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

[Stevens, Ian]

In case someone needs something like this in future, I did this by:
 
- extending ScatterPlot and overriding makeBackground() to draw a
crosshair in the center.
- making the min/max values for the chart's value axes to be equal
offsets from the center point such that the second point is still inside
the chart (eg. xValueAxis.valueMin =
centerPoint-abs(otherPoint.x-centerPoint.x))
- setting the avoidBoundFrac on the value axes so that the second point
doesn't rest on the chart box boundary.
 
Ian.


________________________________

	From: reportlab-users-bounces at reportlab.com
[mailto:reportlab-users-bounces at reportlab.com] On Behalf Of Stevens, Ian
	Sent: Monday, July 07, 2008 7:40 PM
	To: Support list for users of Reportlab software
	Subject: Re: [reportlab-users] Specifying chart join axis to
intersectpointdoes not draw line below that point
	
	
	Is it possible to do this using a Grid and/or axis ticks?  (ie.
make the grid or ticks start and end at the center point)
	 
	thanks,
	Ian.


________________________________

		From: reportlab-users-bounces at reportlab.com
[mailto:reportlab-users-bounces at reportlab.com] On Behalf Of Stevens, Ian
		Sent: Friday, July 04, 2008 7:50 PM
		To: Support list for users of Reportlab software
		Subject: [reportlab-users] Specifying chart join axis to
intersect pointdoes not draw line below that point
		
		
		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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