Bug 408335

It appears that *only* the Lorenz example is affected, octave_examples_{2d,3d}_plots.cws, as well as Maxima's examples show their respective plots.

This is something wrong with `view` command in Octave.
I had checked the output .eps file: there is the plot inside it, but with a lot of empty space on the left of the plot (see atachment below).
Cantor show a part of result .eps (because of too big width) file and this is a left empty part.

Without `view` all works as expected.

Created attachment 120599 [details]
Strange gnuplot output

Yes, indeed, removing that line with `view` has brought the plot back to my screen. Interesting to know that the white space to the left hid behind it.

UPDATE:
1. Remove the line with `view`
2. Press 'Evaluate Worksheet' # should be OK
3. Restart the backend  # should be OK
4. Press 'Evaluate Worksheet' again # Segfault:

Thread 1 "cantor" received signal SIGSEGV, Segmentation fault.
0x00007ffff7cf6062 in Cantor::TextResult::plain() () from /usr/lib/x86_64-linux-gnu/libcantorlibs.so.21
─── Assembly ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
0x00007ffff7cf6058 ? mov    %rdi,%rax
0x00007ffff7cf605b ? mov    0x8(%rdx),%rcx
0x00007ffff7cf605f ? mov    %rcx,(%rdi)
0x00007ffff7cf6062 ? mov    (%rcx),%esi
0x00007ffff7cf6064 ? add    $0x1,%esi
0x00007ffff7cf6067 ? cmp    $0x1,%esi
0x00007ffff7cf606a ? ja     0x7ffff7cf6070 <_ZN6Cantor10TextResult5plainEv+32>
─── Expressions ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
─── History ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
─── Memory ────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
─── Registers ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
   rax 0x00007fffffffbd18    rbx 0x00007fffffffbd18    rcx 0x0000000000000000    rdx 0x0000000000e3b050    rsi 0x000000000099c9a0    rdi 0x00007fffffffbd18    rbp 0x00007fffffffbeb0    rsp 0x00007fffffffbce8
    r8 0x000000000099c9a0     r9 0x0000000000000001    r10 0x0000000000000002    r11 0x0000000000000000    r12 0x0000000000dfcdb0    r13 0x0000000000dfcdb0    r14 0x00007fffcf3975c0    r15 0x00007ffff67c11f9
   rip 0x00007ffff7cf6062 eflags [ PF ZF IF RF ]        cs 0x00000033             ss 0x0000002b             ds 0x00000000             es 0x00000000             fs 0x00000000             gs 0x00000000        
─── Source ────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
─── Stack ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
[0] from 0x00007ffff7cf6062 in Cantor::TextResult::plain()
(no arguments)
[1] from 0x00007fffcf3aacb6
(no arguments)
[+]
─── Threads ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
[6] id 10392 name cantor:disk$0 from 0x00007ffff5c6f3bb in futex_wait_cancelable+27 at ../sysdeps/unix/sysv/linux/futex-internal.h:88
[5] id 10389 name QDBusConnection from 0x00007ffff5d98ba9 in __GI___poll+73 at ../sysdeps/unix/sysv/linux/poll.c:29
[4] id 10388 name gdbus from 0x00007ffff5d98ba9 in __GI___poll+73 at ../sysdeps/unix/sysv/linux/poll.c:29
[3] id 10387 name gmain from 0x00007ffff5d98ba9 in __GI___poll+73 at ../sysdeps/unix/sysv/linux/poll.c:29
[2] id 10386 name QXcbEventReader from 0x00007ffff5d98ba9 in __GI___poll+73 at ../sysdeps/unix/sysv/linux/poll.c:29
[1] id 10382 name cantor from 0x00007ffff7cf6062 in Cantor::TextResult::plain()
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

(In reply to vialav from comment #5)
> UPDATE:
> 1. Remove the line with `view`
> 2. Press 'Evaluate Worksheet' # should be OK
> 3. Restart the backend  # should be OK
> 4. Press 'Evaluate Worksheet' again # Segfault:
> 
> Thread 1 "cantor" received signal SIGSEGV, Segmentation fault.

Thanks, I had create Bug 408351 for this.

*** Bug 421229 has been marked as a duplicate of this bug. ***

This problem hasn't been reproduced on Ubuntu 20.04 with Octave 5.2.0 and Gnuplot 5.2 (patchlevel 8).
So, at least, in modern Ubuntu/Octave this problem have gone.

I think, this is enough evidence for confirming, that the problem origin is Octave itself, because I have build Cantor before and after my OS migration from 19.04 to 20.04 (it have took only few days and for testing I have build some sourcs) - and the problem gone after migration.
So I mark this problem as resolved with upstream reason - looks like this Octave problem resolved in modern Octave versions (or maybe this is gnuplot problem, which used by Octave for graphics - I don't sure). And I will increase recommended Octave version to 5.2.0.