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soundar
32 Posts |
 Posted - 28 Mar 2009 : 21:23:30
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Does RTScrollFrame.MaxDisplayHistory limit apply to each plot attached to an RTScrollFrame or the total number of plots?
For example, I have a 7 plots attached to a single frame, using
AddProcessVar().
I have MaxDisplayHistory set to 100,000
If MaxDisplayHistory applies to the total then I will be limited to approx 14000 per plot. If it does not, then I can have potentially 700,00 points if all plots are displayed.
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quinncurtis
1164 Posts |
Posted - 30 Mar 2009 : 09:20:30
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When used, the MaxDisplayHistory property is applied to each channel individually. The MaxDisplayHistory is not used in most scrolling modes though. It is used when you specify that the x-axis time stamp mode is NOT monotonic, i.e. NOT always increasing. This is never the case with a time-based x-axis, only with numeric-based x-axis.
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soundar
32 Posts |
Posted - 30 Mar 2009 : 13:38:16
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I am using it in a time-based scrolling graph when the user stops data acquisition and graph stops scrolling. I then need a way so user can zoom into areas of interest.Based on one of the examples for zooming, I do the following when the user clicks the Stop button:
' Change to display of all collected data
----> zoom mode on
_graphFrame.ScrollScaleModeX = ChartObj.RT_AUTOSCALE_X_MINMAX
_graphFrame.MaxDisplayHistory = 1000000 'some arbitrarily high limit, I can count how many points are there, but decided on this a temporary approach to save CPU cycles.
' Update first, to display all historical information, then disable to allow for zooming.
Me.UpdateDraw()
_graphFrame.ChartObjEnable = ChartObj.OBJECT_DISABLE
' Turn on zooming
_zoomObj.SetEnable(True)
->when the user restarts data acquisition and graphing
---->zoom mode off
' Turn off zooming
_zoomObj.SetEnable(False)
' Re-establish scroll mode
_graphFrame.ScrollScaleModeX = ChartObj.RT_FIXEDEXTENT_MOVINGSTART_AUTOSCROLL
_graphFrame.ChartObjEnable = ChartObj.OBJECT_ENABLE
' Render graph
Me.UpdateDraw()
Is what I am doing correct/necessary? Is there a better way to do it? |
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quinncurtis
1164 Posts |
Posted - 30 Mar 2009 : 14:33:38
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| We don't see anything obviously wrong. It seems to be based on our examples. |
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MaxDisplayHistory question
