image() opens gnuplot despite image_viewer("xloadimage %s")

[John W. Eaton]

On 28-Sep-2010, address@hidden wrote:

| Debian squeeze, Linux version 2.6.32-5-amd64 (Debian 2.6.32-20)
| (address@hidden) (gcc version 4.3.5 (Debian 4.3.5-2) ) #1 SMP Thu Aug 12
| 13:01:50 UTC 2010
| 
| fresh build today from the mercurial version http://www.octave.org/hg/octave
| 
| GNU Octave, version 3.3.52+
| 
| HowTo reproduce:
| octave -q
| image_viewer("xloadimage %s")
| image(rand(100)*100)
| 
| this opens a gnuplot windows with title "Figure 1" and the axes scaled from
| 1..100 (not expected)
| and the expected xloadimage windows
| 
| Looking deeper into /usr/local/share/octave/3.3.52+/m/image/image.m
| I see that
|   [ax, varargin, nargin] = __plt_get_axis_arg__ ("image", varargin{:});
| opens the gnuplot window. I set a "keyboard" before and after the line. After
| the first "return" the gnuplot windows pops up.
| 
| by the way:
| function __img_via_file__ in image_viewer.m
| calls "status = system (sprintf ("( %s && %s) > /dev/null 2>&1 &", command,
| rm));"
| but because the command is run in background (the last &), status always
| equals to 0
| so the error message "image_viewer: the image viewing command failed" is never
| shown.
| 
| HowTo reproduce:
| octave -q
| octave:1> image_viewer("this_is_no_valid_command %s")
| octave:2> image(rand(200)*100)
| octave:3>
| 
| Opens a empty (only axes) gnuplot windows but I think it is intended,
| 
| that the error message above should be shown instead.
| 
| best regards, Andy

I think the option of using an image viewer other than gnuplot or the
new fltk/opengl plotting system is outdated and should probably be
removed.

If there is some bug in the way Octave displays images with gnuplot or
the fltk/opengl plotting system, please open a bug report in the tracker.

jwe