[reportlab-users] Specifying chart join axis to intersect point does not draw line below that point

[Stevens, Ian]

I need a chart with 2 points on it, with one of the points centered on
the chart intersected by two lines, one parallel to each axis.  The
result ishould be like a crosshair centered in the chart with one point
at the center of the crosshair. I've accomplished most of what I need
with ScatterPlot:
 
    centerPointX = ...
    centerPointY = ...
    plot = ScatterPlot()
    [...]
    plot.xValueAxis.strokeColor = plot.yValueAxis.strokeColor =
colors.white
    plot.xValueAxis.joinAxisMode = plot.yValueAxis.joinAxisMode =
'value'
    plot.xValueAxis.joinAxisPos = centerPointY
    plot.yValueAxis.joinAxisPos = centerPointX
 
This produces a white axis centered on the point, but the lower half of
the y-axis beneath the point is missing.  How can I get the y-axis to
descend to the bottom of the chart?
 
Also, any suggestions as to how I can force the chart to center itself
around the given point?
 
thanks,
Ian.
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