If I start Eclipse with environment variable SWT_GTK3=1, then the QuickSearch plugin does not display its search results.
You can still scroll through the search results and see the preview of the each one, but the three columns (Line, Text, Path) just repeat some random values.
I get this with Eclipse Mars RC3 (after adding the Spring Tool Suite from this URL http://dist.springsource.com/snapshot/TOOLS/nightly/e4.5). I also get this from a fresh install (http://download.springsource.com/snapshot/STS/nightly/dist/e4.5/spring-tool-suite-3.7.0.CI-B255-e4.5-linux-gtk-x86_64.tar.gz)
If I set SWT_GTK3=0, then the quicksearch plugin functions correctly.