I would like to fill the graph within the polygons instead out of it. 

    library(gtrellis)
    library(circlize)
 
    tiff("plot.tiff", units="in", width=11, height=8.5, res=300, compress = "lzw")

    load(system.file("extdata", "DMR.RData", package = "circlize"))
    DMR_hyper_density = circlize::genomicDensity(DMR_hyper, window.size = 1e7)
    head(DMR_hyper_density)
    
    gtrellis_layout(n_track = 4, ncol = 4, byrow = FALSE,
        track_axis = c(FALSE, TRUE, TRUE, FALSE), 
        track_height = unit.c(2*grobHeight(textGrob("chr1")), 
                              unit(1, "null"), 
                              unit(0.5, "null"), 
                              unit(3, "mm")), 
        track_ylim = c(0, 1, 0.013, 0, 0, 0.013, 0, 1),
        track_ylab = c("", "log10(inter_dist)", "density", ""))
    # track for genomic density
    add_lines_track(DMR_hyper_density, DMR_hyper_density[[4]], area = TRUE, 
      gp = gpar(fill = "pink", bg="pink"))
    add_lines_track(DMR_hyper_density, DMR_hyper_density[[4]], area = TRUE, 
      gp = gpar(fill = "pink"))

    dev.off()

Please not that the track containing the graph is in a reverse scale (It starts from the track top - from 0.013 to 0). I tried to use `bg` with `fill` in the `gp` in one track trying to achieve the desired effect without success. 

Some idea how to fill within the line with pink in a reverse scale like that?