Allow loading of pdf themes from jar files

[svenreimers]

Seems that theme files can not be loaded from custom jar files or the classpath in general (correct me if I am wrong).

Having this feature allows for simpler redistribution and reusage, if asciidoctor is embedded in e.g. a test reporting engine.

[mojavelinux]

This issue is a duplicate of / in the same spirit as #420. In that issue you can find a link to a Gradle plugin that @fwilhe created that allows themes to be loaded from git repository until there's a formal solution in place in Asciidoctor PDF.

My position is that the converter is not yet ready to take this formal step, so the Gradle plugin is a good immediate / temporary solution. The theme engine is still stabilizing, so I don't really want themes to rely on loading behavior at this point. We may still need to change things around in the design to accommodate that use case properly. But we will.

[mchmielarz]

Hi, did you make some progress with this issue?

[mojavelinux]

Asciidoctor PDF (running in a JVM) can read a file if it begins with uri:classloader:. So it should be possible to set the pdf-theme to a value that uses this prefix.

So here's what you do:

• Create a folder named themes
• Add the file my-theme.yml to this folder
• Populate the contents with:

  extends: default
  base:
    font-color: #ff0000
  

• jar that folder up as themes.jar
• add that jar to the classpath
• set pdf-theme as follows: -a pdf-theme=uri:classloader:themes/my-theme.yml

Voila! You've loaded a theme from a jar file.

Outside of this, I believe this is a Gradle or Maven plugin issue.