source: trunk/geant4/visualization/OpenGL/History@ 595

$Id: History,v 1.94 2007/08/21 14:05:50 allison Exp $
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     =========================================================
     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
     =========================================================

                      Category History file
                      ---------------------
This file should be used by G4 developers and category coordinators
to briefly summarize all major modifications introduced in the code
and keep track of all category-tags.
It DOES NOT substitute the  CVS log-message one should put at every
committal in the CVS repository !

     ----------------------------------------------------------
     * Reverse chronological order (last date on top), please *
     ----------------------------------------------------------

History file for visualization/OpenGL
-------------------------------------

21st August 2007  John Allison  (opengl-V09-00-00)
- Removed redundant G4OpenGLXViewerMessenger.

25th May 2007  John Allison  (opengl-V08-03-03)
- G4OpenGLSceneHandler and G4OpenGLXViewerMessenger:
  Fixed gcc-4.1.2 compiler warnings.

G4OpenGLXViewer: Trapped glXMakeCurrent in Initialise function.

25th May 2007  John Allison  (opengl-V08-03-02)
- G4OpenGLXViewer: Trapped glXMakeCurrent in Initialise function.

24th May 2007  John Allison  (opengl-V08-03-01)
- Fixes for SUN.

16th May 2007  John Allison  (opengl-V08-03-00)
- Fix compiler warnings on SLC4.
- Bug fixes:
  o Correct path /vis/ogl/set/printMode.
  o Add SetView to pixmap screen dump ("/vis/ogl/set/printMode pixmap"
    and "/vis/ogl/printEPS").

8th May 2007  John Allison  (opengl-V08-02-06)
- Moved vectored PostScript printing to G4OpenGLViewer.
- /vis/ogl/printEPS should work for all viewers, including Win32.
- Introduced /vis/ogl/set/printMode vectored|pixmap, currently only
  effective on X windows (and still somewhat buggy).

4th April 2007  John Allison  (opengl-V08-02-05 - needs visman-V08-02-04)
- Implemented picking for OGLSX ( as well as OGLIX).  Hopefully works
  for OGL*Win32.  Still doesn't work for OGL*Xm.

3rd April 2007  John Allison  (opengl-V08-02-04 - needs visman-V08-02-03)
- G4OpenGLStoredSceneHandler:
  o Re-organised display lists on a per-primitive basis, i.e., one
    display list per primitive.  (This is so that, except for text,
    the colour - or, rather, intensity - can be brought out of the
    display list into the TOList (Transient Object List) and
    controlled for the Display-by-Time feature.  Previously, if more
    than one primitive were drawn between BeginPrimitives and
    EndPrimitives, it would finish up all in one display list, colour
    commands included. Rationalises and fixes a rare bug in the
    Display-by-Time feature - see August 2006.)
  o Added AddPrimitive(const G4Polymarker&) so that it is treated as
    one primoitive to fit with the above re-organisation.
- Implemented picking for OGLIX.

25th March 2007  John Allison  (opengl-V08-02-03)
- Fix compiler warnings.

8th February 2007  John Allison  (opengl-V08-02-02)
- Fixed Windows problem with DBL_MAX.  (Introduced G4OPENGL_DBL_MAX.)
- G4OpenGLXViewer.cc: Small bug fix in print().  (Context was switched
  .but not switched back.  Not serious, because context was always set
  before normal drawing.)

9th January 2007  John Allison  (opengl-V08-02-01)
- Implemented bitmap markers for MarkerSizeType == screen.  (The old
  polygon implementation remains for MarkerSizeType == world.)
- Added G4OpenGLBitMapStore to assist the above.
- G4OpenGLXViewer::CreateGLXContext:
  o Bug fix: Added missing break in colormap lookup routine.

5th January 2007  John Allison  (opengl-V08-02-00)
- G4OpenGLSceneHandler.cc:
  o Followed change of signature of GetLineWidth in visman-V08-02-00.
  o Minor efficiency improvements.

21st November 2006  John Allison  (opengl-V08-01-09)
- Fixed compiler warnings.

1st November 2006  John Allison  (opengl-V08-01-08)
- Replace /vis/oglx/set/printEPS by /vis/oglx/printEPS.  The new command
  actually initiates a print, rather than set a flag for printing.

24th October 2006  John Allison  (opengl-V08-01-07)
- G4OpenGLStoredViewer.cc: Calculate light front horizon properly.
- G4OpenGLViewerMessenger.cc: Make refresh depend on auto-refresh.

