[Octave-bug-tracker] [bug #57271] problems with legend() when labels are empty or spaces only

[Rik]

URL:
  <https://savannah.gnu.org/bugs/?57271>

                 Summary: problems with legend() when labels are empty or
spaces only
                 Project: GNU Octave
            Submitted by: rik5
            Submitted on: Tue 19 Nov 2019 10:04:40 AM PST
                Category: Plotting
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Matlab Compatibility
                  Status: Confirmed
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

Problem #1: empty label replaced by "data1"

Code to reproduce:


x = 1:10;
plot (x,x, x, x+2)
legend ('', 'x + 2')
hl = legend


The first call to legend correctly places blank text next to the legend key
for the first line.  However, when legend is called a second time the blank
label is replaced by the text 'data1'.

My guess is that the legend code which checks whether DisplayName is empty
should also check whether it is a string or numeric.  If the default
DisplayName was '[]' then it would be possible to distinguish between labels
which have never been set and '""' labels which are empty strings and were
intentionally set by the programmer.

Problem #2: Using spaces as labels causes legend keys to be misaligned.

Code to reproduce.


x = 1:10;
plot (x,x, x, x+2)
legend (' ', 'x + 2')


The first line is offset to the right with respect to the second one.  This
effect is only visible on screen.  Printing the figure results in the correct
placement.





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