Yes. We shouldn't block AWT queue. Probably a modal dialog with progress bar
with "Loading NetBeans Platform's metadata" message or something similar? I'll
go that way if anybody (HIE, Jesse, ...) doesn't have other opinion (e.g. some
standard NB approach I've missed)

I think you can disable both Next and Finish buttons while doing computation,
rather than showing a modal progress dialog on top of a wizard, which is sort of
ugly. I am sure there is some example elsewhere, but can't remember where.

By the way, what exactly is so slow that it needs a progress dialog? AFAIK all
the wizard needs to do is check for the platform's display name, which ought to
be pretty fast since it just needs to open a couple of JARs and look for some
bundles. Reporter, any thread dumps or profiler results?

Created attachment 23587 [details]
blocked AWT-EVENT-QUEUE

I attached AWT-EVENT-QUEUE dump. 

The time is spent in 
ModuleList.createModuleListFromBinaries()
There are opened jars of netbeans modules. It takes a lot of time. 

Jesse, do you plan to implement cache for nbplatform? IHMO it is useless to open
all the jars of platform everytime the platchorm is touched. 

For example te cache can contain these informations:
1) the absolute path in filesystem to platform (key)
2) list of all jars in platform
For a jar should be cached these informations:
-location and name in platfrom 
-timestamp and size 
-manifest and layer xml

Isn't this thread dump intended rather for the issue 59550? Attaching threaddump
you probably meant.

Created attachment 23599 [details]
right thread dump

Ah. In NbPCM.setPlatform, in place of

moduleList.setModel(new ComponentFactory.ModuleEntryListModel(plaf.getModules()));

just use e.g.

moduleList.setModel(new DefaultListModel(new Object[] {"Please wait..."});
RequestProcessor.getDefault().post(new Runnable() {
    public void run() {
        final ModuleEntry[] modules = plaf.getModules();
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                moduleList.setModel(new
ComponentFactory.ModuleEntryListModel(modules));
            }
        });
    }
});

I doubt a progress bar is really needed for this; it's only a displayed list,
analogous to the "Required Projects" list in the Open Project dialog.

Thanks. Fixed.

Checking in ui/platform/NbPlatformCustomizerModules.java; 1.2 --> 1.3

v