19th September 2006  John Allison  (opengl-V08-01-06)
- Added time origin for light front.
- Added /vis/ogl/set/transparency.
- G4OpenGLStoredViewer.cc: Bug fix in time range acceptance.

4th September 2006  John Allison  (opengl-V08-01-05)
- Implement cutaways.
- Immediate mode: G4OpenGLImmediateSceneHandler.cc: Flush all
  primitives (see detector being drawn).
- /vis/oglx/set/printEPS: change parameter default to true.

30th August 2006  John Allison  (opengl-V08-01-04)
- G4OpenGLSceneHandler:
  o Implemented line width.
  o Switched off back face culling when clipping so that the inside of
    volumes can be seen.
  o Added CreateSection/CutawayPolyhedron to exploit generic
    sectioning (DCUT) and cutaways.  Currently not activated due to
    instabilities in BooleanProcessor.  Local sectioning still active
    but broken (at least on Mac) due to apparent change in effect of
    clipping planes (polyhedron edges not reconstructed).
  o Rationalised calculation of marker size.
- G4OpenGLStoredSceneHandler:
  o Fixed bug due to recursive calls of AddPrimitive (polymarkers -> markers).
  o Pick up time range from G4VisAttributes.
- G4OpenGLViewer(Messenger):
  o Added position and colour to /vis/ogl/set/displayHeadTime.
  o Added /vis/ogl/set/displayLightFront.
- G4OpenGLStoredViewer.cc:
  o Rationalised CompareForKernelVisit.  (Local sectioning still active.)
  o Added position and colour to DisplayHeadTime.
  o Added DisplayLightFront.
  
16th August 2006  John Allison  (opengl-V08-01-03)
- Corrected Solaris compilation error.
- Added /vis/ogl/set/fade and displayHeadTime.

14th August 2006  John Allison  (opengl-V08-01-02)
- Needs visman-V08-01-02.
- G4OpenGLStored: Implemented display-by-time.  Only available in
  stored mode at present.  Only implemented for circle, square,
  polyline and polymarker at present, enough for currently available
  trajectory models.  Time is communicated via G4AttValues.
- Added G4OpenGLViewerMessenger.
- Added /vis/ogl/set/startTime and endTime of displayed objects.
- All factories: Instantiated G4OpenGLViewerMessenger.
- G4OpenGLViewer: Added fStart/EndTime.
- G4OpenGLXViewer.cc: Graceful recovery from unexpected tokens in
  spewPrimitiveEPS and spewSortedFeedback.

17th July  John Allison  (opengl-V08-01-01)
- Added /vis/oglx/set/printEPS (prints eps file on every update).

3rd July 2006  John Allison  (opengl-V08-01-00)
- Elimination of redundant variable doublebuffer and implementation of
  FinishView in all viewers.

30th May 2006  Joseph Perl  (opengl-V08-00-08)
- G4OpenGLImmediateWin32Viewer: Removed tests on doublebuffer since that
  variable seems to have random behavior and should be assumed false for
  this viewer.

29th May 2006  Joseph Perl  (opengl-V08-00-07)
- G4OpenGLWin32Viewer, G4OpenGLImmediateWin32Viewer, G4OpenGLStoredWin32Viewer:
  Removed common FinishView and instead made separate FinishView for the two different
  versions of this viewer since each wants a different buffer swapping behaviour.

12th May 2006  John Allison  (opengl-V08-00-06)
- G4OpenGLWin32Viewer: Fixed buffer swapping behaviour.

28th April 2006  John Allison  (opengl-V08-00-05 - needs visman-V08-00-14)
- G4OpenGLStoredX/Xm/Win32Viewer.cc: Fixed buffer swapping problem when
  recomputing transients.

24th April 2006  John Allison  (opengl-V08-00-04)
- Fixed compilation problem on Windows.

19th April 2006  John Allison  (opengl-V08-00-03)
- G4OpenGLSceneHandler, G4OpenGLStoredSceneHandler and
  G4OpenGLImmediateSceneHandler:
  o Implemented Begin/EndPrimitives2D (needs visman-V08-00-12 and
    greps-V08-00-02).
  o Migrated to direct access to G4PhysicalVolumeModel.
- G4OpenGLStoredX/Xm/Win32Viewer.cc: bug fix for conditional drawing
  of display lists in DrawView.

