add contour_labels attribute and minor GR contour fixes

src/arg_desc.jl

@@ -43,6 +43,7 @@ const _arg_desc = KW(
 :normalize         	=> "Bool or Symbol. Histogram normalization mode. Possible values are: false/:none (no normalization, default), true/:pdf (normalize to a discrete Probability Density Function, where the total area of the bins is 1), :probability (bin heights sum to 1) and :density (the area of each bin, rather than the height, is equal to the counts - useful for uneven bin sizes).",
 :weights           	=> "AbstractVector. Used in histogram types for weighted counts.",
 :contours          	=> "Bool. Add contours to the side-grids of 3D plots?  Used in surface/wireframe.",
+:contour_labels     => "Bool. Show labels at the contour lines?",
 :match_dimensions  	=> "Bool. For heatmap types... should the first dimension of a matrix (rows) correspond to the first dimension of the plot (x-axis)?  The default is false, which matches the behavior of Matplotlib, Plotly, and others.  Note: when passing a function for z, the function should still map `(x,y) -> z`.",
 :subplot           	=> "Integer (subplot index) or Subplot object.  The subplot that this series belongs to.",
 :series_annotations => "AbstractVector of String or PlotText.  These are annotations which are mapped to data points/positions.",

src/args.jl

@@ -272,6 +272,7 @@ const _series_defaults = KW(
     :normalize         => false,     # do we want a normalized histogram?
     :weights           => nothing,   # optional weights for histograms (1D and 2D)
     :contours          => false,     # add contours to 3d surface and wireframe plots
+    :contour_labels    => false,
     :match_dimensions  => false,     # do rows match x (true) or y (false) for heatmap/image/spy? see issue 196
                                      # this ONLY effects whether or not the z-matrix is transposed for a heatmap display!
     :subplot           => :auto,     # which subplot(s) does this series belong to?
@@ -574,6 +575,7 @@ add_aliases(:gridstyle, :grid_style, :gridlinestyle, :grid_linestyle, :grid_ls,
 add_aliases(:framestyle, :frame_style, :frame, :axesstyle, :axes_style, :boxstyle, :box_style, :box, :borderstyle, :border_style, :border)
 add_aliases(:tick_direction, :tickdirection, :tick_dir, :tickdir, :tick_orientation, :tickorientation, :tick_or, :tickor)
 add_aliases(:camera, :cam, :viewangle, :view_angle)
+add_aliases(:contour_labels, :contourlabels, :clabels, :clabs)
 
 # add all pluralized forms to the _keyAliases dict
 for arg in keys(_series_defaults)

src/backends/gr.jl

@@ -1055,24 +1055,28 @@ function gr_display(sp::Subplot{GRBackend}, w, h, viewport_canvas)
         elseif st == :contour
             zmin, zmax = clims
             GR.setspace(zmin, zmax, 0, 90)
-            if typeof(series[:levels]) <: Array
+            if typeof(series[:levels]) <: AbstractArray
                 h = series[:levels]
             else
-                h = linspace(zmin, zmax, series[:levels])
+                h = series[:levels] > 1 ? linspace(zmin, zmax, series[:levels]) : [(zmin + zmax) / 2]
             end
             if series[:fillrange] != nothing
                 GR.surface(x, y, z, GR.OPTION_CELL_ARRAY)
             else
                 GR.setlinetype(gr_linetype[series[:linestyle]])
                 GR.setlinewidth(max(0, series[:linewidth] / (sum(gr_plot_size) * 0.001)))
-                GR.contour(x, y, h, z, 1000)
+                if plot_color(series[:linecolor]) == plot_color(:black)
+                    GR.contour(x, y, h, z, 0 + (series[:contour_labels] == true ? 1 : 0))
+                else
+                    GR.contour(x, y, h, z, 1000 + (series[:contour_labels] == true ? 1 : 0))
+                end
             end
 
             # create the colorbar of contour levels
             if cmap
                 gr_set_line(1, :solid, yaxis[:foreground_color_axis])
                 gr_set_viewport_cmap(sp)
-                l = round.(Int32, 1000 + (h - ignorenan_minimum(h)) / (ignorenan_maximum(h) - ignorenan_minimum(h)) * 255)
+                l = (length(h) > 1) ? round.(Int32, 1000 + (h - ignorenan_minimum(h)) / (ignorenan_maximum(h) - ignorenan_minimum(h)) * 255) : 1000
                 GR.setwindow(xmin, xmax, zmin, zmax)
                 GR.cellarray(xmin, xmax, zmax, zmin, 1, length(l), l)
                 ztick = 0.5 * GR.tick(zmin, zmax)