# position_annotation takes a Data Frame (df) and returns a ggplot object.
# 
# This plots position tiles for the (up to) three ligands as well as drug
position_annotation=function(plot_df, bg="transparent"){
  x_ats = 12 
  x_tangle = 90 
  x_tts = 20 
  y_tts = 23
  xtt_col    = "black"
  ytt_col    = "black"
  leg_dir = "horizontal" 
  leg_ts = 15 
  leg_tts = 16
  leg_pos = "none" 
  
  #plot_df = generate_distance_colour_map(plot_df, debug=TRUE)
  
  ggplot(plot_df, 
         aes(x=factor(position), # THIS STUPID FUCKING FACTOR THING
         )
  ) +
    geom_tile(aes(y=0, fill= bg_all, colour = bg_all)
    ) +
    geom_tile(aes(y=1, fill= col_bg1, colour = col_bg1)
    ) +
    geom_tile(aes(y=2, fill= col_bg2, colour = col_bg2)
    ) +
    geom_tile(aes(y=3, fill= col_bg3, colour = col_bg3)
    ) +
    
    scale_x_discrete("Position", labels=factor(plot_df$position)) +
    scale_color_manual(values = c(
      "brown"="brown",
      "purple"="purple",
      "transparent"="transparent",
      "blue"="blue", "cyan"="cyan",
      "cornflowerblue"="cornflowerblue"
    ),
    expand=c(0,0)
    ) +
    scale_fill_manual(values = c(
      "brown"="brown",
      "purple"="purple",
      "transparent"="transparent",
      "blue"="blue",
      "cyan"="cyan",
      "cornflowerblue"="cornflowerblue"
    ),
    expand=c(0,0)
    ) +
    #scale_x_continuous(expand=c(0,0)) +
    #scale_y_continuous(expand=c(0,0)) +
    theme_nothing() +
    
    theme(plot.background = element_rect(fill = bg, colour=NA),
          plot.margin = margin(t=0,b=0)) +
    labs(x = NULL, y = NULL)
}