14th March 2006  John Allison  (opengl-V08-00-02)
- Refined display list building and re-drawing algorithm.
  o G4OpenGLStoredSceneHandler::EndModeling: Changed to GL_COMPILE_AND_EXECUTE.
  o Avoided unnecessary re-execution in DrawView (X, Xm and Win32).
- G4OpenGLStoredSceneHandler::RequestPrimitives: Refined display list
  re-use algorithm.  In test19 with global culling off, numbers of
  display lists used are:
  o 191  No re-use:
  o  73  Before this change: re-use except replicas (includes parameterised).
  o  33  After this change: re-use except parameterised and replicas in radius.

26th January 2006  John Allison  (opengl-V08-00-01)
- Coworks with visman-V08-00-04 (removed fModified).
- Removed references to fModified.
- Tidying: Removed unnecessary ClearView.
- G4OpenGLSceneHandler.cc: Added some (commented out) code for
  possible future implementation of 2D drawing.
- G4OpenGLXViewer.cc: Improved exception printing.

11th January 2006  John Allison  (opengl-V08-00-00)
- Improved efficiency: all DrawView's:
  o Don't call ClearView.
  o Set flag so SetView will not be called in ProcessView.
  o Leave background colour to ClearView.
- Used dynamic_cast<G4OpenGLViewer*>, no need for G4OpenGLViewerDataStore.
- G4OpenGLXmViewerMessenger: Made a smart singleton; interrogates vis manager
  for current viewer.

24th November 2005  John Allison  (opengl-V07-01-09)
- Protected G4OpenGLXmViewerMessenger with #ifdef G4VIS_BUILD_OPENGLXM_DRIVER.

22nd November 2005  John Allison  (opengl-V07-01-08)
- Added G4OpenGLXmViewerMessenger.
- Corrected text position.
- Made depth test for polyhedron GL_LEQUAL (slightly dominant).

17th November 2005  Gabriele Cosmo
- Fixed settings of background style for WIN32 viewers.

13th November 2005  John Allison  (opengl-V07-01-07)
- Implemented X-Window-style geometry hints in G4OpenGLXViewer.

13th October 2005  John Allison  (opengl-V07-01-06)
- Allowed any colour background.
- Implemented non-uniform scaling.
- Migration to <sstream>.

29th September 2005  John Allison  (opengl-V07-01-05)
- Added G4OpenGLViewerDataStore to facilitate access of viewer data by
  scene handler.
- Re-implemented transparency button in OpenGLXm.

13th September 2005  John Allison  (opengl-V07-01-04 - needs visman-V07-01-02)
- Implemented white background for all OGL viewers.
- G4OpenGLSceneHandler.cc:
  o Fixed hidden line removal (bug introduced in opengl-V07-01-02).
  o Fixed treatment of triangular polygons for drawing of auxiliary/soft lines.
  o Corrected GetTextColour(text).
  o Corrected GetColour(polyhedron).

5th September 2005  John Allison  (opengl-V07-01-03)
- Bug fix: stored transparent objects were being lost.

2nd September 2005  John Allison  (opengl-V07-01-02 - needs visman-V07-01-01)
- Bug fix: edgeflags problem introduced with smooth shading in
  opengl-V07-01-00.
- Implementation of a "better algorithm" for the rendering of
  transparent polyhedron objects.  It renders all opaque objects
  first, then renders the transparent objects with the depth buffer in
  read-only mode (see OpenGL Programming Guide).  It uses the new
  facility in G4VSceneHandler::ProcessScene for an optional second pass
  of the run-duration models in the scene.  Note this algorithm is
  still only an approximation.  It will still give the wrong blended
  colour if two transparent objects are rendered front first.  For
  nested transparent objects, this is unfortunate, because
  G4PhysicalVolumeModel traverses Geant4's mother-daughter hierarchy
  in such a way that mothers come first.  Also, there is no guaranteed
  relationship between the order of rendering and the depth of two
  transparent objects if they are at the same level or in different
  branches of the hierarchy.  Still, the only error will be an
  incorrect colour - the objects will still give the appearance of
  transparency, so it's a pretty good algorithm.  (An even better
  algorithm would be to attempt to render the facets in depth order,
  deepest first.  But how do you calculate the depth - centre of area,
  deepest corner?  One can still imagine pathalogical cases that would
  sometimes give the wrong colour.  Also, for stored mode, the order
  is fixed in a display list so when the user rotates the view, one
  would lose the depth ordering.  I think we have to accept that
  blending in OpenGL is only ever an approximation.  For accurate
  blending, use RayTracer.)

