[gnumeric] xslx: don't set explicit cross-axis-id unless necessary.

[Morten Welinder <mortenw src gnome org>]

commit aa18f4f97400d2495fc71d722fbb45ad396d31ba
Author: Morten Welinder <terra gnome org>
Date:   Tue Jan 20 18:23:12 2015 -0500

    xslx: don't set explicit cross-axis-id unless necessary.
    
    This helps round-tripping.

 plugins/excel/xlsx-read-drawing.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)
---
diff --git a/plugins/excel/xlsx-read-drawing.c b/plugins/excel/xlsx-read-drawing.c
index dcd1f58..8f6498d 100644
--- a/plugins/excel/xlsx-read-drawing.c
+++ b/plugins/excel/xlsx-read-drawing.c
@@ -2148,6 +2148,7 @@ cb_axis_set_position (GObject *axis, XLSXAxisInfo *info,
        GogObject *obj = NULL;
        if (info->cross_id) {
                XLSXAxisInfo *cross_info = g_hash_table_lookup (state->axis.by_id, info->cross_id);
+
                g_return_if_fail (cross_info != NULL);
                obj = GOG_OBJECT (cross_info->axis);
                if (go_finite (cross_info->cross_value)) {
@@ -2158,7 +2159,14 @@ cb_axis_set_position (GObject *axis, XLSXAxisInfo *info,
                }
                if (gog_axis_is_inverted (GOG_AXIS (axis)))
                        cross_info->cross = 2 - cross_info->cross; /* KLUDGE */
-               g_object_set (obj, "pos", cross_info->cross, "cross-axis-id", gog_object_get_id (GOG_OBJECT 
(axis)), NULL);
+               g_object_set (obj, "pos", cross_info->cross, NULL);
+
+               /*
+                * Set the cross-axis-id if it makes a difference, i.e., if it is different
+                * from the implied value.  This helps roundtripping.
+                */
+               if ((GogAxis*)axis != gog_axis_base_get_crossed_axis (GOG_AXIS_BASE (obj)))
+                       g_object_set (obj, "cross-axis-id", gog_object_get_id (GOG_OBJECT (axis)), NULL);
        }
        if (info->deleted) {
                GSList *l = gog_chart_get_axes (state->chart, gog_axis_get_atype (GOG_AXIS (axis))), *cur;