[rrd-developers] Re: placement of y-axis gridlines

Tobias Oetiker oetiker at ee.ethz.ch
Mon Apr 15 23:30:19 MEST 2002

Today Peter Speck wrote:

> Hi Tobi et.al.,
> Here's the patch for evenly-spaced y-axis gridlines.
> I had to split horizontal_grid() into calc_horizontal_grid and
> draw_horizontal_grid as the calculated info is needed in the adjustment
> code. My previous patch had the problem that it adjusted the y-axis too
> late, e.g. after the data lines was drawn.
> The result of the calc is stored in struct ygrid_scale_t which
> image_desc_t has as a member.
> --no-gridfit is implemented.
> The round-to-integer coordinates for png is moved to the libart code in
> rrd_gfx. The 'close path' code is cleaned up so the node list is left
> unchanged if you want to save the same graph in multiple formats in one
> run. The rounding is done on the scaled coordinates (zoom).
> I have made a simple version for logarithmic y scales as such a scale
> might have 5 gridlines with 4 difference spacings. This version only
> uses y = 10^x values for modifying the scale.
> My old patch often reduced the scale. That bug is fixed, and I have
> added alignment of first gridline if im->minval happended to place that
> on non-integer y pixel pos.
> http://www.vitality.dk/rrdtool/patches/2002-04-15-gridfit.diff


thanks for the patch, it is in. Please also send an update for the
doc/rrd_...src files



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