Calculate margin of drawshape!() as relative quantity

Author: wsshin

src/util/plotting.jl

@@ -1,5 +1,5 @@
-const ϵmach = eps()  # machine epsilon
-const N_PLOT_SAMPLING_POINTS = 100
+const ϵrel = Base.rtoldefault(Float64)  # machine epsilon
+const N_PLOT_SAMPLING_POINTS = 101
 
 # Define drawshape() and drawshape!() functions.
 @recipe(DrawShape) do scene
@@ -27,9 +27,10 @@ end
 # Define the new signature of contour!() used in drawshape!() for 2D shapes.
 function Makie.convert_arguments(P::SurfaceLike, shp::Shape{2})
     lower, upper = bounds(shp)
+    ∆ = upper - lower
 
-    xs = range(lower[1]-ϵmach, upper[1]+ϵmach, length=N_PLOT_SAMPLING_POINTS)
-    ys = range(lower[2]-ϵmach, upper[2]+ϵmach, length=N_PLOT_SAMPLING_POINTS)
+    nw = 1; xs = range(lower[nw] - ϵrel*∆[nw], upper[nw] + ϵrel*∆[nw], length=N_PLOT_SAMPLING_POINTS)
+    nw = 2; ys = range(lower[nw] - ϵrel*∆[nw], upper[nw] + ϵrel*∆[nw], length=N_PLOT_SAMPLING_POINTS)
 
     lvs = [level(@SVector([x,y]), shp) for x = xs, y = ys]
 
@@ -51,9 +52,10 @@ function Makie.convert_arguments(P::SurfaceLike, shp::Shape{3},
     ŵ = SVector(ntuple(identity,Val(3))) .== nw
 
     lower, upper = bounds(shp)
+    ∆ = upper - lower
 
-    us = range(lower[nu]-ϵmach, upper[nu]+ϵmach, length=N_PLOT_SAMPLING_POINTS)
-    vs = range(lower[nv]-ϵmach, upper[nv]+ϵmach, length=N_PLOT_SAMPLING_POINTS)
+    us = range(lower[nu] - ϵrel*∆[nu], upper[nu] + ϵrel*∆[nu], length=N_PLOT_SAMPLING_POINTS)
+    vs = range(lower[nv] - ϵrel*∆[nv], upper[nv] + ϵrel*∆[nv], length=N_PLOT_SAMPLING_POINTS)
 
     lvs = [level(u*û + v*v̂ + cept*ŵ, shp) for u = us, v = vs]