[goffice] Fix rendering of XLContourPlot.

[Jean Bréfort <jbrefort src gnome org>]

commit c47319b4f2ed15b6d1d838a256a5e6c9250ee0b2
Author: Jean Brefort <jean brefort normalesup org>
Date:   Mon Oct 23 11:36:19 2017 +0200

    Fix rendering of XLContourPlot.

 ChangeLog                         |    5 +++++
 NEWS                              |    2 +-
 plugins/plot_surface/xl-surface.c |    1 +
 3 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 0fdf402..beaa29b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2017-10-23  Jean Brefort  <jean brefort normalesup org>
 
+       * plugins/plot_surface/xl-surface.c (xl_contour_plot_build_matrix): fix
+       rendering.
+
+2017-10-23  Jean Brefort  <jean brefort normalesup org>
+
        * plugins/plot_surface/xl-surface.c (xl_xyz_series_init): don't show these
        series in the legend. [#788861]
 
diff --git a/NEWS b/NEWS
index ca53f98..a9d5dd6 100644
--- a/NEWS
+++ b/NEWS
@@ -3,7 +3,7 @@ goffice 0.10.36:
 Jean:
        * Fix engineering format. [#785669]
        * Fix crash in 3D plots when X or Y values are missing. [#788437]
-       * Don't use invalid styles in legned from contour or surface plots imported
+       * Don't use invalid styles in legend from contour or surface plots imported
        from Excel. [#788861]
 
 --------------------------------------------------------------------------
diff --git a/plugins/plot_surface/xl-surface.c b/plugins/plot_surface/xl-surface.c
index bf7745e..8d1d6c5 100644
--- a/plugins/plot_surface/xl-surface.c
+++ b/plugins/plot_surface/xl-surface.c
@@ -276,6 +276,7 @@ xl_contour_plot_build_matrix (GogXYZPlot *plot, gboolean *cardinality_changed)
                series->num_elements = has_scale? 1: max;
                *cardinality_changed = TRUE;
        }
+       GOG_CONTOUR_PLOT (plot)->max_colors = max;
        gog_axis_map_free (map);
        return data;
 }