Direct SurfaceFlinger access as root
Copyright © 2020 Jorrit Chainfire Jongma
This code is released under the Apache License version 2.0.
If you use this library (or code inspired by it) in your projects, crediting me is appreciated.
If you modify the library itself when you use it in your projects, you are kindly requested to share the sources of those modifications.
This library is part of the Spaghetti Sauce Project.
A long time ago in Android 2.x days, there were the Live Logcat Boot Animation, Live Dmesg Boot Animation, and Mobile ODIN root apps, as well as the original CF-Auto-Root packages. These provided their screen output by directly blitting into the Linux framebuffer, using the first incarnation of libCFSurface.
Android changed significantly between 2.x and 4.x (we don't speak of 3.x) and easy framebuffer access is one of the things that was lost. At first just in Android itself, but later also in recovery mode.
For LiveBoot (successor to Live Logcat/Dmesg Boot Animation) and FlashFire (successor to Mobile ODIN), SurfaceFlinger had to be used to get anything on-screen when Android itself wasn't fully loaded.
This code is the third incarnation of libCFSurface. As LiveBoot was my first app that used it, it grew there, and was later separated out when FlashFire was created. This incarnation is based on libRootJava and uses only Java and reflection.
I've provided the previous (second) incarnation, which was C++-based (and a horrendous mess to get to build in the NDK, with lots of files and code copy/pasted from AOSP), in the git history for those interested in these things. Of course, that will not work on any recent Android version.
The original framebuffer-using code is probably somewhere, though certainly not here.
Some of the GL-related code is partially copy/pasted from some GL code Google released somewhere, but though I saved the copyright notice I don't remember it's exact origin.
I doubt anyone will use this library for anything, but you can't build LiveBoot without it, and as I'm uploading that, I need to upload this.
I'm not going to provide proper example code. You can look at LiveBoot's source if so inclined.
It's meant to run as a
libRootJava process' main
loop. You run your own descendant of SurfaceHost,
implementing the abstract methods, as well as exactly one of the
IGLRenderCallback, ICanvasRenderCallback, IHardwareCanvasRenderCallback,
or ISurfaceRenderCallback interfaces.
The callbacks are called in a separate thread, that thread (and execution)
ends once your implementation of SurfaceHost::onMainLoop() returns.
My own code using this library is all GL-based, hence the GL utility and helper classes. The Canvas-based callbacks were tested when their support was written, but are not actively used anywhere, I merely assume they still work.
This code has barely been touched in the past few years, aside from yearly updates to LiveBoot. Experience shows every major Android release it needs to be updated as the signatures of the methods used through reflection changes.
Comments (if any) may be outdated or plain wrong.
I did not check anything prior to release other than that it builds and works for LiveBoot on a Pixel2XL running Android 11. Otherwise I'd never get around to pushing it to GitHub.
Root build.gradle:
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}
Module build.gradle:
dependencies {
implementation 'eu.chainfire:libcfsurface:1.1.0'
}