/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkXOpenGLRenderWindow.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/

#include "vtkXOpenGLRenderWindow.h"
#include "vtkOpenGLRenderer.h"

#include "vtk_glew.h"
// Define GLX_GLXEXT_LEGACY to prevent glx.h from including the glxext.h
// provided by the system.
//#define GLX_GLXEXT_LEGACY

// Ensure older version of glx.h define glXGetProcAddressARB
#define GLX_GLXEXT_PROTOTYPES

// New Workaround:
// The GLX_GLXEXT_LEGACY definition was added to work around system glxext.h
// files that used the GLintptr and GLsizeiptr types, but did not define them.
// However, this broke multisampling (See PR#15433). Instead of using that
// define, we're just defining the missing typedefs here.
typedef ptrdiff_t GLintptr;
typedef ptrdiff_t GLsizeiptr;
#include "GL/glx.h"


#ifndef GLAPI
#define GLAPI extern
#endif

#ifndef GLAPIENTRY
#define GLAPIENTRY
#endif

#ifndef APIENTRY
#define APIENTRY GLAPIENTRY
#endif

#include "vtkCommand.h"
#include "vtkIdList.h"
#include "vtkNew.h"
#include "vtkObjectFactory.h"
#include "vtkOpenGLShaderCache.h"
#include "vtkRendererCollection.h"
#include "vtkRenderTimerLog.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkStringOutputWindow.h"
#include "vtksys/SystemTools.hxx"
#include "vtkToolkits.h"

#include <sstream>

#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/cursorfont.h>

#define GLX_CONTEXT_MAJOR_VERSION_ARB       0x2091
#define GLX_CONTEXT_MINOR_VERSION_ARB       0x2092
typedef GLXContext (*glXCreateContextAttribsARBProc)(Display*, GLXFBConfig, GLXContext, Bool, const int*);
typedef void ( * glXSwapIntervalEXTProc) (Display* dpy, GLXDrawable drawable, int interval);

class vtkXOpenGLRenderWindow;
class vtkRenderWindow;
class vtkXOpenGLRenderWindowInternal
{
  friend class vtkXOpenGLRenderWindow;
private:
  vtkXOpenGLRenderWindowInternal(vtkRenderWindow*);

  GLXContext ContextId;
  GLXFBConfig FBConfig;

  // store previous settings of on screen window
  int ScreenDoubleBuffer;
  int ScreenMapped;
};

vtkXOpenGLRenderWindowInternal::vtkXOpenGLRenderWindowInternal(
  vtkRenderWindow *rw)
{
  this->ContextId = nullptr;
  this->FBConfig = None;

  this->ScreenMapped = rw->GetMapped();
  this->ScreenDoubleBuffer = rw->GetDoubleBuffer();
}

vtkStandardNewMacro(vtkXOpenGLRenderWindow);

#define MAX_LIGHTS 8

GLXFBConfig vtkXOpenGLRenderWindowTryForFBConfig(Display *DisplayId,
                                                  int drawable_type,
                                                  int doublebuff,
                                                  int stereo,
                                                  int multisamples,
                                                  int stencil,
                                                  bool srgb)
{
  int           index;
  static int    attributes[50];

  // setup the default stuff we ask for
  index = 0;
  attributes[index++] = GLX_DRAWABLE_TYPE;
  attributes[index++] = drawable_type;
  attributes[index++] = GLX_RENDER_TYPE;
  attributes[index++] = GLX_RGBA_BIT;
  attributes[index++] = GLX_RED_SIZE;
  attributes[index++] = 1;
  attributes[index++] = GLX_GREEN_SIZE;
  attributes[index++] = 1;
  attributes[index++] = GLX_BLUE_SIZE;
  attributes[index++] = 1;
  attributes[index++] = GLX_DEPTH_SIZE;
  attributes[index++] = 1;
  attributes[index++] = GLX_ALPHA_SIZE;
  attributes[index++] = 1;
  if (doublebuff)
  {
    attributes[index++] = GLX_DOUBLEBUFFER;
    attributes[index++] = True;
  }
  if (stencil)
  {
    attributes[index++] = GLX_STENCIL_SIZE;
    attributes[index++] = 8;
  }
  if (stereo)
  {
    // also try for STEREO
    attributes[index++] = GLX_STEREO;
    attributes[index++] = True;
  }
  if (multisamples)
  {
#ifdef GLX_SAMPLE_BUFFERS_SGIS
    attributes[index++] = GLX_SAMPLE_BUFFERS_SGIS;
    attributes[index++] = 1;
    attributes[index++] = GLX_SAMPLES_SGIS;
    attributes[index++] = multisamples;
#endif
  }

  if ( srgb )
  {
    attributes[index++] = 0x20B2;
    attributes[index++] = True;
  }

  attributes[index++] = None;

  // cout << "Trying config: " << endl
  //      << "         DisplayId : " << DisplayId << endl
  //      << "     drawable_type : " << drawable_type << endl
  //      << "        doublebuff : " << doublebuff << endl
  //      << "            stereo : " << stereo << endl
  //      << "      multisamples : " << multisamples << endl
  //      << "    alphaBitPlanes : " << alphaBitPlanes << endl
  //      << "           stencil : " << stencil << endl;
  int tmp;
  GLXFBConfig* fb = glXChooseFBConfig(DisplayId, XDefaultScreen(DisplayId),
                                      attributes, &tmp);
  if (fb && tmp > 0)
  {
    // cout << "            STATUS : SUCCESS!!!" << endl;
    GLXFBConfig result = fb[0];
    XFree(fb);
    return result;
  }
  // cout << "            STATUS : FAILURE!!!" << endl;
  return None;
}

XVisualInfo *vtkXOpenGLRenderWindowTryForVisual(Display *DisplayId,
                                                int doublebuff, int stereo,
                                                int multisamples,
                                                int stencil, bool srgb)
{
  GLXFBConfig fbc = vtkXOpenGLRenderWindowTryForFBConfig(DisplayId,
       GLX_WINDOW_BIT,
       doublebuff,
       stereo, multisamples,
       stencil, srgb);

  XVisualInfo *v = glXGetVisualFromFBConfig( DisplayId, fbc);

  return v;
}

GLXFBConfig vtkXOpenGLRenderWindowGetDesiredFBConfig(
  Display *DisplayId,
  int &win_stereo,
  int &win_multisamples,
  int &win_doublebuffer,
  int drawable_type,
  int &stencil,
  bool srgb)
{
  GLXFBConfig   fbc = None;
  int           multi;
  int           stereo = 0;

