for Google, especially given how OEMs have been offering it for years now. The upcoming Android 8.1 Oreo build was already confirmed as not featuring a one-handed mode and Google has yet to give any indication that it's working on adding it to the OS in the near future.