Update (06/14): It’s the news that Substratum fans have been dreading. On a post on its Issue Tracker forum, Google confirmed that the Android P developer preview intentionally blocks the use of non-system overlays. This means support for Substratum will not be returning in the final version of Android P.
In the post, first spotted by Android Police, Google cited security issues as the reason for the change. It also said that the Overlay Manager Service that allowed overlays was never intended to be a public developer feature and is not designed for “generic theming” You can read the full comment here.
Original article (03/08): Bad news for those of you out there who love Substratum themes: Android P contains code that blocks all non-system overlays. That means that, whether rooted or not, Substratum theming will be impossible once you upgrade to Android P.
For those of you unfamiliar with Substratum, we’ll fill you in. When CyanogenMod was still around, it came with a proprietary theming engine that allowed you to quickly and easily change pretty much all visual aspects of the Android operating system. When CyanogenMod became Cyanogen (and then eventually folded altogether, killing the theme engine), a new theming engine popped up: Substratum.
Rooted users could install Substratum and then install pre-made themes from the Google Play Store. What’s more, most themes let you tweak each themed setting to your liking, giving you virtually limitless control over how your device looks.
With Android 8.0 Oreo, Google implemented Sony’s Overlay Manager Service (OMS), which the developers of Substratum realized could let users tweak themes without root. To install Substratum on an unrooted device, you would install another app called Andromeda, which had the specific job of putting the OMS to work. Unfortunately, the Substratum team decided to make Andromeda a paid app, which was controversial at the time.
Now, with Android P, it looks like Substratum and Andromeda will have no effect whatsoever on the look of Android. Any attempt to install Substratum results in an error from the Package Manager. XDA Developers assures us that even with root access, Substratum will not work in Android P.
To their credit, the Substratum team states that the Andromeda add-on is an in-progress app, so your money may not have been wasted. The team is going to put together a petition to get Google to bring back Substratum functionality in the eventual public release of Android P; but ultimately, Google has the final say.
Why would Google do this? Most likely the company is worried about Material Design 2, the newest iteration of its Google-ecosystem style guide. If themers can bypass Material Design 2, then the entire style guide is for naught.
However, the fact that overlays can still be installed by the Android P system itself leaves at least a little hope that Google could introduce its own theming system for Android, one which it controls and can force themes to abide by Material Design 2 guidelines. However, this seems unlikely, as Google is probably more interested in keeping theming out altogether.
Are you a Substratum user? Would this prevent you from upgrading to Android P?