  // try every possibility stoping when we find one that works
  // start by adjusting stereo and multisamples
  for (stereo = win_stereo; !fbc && stereo >= 0; stereo--)
  {
    for (multi = win_multisamples; !fbc && multi >= 0; multi--)
    {
      fbc = vtkXOpenGLRenderWindowTryForFBConfig(DisplayId,
                                                 drawable_type,
                                                 win_doublebuffer,
                                                 stereo, multi,
                                                 stencil, srgb);
      if (fbc)
      {
        // found a valid config
        win_stereo = stereo;
        win_multisamples = multi;
        return fbc;
      }
    }
  }

  // OK adjusting stereo and multisamples did not work
  // try flipping the double buffer requirement and try again
  for (stereo = win_stereo; !fbc && stereo >= 0; stereo--)
  {
    for (multi = win_multisamples; !fbc && multi >= 0; multi--)
    {
      fbc = vtkXOpenGLRenderWindowTryForFBConfig(DisplayId,
                                                 drawable_type,
                                                 !win_doublebuffer,
                                                 stereo, multi,
                                                 stencil, srgb);
      // we found a valid result
      if (fbc)
      {
        win_doublebuffer = !win_doublebuffer;
        win_stereo = stereo;
        win_multisamples = multi;
        return fbc;
      }
    }
  }

  // we failed
  return ( None );
}

XVisualInfo *vtkXOpenGLRenderWindow::GetDesiredVisualInfo()
{
  XVisualInfo   *v = nullptr;

  // get the default display connection
  if (!this->DisplayId)
  {
    this->DisplayId = XOpenDisplay(static_cast<char *>(nullptr));

    if (this->DisplayId == nullptr)
    {
      vtkErrorMacro(<< "bad X server connection. DISPLAY="
        << vtksys::SystemTools::GetEnv("DISPLAY") << ". Aborting.\n");
      abort();
    }

    this->OwnDisplay = 1;
  }
  this->Internal->FBConfig =
    vtkXOpenGLRenderWindowGetDesiredFBConfig(
      this->DisplayId,
      this->StereoCapableWindow,
      this->MultiSamples,
      this->DoubleBuffer,
      GLX_WINDOW_BIT,
      this->StencilCapable,
      this->UseSRGBColorSpace);

  if (!this->Internal->FBConfig)
  {
    vtkErrorMacro(<< "Could not find a decent config\n");
  }
  else
  {
    v = glXGetVisualFromFBConfig( this->DisplayId,
      this->Internal->FBConfig);
    if (!v)
    {
      vtkErrorMacro(<< "Could not find a decent visual\n");
    }
  }
  return ( v );
}

vtkXOpenGLRenderWindow::vtkXOpenGLRenderWindow()
{
  this->ParentId = static_cast<Window>(0);
  this->ScreenSize[0] = 0;
  this->ScreenSize[1] = 0;
  this->OwnDisplay = 0;
  this->CursorHidden = 0;
  this->ForceMakeCurrent = 0;
  this->UsingHardware = 0;
  this->DisplayId = static_cast<Display *>(nullptr);
  this->WindowId = static_cast<Window>(0);
  this->NextWindowId = static_cast<Window>(0);
  this->ColorMap = static_cast<Colormap>(0);
  this->OwnWindow = 0;

  this->Internal = new vtkXOpenGLRenderWindowInternal(this);

  this->XCCrosshair = 0;
  this->XCArrow     = 0;
  this->XCSizeAll   = 0;
  this->XCSizeNS    = 0;
  this->XCSizeWE    = 0;
  this->XCSizeNE    = 0;
  this->XCSizeNW    = 0;
  this->XCSizeSE    = 0;
  this->XCSizeSW    = 0;
  this->XCHand      = 0;
}

// free up memory & close the window
vtkXOpenGLRenderWindow::~vtkXOpenGLRenderWindow()
{
  // close-down all system-specific drawing resources
  this->Finalize();

  vtkRenderer *ren;
  vtkCollectionSimpleIterator rit;
  this->Renderers->InitTraversal(rit);
  while ( (ren = this->Renderers->GetNextRenderer(rit)) )
  {
    ren->SetRenderWindow(nullptr);
  }

  delete this->Internal;
}

// End the rendering process and display the image.
void vtkXOpenGLRenderWindow::Frame()
{
  this->MakeCurrent();
  if (!this->AbortRender && this->DoubleBuffer && this->SwapBuffers
      && this->WindowId!=0)
  {
    this->RenderTimer->MarkStartEvent("glXSwapBuffers (may stall for VSync)");
    glXSwapBuffers(this->DisplayId, this->WindowId);
    this->RenderTimer->MarkEndEvent();

    vtkDebugMacro(<< " glXSwapBuffers\n");
  }
}

bool vtkXOpenGLRenderWindow::InitializeFromCurrentContext()
{
  GLXContext currentContext = glXGetCurrentContext();
  if (currentContext != nullptr)
  {
    this->SetDisplayId((void*)glXGetCurrentDisplay());
    this->SetWindowId((void*)glXGetCurrentDrawable());
    this->Internal->ContextId = currentContext;
    return this->Superclass::InitializeFromCurrentContext();
  }
  return false;
}

//
// Set the variable that indicates that we want a stereo capable window
// be created. This method can only be called before a window is realized.
//
void vtkXOpenGLRenderWindow::SetStereoCapableWindow(int capable)
{
  if (!this->Internal->ContextId)
  {
    vtkOpenGLRenderWindow::SetStereoCapableWindow(capable);
  }
  else
  {
    vtkWarningMacro(<< "Requesting a StereoCapableWindow must be performed "
                    << "before the window is realized, i.e. before a render.");
  }
}

static int PbufferAllocFail = 0;
extern "C"
{
  int vtkXOGLPbufferErrorHandler(Display*, XErrorEvent*)
  {
    PbufferAllocFail = 1;
    return 1;
  }
}

extern "C"
{
  int vtkXOGLContextCreationErrorHandler(Display*, XErrorEvent*)
  {
    return 1;
  }
}

void vtkXOpenGLRenderWindow::CreateAWindow()
{
  XVisualInfo  *v, matcher;
  XSetWindowAttributes  attr;
  int x, y, width, height, nItems;
  XWindowAttributes winattr;
  XSizeHints xsh;

  xsh.flags = USSize;
  if ((this->Position[0] >= 0)&&(this->Position[1] >= 0))
  {
    xsh.flags |= USPosition;
    xsh.x =  static_cast<int>(this->Position[0]);
    xsh.y =  static_cast<int>(this->Position[1]);
  }

  x = ((this->Position[0] >= 0) ? this->Position[0] : 5);
  y = ((this->Position[1] >= 0) ? this->Position[1] : 5);
  width = ((this->Size[0] > 0) ? this->Size[0] : 300);
  height = ((this->Size[1] > 0) ? this->Size[1] : 300);

  xsh.width  = width;
  xsh.height = height;

