Since commit 4d535c4f867d86d40786788e5e5c9fd061a65673, slideshow has additional white borders at bottom and right edge. Steps: 1. Create a new presentation. 2. Set slide area to e.g. green. 3. Press F5. See that there is 1-pixel white border at bottom and right. It's also visible if you make a screenshot. (The screenshot would also make it obvious that those bottom and right edges have also 1-pixel black borders, but that was already present before.)
*** This bug has been marked as a duplicate of bug 150102 ***