3 files changed, 15 insertions, 5 deletions

diff --git a/conf/config.php b/conf/config.php
index 99190f1..c734b09 100644
--- a/conf/config.php
+++ b/conf/config.php
@@ -45,6 +45,9 @@ $CONFIG['network_datasize'] = 'bytes';
 # png or canvas graphs
 $CONFIG['graph_type'] = 'png';
 
+# use the negative X-axis in I/O graphs
+$CONFIG['negative_io'] = false;
+
 # browser cache time for the graphs (in seconds)
 $CONFIG['cache'] = 90;
 
diff --git a/type/Default.class.php b/type/Default.class.php
index c9220fa..0250d52 100644
--- a/type/Default.class.php
+++ b/type/Default.class.php
@@ -16,7 +16,7 @@ class Type_Default {
         var $rrd_title;
         var $rrd_vertical;
         var $rrd_format;
-        var $scale;
+        var $scale = 1;
         var $width;
         var $heigth;
 
@@ -37,6 +37,7 @@ class Type_Default {
                 $this->heigth = GET('y');
                 if (empty($this->heigth)) $this->heigth = $config['heigth'];
                 $this->graph_type = $config['graph_type'];
+                $this->negative_io = $config['negative_io'];
         }
 
         function rainbow_colors() {
diff --git a/type/GenericIO.class.php b/type/GenericIO.class.php
index 0cf3e22..3425f3e 100644
--- a/type/GenericIO.class.php
+++ b/type/GenericIO.class.php
@@ -16,7 +16,7 @@ class Type_GenericIO extends Type_Default {
                 foreach ($this->tinstances as $tinstance) {
                         foreach ($this->data_sources as $ds) {
                                 $rrdgraph[] = sprintf('DEF:min_%s%s=%s:%s:MIN', crc32hex($sources[$i]), $raw, $this->parse_filename($this->files[$tinstance]), $ds);
-                                $rrdgraph[] = sprintf('DEF:avg_%s%s=%s:%s:AVERAGE', crc32hex($sources[$i]), $raw, $this->parse_filename($this->files[$tinstance]), $ds);
+                                $rrdgraph[] = sprintf('DEF:avg_%s_raw=%s:%s:AVERAGE', crc32hex($sources[$i]), $this->parse_filename($this->files[$tinstance]), $ds);
                                 $rrdgraph[] = sprintf('DEF:max_%s%s=%s:%s:MAX', crc32hex($sources[$i]), $raw, $this->parse_filename($this->files[$tinstance]), $ds);
                                 if (!$this->scale)
                                         $rrdgraph[] = sprintf('VDEF:tot_%s=avg_%1$s,TOTAL', crc32hex($sources[$i]));
@@ -30,17 +30,21 @@ class Type_GenericIO extends Type_Default {
                                         $rrdgraph[] = sprintf('CDEF:min_%s=min_%1$s_raw,%s,*', crc32hex($sources[$i]), $this->scale);
                                         $rrdgraph[] = sprintf('CDEF:avg_%s=avg_%1$s_raw,%s,*', crc32hex($sources[$i]), $this->scale);
                                         $rrdgraph[] = sprintf('CDEF:max_%s=max_%1$s_raw,%s,*', crc32hex($sources[$i]), $this->scale);
+                                        if ($i == 1)
+                                                $rrdgraph[] = sprintf('CDEF:avg_%s_neg=avg_%1$s_raw,%s%s,*', crc32hex($sources[$i]), $this->negative_io ? '-' : '', $this->scale);
                                         $rrdgraph[] = sprintf('VDEF:tot_%1$s=avg_%1$s,TOTAL', crc32hex($sources[$i]));
                                         $i++;
                                 }
                         }
                 }
 
-                $rrdgraph[] = sprintf('CDEF:overlap=avg_%s,avg_%s,LT,avg_%1$s,avg_%2$s,IF',
+                $rrdgraph[] = sprintf('CDEF:overlap=avg_%s,avg_%s_neg,LT,avg_%1$s,avg_%2$s_neg,IF',
                                                 crc32hex($sources[0]), crc32hex($sources[1]));
 
+                $i = 0;
                 foreach($sources as $source) {
-                        $rrdgraph[] = sprintf('AREA:avg_%s#%s', crc32hex($source), $this->get_faded_color($this->colors[$source]));
+                        $rrdgraph[] = sprintf('AREA:avg_%s%s#%s', crc32hex($source), $i == 1 ? '_neg' : '', $this->get_faded_color($this->colors[$source]));
+                        $i++;
                 }
 
                 $rrdgraph[] = sprintf('AREA:overlap#%s',
@@ -50,14 +54,16 @@ class Type_GenericIO extends Type_Default {
                         )
                 );
 
+                $i = 0;
                 foreach($sources as $source) {
                         $dsname = $this->ds_names[$source] != '' ? $this->ds_names[$source] : $source;
-                        $rrdgraph[] = sprintf('"LINE1:avg_%s#%s:%s"', crc32hex($source), $this->colors[$source], $this->rrd_escape($dsname));
+                        $rrdgraph[] = sprintf('"LINE1:avg_%s%s#%s:%s"', crc32hex($source), $i == 1 ? '_neg' : '', $this->colors[$source], $this->rrd_escape($dsname));
                         $rrdgraph[] = sprintf('"GPRINT:min_%s:MIN:%s Min,"', crc32hex($source), $this->rrd_format);
                         $rrdgraph[] = sprintf('"GPRINT:avg_%s:AVERAGE:%s Avg,"', crc32hex($source), $this->rrd_format);
                         $rrdgraph[] = sprintf('"GPRINT:max_%s:MAX:%s Max,"', crc32hex($source), $this->rrd_format);
                         $rrdgraph[] = sprintf('"GPRINT:avg_%s:LAST:%s Last"', crc32hex($source), $this->rrd_format);
                         $rrdgraph[] = sprintf('"GPRINT:tot_%s:%s Total\l"',crc32hex($source), $this->rrd_format);
+                        $i++;
                 }
                 
                 return $rrdgraph;