Does the emission of pre-seminal fluid—by any means whatsoever, such as watching pornography with masturbation—invalidate the fast, or is the fast sound?

Masturbation and watching pornography are forbidden (haram), and their punishment is more severe in Ramadan. The emission of pre-seminal fluid (madhiy) due to masturbation or watching pornography does not invalidate the fast, according to the preponderant and fatwa-given opinion.