luci-statistics: don't plot data points where there are no data.

Converting NaN to zero for the sake of the cumulative stack in non-overlay
mode is all very well. But we shouldn't then use that for displaying the
graph. Make another variable %s_plot which *preserves* NaN from the input
data, and then we don't get bogus data points drawn. Especially at the end
of the graph this was problematic.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --git a/applications/luci-statistics/luasrc/statistics/rrdtool.lua b/applications/luci-statistics/luasrc/statistics/rrdtool.lua
index 844c157..45deb85 100644 (file)
--- a/applications/luci-statistics/luasrc/statistics/rrdtool.lua
+++ b/applications/luci-statistics/luasrc/statistics/rrdtool.lua
@@ -180,20 +180,23 @@ function Graph._generic( self, opts, plugin, plugin_instance, dtype, index )
 
                -- is first source in stack or overlay source: source_stk = source_nnl
                if not prev or source.overlay then
-                       -- create cdef statement
+                       -- create cdef statement for cumulative stack (no NaNs) and also
+                        -- for display (preserving NaN where no points should be displayed)
                        _tif( _args, "CDEF:%s_stk=%s_nnl", source.sname, source.sname )
+                       _tif( _args, "CDEF:%s_plot=%s_avg", source.sname, source.sname )
 
                -- is subsequent source without overlay: source_stk = source_nnl + previous_stk
                else
                        -- create cdef statement
                        _tif( _args, "CDEF:%s_stk=%s_nnl,%s_stk,+", source.sname, source.sname, prev )
+                       _tif( _args, "CDEF:%s_plot=%s_avg,%s_stk,+", source.sname, source.sname, prev )
                end
 
                -- create multiply by minus one cdef if flip is enabled
                if source.flip then
 
                        -- create cdef statement: source_stk = source_stk * -1
-                       _tif( _args, "CDEF:%s_neg=%s_stk,-1,*", source.sname, source.sname )
+                       _tif( _args, "CDEF:%s_neg=%s_plot,-1,*", source.sname, source.sname )
 
                        -- push to negative stack if overlay is disabled
                        if not source.overlay then
@@ -253,11 +256,11 @@ function Graph._generic( self, opts, plugin, plugin_instance, dtype, index )
                -- derive area background color from line color
                area_color = self.colors:to_string( self.colors:faded( area_color ) )
 
-               -- choose source_stk or source_neg variable depending on flip state
+               -- choose source_plot or source_neg variable depending on flip state
                if source.flip then
                        var = "neg"
                else
-                       var = "stk"
+                       var = "plot"
                end
 
                -- create legend