Window was a popular subject in art history in general and was, symbolically and visually, treated differently according to the period. Since Alberti's stated that a (framed) painting should be treated as a window on the world, I'm guessing a lot of Avant-garde artist who dealt with this subject had a different approach, following the general idea of breaking up
with the tradition.
What do you think or know about the meaning behind windows in Avant-garde art? Please state the artist and/or essays you are referring to.