Bug? Tab control breaks graph autoscale (+workaround)

[Anthony_de_Vries]

I had this really annoying problem where two of my graphs did autoscale and the other two didn't... Although all the code and graph properties were exactly the same.

I finally figured it out...  The graphs are in a tab control. And only the graphs that are on top get autoscaling.  Labview 'forgets' to autoscale the other graphs when you show those other tabs. Even when I use a property node, I can't force the graphs to autoscale, unless they are on the showing tab.

Feels like a bug to me.... I can understand that graphs aren't updated/autoscaled when they're not shown for performance reasons... but I think the axis should then be updated/autoscaled as soon as the corresponding tab is shown.  And it certainly would be nice if the axis does autoscale when I explicitely ask for it using the property node...

Now that I understood the problem, I could also make a work-around.   I made a 'value changed' event for the tab control, and put the property node autoscale code in it.  That way, I ask for an autoscale right after showing the new tab page.  (See attached vi for example of the problem and work-around.)

The workaround works fine... but I think that this should be default built-in behaviour for graphs in tabs that have the autoscale enabled.

[Jarrod_S.]

Hi Anthony,

This is a known issue that was partially fixed in LabVIEW 8, which you appear to be using. By partially, I mean that the behavior only persists when you update the value of your graph using a property node (either Value or Value Signaling). If you update the value using a direct wire connection to the graph terminal, or using a local variable, then the problem goes away. I would recommend using either of these methods, because they will fix your issue. Also, in general a direct wire connection or a local variable will greatly improve LabVIEW's efficiency in terms of updating the front panel. The only situation where this fails is if you need to update your graphs from inside a subVI using control references.

Because that last note is a very real situation, we will notify R&D of this matter so that they can investigate this further. Thanks for bringing this to our attention.

[Lee_Jay]

I'm wondering if I'm having a similar problem.  I have a waveform chart with 6 y-axes on it.  They are in a tab control and the values are getting updated with a property node with control references.  Y-axes 2 through 6 autoscale properly.  Y-axis 1 will never go below 350 as the top unit but it will autoscale up from there.  I am using 8.0.1.  Is this the same issue?

Lee Jay