c <- circleGrob(r=.25, gp=gpar(col=NA, fill="white"))
r <- rectGrob(x=c(1, 1, 3, 3)/4, y=c(1, 3, 3, 1)/4,
              width=.3, height=.3, 
              gp=gpar(col=NA, fill="grey"))
p <- pattern(gTree(children=gList(r, c)),
             x=.5, y=.5, 
             width=unit(2, "cm"), height=unit(2, "cm"))
grid.rect(name="r3")
grid.patternFill("r3", p)


library(ggplot2)
cxc <- ggplot(mtcars, aes(x = factor(cyl))) +
       geom_bar(width = 1, colour = "black") +
       coord_polar(theta = "y")
gg <- ggplotGrob(cxc)
p <- pattern(gg, x=.5, y=.5, 
             width=unit(4, "cm"), height=unit(4, "cm"))
grid.rect(name="r4")
grid.patternFill("r4", p)


pdf(NULL, width=12, height=3)
# grid.newpage()
pushViewport(viewport(x=1/4, width=.4, height=.8))
c <- circleGrob(r=.25, gp=gpar(col=NA, fill="white"))
r <- rectGrob(x=c(1, 1, 3, 3)/4, y=c(1, 3, 3, 1)/4,
              width=.3, height=.3, 
              gp=gpar(col=NA, fill="grey"))
p <- pattern(gTree(children=gList(r, c)),
             x=.5, y=.5, 
             width=unit(2, "cm"), height=unit(2, "cm"))
grid.rect(name="r3")
grid.patternFill("r3", p)
popViewport()
pushViewport(viewport(x=3/4, width=.4, height=.8))
library(ggplot2)
cxc <- ggplot(mtcars, aes(x = factor(cyl))) +
       geom_bar(width = 1, colour = "black") +
       coord_polar(theta = "y")
gg <- ggplotGrob(cxc)
p <- pattern(gg, x=.5, y=.5, 
             width=unit(4, "cm"), height=unit(4, "cm"))
grid.rect(name="r4")
grid.patternFill("r4", p)
popViewport()
grid.export("Figures/export-patternfill2.svg")
dev.off()
system("chromium-browser --headless --screenshot=Figures/export-patternfill2.png --window-size=880x220 Figures/export-patternfill2.svg")
system("cp Figures/export-patternfill2.png Web/export-patternfill2.png")