28th August 2005  John Allison  (opengl-V07-01-01)
- Half-way implementation of rendering of transparent polyhedron
  objects.  In this implementation, no account is taken of the order
  of rendering.  Transparent objects are rendered with depth testing
  off so that objects behind can still be seen.  But this means that
  opaque objects in front do not obscure them - and they jolly well
  should!  A better algorithm is to render all opaque objects first,
  then render the transparent objects with the depth buffer in
  read-only mode (see OpenGL Programming Guide).  This is going to
  take a little more thought - see opengl-V07-01-02.

20th July 2005  John Allison  (opengl-V07-01-00)
- Introduced smooth shading, taking advantage of hitherto un-noticed
  feature of HepPolyhedron::GetNextFacet that calculates the normals
  at each vertex so that curved surfaces are rendered more
  realistically (Gouraud shading).
- G4OpenGLImmediateSceneHandler.cc: Removed unnecessary #include's.
- G4OpenGLXmViewer.cc: Fixed to use window size hints.  This changes
  the default window size.  It used to be 400x400, hardcoded in
  G4OpenGLXmViewer.cc, but now it picks up the
  G4ViewParameters::GetWindowSizeHintX/Y, which defaults to 600x600.
  The user may change it on the command line, e.g:
    /vis/open OGLSXm 500
  or
    /vis/viewer/create ! ! 500

30th May 2005  John Allison  (opengl-V07-00-03)
- Fixed compilation problem in OpenGL on SUN.  (Replaced multimap by
  map of vectors in G4OpenGLFontBaseStore.)

4th May 2005  John Allison  (opengl-V07-00-02)
- Restored sequence Set/Clear/DrawView in ClearTransientStore.  (It
  was taken out to prevent recursive calling, but that seems to be OK,
  and it is needed to implement refresh at end of event/run.)

22nd April 2005  John Allison  (opengl-V07-00-01)
- Rationalised work of opengl-V07-00-00.  Functionality unchanged.
  o G4OpenGLViewer.hh: Created virtual void CreateFontLists(){}.
  o In all concrete viewers, added call to CreateFontLists().
  o Moved font code for X to G4OpenGLXViewer::CreateFontLists().
  o There is no longer a need to implement in the XmViewer, since it
    now inherits.  Thus the font code now only appears once for X.
  o Awaiting implementation for WIN32.

17th April 2005  John Allison  (opengl-V07-00-00)
- Based on vis-V07-00-13.
- Implemented text for X-Windows viewers.  Uses glXUseXFont, which
  creates display lists for nominated fonts.  Simple-minded scheme in
  which each viewer creates its own font display lists for a variety
  of sizes, which are accessed by the scene handler through a new
  class, G4OpenGLFontBaseStore.  Affected methods:
    G4OpenGLXViewer::CreateMainWindow()
    G4OpenGLXmViewer::CreateMainWindow()
    G4OpenGLSceneHandler::AddPrimitive (const G4Text& text)

18th November 2004  John Allison  (opengl-V06-02-07)
- Removed redundant fLastVP from G4OpenGLStoredSceneHandler.

15th November 2004  Guy Barrand
- G4OpenGLWin32Viewer::ShowView : glFlush was not sufficient 
  to see trajectories (for example with N03). Correct so that
  ShowView do a FinishView that does : glFlush, wglSwapBuffer
  and empty the Windows message queue.

22nd September 2004  John Allison  (opengl-V06-02-06)
- doxygen output to tmp area.
- Trap non-regular polyhedrons.

13th September 2004  Gabriele Cosmo  (opengl-V06-02-05)
- G4OpenGLTransform3D.cc: simplified implementation for GetMatrix()
  to allow for porting on CLHEP-1.9.X series.

23rd July 2004  John Allison
- Draws auxiliary edges if required.
- Added auxiliary edge button.

16th July 2004  John Allison  (opengl-V06-02-04)
- Refinements to hidden line, hidden surface removal.

14th July 2004  John Allison  (opengl-V06-02-03)
- Removed superfluous #include "G4VisManager.hh" from G4OpenGLXmViewer.cc.

13th July 2004  John Allison  (opengl-V06-02-02)
- Hidden line *and* hidden surface removal now works.

