if the graph goes 'down' minval must be hanged instead

[rrdtool.git] / src / rrd_graph.c

diff --git a/src/rrd_graph.c b/src/rrd_graph.c
index e16e5d8..7e607bb 100644 (file)
--- a/src/rrd_graph.c
+++ b/src/rrd_graph.c
@@ -497,7 +497,10 @@ apply_gridfit(image_desc_t *im)
     double new_range = factor * (im->maxval - im->minval);
     double gridstep = im->ygrid_scale.gridstep;
     double minor_y, minor_y_px, minor_y_px_frac;
-    im->maxval = im->minval + new_range;
+    if (im->maxval > 0.0)
+      im->maxval = im->minval + new_range;
+    else
+      im->minval = im->maxval - new_range;
     ytr(im,DNAN); /* reset precalc */
     /* make sure first minor gridline is on integer pixel y coord */
     minor_y = gridstep * floor(im->minval / gridstep);