One wave's samples, and the window they cover. Per WAVE, not per view. What the viewer needs to know is "does this wave have the cycles it is being drawn over", and that is a question about one wave: a wave just added to the selection is missing while every other wave is fine, and a window that has moved leaves them all missing together. Keying by wave says both without a special case, where one entry for the whole view could only say "all" or "none". Waves fetched together share one array - a reply is signal-major and copying it apart would be the only copy in the path - so each entry carries where its own row starts.