Cursor bug in XY Graph in LV 2014 and LV 2017

[Herbert]

If you have several cursors in an XY Graph and zoom in considerably, you can no longer grab and move the cursors. If you try anyway, LV sometimes displaces a far away cursors with no obvious reason.

Context: In laser spectroscopy, we determine the tuning of a laser diode using a so called etalon that produces a fringe pattern that generally chirps. In the sometimes noisy data, max and min of these fringes have to be located to finally obtain the tuning curve. I have develloped an algorithm that works pretty well, but I want the user to be able to inspect and maybe correct the results of the algorithm. To do this, I display the raw data, the range used, the location of the fringe maxes and mins and postion cursors at the exact location of the extrema. As we now have lasers with wide tuning range and strong chirping, the user must zoom in to make adjustments to the cursors at the end. However, when "too much" zooming is done, it is no longer possible to select any cursor. I noticed that this also happens in a graph with only two cursors. Further I found out that this bug exists both in LabVIEW 2014 and 2017 for Windows, the cursor tool however works correctly with LabVIEW for Macintosh 2016.

The image below shows the graph zoomed out with the cursor tool working.

The next image shows the zoomed graph where a cross is displayed instead of the cursor selection tool.

The attached vi has the graph and by setting the number of cursors to 122, you can observe the above behaviour. Setting it to 1, cursor selection is possible also with extreme zoom.

Herbert