This 1948 movie starred Arturo de Cordova as Casanova, along with Turhan Bey and John Sutton.
They changed his character - instead of a lover, he's also an Italian "Zorro" - returning to his home to fight against the invaders, in this case the villainous Comte de Brissac played by John Sutton. Sutton of course steals the films, in his all-too-few scenes.
The actor who plays Bernardo is Fritz Leiber, the father of Fritz Leiber Jr., the science fiction writer. [Leiber Jr, wrote a funny (albeit confessional) story entitled "237 Talking Statues, etc.", inspired by his difficult relationship with his father, in which Francis LeGrand II is confronted by the statues and paintings of the title, all self-portraits of his father in various roles, with which he discusses his relationship with his father.]
(Sorry it's in so many parts but my laptop was behaving very badly while I was doing this).