"Send to Data Explorer" button shows long list of data

[DrPaulSharp]

When pressing the "Send to Data Explorer" button on a 1D slicer plot for a brand new slicer, a single entry is added to the Data Explorer. However, when the slicer parameters are modified and the button is pressed again, additional entries are added to the Data Explorer. There are three entries after the first modification, five entries after the second modification and so on.

There are two causes of this:

1. As identified by @krzywon in Restricts custom plot button to send to data explorer #3828 for residual plots, two identical objects are sent to the data explorer. This occurs when a plot is replaced rather than created, and results from a call to the replacePlot routine in slicerUtils._update_existing_plot(), aklongside emitting a signal that ultimately calls replacePlot a second time.

2. In Ess gui plotting issues #1371, @rozyczko changed two lines in Plotter.plot() from self.data = data to self.data.append(data). Can you confirm why this changed was made please? Depending on the reasoning, we could either ensure only one dataset per slicer is stored in the list, or change the behaviour of the "Send to Data Explorer" button to only take selected datasets from the list.

Once I am clear on the need for storing multiple datasets for each slicer as it is modified, I will work on a fix.

[butlerpd]

@DrPaulSharp. This looks like a 6.2 bug. Is it? Should this be a a sub issue of #3955?

[DrPaulSharp]

@butlerpd Yes, this is a bug in a 6.2 feature. I've solved it a bit quicker than expected, so we may be able to includes the PRs #4006 and #4014 into the release. I've mentioned this to @jellybean2004, so he will decide.

[jellybean2004]

@butlerpd @DrPaulSharp, since we are already past the beta testing stage, I'm hesitant to put this in now unless there is a strong argument to include it.

Also, I found more issues with the button that need to be discussed tomorrow.