For those who would not like to use GDK_NATIVE_WINDOWS as a workaround consider using the hotkeys of those buttons instead of the mouse (which works just fine) until the eclipse team adjusted their software to the "new" GTK+ behaviour.
For those who would not like to use GDK_NATIVE_WINDOWS as a workaround consider using the hotkeys of those buttons instead of the mouse (which works just fine) until the eclipse team adjusted their software to the "new" GTK+ behaviour.