On Thu, Sep 25, 2008 at 10:05 AM, Davide Cesari <[EMAIL PROTECTED]> wrote:
> I would like to repeatedly enable/disable viewport clipping while
> plotting, in order to draw lines, symbols, etc. in a legend outside the
> plot, while retaining clipping when data is plotted. Is there a simple
> way to do this in plplot, or is clipping-disable in the TODO list?
> Up to now i found a suboptimal solution (see fortran subroutine further
> in text) by calling plgvpd/plgvpw to get viewport/window settings,
> setting viewport to [0.,1.],[0.,1.] and enlarging correspondingly the
> plotting window, then switching back to the initial settings when
> desired. However in this way, after a disable/enable cycle, the plotting
> window is not the same as before because the values obtained by plgwpd
> are not exactly the one previously passed to plwind, a little correction
> of 1.e-5 is made in the plwind code. Maybe adding a function similar to
> the one I propose in the C api (with exact window settings) could be a
> simple approach!? I could try provide a patch if this may help.
While I do not have a better method to propose at this time, I have
faced the same plgvpw offset issue. This 1.0e-5 offset seems to be an
intentional adjustment - see plwind.c, starting at line 56:
--- FROM plwind.c, STARTING AT LINE 56 ---
dx = (xmax - xmin) * 1.0e-5;
dy = (ymax - ymin) * 1.0e-5;
/* The true plot window is made slightly larger than requested so that */
/* the end limits will be on the graph */
plsc->vpwxmi = xmin - dx;
plsc->vpwxma = xmax + dx;
plsc->vpwymi = ymin - dy;
plsc->vpwyma = ymax + dy;
--- END OF plwind.c PASTE ---
plsc->pvpw* are the values returned by plgvpw. The simplest immediate
solution would be to invert the above viewport adjustments to retrieve
the original viewport dimensions.
For the PLplot core developers - would it be an acceptable change to
have plgvpw return the proper xmin, xmax, ymin, ymax values rather
than these adjusted values? It would probably be less surprising for
a user than the current function return values. It is a change from
how the function has worked in the past but I think it may be a
worthwhile one.
If this is an acceptable change I would be happy to supply a patch to
implement this. Another option would be to create a new function which
returns the properly transformed plot limits.
Hez
--
Hezekiah M. Carty
Graduate Research Assistant
University of Maryland
Department of Atmospheric and Oceanic Science
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