building src/graphics/...

[John W. Eaton]

Here are the build problems I noticed:

* There don't seem to be any rules in the src/Makefile.in file to
  descend into the src/graphics directory, and even the
  src/graphics/Makefile.in file doesn't have any rules to descend into
  the fltk_backend directory.  Also, since the src/graphics directory
  tree contains only three source files, maybe we should move them to
  the src and src/DLD_FUNCTIONS directories and modify src/Makefile.in
  as needed?

* The fltk_backend/Makefile.in file doesn't seem to know about -fPIC,
  which is needed on some systems.

* The ftgl check in configure.in should not modify CXXFLAGS, because
  CXXFLAGS is reserved for users (with a default of -g -O2).  If the
  configure script adds library-specific options to CXXFLAGS, then if
  users build with something like

    make CXXFLAGS=-g

  I think the added options will be lost.  At the least, that's
  confusing.  The library-specific options should probably be set in a
  separate variable so they can be used only where needed in the
  Makefiles.  It looks like FT2_CFLAGS is already defined, so we could
  just use that.

* There should be rules for generating autoloads for the functions in
  src/graphics/fltk_backend/fltk_backend.cc and placing them in a
  PKG_ADD file.  I think this would be handled automatically if
  fltk_backend.cc were moved to the src/DLD_FUNCTIONS directory.

* If we keep the src/graphics/opengl directory, then it should be
  added to the LD_LIBRARY_PATH in the run-octave.in file and the
  liboctgraphics_gl.so should be added to LD_PRELOAD.  If we move
  gl-render.{h,cc} to the src directory, then this change would not be
  needed.

I think it would simplify things a lot to move the files.  Is there
any reason to not do that?

jwe