Re: [Plplot-general] unable to load wxwidgets driver

[Alan W. I. <ir...@be...>]

On 2006-09-13 10:11-0700 Joe Chuma wrote:

> So, the answer is that if the plplot wxwidgets driver is used within an
> application, the plplot library must be installed on the target machine?

Yes.

> There is no way to distribute a self-contained executable image of an 
> application which uses the wxwidgets driver?

No.  As I explained, wxwidgets.so and libplplot.so normally must be separate
since they are written in two different languages (C++ and C).

> Building the plplot libs, with the wxwidgets driver, requires the target
> machine to also have the wxwidgets package already installed.

Yes.  In fact, to use wxwidgets.so you must have the wxwidgets software
package installed since all wxwidgets.so does is provide an interface
between PLplot and the wxwidgets software package.

> So, an
> app which uses the plplot wxwidgets driver cannot be distributed as an
> executable image.

That conclusion is incorrect.  If you link your app correctly, and supply
all the required bits and pieces of PLplot, there should be no problems.

The whole point of shared libraries and plug-ins is to keep logically
distinct things separate rather than putting all code into one giant
library.  This approach actually minimizes the size of what you have to
distribute since you only have to include the bits and pieces of PLplot that
you need rather than everything.  However, the trick is figuring out the
exact bits and pieces that you need (see below).

Your C app should link to the core PLplot library which supplies fundamental
plotting routines such as the surface plots that you need. When your app
asks for the wxwidgets device, then that core library dynamically loads the
wxwidgets.so plug-in which supplies a PLplot interface to the wxwidgets
library which your application can use with normal PLplot commands. So you
only have to distribute the core PLplot library (consisting of the actual
library and some additional support files) and wxwidgets.so, and your user
has to have the wxwidgets package of software installed.  As I explained at
the start of this thread, this approach is not particularly easy to figure
out.  There will not be a lot of additional support files you have to
distribute from your PLplot install on your original machine, but you will
have to do some experimentation to see which files are actually required.

The approach of using shared libraries and plug-ins is standard for most
software these days.  Therefore, you should familiarize yourself with this
approach if you plan to distribute software.

PLplot also provides the old-fashioned way of doing things; use static
libraries and disable dynamic devices with all device driver code lumped
into the core library.  One disadvantage of that approach is your various
apps become huge in size since they all contain duplicated code.  More
fundamentally, that old-fashioned approach does not work for wxwidgets.so
since that device is written in C++ (as in the wxwidgets software package),
and the PLplot core code is written in C.  Mixing C and C++ code in the same
library should be avoided because it can cause linking problems.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the Yorick front-end to PLplot (yplot.sf.net); the
Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
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Linux-powered Science
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