GRID 刻度网格

您可以通过设置达到以下效果：

需要注意刻度会被绘制在highlights上，但是会在其它数据之下。

show_grid  = yes

<ticks>

 grid_start     = 0.5r
 grid_end       = 0.975r
 grid_color     = black
 grid_thickness = 2p
 ...
 <tick>
  spacing = 1u
  ...
  grid           = yes
  grid_color     = grey
  grid_thickness = 1
  grid_start     = 0.55r
  grid_end       = 0.95r
 </tick>
 <tick>
  spacing = 5u
  ...
  grid           = yes
  grid_color     = dgrey
  grid_thickness = 2
  grid_start     = 0.6r
  grid_end       = 0.925r
 </tick>
 <tick>
  spacing = 10u
  ...
  grid           = yes
  grid_color     = black
  grid_thickness = 2
 </tick>
</ticks>