Add Scale.color_none to supress default color scales. Fixes #527

doc/scale_color_none.md

@@ -0,0 +1,24 @@
+---
+title: color_none
+author: Daniel C. Jones
+part: Scale
+order: 2009
+...
+
+Supress a default color scale. Some statistics impose a default color scale.
+When no color scale is desider, explicitly including `Scale.color_none` will
+supress this default.
+
+# Examples
+
+```{.julia hide="true" results="none"}
+using Gadfly
+```
+
+```julia
+xs = 1:10.
+ys = 1:10.
+zs = Float64[x^2*log(y) for x in xs, y in ys]
+plot(x=xs, y=ys, z=zs, Geom.contour, Scale.color_none)
+```
+

src/scale.jl

@@ -451,6 +451,26 @@ function apply_scale(scale::DiscreteScale, aess::Vector{Gadfly.Aesthetics},
 end
 
 
+immutable NoneColorScale <: Gadfly.ScaleElement
+end
+
+
+const color_none = NoneColorScale
+
+
+function element_aesthetics(scale::NoneColorScale)
+    [:color]
+end
+
+
+function apply_scale(scale::NoneColorScale,
+                     aess::Vector{Gadfly.Aesthetics}, datas::Gadfly.Data...)
+    for aes in aess
+        aes.color = nothing
+    end
+end
+
+
 immutable DiscreteColorScale <: Gadfly.ScaleElement
     f::Function # A function f(n) that produces a vector of n colors.