  // get the default display connection
  if (!this->DisplayId)
  {
    this->DisplayId = XOpenDisplay(static_cast<char *>(nullptr));
    if (this->DisplayId == nullptr)
    {
      vtkErrorMacro(<< "bad X server connection. DISPLAY="
        << vtksys::SystemTools::GetEnv("DISPLAY") << ". Aborting.\n");
      abort();
    }
    this->OwnDisplay = 1;
  }

  attr.override_redirect = False;
  if (this->Borders == 0.0)
  {
    attr.override_redirect = True;
  }

  // create our own window ?
  this->OwnWindow = 0;
  if (!this->WindowId)
  {
    v = this->GetDesiredVisualInfo();
    if (!v)
    {
      vtkErrorMacro(<< "Could not find a decent visual\n");
      abort();
    }
    this->ColorMap = XCreateColormap(this->DisplayId,
                                     XRootWindow(this->DisplayId,v->screen),
                                     v->visual, AllocNone);

    attr.background_pixel = 0;
    attr.border_pixel = 0;
    attr.colormap = this->ColorMap;
    attr.event_mask = StructureNotifyMask | ExposureMask;

    // get a default parent if one has not been set.
    if (! this->ParentId)
    {
      this->ParentId = XRootWindow(this->DisplayId, v->screen);
    }
    this->WindowId =
      XCreateWindow(this->DisplayId,
                    this->ParentId,
                    x, y, static_cast<unsigned int>(width),
                    static_cast<unsigned int>(height), 0, v->depth,
                    InputOutput, v->visual,
                    CWBackPixel | CWBorderPixel | CWColormap |
                    CWOverrideRedirect | CWEventMask,
                    &attr);
    XStoreName(this->DisplayId, this->WindowId, this->WindowName);
    XSetNormalHints(this->DisplayId,this->WindowId,&xsh);
    this->OwnWindow = 1;
  }
  else
  {
    XChangeWindowAttributes(this->DisplayId,this->WindowId,
                            CWOverrideRedirect, &attr);
    XGetWindowAttributes(this->DisplayId,
                         this->WindowId,&winattr);
    matcher.visualid = XVisualIDFromVisual(winattr.visual);
    matcher.screen = XDefaultScreen(DisplayId);
    v = XGetVisualInfo(this->DisplayId, VisualIDMask | VisualScreenMask,
                       &matcher, &nItems);

    // if FBConfig is not set, try to find it based on the window
    if (!this->Internal->FBConfig)
    {
      int fbcount = 0;
      GLXFBConfig* fbc = glXGetFBConfigs(this->DisplayId, matcher.screen, &fbcount);
      if ( fbc )
      {
        int i;
        for (i=0; i<fbcount; ++i)
        {
          XVisualInfo *vi = glXGetVisualFromFBConfig( this->DisplayId, fbc[i] );
          if ( vi && vi->visualid == matcher.visualid)
          {
            this->Internal->FBConfig = fbc[i];
          }
        }
        XFree(fbc);
      }
    }

  }

  if (this->OwnWindow)
  {
    // RESIZE THE WINDOW TO THE DESIRED SIZE
    vtkDebugMacro(<< "Resizing the xwindow\n");
    XResizeWindow(this->DisplayId,this->WindowId,
                  ((this->Size[0] > 0) ?
                   static_cast<unsigned int>(this->Size[0]) : 300),
                  ((this->Size[1] > 0) ?
                   static_cast<unsigned int>(this->Size[1]) : 300));
    XSync(this->DisplayId,False);
  }

  // is GLX extension is supported?
  if(!glXQueryExtension(this->DisplayId, nullptr, nullptr))
  {
    vtkErrorMacro("GLX not found.  Aborting.");
    if (this->HasObserver(vtkCommand::ExitEvent))
    {
      this->InvokeEvent(vtkCommand::ExitEvent, nullptr);
      return;
    }
    else
    {
      abort();
    }
  }

  // try for 32 context
  if (this->Internal->FBConfig)
  {
    // NOTE: It is not necessary to create or make current to a context before
    // calling glXGetProcAddressARB
    glXCreateContextAttribsARBProc glXCreateContextAttribsARB =
     (glXCreateContextAttribsARBProc)
      glXGetProcAddressARB( (const GLubyte *) "glXCreateContextAttribsARB" );

    int context_attribs[] =
      {
      GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
      GLX_CONTEXT_MINOR_VERSION_ARB, 2,
      //GLX_CONTEXT_FLAGS_ARB        , GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
      0
      };

    if (glXCreateContextAttribsARB)
    {
      XErrorHandler previousHandler = XSetErrorHandler(vtkXOGLContextCreationErrorHandler);
      this->Internal->ContextId = nullptr;
      // we believe that these later versions are all compatible with
      // OpenGL 3.2 so get a more recent context if we can.
      int attemptedVersions[] = {4,5, 4,4, 4,3, 4,2, 4,1, 4,0, 3,3, 3,2};
      for (int i = 0; i < 8 && !this->Internal->ContextId; i++)
      {
        context_attribs[1] = attemptedVersions[i*2];
        context_attribs[3] = attemptedVersions[i*2+1];
        this->Internal->ContextId =
          glXCreateContextAttribsARB( this->DisplayId,
            this->Internal->FBConfig, nullptr,
            GL_TRUE, context_attribs );
        // Sync to ensure any errors generated are processed.
        XSync( this->DisplayId, False );
      }
      XSetErrorHandler(previousHandler);
      if ( this->Internal->ContextId )
      {
        this->SetContextSupportsOpenGL32(true);
      }
    }
  }

