Re: print -dashed fails with gnuplot backend

[Ben Abbott]

On Nov 10, 2010, at 7:19 PM, Jarno Rajahalme wrote:

> I used to get the different dashed lines with gnuplot, but with the current 
> tip I get an error instead (gnuplot 4.4.2, was the same with 4.4.0):
> 
> octave:1> plot([10 5; 2 16; 3 7], '-')
> octave:2> legend('a', 'b')
> octave:3> print test.eps -dashed -deps
> error: set: invalid handle (= -16.0668)
> error: called from:
> error:   [...]octave/scripts/plot/print.m at line 377, column 9
> octave:3> 
> 
> Playing with it, sometimes it works, but even then the dashes are all the 
> same simple ones.
> 
> Any ideas?
> 
>  Jarno

In order to consolidate the print function for all backends, Octave now handles 
the dashed lines itself. It is possible that I did not implement the "-dashed" 
option in the proper way. What I did was to *temporarily* set the linestyle 
property for all line objects to "--".

If I got that wrong, we may want to enter a bug in the tracker.

Regarding the crash, I modified your example to try to isolate the problem.

plot([10 5; 2 16; 3 7], '-')
legend('a', 'b')
h_before = findall (gcf, "-property", "linestyle", "visible", "on");
try
  print test.eps -dashed -deps
catch
  h_after = findall (gcf, "-property", "linestyle", "visible", "on");
  cmp = h_before == h_after;
  printf ("handle before = %8.4f, handle after = %8.4f, %d\n", [h_before, 
h_after, cmp]')
  tag = get (unique (cell2mat (get (h_after(!cmp), "parent"))), "tag")
end_try_catch

With this modification, I get ...

handle before = -17.2920, handle after = -17.2920, 1
handle before = -16.4276, handle after = -16.4276, 1
handle before = -15.3394, handle after = -15.3394, 1
handle before = -14.8455, handle after = -14.8455, 1
handle before = -13.6448, handle after = -13.6448, 1
handle before = -12.0651, handle after = -12.0651, 1
handle before = -10.6675, handle after = -10.6675, 1
handle before =  -9.0918, handle after =  -9.0918, 1
handle before =  -8.6763, handle after =  -8.6763, 1
handle before =  -7.1982, handle after =  -7.1982, 1
handle before =  -6.2106, handle after =  -6.2106, 1
handle before =  -5.3132, handle after =  -5.3132, 1
handle before =  -4.8541, handle after =  -4.4170, 0
handle before =  -3.4331, handle after =  -3.1299, 0
handle before =  -2.0219, handle after =  -2.0219, 1
tag = legend

it appears the handles for the line objects of the legend axes are changing 
during the print process.

I've cc'd David since he worked on that part.

A solution may be to check that the lines are not part of a legend axis before 
substituting the dashed linestyle, but I'll wait on David's thoughts before 
implementing that. Perhaps he'll have a better idea.

Ben