Is ghusl obligatory if a viscous white fluid is discharged merely by thinking or talking about sex, even if no orgasm occurs?

If what is discharged is maniyy (spermatic fluid), then it necessitates ghusl (ritual bath). It is recognized by its smell, which resembles the smell of wet dough or egg whites, or by the pleasure felt upon its discharge followed by languor, or by its gushing forth. However, if it is not maniyy, then it is madhiy (pre-seminal fluid), which is impure and necessitates washing whatever it touches of the body or clothing. It nullifies wudu' (ablution) but does not necessitate ghusl. It is advised to avoid thinking about sexual images or anything that arouses lust.