As above really; working on this: cf.
Review needed for -5-0:
https://gerrit.libreoffice.org/18103 tdf#93529 - add glDebugMessageInsert wrappers to help with API tracing.
https://gerrit.libreoffice.org/18104 tdf#93529 - use debug messages while rendering to break up the trace.
This makes API tracing hugely easier =) and it'd be good to keep the branches in sync too.