9th July 2004  John Allison  (opengl-V06-02-01)
- Fixed long-standing problem with hidden line removal.
- Improved messages on failure to get visual.
- Added GLX_STENCIL_SIZE explicit request to visual attributes - most
  systems provided by default anyway, so no effect.

1st July 2004  John Allison  (opengl-V06-02-00)
- Rationalised G4OpenGLSceneHandler ready for hidden line removal.
- Bug fix in G4OpenGLXmPanningCallbacks.cc for dolly control.

18th June 2004  Gunter Folger (geant4-06-02)
9th June 2004  Gabriele Cosmo  (vis-V06-01-03)
7th June 2004  Gabriele Cosmo  (vis-V06-01-02)
- GNUmakefile and disclaimer changes - see visualization/History.

9th April 2004  John Allison  (vis-V06-01-01 + interfaces-V06-01-00)
- Tagged OpenGL as below.  Joint with interfaces-V06-01-00.

7th April 2004  Guy Barrand
- visualization/OpenGL/* : use the G4OpenGL.hh file.
- Added : visualization/OpenGL/include/G4OpenGL.hh to encapsulate
  the include of gl/gl.h and gl/glu.h that may be platform dependant.
  It permits to rm some #ifdef WIN32 spread in the code. It opens also
  the way to the usage of the Apple OpenGL on a Mac.

17th February 2004  John Allison  (opengl-V06-00-00)
- Fixed bug #581: wrong order of statements in
  G4OpenGLXViewer::~G4OpenGLXViewer (see bug report).

4th October 2003  Gabriele Cosmo  (vis-V05-02-01)
- GNUmakefile:
  o replaced "digits+hits" with "digits_hits".
- Coworks with "geometry-V05-02-00" and "digits_hits-V05-02-00".

22nd September 2003  John Allison  (vis-V05-02-00, greps-V05-02-00)
- Cosmetic change to regularise names:
  o changed _Feedback3Dcolo to G4OpenGLXViewerFeedback3Dcolor.
  o changed _DepthIndex to G4OpenGLXViewerDepthIndex.

23rd June 2003  Guy Barrand  (opengl-V05-01-02)
- Commit a first implementation of G4OpenGLWin32Viewer.

10th June 2003  Gabriele Cosmo  (opengl-V05-01-01)
- More fixes for warnings in viewers classes.
- Added inclusion of <windows.h> for WIN32 platforms when GL headers
  are included.

05th June 2003  Gabriele Cosmo  (opengl-V05-01-00)
- Fixes for porting compilation on WIN32:
  o G4OpenGLWin32Viewer[.hh.cc]: removed inclusion of <GL/glx.h>.
  o G4OpenGLViewer.cc: replaced local variables near/far with pnear/pfar
    since declared 'obsolete' in WIN32 platforms.

27th November 2002  John Allison  (vis-V04-01-08)
- Improved algorithm of CompareForKernelVisit.

11th November 2002  John Allison  (opengl-V04-01-02)
- Corrected inclusion of G4OpenGLXViewer #ifdef X_DRIVER.
- Added G4OpenGLSceneHandler::AddThis for trajectories and hits - simply
  call default but there as a marker and encourager.
- Added tracking and digits+hits/hits to GNUmakefile.

16th October 2002  John Allison  (opengl-V04-01-01)
- Fix for WIN32.  Now compiles but viewer not implemented.

24th June 2002  John Allison  (opengl-V04-01-00)
- Further cosmetic changes in G4OpenGLXViewer.cc for DEC compiler.

10th June 2002  John Allison  (opengl-V04-00-03)
- Cosmetic changes for SUN-CC in G4OpenGLXmConvenienceRoutines.cc.

6th June 2002  John Allison  (opengl-V04-00-02)
- Cosmetic changes for GNU compiler in G4OpenGLXViewer.cc.

23rd February 2002  John Allison  (opengl-V04-00-01)
- Changes to encourage compilation on Windows in preparation for
  implementation of G4OpenGLWin32Viewer.  Removed spurious includes of
  glx.h, unistd.h and assert.h.

24th August 2001  John Allison  (vis-V03-02-13)
- Limited the printing of warnings in
  G4OpenGLSceneHandler::AddPrimitive (const G4Text& text).

