How have courts interpreted rule 428(b)(4) of the Criminal Code in the context of personal firearm use enhancement?

We construed rule 428(b) in People v. Edwards (1993) 13 Cal.App.4th 75, 16 Cal.Rptr.2d 572. There, after the defendant shot his girlfriend, he pleaded guilty to assault with a firearm and admitted a personal firearm use enhancement allegation. (Id., at p. 77, 16 Cal.Rptr.2d 572.) The trial court sentenced the defendant to the upper term on the enhancement, based on the fact that he had been on probation at the time of the offense (see rule 421(b)(4)). (Id., at p. 78, 16 Cal.Rptr.2d 572.) We began by noting that "in respect to sentencing a defendant for the crime of which he was convicted, ... rule 421[ ] subdivides aggravating circumstances into two categories: facts relating to the crime and facts relating to the defendant. Aggravating circumstances arising from facts relating to the crime are found in rule 421(a) and aggravating facts relating to the defendant are found in rule 421(b). [p] We believe it is proper to analyze the meaning of 'circumstances in aggravation that relate directly to the fact giving rise to the enhancement' by applying this distinction that has been made in ... rule 421 between facts relating to the crime and those relating to the defendant." (Id., at pp. 78-79, 16 Cal.Rptr.2d 572, fn. omitted.) We concluded that an aggravating factor used to impose the upper term on an enhancement "must relate to the commission of the act constituting the alleged enhancement, not to the defendant personally." (Id., at p. 79, 16 Cal.Rptr.2d 572.)