In logarithmic plots it is not easy to spot which event are longer than
60 seconds. A thin grey line help with this.
Also: fixed the marker lines (zoom area) which broke when y-ranges were
introduced. The lines were not drawn correctly, when the y-axis offset
was greater than 0.
Gnuplot supports differen coordinate systems. 'graph' is relative to the
area within the axes, 0,0 is bottom left and 1,1 is top right. And
'first' is based on the values of the x1 axis.
By using "graph 0.25,0" we say that the starting point is 25% of the
x-axis and 0% of the y-axis without having to compute the exact values.
Andreas Huber
a4d04ebece