Thanks for the D2D.
There are measurements given in dental textbooks about the “ideal” amount of gums to be shown when smiling, but I honestly think beauty is in the eyes of the beholder. So I may think that the patient is too “gummy”, but the patient may be very satisfied with his or her smile.
It all depends on what the patient wants to achieve. If both the patient and dentist agree that the smile is too gummy, I usually use an instrument to show the patient where I would trim to the gums to. And the patient has to agree that that length is good for him/her.
Sometimes I even “fake” the future length of the teeth by putting tooth coloured material on the gums to allow the patient to visualise how he or she would look with longer teeth and less gums showing.