Write a patch making guide or tutorial

[EarldridgeJazzedPineda]

About

This was requested by u/The_Frozen_Duck on the ReVanced subreddit.

For context, I'm new to making patches for ReVanced. I spent the past 4 days trying to make one for Duolingo (I haven't wrote any patch code yet).

Currently, there isn't a guide or tutorial on making ReVanced patches. There is the ReVanced Patcher documentation, but it's more of a reference than a guide.

Without further ado, here is the proposal:

It should be a fairly comprehensive guide/tutorial on the process of making ReVanced patches. It should cover the prequisites for making patches, such as Dalvik bytecode, and reverse engineering. It serves as the main resource for beginners, while also serving as a supplement for advanced patch makers.

Here is what I would do in the guide/tutorial:

• Document most, if not all APIs and helper functions/methods (especially the most commonly used ones such as getInstruction, addResources, and returnEarly).
• Teach the reader on Java, Kotlin, and Dalvik bytecode by showing what the Java/Kotlin code and its corresponding Dalvik bytecode look like, for example:

Java:

static int example(int num) {
        return num + 1;
    }

Smali/Dalvik:

.method static example(I)I
    .registers 1
    add-int/lit8 p0, p0, 0x1
    return p0
.end method

Kotlin:

fun example(num: Int) = num + 1

Smali/Dalvik:

method public static final example(I)I
    .registers 2
    .param p0, "num" 
    add-int/lit8 v0, p0, 0x1
    return v0
.end method

There should be many code snippets showing the commonly used features of Java and Kotlin. A list of all Dalvik opcodes and their corresponding Opcode constants is also helpful.

• Show the reader on how to install, set up, and use essential tools such as jadx, emulators, and debuggers.
  Edit: I will clarify that those tools are not required to use ReVanced, nor are they required to merely build ReVanced Patches (only a JDK is required). However, they are most likely needed to write patches.
• Have an open-source demo app with features such as ads and code obfuscation that can be used to demonstrate the patch making process.
• And this is the main part, guide the reader on making some patches (e.g. hide ads, hide UI elements, themes/custom branding, sanitize shared links) for the demo app. It involves finding the code that needs to be modified, testing changes to that code, and writing the patch itself.

The layout should look like this:

1. Introduction and basic concepts
2. Setting up the developer environment
3. A crash course on Java/Kotlin and Dalvik bytecode
4. Reverse-engineering the app and testing modifications
5. Writing the patch code
6. Testing and submitting the patch
7. What's next
8. Appendices (parameter/return types and Dalvik opcodes)

The guide/tutorial should go in the revanced-documentation repository.

Acknowledgements

• I have checked all general discussions and this is not a duplicate.
• I have chosen an appropriate title.
• All requested information has been provided properly.
• This discussion is not a bug report or feature request

[oSumAtrIX]

The docs simply expect the reader to have knowledge of Java, Kotlin, Dalvik bytecode, and reverse engineering skills.

Yes, those are prerequisites that are not covered but necessary for ReVanced development

Parameter and return types (which use JVM type signatures) and constants representing Dalvik opcodes such as Opcode.CONST_STRING are not documented in detail.

This is dalvik specific, not related to ReVanced Patchers, but Dexlib/smali related.

APIs and helper functions/methods commonly used in ReVanced Patches such as getInstruction, addResources, and returnEarly are not documented.

Those are patches specific helper functions, not patcher APIs, these cant be documented in the patcher repository.

Teach the reader on Java, Kotlin, and Dalvik bytecode by showing what the Java/Kotlin code and its corresponding Dalvik bytecode look like, for example:

Learning Kotlin, Java or Dalvik is not in scope of ReVanced. The respective tools have their own documentation irrespectively of ReVanced. The chain of learning goes as far back as necessary so if you have a prerequisite you dont understand you need to learn the prerequisite.

Show the reader on how to install, set up, and use essential tools such as jadx, emulators, and debuggers.

Tools like JADX emulators or debuggers are not mandatory for ReVanced.

Have an open-source demo app with features such as ads and code obfuscation that can be used to demonstrate the patch making process.

The patcher docs are specifically carved out for the purpose of documenting patcher, things like this are out of patchers scope.

If my proposed improvements are not suitable for the revanced-patcher repository, then the docs/guide should be split into its own repository.

Thats possible, however it needs separate and dedicated planning for which you'd have to invest time in. If you like, you can help us with such a documentation.

[EarldridgeJazzedPineda]

I've shifted the focus from improving the ReVanced Patcher documentation to writing a separate patch making guide.

[oSumAtrIX]

Keep us posted