[CMake] cpack bundle generator qq

[Timothy M. Shead]

The problem that I was trying to solve with the bundle generator was how 
to install complex systems in a cross-platform way.  Assume that you 
have an application "foo" that is run by end-users, plus helper 
applications "a" and "b" that are run indirectly by foo, and third-party 
dependencies.  You want to package everything in a consistent way on all 
platforms.  So you do

INSTALL(TARGET foo a b DESTINATION bin)
INSTALL(FILES dependencies DESTINATION lib)

With *nix and NSIS, this is straightforward and works fine.  With 
bundles, it's trickier.  You don't want separate bundles for foo, a, and 
b in this case, you want a single bundle where foo is what gets executed 
when the user double-clicks on it, but a and b are included where foo 
can find them.  That immediately eliminates the MACOSX_BUNDLE approach 
off-the-bat, because it creates separate bundles for each executable. 
Even if you omit MACOSX_BUNDLE for a and b, you still have no mechanism 
to install them into the bundle created for foo.  The same applies to 
third-party dependencies.

Thus, the approach taken by the bundle generator is to create a single 
bundle, populate its contents based on your CMake INSTALL commands, then 
add the necessary metadata to define *which* binary is executed when 
end-users click on the bundle, then create the dmg.

I've never run across a dmg that contained multiple bundles,  but adding 
a feature to create multiple bundles based on components sounds like a 
good idea.  I guess that in an ideal world you would like to set 
per-component properties (if there were such a thing) that could be used 
by the bundle generator to setup the bundles, but other workarounds 
should be possible.

Cheers,
Tim

-- 
Timothy M. Shead
Data Analysis & Visualization (1424)
Sandia National Laboratories
505-284-0139