  // old failsafe
  if (this->Internal->ContextId == nullptr)
  {
    this->Internal->ContextId =
      glXCreateContext(this->DisplayId, v, nullptr, GL_TRUE);
  }

  if(!this->Internal->ContextId)
  {
    vtkErrorMacro("Cannot create GLX context.  Aborting.");
    if (this->HasObserver(vtkCommand::ExitEvent))
    {
      this->InvokeEvent(vtkCommand::ExitEvent, nullptr);
      return;
    }
    else
    {
      abort();
    }
  }

  if(this->OwnWindow && !this->OffScreenRendering)
  {
    vtkDebugMacro(" Mapping the xwindow\n");
    XMapWindow(this->DisplayId, this->WindowId);
    XSync(this->DisplayId,False);
    XGetWindowAttributes(this->DisplayId,
                         this->WindowId,&winattr);
    // guarantee that the window is mapped before the program continues
    // on to do the OpenGL rendering.
    while (winattr.map_state == IsUnmapped)
    {
      XGetWindowAttributes(this->DisplayId,
                           this->WindowId,&winattr);
    }
  }
  // free the visual info
  if (v)
  {
    XFree(v);
  }
  this->Mapped = 1;
  this->Size[0] = width;
  this->Size[1] = height;

}

void vtkXOpenGLRenderWindow::DestroyWindow()
{
  // free the cursors
  if (this->DisplayId)
  {
    if (this->WindowId)
    {
      // we will only have a cursor defined if a CurrentCursor has been
      // set > 0 or if the cursor has been hidden... if we undefine without
      // checking, bad things can happen (BadWindow)
      if (this->GetCurrentCursor() || this->CursorHidden)
      {
        XUndefineCursor(this->DisplayId,this->WindowId);
      }
    }
    if (this->XCArrow)
    {
      XFreeCursor(this->DisplayId,this->XCArrow);
    }
    if (this->XCCrosshair)
    {
      XFreeCursor(this->DisplayId,this->XCCrosshair);
    }
    if (this->XCSizeAll)
    {
      XFreeCursor(this->DisplayId,this->XCSizeAll);
    }
    if (this->XCSizeNS)
    {
      XFreeCursor(this->DisplayId,this->XCSizeNS);
    }
    if (this->XCSizeWE)
    {
      XFreeCursor(this->DisplayId,this->XCSizeWE);
    }
    if (this->XCSizeNE)
    {
      XFreeCursor(this->DisplayId,this->XCSizeNE);
    }
    if (this->XCSizeNW)
    {
      XFreeCursor(this->DisplayId,this->XCSizeNW);
    }
    if (this->XCSizeSE)
    {
      XFreeCursor(this->DisplayId,this->XCSizeSE);
    }
    if (this->XCSizeSW)
    {
      XFreeCursor(this->DisplayId,this->XCSizeSW);
    }
    if (this->XCHand)
    {
      XFreeCursor(this->DisplayId,this->XCHand);
    }
  }

  this->XCCrosshair = 0;
  this->XCArrow     = 0;
  this->XCSizeAll   = 0;
  this->XCSizeNS    = 0;
  this->XCSizeWE    = 0;
  this->XCSizeNE    = 0;
  this->XCSizeNW    = 0;
  this->XCSizeSE    = 0;
  this->XCSizeSW    = 0;
  this->XCHand      = 0;

  if (this->OwnContext && this->Internal->ContextId)
  {
    this->MakeCurrent();
    this->ReleaseGraphicsResources(this);

    if (this->Internal->ContextId)
    {
      glFinish();
      glXDestroyContext(this->DisplayId, this->Internal->ContextId);
      glXMakeCurrent(this->DisplayId, None, nullptr);
    }
  }
    this->Internal->ContextId = nullptr;

  if (this->DisplayId && this->WindowId)
  {
    if (this->OwnWindow)
    {
      // close the window if we own it
      XDestroyWindow(this->DisplayId,this->WindowId);
      this->WindowId = static_cast<Window>(0);
    }
    else
    {
      // if we don't own it, simply unmap the window
      XUnmapWindow(this->DisplayId, this->WindowId);
    }
  }

  this->CloseDisplay();

  // make sure all other code knows we're not mapped anymore
  this->Mapped = 0;

}

void vtkXOpenGLRenderWindow::CreateOffScreenWindow(int width, int height)
{
  this->DoubleBuffer = 0;
  if(!this->CreateHardwareOffScreenWindow(width,height))
  {
    vtkErrorMacro(<< "failed to create offscreen window");
  } // if not hardware offscreen
  this->Mapped = 0;
  this->Size[0] = width;
  this->Size[1] = height;
  this->MakeCurrent();

  // tell our renderers about us
  vtkRenderer* ren;
  for (this->Renderers->InitTraversal();
       (ren = this->Renderers->GetNextItem());)
  {
    ren->SetRenderWindow(nullptr);
    ren->SetRenderWindow(this);
  }

  this->OpenGLInit();
}

void vtkXOpenGLRenderWindow::DestroyOffScreenWindow()
{
  // release graphic resources.
  this->ReleaseGraphicsResources(this);
  if(this->OffScreenUseFrameBuffer)
  {
    this->DestroyHardwareOffScreenWindow();
  }
}

void vtkXOpenGLRenderWindow::ResizeOffScreenWindow(int width, int height)
{
  if(!this->OffScreenRendering)
  {
    return;
  }

  if(this->OffScreenUseFrameBuffer)
  {
    this->DestroyOffScreenWindow();
    this->CreateOffScreenWindow(width, height);
  }
}

// Initialize the window for rendering.
void vtkXOpenGLRenderWindow::WindowInitialize (void)
{
  this->CreateAWindow();

  this->MakeCurrent();

  // tell our renderers about us
  vtkRenderer* ren;
  for (this->Renderers->InitTraversal();
       (ren = this->Renderers->GetNextItem());)
  {
    ren->SetRenderWindow(nullptr);
    ren->SetRenderWindow(this);
  }

  this->OpenGLInit();
}

// Initialize the rendering window.
void vtkXOpenGLRenderWindow::Initialize (void)
{
  if (!this->OffScreenRendering && !this->Internal->ContextId)
  {
    // initialize the window
    this->WindowInitialize();
  }
  else if (this->OffScreenRendering && !(this->OffScreenUseFrameBuffer))
  {
    // initialize offscreen window
    int width = ((this->Size[0] > 0) ? this->Size[0] : 300);
    int height = ((this->Size[1] > 0) ? this->Size[1] : 300);
    this->CreateOffScreenWindow(width, height);
  }
}

void vtkXOpenGLRenderWindow::Finalize (void)
{

  // clean up offscreen stuff
  this->SetOffScreenRendering(0);

  // clean and destroy window
  this->DestroyWindow();

