message: Add more to the TODO list.
diff: // start graph at a specific location
  // find event in graph
  +//$ TODO: in graph tooltip, show distance to previous and next vblank
  +
  +//$ TODO: allow ability to filter vblanks based on crtc: crtc0, crtc1, crtc0+1
  +
  +//$ TODO: Enable showing vblank with shortest interval by default
  +
  +//$ TODO: Add ability to show row for an event with a parameter?
  +
  +//$ TODO: Need to handle lots of rows, ie ~100
  +
  // popup graph tooltip shows events around location you're at?
  static SDL_threadID g_main_tid = -1;
  