What does this sentence mean?

My father, who doesn't waste energy with dramatic reactions to things and keeps his feelings to himself, had a series of facial expressions, each meant to communicate something specific. He was so consistent with these glances that they could be PATENTED, since each glance communicated exactly his response to a given situation. All he had to do was glance at me and I knew exactly what he would have said had he opened his mouth and used words to say it.