}

// Change the window to fill the entire screen.
void vtkXOpenGLRenderWindow::SetFullScreen(int arg)
{
  int *temp;

  if (this->OffScreenRendering)
  {
    return;
  }

  if (this->FullScreen == arg) return;

  if (!this->Mapped)
  {
    this->PrefFullScreen();
    return;
  }

  // set the mode
  this->FullScreen = arg;
  if (this->FullScreen <= 0)
  {
    this->Position[0] = this->OldScreen[0];
    this->Position[1] = this->OldScreen[1];
    this->Size[0] = this->OldScreen[2];
    this->Size[1] = this->OldScreen[3];
    this->Borders = this->OldScreen[4];
  }
  else
  {
    // if window already up get its values
    if (this->WindowId)
    {
      XWindowAttributes attribs;

      //  Find the current window size
      XGetWindowAttributes(this->DisplayId,
                           this->WindowId, &attribs);

      this->OldScreen[2] = attribs.width;
      this->OldScreen[3] = attribs.height;;

      temp = this->GetPosition();
      this->OldScreen[0] = temp[0];
      this->OldScreen[1] = temp[1];

      this->OldScreen[4] = this->Borders;
      this->PrefFullScreen();
    }
  }

  // remap the window
  this->WindowRemap();

  this->Modified();
}

// Set the preferred window size to full screen.
void vtkXOpenGLRenderWindow::PrefFullScreen()
{
  // use full screen
  this->Position[0] = 0;
  this->Position[1] = 0;

  if (this->OffScreenRendering)
  {
    this->Size[0] = 1280;
    this->Size[1] = 1024;
  }
  else
  {
    int *size;
    size = this->GetScreenSize();
    this->Size[0] = size[0];
    this->Size[1] = size[1];
  }

  // don't show borders
  this->Borders = 0;
}

// Resize the window.
void vtkXOpenGLRenderWindow::WindowRemap()
{
  // shut everything down
  this->Finalize();

  // set the default windowid
  this->WindowId = this->NextWindowId;
  this->NextWindowId = static_cast<Window>(0);

  // set everything up again
  this->Initialize();
}

// Begin the rendering process.
void vtkXOpenGLRenderWindow::Start(void)
{
  this->Initialize();

  // When mixing on-screen render windows with offscreen render windows,
  // the active context state can easily get messed up. Ensuring that before we
  // start rendering we force making the context current is a reasonable
  // workaround for now.
  this->SetForceMakeCurrent();

  // set the current window
  this->MakeCurrent();
}


// Specify the size of the rendering window.
void vtkXOpenGLRenderWindow::SetSize(int width,int height)
{
  if ((this->Size[0] != width)||(this->Size[1] != height))
  {
    this->Superclass::SetSize(width, height);

    if (this->Interactor)
    {
      this->Interactor->SetSize( width, height );
    }

    if(this->OffScreenRendering)
    {
      this->ResizeOffScreenWindow(width,height);
    }
    else if(this->WindowId && this->Mapped)
    {
      XResizeWindow(this->DisplayId,this->WindowId,
                    static_cast<unsigned int>(width),
                    static_cast<unsigned int>(height));
      // this is an async call so we wait until we
      // know it has been resized. To avoid infinite
      // loops we put in a count limit just to be safe
      XWindowAttributes attribs;
      int count = 20000;
      do
      {
        XSync(this->DisplayId,False);

        //  Find the current window size
        XGetWindowAttributes(this->DisplayId,
                             this->WindowId, &attribs);
        count--;
      }
      while (count && (attribs.width != width || attribs.height != height));
      if (!count)
      {
        vtkWarningMacro("warning window did not resize in the allotted time");
      }
    }

    this->Modified();
  }
}

bool vtkXOpenGLRenderWindow::SetSwapControl(int i)
{
  glXSwapIntervalEXTProc glXSwapIntervalEXT =
   (glXSwapIntervalEXTProc)
    glXGetProcAddressARB( (const GLubyte *) "glXSwapIntervalEXT" );

  if (!glXSwapIntervalEXT)
  {
    return false;
  }

  // if (i < 0)
  // {
  //   if (glxewIsSupported("GLX_EXT_swap_control_tear"))
  //   {
  //     glXSwapIntervalEXT(i);
  //     return true;
  //   }
  //   return false;
  // }

  glXSwapIntervalEXT(this->DisplayId, this->WindowId, i);
  return true;
}



int vtkXOpenGLRenderWindow::GetDesiredDepth()
{
  XVisualInfo *v;
  int depth = 0;

  // get the default visual to use
  v = this->GetDesiredVisualInfo();

  if (v)
  {
    depth = v->depth;
    XFree(v);
  }

  return depth;
}

// Get a visual from the windowing system.
Visual *vtkXOpenGLRenderWindow::GetDesiredVisual ()
{
  XVisualInfo *v;
  Visual *vis=nullptr;

  // get the default visual to use
  v = this->GetDesiredVisualInfo();

  if (v)
  {
    vis = v->visual;
    XFree(v);
  }

  return vis;
}


// Get a colormap from the windowing system.
Colormap vtkXOpenGLRenderWindow::GetDesiredColormap ()
{
  XVisualInfo *v;

  if (this->ColorMap) return this->ColorMap;

  // get the default visual to use
  v = this->GetDesiredVisualInfo();

  if (v)
  {
    this->ColorMap = XCreateColormap(this->DisplayId,
                                     XRootWindow(this->DisplayId, v->screen),
                                     v->visual, AllocNone);
    XFree(v);
  }

  return this->ColorMap;
}

void vtkXOpenGLRenderWindow::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os,indent);

  os << indent << "ContextId: " << this->Internal->ContextId << "\n";
  os << indent << "Color Map: " << this->ColorMap << "\n";
  os << indent << "Display Id: " << this->GetDisplayId() << "\n";
  os << indent << "Next Window Id: " << this->NextWindowId << "\n";
  os << indent << "Window Id: " << this->GetWindowId() << "\n";
}

// the following can be useful for debugging XErrors
// When uncommented (along with the lines in MakeCurrent)
// it will cause a segfault upon an XError instead of
// the normal XError handler
 // extern "C" {int vtkXError(Display *display, XErrorEvent *err)
 // {
 // // cause a segfault
 //   *(float *)(0x01) = 1.0;
 //   return 1;
 // }}

void vtkXOpenGLRenderWindow::MakeCurrent()
{
  // when debugging XErrors uncomment the following lines
  // if (this->DisplayId)
  //   {
  //     XSynchronize(this->DisplayId,1);
  //   }
  //  XSetErrorHandler(vtkXError);
  if (this->Internal->ContextId &&
      ((this->Internal->ContextId != glXGetCurrentContext())
       || this->ForceMakeCurrent))
  {
    glXMakeCurrent(this->DisplayId,this->WindowId,
        this->Internal->ContextId);
    this->ForceMakeCurrent = 0;
  }
}

