CVS version of gnuplot allows zooming and refresh of piped data

[Ethan Merritt]

John Eaton has suggested that I forward this information from the
gnuplot patch tracking site on SourceForge.  It is relevant to Octave
users because a relatively recent change in Octave's method of passing
data to gnuplot broke mouse operations, particularly zooming.

This problem is fixed, or at least ameliorated, if you build gnuplot
from the latest CVS source tree.

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[ gnuplot-Patches-1723715 ] Refresh plot or zoom without re-reading data

Initial Comment:
This patch adds a new command 'refresh' that acts similarly to 'replot'
except that it does not re-read or recalculate the input data.
This allows you to zoom, add labels, or otherwise modify the current plot
even if the input data is transient. In particular it allows you to zoom
or otherwise  modify a plot whose data came from stdin, e.g. plot '-'.

Comment By: Ethan Merritt (sfeam)
Date: 2007-08-31 19:42
Because the current Octave requires some way to zoom or replot volatile
data, I am moving this patchset into CVS.  I acknowledge that it is not a
perfect solution, but we need something in place for Octave users even if
we replace it with a better solution later on.  

To facilitate later replacement, if necessary, I have set off the code
pieces with #ifdef VOLATILE_REFRESH and placed this under the control of a
new configuration option   --enable-volatile-data
File Added: persistent_plot_data_31aug2007.patch

Comment By: Petr Mikulik (mikulik)
Date: 2007-08-31 20:58
Gnuplot compiled from cvs; now zooming works fine with Octave 2.9.x,
thanks.


#       Known limitations:
#
#       - Clipping of zoomed 3D contour plots is not correct.
#
#       - previous/next zoom works OK, but "unzoom" is flaky if the plot has
#         changed since the original zoom operation.  Probably the saved state
#         should be invalidated at some point, but when?  The next plot?
#         The next "set [xy]range" or "set auto" statement?  "reset"?
#
#       - splot volatile with image + zoom + unzoom is flaky
#
#       - If you include a range in the plot command, e.g. plot [-pi:pi] sin(x)
#         then "replot" re-applies this range, whereas "refresh" does not.
#         Arguably, the action of "refresh" is more correct - but it's a change.
#
#       - plot -> zoom -> set grid -> unzoom   loses the grid setting.
#         This is a consequence of storing the grid setting in (struct axis).
#         Proposed fix is to move the grid setting somewhere else.



-- 
Ethan A Merritt