[rrd-developers] Re: proposed TICK bug fix for negative values

[Tobias Oetiker]

Hi Dave,

try the following patch

Index: rrd_graph.c
===================================================================
--- rrd_graph.c (revision 746)
+++ rrd_graph.c (working copy)
@@ -2468,13 +2468,28 @@
           if (!isnan(im->gdes[i].p_data[ii]) &&
               im->gdes[i].p_data[ii] > 0.0)
             {
+             double ya = ytr(im,0);
+             double yb = ytr(im,0) - (im -> gdes[i].yrule * im -> ysize);
+
+             if (ya > im->yorigin)
+                 ya = im->yorigin;
+             if (ya < im->yorigin - im->ysize)
+                 ya = im->yorigin - im->ysize;
+
+             if (yb > im->yorigin)
+                 yb = im->yorigin;
+             if (yb < im->yorigin - im->ysize)
+                 yb = im->yorigin - im->ysize;
+
               /* generate a tick */
-              gfx_new_line(im->canvas, im -> xorigin + ii,
-                           im -> yorigin - (im -> gdes[i].yrule * im -> ysize),
-                           im -> xorigin + ii,
-                           im -> yorigin,
-                           1.0,
-                           im -> gdes[i].col );
+             if (ya != yb)
+                     gfx_new_line(im->canvas, im -> xorigin + ii,
+                                  ya,
+                                  im -> xorigin + ii,
+                                  yb,
+                                  1.0,
+                                  im -> gdes[i].col );
+
             }
         }
       break;


cheers
tobi
Jan 24 Dave Plonka wrote:

> Hi folks,
>
> Please note the 5% TICK marks along the bottom of the attached sample
> graph, which shows Holt-Winters threshold failures for outbound and
> inbound traffic (with confidence bands) simumtaneously...
> (I did this graph with RRGrapher.)
>
> It surprised me that TICKs are drawn atop the lower boundary of the
> graph region instead of on the x-axis (zero value on y-axis).
>
> Also, if you graph a negative tick value, the ticks are actually
> plotted outside the graph region (overwriting the legends, etc.).  It
> seems to me to be a bug that negative TICK values get plotted outside
> the graph region.
>
> I propose that it would be better, and more useful, if the TICKs were
> plotted as a percentage between the x-axis (zero on y-axis) and the top
> of the graph for positive values and as a percentage between the x-axis
> (zero on y-axis) and the top of the graph for negative values.  I don't
> think this will break existing graphs that only plot positive ticks
> which is presumably the typical case.  Since the negative values
> incorrectly plot outside the graph region, I'd like to fix that.
>
> Does anyone disagree that such a change would be a good way to fix this
> bug, and simultanously add a bit of functionality for these sort of
> outbound/inbound graphs?
>
> BTW, I haven't written a patch... I suspect it might be non-trivial for
> someone not familiar with that part of the code.  If someone is willing
> to write it please let us know.
>
> Dave
>
>

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