// ----------------------------------------------------------------------------
// Description:
// Tells if this window is the current OpenGL context for the calling thread.
bool vtkXOpenGLRenderWindow::IsCurrent()
{
  bool result=false;
  if(this->Internal->ContextId)
  {
    result=this->Internal->ContextId==glXGetCurrentContext();
  }
  return result;
}

void vtkXOpenGLRenderWindow::PushContext()
{
  GLXContext current = glXGetCurrentContext();
  this->ContextStack.push(current);
  this->DisplayStack.push(glXGetCurrentDisplay());
  this->DrawableStack.push(glXGetCurrentDrawable());
  if(this->Internal->ContextId != current)
  {
    this->MakeCurrent();
  }
}

void vtkXOpenGLRenderWindow::PopContext()
{
  GLXContext current = glXGetCurrentContext();
  GLXContext target = static_cast<GLXContext>(this->ContextStack.top());
  this->ContextStack.pop();
  if (target && target != current)
  {
    glXMakeCurrent(this->DisplayStack.top(),
      this->DrawableStack.top(),
      target);
  }
  this->DisplayStack.pop();
  this->DrawableStack.pop();
}

void vtkXOpenGLRenderWindow::SetForceMakeCurrent()
{
  this->ForceMakeCurrent = 1;
}

int vtkXOpenGLRenderWindowFoundMatch;

extern "C"
{
  Bool vtkXOpenGLRenderWindowPredProc(Display *vtkNotUsed(disp),
                                      XEvent *event,
                                      char *arg)
  {
    Window win = (Window)arg;

    if (((reinterpret_cast<XAnyEvent *>(event))->window == win) &&
        ((event->type == ButtonPress)))
    {
      vtkXOpenGLRenderWindowFoundMatch = 1;
    }

    return 0;
  }
}

void *vtkXOpenGLRenderWindow::GetGenericContext()
{
  static GC gc = static_cast<GC>(nullptr);
  if (!gc)
  {
    gc = XCreateGC(this->DisplayId, this->WindowId, 0, nullptr);
  }
  return static_cast<void *>(gc);
}

int vtkXOpenGLRenderWindow::GetEventPending()
{
  XEvent report;

  vtkXOpenGLRenderWindowFoundMatch = 0;
  if (this->OffScreenRendering)
  {
    return vtkXOpenGLRenderWindowFoundMatch;
  }
  XCheckIfEvent(this->DisplayId, &report, vtkXOpenGLRenderWindowPredProc,
                reinterpret_cast<char *>(this->WindowId));
  return vtkXOpenGLRenderWindowFoundMatch;
}

// Get the size of the screen in pixels
int *vtkXOpenGLRenderWindow::GetScreenSize()
{
  // get the default display connection
  if (!this->DisplayId)
  {
    this->DisplayId = XOpenDisplay(static_cast<char *>(nullptr));
    if (this->DisplayId == nullptr)
    {
      vtkErrorMacro(<< "bad X server connection. DISPLAY="
        << vtksys::SystemTools::GetEnv("DISPLAY") << ". Aborting.\n");
      abort();
    }
    else
    {
      this->OwnDisplay = 1;
    }
  }

  this->ScreenSize[0] =
    XDisplayWidth(this->DisplayId, XDefaultScreen(this->DisplayId));
  this->ScreenSize[1] =
    XDisplayHeight(this->DisplayId, XDefaultScreen(this->DisplayId));

  return this->ScreenSize;
}

// Get the position in screen coordinates (pixels) of the window.
int *vtkXOpenGLRenderWindow::GetPosition(void)
{
  XWindowAttributes attribs;
  int x,y;
  Window child;

  // if we aren't mapped then just return the ivar
  if (!this->Mapped)
  {
    return this->Position;
  }

  //  Find the current window size
  XGetWindowAttributes(this->DisplayId, this->WindowId, &attribs);
  x = attribs.x;
  y = attribs.y;

  XTranslateCoordinates(this->DisplayId,this->WindowId,
                        XRootWindowOfScreen(XScreenOfDisplay(
                                              this->DisplayId,0)),
                        x,y,&this->Position[0],&this->Position[1],&child);

  return this->Position;
}

// Get this RenderWindow's X display id.
Display *vtkXOpenGLRenderWindow::GetDisplayId()
{
  vtkDebugMacro(<< "Returning DisplayId of " << static_cast<void *>(this->DisplayId) << "\n");

  return this->DisplayId;
}

// Get this RenderWindow's parent X window id.
Window vtkXOpenGLRenderWindow::GetParentId()
{
  vtkDebugMacro(<< "Returning ParentId of " << reinterpret_cast<void *>(this->ParentId) << "\n");
  return this->ParentId;
}

// Get this RenderWindow's X window id.
Window vtkXOpenGLRenderWindow::GetWindowId()
{
  vtkDebugMacro(<< "Returning WindowId of " << reinterpret_cast<void *>(this->WindowId) << "\n");
  return this->WindowId;
}

// Move the window to a new position on the display.
void vtkXOpenGLRenderWindow::SetPosition(int x, int y)
{
  // if we aren't mapped then just set the ivars
  if (!this->Mapped)
  {
    if ((this->Position[0] != x)||(this->Position[1] != y))
    {
      this->Modified();
    }
    this->Position[0] = x;
    this->Position[1] = y;
    return;
  }

  XMoveWindow(this->DisplayId,this->WindowId,x,y);
  XSync(this->DisplayId,False);
}

// Sets the parent of the window that WILL BE created.
void vtkXOpenGLRenderWindow::SetParentId(Window arg)
{
//   if (this->ParentId)
//     {
//     vtkErrorMacro("ParentId is already set.");
//     return;
//     }

  vtkDebugMacro(<< "Setting ParentId to " << reinterpret_cast<void *>(arg) << "\n");

  this->ParentId = arg;
}

// Set this RenderWindow's X window id to a pre-existing window.
void vtkXOpenGLRenderWindow::SetWindowId(Window arg)
{
  vtkDebugMacro(<< "Setting WindowId to " << reinterpret_cast<void *>(arg) << "\n");

  this->WindowId = arg;

  if (this->CursorHidden)
  {
    this->CursorHidden = 0;
    this->HideCursor();
  }
}

// Set this RenderWindow's X window id to a pre-existing window.
void vtkXOpenGLRenderWindow::SetWindowInfo(char *info)
{
  int tmp;

