I've put together some information, and I hope this will help.
Q: The app requests a ton of permissions
A: All thre permission are used for app inside VirtualXposed, i don't know what apps will be added to VirtualXposed, so i must request all the permission in advance. If VirtualXposed doesn't have a permission of one app, the app may can not work properly in VirtualXposed.
I am planning to upgrade the targetSdkVersion to 23, then there are little permission requests when install it (VirtualXposed will request permission dynamicly, but if you refuse some permission of one app in VirtualXposed, all the app in VirtualXposed won't grant that permission; this is truly frustrating, XPrivicyLua can not work properly in VirtualXposed: https://github.com/android-hacker/Vi...posed/issues/7, I am trying to add a built-in permission control in VirtualXposed: https://github.com/android-hacker/Vi...osed/issues/33, but there are lot of work to do...
Q: New modules are seemingly often not changed even after re-installing. Un-installed virtual apps are sometimes detected as still being present by the xposed module (?!)
A: This is a bug, the state of installation and launcher3 are not the same.
Q: Epic library's readme says not supported for arm32, x86_64 and mips device architectures for ART.
A: Yes, Epic doesn't support arm32, x86. you can install it on x86 device, but Xposed won't work.
Q: If you have enabled an Xposed Module outside of VirtualXposed, it will still affect apps inside it - So its recommended to turn the module off outside.
A: Yes, Xposed in system will take effect in VirtualXposed, and sometimes may cause conflicts if you enable the same module both in Xposed outside and VirtualXposed.
Q: The original developer seems to not speak perfect English, and the current users are mostly all Chinese.
A: Yes, my English speaking is poor, but my reading skills is good, there are no obstacles to understand what you say
The current users are mostly all Chinese, in fact, there are more than one million users in total If you think it is useful, please tell it to your friends, this is the best way to encourage me to make VirtualXposed better and better.
Q: is there any part of the source code of VirtualXposed (or any of its dependecies) that is proprietary/closed-source
A: No, VirtualXposed is fully open source, but the License is complex. I have no idea of it totally.
Q: If you have some free time later, can you explain in some detail (such as with links to relevant folders/files in Github) how VirtualApp, Epic and VirtualXposed work?
A: See below
Q: How VirtualApp works?
First, you can read my blog and follow my tutorial:
My Blog: http://weishu.me/2016/01/28/understa...work-overview/
My Tutorial: https://github.com/tiann/understand-plugin-framework
These articles tell you how Android Framework works and how Plugin-Framework hooks into system to establish a virtual environment.
If you are familar with Android Framework, you can read the source code of demo.
But sorry, it is fully Chinese, lots of Chinese say it is the best way to understand DroidPlugin/VirtualApp
Then, you can read the VirtyalAppDoc: https://github.com/prife/VirtualAppDoc.
In VirtualXposed, source code of VirtualApp lies in https://github.com/android-hacker/Vi...VirtualApp/lib
The structure of VirtualApp:
https://github.com/android-hacker/Vi...jni/Foundation and https://github.com/android-hacker/Vi...c/main/jni/Jni :mainly for IO redirect to make app inside VirtualApp access the corret file system, and also, it do some native hooks for special API(for example, Camera must be hook in native, disable JIT, etc..)
https://github.com/android-hacker/Vi...in/jni/HookZz: This is an inline hook library, it is fully open source, this is the project: https://github.com/jmpews/HookZz
https://github.com/android-hacker/Vi...jni/Substrate: Another inline hook library, it seems to be closed source, but i don't know how the author of VirtualApp get the source code...
https://github.com/android-hacker/Vi...c/main/jni/fb: the JNI framework of facebook.
https://github.com/android-hacker/Vi...n/java/mirror: the reflection framework of VirtualApp, it is used for use reflection conveniently, it is really elegant.
https://github.com/android-hacker/Vi.../java/android: some hidden API of Android Framework, copy it here for compile.
https://github.com/android-hacker/Vi...irtual/server: the server process of VirtualApp, for example, Android Framework has ActivityManagerService, PackageManagerService, in VirtualApp, there are VActivityManagerService, the procedure of a process to communicate with Android Framework is: Client process -> VitualApp's server process(Virtual System servier) -> Android Framework's system service.
https://github.com/android-hacker/Vi...irtual/client: mainly for hooks in client process(App run inside VirtualApp are all client process); There are four type of process in VirtualApp: 1. Virtual Server process(with hook of AMS & PMS) 2. Virtual client process(with hook of All Android System Service) 3. UI process(a normal process) 4. other process(such as native process)
https://github.com/android-hacker/Vi...dy/virtual/os: the multi-user system of VirtualApp and the some envionment variants, such as directory structure.
https://github.com/android-hacker/Vi...irtual/remote: Parcel data stucture for IPC between Virtual client process and virtual server process.
If you want to read source code of VirtualApp, this class is the best entry:
Q: How Epic works?
You can refer my design procedure of Epic: http://weishu.me/2017/11/23/dexposed-on-art/
The article introduces many way to hook and tells you how epic solve the problems in the past and why epic does it that way.
Sorry for it is Chinese again...
And then, yon can read the paper : https://publications.cispa.saarland/143/ It is strongly recommended to read that!
In fact, Epic was inspired by https://github.com/mar-v-in/ArtHook, you can also read the source code.
Q: How VirtualXposed work?
VirtualXposed loads Xposed Modules in the entry of VirtualApp's client process, and inject the Xposed ClassLoader to that process to make Xposed module can call Xposed API, and epic provides the abilities to hook, That's all.
All this work is done in https://github.com/android-hacker/exposed
If you have any doubt with VirtualApp/Epic/exposed, feel free to ask me
In addition, I made an origination named android-hacker when i create VirtualXposed, if you want to contribute to VirtualXposed, welcome to join it!(tell me to invite you)