Document proguard rules

[mikedawson]

Hi,

When I use Proguard on my project (I'm using VLCJ in a Compose/Desktop JVM application), the discovery providers (which are loaded via Java SPI) are removed.

I think the following rules are needed:

# Not always compiling on Mac
-dontwarn com.apple.eawt.**

# Keep DiscoveryDirectoryProviders loaded via SPI
#-keep class * implements uk.co.caprica.vlcj.factory.discovery.provider.DiscoveryDirectoryProvider { *; }
#-keep interface uk.co.caprica.vlcj.factory.discovery.provider.DiscoveryDirectoryProvider { *; }

The keep rule specified here https://www.guardsquare.com/manual/configuration/examples#native is also required. I think most Proguard setups have that, but might be good to mention.

[caprica]

The eawt stuff is obsolete now.

[caprica]

So this is purely for purposes of minification, not obfuscation, right?

What I mean is, vlcj is Open Source so there's no point to obfuscate the source code as such. Making a small bundle size is fair enough I suppose.

[mikedawson]

Thanks for the super quick reply! Yes the main point is the bundle size. Secondary reason is performance gain. My jars (also open source) are about 157MB before shrinking and obfuscation, and about 78MB afterwards (I documented a bit of it here on this article).

[mikedawson]

Just to clarify: we are using obfuscation, only because it further shrinks the bundle size and should improve performance of remaining code. I find without obfuscation enabled, my jars are about 12MB bigger.

[caprica]

Sure, that's what I suspected.

I am happy to add something to document this. But in the immediate term I need to think about a bit more because the upcoming version of vlcj has some more stuff that will need to be excluded.

[mikedawson]

Adding docs would be great, thanks! On Android, libraries can publish proguard rules that are consumed automatically. Unfortunately, that hasn't hit the JVM world yet.

[caprica]

is there any value just putting a proguard config file (or partial config file) in the main repo itself I wonder?

[mikedawson]

I think putting in the repo (convention is META-INF/library-name.pro e.g. META-INF/vlcj.pro) would make sense. I think it would still need mentioned somewhere in the docs. On Android, those rules can be consumed automatically. On JVM, they need to be copy/pasted in manually.