  // get the default display connection
  if (!this->DisplayId)
  {
    this->DisplayId = XOpenDisplay(static_cast<char *>(nullptr));
    if (this->DisplayId == nullptr)
    {
      vtkErrorMacro(<< "bad X server connection. DISPLAY="
        << vtksys::SystemTools::GetEnv("DISPLAY") << ". Aborting.\n");
      abort();
    }
    else
    {
      this->OwnDisplay = 1;
    }
  }

  sscanf(info,"%i",&tmp);

  this->SetWindowId(static_cast<Window>(tmp));
}

// Set this RenderWindow's X window id to a pre-existing window.
void vtkXOpenGLRenderWindow::SetNextWindowInfo(char *info)
{
  int tmp;
  sscanf(info,"%i",&tmp);

  this->SetNextWindowId(static_cast<Window>(tmp));
}

// Sets the X window id of the window that WILL BE created.
void vtkXOpenGLRenderWindow::SetParentInfo(char *info)
{
  int tmp;

  // get the default display connection
  if (!this->DisplayId)
  {
    this->DisplayId = XOpenDisplay(static_cast<char *>(nullptr));
    if (this->DisplayId == nullptr)
    {
      vtkErrorMacro(<< "bad X server connection. DISPLAY="
        << vtksys::SystemTools::GetEnv("DISPLAY") << ". Aborting.\n");
      abort();
    }
    else
    {
      this->OwnDisplay = 1;
    }
  }

  sscanf(info,"%i",&tmp);

  this->SetParentId(static_cast<Window>(tmp));
}

void vtkXOpenGLRenderWindow::SetWindowId(void *arg)
{
  this->SetWindowId(reinterpret_cast<Window>(arg));
}
void vtkXOpenGLRenderWindow::SetParentId(void *arg)
{
  this->SetParentId(reinterpret_cast<Window>(arg));
}

const char* vtkXOpenGLRenderWindow::ReportCapabilities()
{
  MakeCurrent();

  if (!this->DisplayId)
  {
    return "display id not set";
  }

  int scrnum = XDefaultScreen(this->DisplayId);
  const char *serverVendor = glXQueryServerString(this->DisplayId, scrnum,
                                                  GLX_VENDOR);
  const char *serverVersion = glXQueryServerString(this->DisplayId, scrnum,
                                                   GLX_VERSION);
  const char *serverExtensions = glXQueryServerString(this->DisplayId, scrnum,
                                                      GLX_EXTENSIONS);
  const char *clientVendor = glXGetClientString(this->DisplayId, GLX_VENDOR);
  const char *clientVersion = glXGetClientString(this->DisplayId, GLX_VERSION);
  const char *glxExtensions = glXQueryExtensionsString(this->DisplayId,scrnum);
  const char *glVendor = reinterpret_cast<const char *>(glGetString(GL_VENDOR));
  const char *glRenderer = reinterpret_cast<const char *>(glGetString(GL_RENDERER));
  const char *glVersion = reinterpret_cast<const char *>(glGetString(GL_VERSION));

  std::ostringstream strm;
  strm << "server glx vendor string:  " << serverVendor << endl;
  strm << "server glx version string:  " << serverVersion << endl;
  strm << "server glx extensions:  " << serverExtensions << endl;
  strm << "client glx vendor string:  " << clientVendor << endl;
  strm << "client glx version string:  " << clientVersion << endl;
  strm << "glx extensions:  " << glxExtensions << endl;
  strm << "OpenGL vendor string:  " << glVendor << endl;
  strm << "OpenGL renderer string:  " << glRenderer << endl;
  strm << "OpenGL version string:  " << glVersion << endl;
  strm << "OpenGL extensions:  " << endl;
  int n = 0;
  glGetIntegerv(GL_NUM_EXTENSIONS, &n);
  for (int i = 0; i < n; i++)
  {
    const char *ext = (const char *)glGetStringi(GL_EXTENSIONS, i);
    strm << "  " << ext << endl;
  }

  strm << "X Extensions:  ";

  char **extlist = XListExtensions(this->DisplayId, &n);

  for (int i = 0; i < n; i++)
  {
    if (i != n-1)
    {
      strm << extlist[i] << ", ";
    }
    else
    {
      strm << extlist[i] << endl;
    }
  }

  delete[] this->Capabilities;

  size_t len = strm.str().length();
  this->Capabilities = new char[len + 1];
  strncpy(this->Capabilities, strm.str().c_str(), len);
  this->Capabilities[len] = 0;

  return this->Capabilities;
}

void vtkXOpenGLRenderWindow::CloseDisplay()
{
  // if we create the display, we'll delete it
  if (this->OwnDisplay && this->DisplayId)
  {
    XCloseDisplay(this->DisplayId);
    this->DisplayId = nullptr;
    this->OwnDisplay = 0;
  }
}

int vtkXOpenGLRenderWindow::IsDirect()
{
  this->MakeCurrent();
  this->UsingHardware = 0;
  if (this->DisplayId && this->Internal->ContextId)
  {
    this->UsingHardware = glXIsDirect(this->DisplayId,
                                      this->Internal->ContextId) ? 1:0;
  }
  return this->UsingHardware;
}


void vtkXOpenGLRenderWindow::SetWindowName(const char * cname)
{
  char *name = new char[ strlen(cname)+1 ];
  strcpy(name, cname);
  XTextProperty win_name_text_prop;

  this->vtkOpenGLRenderWindow::SetWindowName( name );

  if (this->Mapped)
  {
    if( XStringListToTextProperty( &name, 1, &win_name_text_prop ) == 0 )
    {
      XFree (win_name_text_prop.value);
      vtkWarningMacro(<< "Can't rename window");
      delete [] name;
      return;
    }

    XSetWMName( this->DisplayId, this->WindowId, &win_name_text_prop );
    XSetWMIconName( this->DisplayId, this->WindowId, &win_name_text_prop );
    XFree (win_name_text_prop.value);
  }
  delete [] name;
}


// Specify the X window id to use if a WindowRemap is done.
void vtkXOpenGLRenderWindow::SetNextWindowId(Window arg)
{
  vtkDebugMacro(<< "Setting NextWindowId to " << reinterpret_cast<void *>(arg) << "\n");

  this->NextWindowId = arg;
}

void vtkXOpenGLRenderWindow::SetNextWindowId(void *arg)
{
  this->SetNextWindowId(reinterpret_cast<Window>(arg));
}