14th August 2001  John Allison  (vis-V03-02-11)
- Improved KernelVisitDecision.
- Fixed a few small bugs in multiple "stored" viewers, but see next item.
- There's an outstanding bug in OpenGL Stored.  If there is more than
  one viewer controlled by a scene handler, after a ClearStore on the
  scene handler, e.g., with /vis/scene/notifyHandlers, the first
  viewer to get refreshed should trigger the display list rebuild, but
  the second need not.  However, when the second viewer's turn comes,
  the display lists are there, and are called, e.g.,
  G4OpenGLStoredXViewer::DrawView calls
  G4OpenGLStoredViewer::DrawDisplayLists that calls glCallList, but
  nothing appears on the screen.  To overcome this there is some
  temporary code in G4VViewer::NeedKernelVisit which marks *all*
  viewers to force a rebuild.  To see the symptoms, comment out that
  temporary code and issue these commands:
    /vis/verbose c
    /control/verbose 2
    /vis/scene/create
    /vis/scene/add/volume
    /vis/sceneHandler/create OGLSX
    /vis/viewer/create ! ! 1
    /run/beamOn
    /vis/viewer/create ! ! 1
    /vis/viewer/select viewer-0
    /vis/viewer/viewpointThetaPhi 20 20
    /vis/viewer/select viewer-1
    /vis/viewer/viewpointThetaPhi 40 40
    /vis/viewer/set/style surface
    /vis/viewer/refresh
    /vis/viewer/select viewer-0
    /vis/viewer/refresh
    /vis/viewer/select viewer-1
    /vis/viewer/set/style wireframe
    /vis/scene/notifyHandlers
  You may have to do this too:
    /vis/viewer/select viewer-0
    /vis/scene/notifyHandlers
  One of the viewers is empty.  Curious!!

9th August 2001  John Allison  (vis-V03-02-10-00)
- Implemented G4OpenGLStoredSceneHandler::ClearTransientStore()
- Removed G4OpenGLSceneHandler::AddPrimitive (const G4Polymarker&) (it only
  invoked G4VSceneHandler::AddPrimitive (const G4Polymarker&) which is
  picked up by inheritance anyway.
- Removed lots of unnecessary header files from G4OpenGLStoredSceneHandler.cc.
- Corrected order of calling base class functions in
  G4OpenGLStoredSceneHandler::Begin/EndModeling.

24th July 2001  John Allison  (vis-V03-02-06)
- G4OpenGLSceneHandler::AddPrimitive (const G4Text&) handles transformation.

14th July 2001  John Allison (opengl-V03-02-00)
- Fixed crash in optimised mode: added Initialise() to viewers so
  that windows are opened after viewers are fully constructed.

2nd April 2001  John Allison (opengl-V03-00-01 wrt vis-V03-00-09)
- Tidied G4OpenGLXmViewer callback code.  Removed superfluous header files.

7th March 2001  John Allison
- Changed char* to const char* in many places and that gave problems in
  calls to Xt and Xm.  Hope all's OK.  Differences:
    cvs diff -r vis-V03-00-06 vis-V03-00-07

25th January 2001  John Allison  (opengl-V03-00-00)
- Implemented running re-calculation of up-vector in the case of "object
  rotation" (lights move with camera) to prevent "flipping" of view when
  camera passes through up-vector.  Note that the default is "camera
  rotation" (lights do not move with camera, i.e., remain fixed relative
  to object) so the default is that this "flipping" can happen.  To set
  "object rotation" (lights move with camera) use
  /vis/lights/move_with_camera true (soon to be
  /vis/viewer/set/lights move-with-camera) or click "Object" radio button
  on Rotation Panel in OpenGLXm mode.
- Changed some objects to references for efficiency.  E.g.:
  const G4Vector3D& vp = pView->fVP.GetViewpointDirection ().unit ();

22nd May 2000  John Allison  (opengl-V01-01-00)
- Fixed slow response of 2nd window of OpenGLXm.  Worked around Mesa bug
  by sharing static visuals in G4OpenGLXViewer (Guy Barrand):
    static XVisualInfo* vi_single_buffer;
    static XVisualInfo* vi_double_buffer;
- Removed ChooseVisual from G4OpenGLXmViewer.cc - done in base class
  G4OpenGLXViewer.
- Protected double deletion of window in destructors of G4OpenGLXmViewer
  and G4OpenGLXViewer (Guy Barrand).
- Changed requested bits per colour to r,g,b = 1,1,1 in G4OpenGLViewer.cc.
- Corrected order of CreateMainWindow() and InitializeGLView() in X*Viewer
  constructors.