[Kst] [Bug 118726] New: Axes: expression vs fixed limits and save/restore problem

[Nicolas Brisset]

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http://bugs.kde.org/show_bug.cgi?id=118726         
           Summary: Axes: expression vs fixed limits and save/restore
                    problem
           Product: kst
           Version: unspecified
          Platform: unspecified
        OS/Version: Solaris
            Status: NEW
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: kst kde org
        ReportedBy: nicolas.brisset eurocopter com


Version:           1.2.0_devel (using KDE 3.4.0, compiled sources)
Compiler:          gcc version 3.4.3
OS:                SunOS (sun4u) release 5.8

Some zoom settings (or axis states) are not correctly saved and restored. Example:
- plot one variable (say var1 vs time) from any file
- plot dialog->Limits: set expressions to be [var1-Max]-10 to [var1-Max]
- now, scroll with arrow keys or the mouse (which is like setting fixed values in the expression fields)
- Hit "R" and look at the limit settings: the expression is gone 

Expected behavior: the expression is preserved and can be restored. 

Thinking about this in a more general way, I think the issue we have here is that we merged 'fixed values' and 'expressions', while they correspond to different approaches:
- with fixed values you want to look at a precise place, and if you come back to it later you expect to see the exact same [xmin,xmax,ymin,ymax] view
- with expressions you want to plot a logical part of your data (last n seconds, or values close to the max, etc) and if the data changes, you expect the view to change as well.

I actually remember I was confused the first time I tried to set fixed numerical values, as I thought "expressions" would only be equations :-) I don't think it is a good idea to add options in the already-quite-crowded UI, but maybe changing the text from "Expression" to "Expression or fixed values" and making sure that expressions are saved and restored would be the right way to do it.
Another approach might be to have an editable combo where we'd store values input by hand (not those set by mouse/keyboard zoom actions to avoid getting a huge list), so that it is easy to come back to them later.