SyncPlayer 1.6.12 - a crop window that shows a picture

Fixed

• A captured frame that is technically not blank but visually black (brightest content
  below about 60 of 255) reached the crop window and looked like an empty box. Frames are
  now judged on their brightest content rather than their average, and such frames are
  lifted into a viewable range. A normal frame is left untouched.
• The crop window no longer depends on a single configure event to draw its image: it also
  draws when the window is mapped and shortly after opening.
• The crop window reports what it is showing - frame size, average and brightest
  luminance, items drawn, and the route that produced the frame - so an empty window can
  be told apart from a failed capture.