I thought this was a driver bug; but it appears we are triggering clipped re-rendering of areas underneath tooltip pop-ups (for no apparent reason - we have a back-buffer with that information) - and that we clip to the visible range. Unfortunately - GL clipping was not working.
Created attachment 121677 [details] example display dirt.
pushed fixes to gerrit for master and 5-1-
Michael Meeks committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=c798c1baf176f62964e1accc5edfddf48e1102be tdf#96858 - opengl - fix off-by-1 in glScissor clipping. It will be available in 5.2.0. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Michael Meeks committed a patch related to this issue. It has been pushed to "libreoffice-5-1": http://cgit.freedesktop.org/libreoffice/core/commit/?id=4b5e574703278c942f280b05b27ef99091ca84da&h=libreoffice-5-1 tdf#96858 - opengl - fix off-by-1 in glScissor clipping. It will be available in 5.1.0.2. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.