He shook his head. “No. You were forced to wed him. I’ve seen your aunt bully you. She made you do it.”
Deirdre laughed shortly. “You cretin, I proposed to him!” She wiped the back of her hand across her brow. “I’ve loved that stubborn idiot for years. It broke my heart when I thought he’d marry my cousin.”
Something in her voice seemed to pierce his delusion at last. He gazed at her as if he’d never seen her before. “But. . . you saw how I loved you. You saw and you smiled to see it! What sort of monster are you, that you would toy with me so?” (Celeste Bradley, The Duke Next Door)
To infinitive’s seeing time seems equal with your smiling and the seeing is the reason or condition for smiling. Are these all right or do I have to see otherwise? (for example, seeing is anterior to smiling, and to see is, in fact, to have seen, and the latter is replaced by the former, as a tense simplification (CGEL,p158). For you know the time sequence well, without perfect tense.)