embed_fonts() causes broken wireframe when drape is translucent

[linyangchen]

When making translucent wireframe plots using the lattice package, embed_fonts() causes the wires to be rendered as dashed lines when they should be solid lines.

# R version 3.1.1
# x86_64-apple-darwin13.1.0
# OS X 10.9.4

require(extrafont)
loadfonts(device = 'pdf')

require(lattice)

# translucent colours for drape
col.regions <- paste(grey(seq(0, 1, length.out = 100)), '99', sep = '')

pdf('volcano.pdf')

wireframe(
    volcano,
    lty = 1,
    drape = T, col.regions = col.regions
)

dev.off()
embed_fonts('volcano.pdf')

This happens whatever the value of the family argument in pdf(), and only when translucent colours are used.