New spy implementation

src/recipes.jl

@@ -945,23 +945,21 @@ end
 @recipe function f(::Type{Val{:spy}}, x,y,z)
     yflip := true
     aspect_ratio := 1
+    
     rs, cs, zs = findnz(z.surf)
-    xlim := ignorenan_extrema(cs)
-    ylim := ignorenan_extrema(rs)
-    if plotattributes[:markershape] == :none
-        markershape := :circle
+    newz = fill(NaN, size(z)...)
+
+    for i in eachindex(zs)
+        newz[rs[i],cs[i]] = zs[i]
     end
-    if plotattributes[:markersize] == default(:markersize)
-        markersize := 1
-    end
-    markerstrokewidth := 0
-    marker_z := zs
-    label := ""
-    x := cs
-    y := rs
-    z := nothing
-    seriestype := :scatter
+
+    seriestype := :heatmap
     grid --> false
+    framestyle --> :box
+
+    x := x
+    y := y
+    z := Surface(newz)
     ()
 end