Bug 11437 jar packager: no error message but buttons disabled
20020314 on the 'jar manifest' wizard page, if you select to use existing manifest file there's no error message but next and finish are disabled user should be informed what to do to make the wizard happy
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarManifestWizardPage.java
dialog.addFilter(new LibraryFilter());
		dialog.addFilter(new SealPackagesFilter(packages));
		dialog.setValidator(new ISelectionValidator() {
			public IStatus validate(Object[] selection) {
				StatusInfo res= new StatusInfo();
				for (int i= 0; i < selection.length; i++) {
					if (!(selection[i] instanceof IPackageFragment)) {
						res.setError(JarPackagerMessages.getString("JarManifestWizardPage.error.mustContainPackages")); 
						return res;
					}
				}
				res.setOK();
				return res;
			}
		});
		return dialog;		
	}
	/**
	 * Converts selection dialog results into an array of IPackageFragments.
	 * An empty array is returned in case of errors.
	 * @throws ClassCastException if results are not IPackageFragments
	 */
	protected IPackageFragment[] getPackagesFromDialog(SelectionDialog dialog) {
		if (dialog.getReturnCode() == dialog.OK && dialog.getResult().length > 0)
			return (IPackageFragment[])Arrays.asList(dialog.getResult()).toArray(new IPackageFragment[dialog.getResult().length]);
		else
			return new IPackageFragment[0];
	}
	/**
	 * Creates and returns a dialog to choose an existing workspace file.