Plot size depending on label size, circlize R package

Question

How can I automatically increase the generated picture when increasing the label size with the cex parameter?

With the attached code the labels are not shown completly.

install.packages("circlize")
library(circlize)
pdf("margin_test.pdf")
par(mar = rep(0,4), cex = 2)    
circos.initializeWithIdeogram(plotType = c("axis", "ideogram", "labels"))
circos.clear()
dev.off()