Eclipse - extending project/package explorer to handle custom file types as trees

If an Eclipse project includes a .jar file, the package explorer treats it like a tree and enables the user to click the "+" sign to the left of the file name to expand the tree and show the files in the .jar archive.

I would like the package explorer to treat other file types the same way. A really simple example would be if the file test.txt containing:

First line
Second line
Third line

was shown as:

-test.txt
--First Line
--Second Line
--Third line

I've been trying to find a suitable extension point to do this, but n开发者_高级运维o progress so far. Could someone point my in the right direction? I would like Eclipse to use my plug-in for interpreting the file as a tree as soon as it's added to the project.

you could try to use the common navigation framework: CNF