totalSpan property
The timespan between vsync start and raster finish.
To achieve the lowest latency on an X fps display, this should not exceed 1000/X milliseconds. That's about 16ms for 60fps, and 8ms for 120fps.
See also vsyncOverhead, buildDuration and rasterDuration.
Implementation
Duration get totalSpan => _rawDuration(FramePhase.rasterFinish) - _rawDuration(FramePhase.vsyncStart);