Fixed "legend" function, to skip components that do not have a valid key definition

src/Winston.jl

@@ -230,6 +230,38 @@ function data_to_device{T<:Real}(ctx::PlotContext, x::Union(T,AbstractArray{T}),
     project(ctx.geom, x, y)
 end
 
+# PlotGroup ------------------------------------------------------------------
+
+type PlotGroup <: PlotComponent
+    attr::PlotAttributes
+    components::Vector{Any}
+
+    function PlotGroup(components)
+        self = new(Dict())
+        iniattr(self)
+        self.components = components
+        self
+    end
+end
+PlotGroup(components...) = PlotGroup(components)
+
+function make_key(self::PlotGroup, bb::BoundingBox)
+    GroupPainter([make_key(pc, bb) for pc in self.components]...)
+end
+
+
+function limits(self::PlotGroup, window::BoundingBox)
+    lim = BoundingBox()
+    for comp in self.components
+        lim += limits(comp, window)
+    end
+    lim
+end
+
+function make(self::PlotGroup, context::PlotContext)
+    GroupPainter([make(pc, context) for pc in self.components]...)
+end
+
 # Legend ----------------------------------------------------------------------
 
 type Legend <: PlotComponent

src/plot.jl

@@ -597,11 +597,22 @@ function legend(p::FramedPlot, lab::AbstractVector, args...; kvs...)
     end
     # TODO: define other legend positions
     plotcomp = getcomponents(p)
-    nitems = min(length(lab), length(plotcomp))
-    for c in 1:nitems
-        setattr(plotcomp[c], label=lab[c])
+    target = Array(Integer,0)
+    c = 0
+    for s in lab
+        while c < length(plotcomp)
+            c += 1
+            if method_exists(make_key, (typeof(plotcomp[c]), BoundingBox)) &&
+              typeof(make_key(plotcomp[c], BoundingBox(0,1,0,1))) <: GroupPainter
+                setattr(plotcomp[c], label=s)
+                push!(target, c)
+                break
+            end
+        end
+    end
+    if length(target) > 0
+        add(p, Legend(position..., plotcomp[target], args...; kvs...))
     end
-    add(p, Legend(position..., plotcomp[1:nitems], args...; kvs...))
 end
 legend(lab::AbstractVector, args...; kvs...) = legend(_pwinston, lab, args...; kvs...)