// Set the X display id for this RenderWindow to use to a pre-existing
// X display id.
void vtkXOpenGLRenderWindow::SetDisplayId(Display  *arg)
{
  vtkDebugMacro(<< "Setting DisplayId to " << static_cast<void *>(arg) << "\n");

  this->DisplayId = arg;
  this->OwnDisplay = 0;

}
void vtkXOpenGLRenderWindow::SetDisplayId(void *arg)
{
  this->SetDisplayId(static_cast<Display *>(arg));
  this->OwnDisplay = 0;
}

void vtkXOpenGLRenderWindow::Render()
{
  XWindowAttributes attribs;

  // To avoid the expensive XGetWindowAttributes call,
  // compute size at the start of a render and use
  // the ivar other times.
  if (this->Mapped)
  {
    //  Find the current window size
    XGetWindowAttributes(this->DisplayId,
                         this->WindowId, &attribs);

    this->Size[0] = attribs.width;
    this->Size[1] = attribs.height;
  }

  // Now do the superclass stuff
  this->vtkOpenGLRenderWindow::Render();
}

//----------------------------------------------------------------------------
void vtkXOpenGLRenderWindow::HideCursor()
{
  static char blankBits[] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

  static XColor black = { 0, 0, 0, 0, 0, 0 };

  if (!this->DisplayId || !this->WindowId)
  {
    this->CursorHidden = 1;
  }
  else if (!this->CursorHidden)
  {
    Pixmap blankPixmap = XCreateBitmapFromData(this->DisplayId,
                                               this->WindowId,
                                               blankBits, 16, 16);

    Cursor blankCursor = XCreatePixmapCursor(this->DisplayId, blankPixmap,
                                             blankPixmap, &black, &black,
                                             7, 7);

    XDefineCursor(this->DisplayId, this->WindowId, blankCursor);

    XFreePixmap(this->DisplayId, blankPixmap);

    this->CursorHidden = 1;
  }
}

//----------------------------------------------------------------------------
void vtkXOpenGLRenderWindow::ShowCursor()
{
  if (!this->DisplayId || !this->WindowId)
  {
    this->CursorHidden = 0;
  }
  else if (this->CursorHidden)
  {
    XUndefineCursor(this->DisplayId, this->WindowId);
    this->CursorHidden = 0;
  }
}


//============================================================================
// Stuff above this is almost a mirror of vtkXOpenGLRenderWindow.
// The code specific to OpenGL Off-Screen stuff may eventually be
// put in a supper class so this whole file could just be included
// (mangled) from vtkXOpenGLRenderWindow like the other OpenGL classes.
//============================================================================

void vtkXOpenGLRenderWindow::SetOffScreenRendering(int i)
{
  if (this->OffScreenRendering == i)
  {
    return;
  }

  // invoke super
  this->vtkRenderWindow::SetOffScreenRendering(i);

  if(this->OffScreenRendering)
  {
    this->Internal->ScreenDoubleBuffer = this->DoubleBuffer;
    this->DoubleBuffer = 0;
    if(this->Mapped)
    {
      this->DestroyWindow();
    }

    // delay initialization until Render
  }
  else
  {
    this->DestroyOffScreenWindow();

    this->DoubleBuffer = this->Internal->ScreenDoubleBuffer;

    // reset size based on screen window
    if(this->Mapped && this->WindowId)
    {
      XWindowAttributes a;
      XGetWindowAttributes(this->DisplayId, this->WindowId, &a);

      this->Size[0] = a.width;
      this->Size[1] = a.height;
    }
    // force context switch as we might be going from osmesa to onscreen
    this->SetForceMakeCurrent();
  }
}

// This probably has been moved to superclass.
void *vtkXOpenGLRenderWindow::GetGenericWindowId()
{
  return reinterpret_cast<void*>(this->WindowId);
}

void vtkXOpenGLRenderWindow::SetCurrentCursor(int shape)
{
  if ( this->InvokeEvent(vtkCommand::CursorChangedEvent,&shape) )
  {
    return;
  }
  this->Superclass::SetCurrentCursor(shape);
  if (!this->DisplayId || !this->WindowId)
  {
    return;
  }

  if (shape == VTK_CURSOR_DEFAULT)
  {
    XUndefineCursor(this->DisplayId,this->WindowId);
    return;
  }

  switch (shape)
  {
    case VTK_CURSOR_CROSSHAIR:
      if (!this->XCCrosshair)
      {
        this->XCCrosshair = XCreateFontCursor(this->DisplayId, XC_crosshair);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCCrosshair);
      break;
    case VTK_CURSOR_ARROW:
      if (!this->XCArrow)
      {
        this->XCArrow = XCreateFontCursor(this->DisplayId, XC_top_left_arrow);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCArrow);
      break;
    case VTK_CURSOR_SIZEALL:
      if (!this->XCSizeAll)
      {
        this->XCSizeAll = XCreateFontCursor(this->DisplayId, XC_fleur);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCSizeAll);
      break;
    case VTK_CURSOR_SIZENS:
      if (!this->XCSizeNS)
      {
        this->XCSizeNS = XCreateFontCursor(this->DisplayId,
                                           XC_sb_v_double_arrow);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCSizeNS);
      break;
    case VTK_CURSOR_SIZEWE:
      if (!this->XCSizeWE)
      {
        this->XCSizeWE = XCreateFontCursor(this->DisplayId,
                                           XC_sb_h_double_arrow);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCSizeWE);
      break;
    case VTK_CURSOR_SIZENE:
      if (!this->XCSizeNE)
      {
        this->XCSizeNE = XCreateFontCursor(this->DisplayId,
                                           XC_top_right_corner);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCSizeNE);
      break;
    case VTK_CURSOR_SIZENW:
      if (!this->XCSizeNW)
      {
        this->XCSizeNW = XCreateFontCursor(this->DisplayId,
                                           XC_top_left_corner);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCSizeNW);
      break;
    case VTK_CURSOR_SIZESE:
      if (!this->XCSizeSE)
      {
        this->XCSizeSE = XCreateFontCursor(this->DisplayId,
                                           XC_bottom_right_corner);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCSizeSE);
      break;
    case VTK_CURSOR_SIZESW:
      if (!this->XCSizeSW)
      {
        this->XCSizeSW = XCreateFontCursor(this->DisplayId,
                                           XC_bottom_left_corner);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCSizeSW);
      break;
    case VTK_CURSOR_HAND:
      if (!this->XCHand)
      {
        this->XCHand = XCreateFontCursor(this->DisplayId,
                                         XC_hand1);
      }
      XDefineCursor(this->DisplayId, this->WindowId, this->XCHand);
      break;
  }
}