I have added a CustomUsageSearcher which returns non-navigatable results. But every result is shown in the usage view tree as a leaf below a "1 results" node:
I used EP com.intellij.fileStructureGroupRuleProvider which allows me to group the results under each node but I still have a first-level node for every usage:
I use two grouping rules with orders 0 and 1. How can I group results so that all are below the first level group, some in a couple of second level groups and of those some in multiple third level groups. So I want e.g. "13 results", two "A project" nodes and in those file nodes which contain leaves.
I assume I have to create one ProjectUsageGroup for each project node and ClassUsageGroup for each class node in that but I'm still unclear on the top-level grouping.
My usages implement UsageInFile and return a dummy file.