A different offset for x and y

[larmarange]

Let start with this example provided with the package:

data(Titanic)
titanic <- as.data.frame(Titanic)
titanic$Survived <- factor(titanic$Survived, levels=c("Yes", "No"))


ggplot(data=titanic) +
  geom_mosaic(aes(weight=Freq, x=product(Class), fill=Survived))

I would like to have a 0 offset for Y axis while keeping a positive offset for X axis.

Right now, only one value can be given.