Gerund with a change of subject

Question

The question is: “_____ los formularios el bolígrafo se quedó sin tinta.”

I chose “Mientras yo llenaba” since the translation was “While I was filling out the forms, the pen ran out of ink.”

Kwizbot says that “rellenando” is also correct, and I’m not sure why. The sentence “Rellenando los formularios el bolígrafo se quedó sin tinta” sounds as though the pen was doing the filling out—there’s no other subject expressed.

Accepted Answer

Hola Diane
In Spanish, this construction admits two different subjects, like in that sentence you mentioned. If one of the subjects is inanimate (not referring to a person) then there is no ambiguity. The problem may come when we have two animate subjects; in that case we may have to clarify who the subject of the gerund form is. For example:

Entrando en la cafetería mi marido se tropezó. 
When entering the cafe (who???) my husband tripped over something.

Here the listener may wonder who was going in the cafe, as it could be also a plural subject too: we

Entrando nosotros en la cafetería, mi marido se tropezó.
Entrando mi marido en la cafetería, mi marido se tropezó.

So it may need a bit of clarification in this case, but it is still grammatically correct in Spanish.
I hope it clarified it.
Saludos