Type Alias NcStreamCb 

pub type NcStreamCb = fn(&mut NcVisual, &mut NcVisualOptions, &NcTime, Option<&mut NcPlane>) -> NcResult_i32;

Called for each frame rendered from an NcVisual

If anything but 0 is returned, the streaming operation ceases immediately, and that value is propagated out.

The recommended absolute display time target is passed in ‘tspec’.