If TRUE, the GtkProgress is in activity mode, meaning that it signals something is happening, but not how much of the activity is finished. This is used when you're doing something but don't know how long it will take.
EGIA bada, GtkProgress jarduera-moduan egongo da; horrek esan nahi du zerbait gertatzen ari dela adieraziko duela, baina ez jarduera zenbateraino dagoen bukatuta. Hori erabiltzen da zerbait egiten ari zarenean eta horretan zenbat denbora emango duzun ez dakizunean.