From Mathias Froehlich, "I have extended the X11 pbuffer code to use either the complete set of glx 1.3

pbuffer functions or exactly ask for the extensions we need to call the
apropriate glx extension functions for and around pbuffers extensions.
The glx 1.3 version of this functios are prefered. If this is not pressent we
are looking for the glx extensions and check for them.
Prevously we just used some mix of the glx 1.3 functions or the extension
functions without making sure that this extension is present.
"

include/osg/GLExtensions

@@ -28,6 +28,10 @@ namespace osg {
 */
 extern OSG_EXPORT float getGLVersionNumber();
 
+/** Return true if "extension" is contained in "extensionString".
+*/
+extern OSG_EXPORT bool isExtensionInExtensionString(const char *extension, const char *extensionString);
+
 /** Return true if OpenGL "extension" is supported.
   * Note: Must only be called within a valid OpenGL context,
   * undefined behavior may occur otherwise.

include/osgViewer/api/X11/PixelBufferX11

@@ -77,7 +77,6 @@ class OSGVIEWER_EXPORT PixelBufferX11 : public osg::GraphicsContext
 
         Display* getDisplay() const { return _display; }
         
-        Window& getParent() { return _parent; }
         GLXPbuffer& getPbuffer() { return _pbuffer; }
         GLXContext& getGLXContext() { return _glxContext; }
 
@@ -91,13 +90,14 @@ class OSGVIEWER_EXPORT PixelBufferX11 : public osg::GraphicsContext
 
         bool            _valid;
         Display*        _display;
-        Window          _parent;
         GLXPbuffer      _pbuffer;
         XVisualInfo*    _visualInfo;
         GLXContext      _glxContext;
 
         bool            _initialized;
         bool            _realized;
+
+        bool            _useGLX1_3;
 };
 
 }

src/osg/GLExtensions.cpp

@@ -48,6 +48,22 @@ float osg::getGLVersionNumber()
     return( atof( vs.substr( 0, vs.find( " " ) ).c_str() ) );
 }
 
+bool osg::isExtensionInExtensionString(const char *extension, const char *extensionString)
+{
+    const char *startOfWord = extensionString;
+    const char *endOfWord;
+    while ((endOfWord = strchr(startOfWord,' ')) != 0)
+    {
+        if (strncmp(extension, startOfWord, endOfWord - startOfWord) == 0)
+            return true;
+        startOfWord = endOfWord+1;
+    }
+    if (*startOfWord && strcmp(extension, startOfWord) == 0)
+        return true;
+   
+   return false;
+}
+
 bool osg::isGLExtensionSupported(unsigned int contextID, const char *extension)
 {
     ExtensionSet& extensionSet = s_glExtensionSetList[contextID];

src/osgViewer/PixelBufferX11.cpp

@@ -18,6 +18,7 @@
 
 #include <osgViewer/api/X11/PixelBufferX11>
 #include <osgViewer/api/X11/GraphicsWindowX11>
+#include <osg/GLExtensions>
 
 #include <X11/Xlib.h>
 
@@ -25,38 +26,15 @@
 
 using namespace osgViewer;
 
-#ifdef GLX_VERSION_1_3
-static GLXFBConfig getFBConfigFromVisual(::Display* dpy, XVisualInfo* visualInfo)
-{
-#if defined(__APPLE__) || defined(_AIX) || defined(__hpux)
-    int screen = visualInfo->screen;
-    int nelements;
-    GLXFBConfig *configs = glXGetFBConfigs(dpy, screen, &nelements);
-    for( int i = 0; i < nelements; i++ )
-    {
-        int visual_id;
-        if( glXGetFBConfigAttrib( dpy, configs[i], GLX_VISUAL_ID, &visual_id ) == 0 )
-        {
-            if( (unsigned int)visual_id == visualInfo->visualid )
-                return configs[i];
-        }
-    }
-    return NULL;
-#else
-    return glXGetFBConfigFromVisualSGIX( dpy, visualInfo );
-#endif
-}
-#endif
-
 PixelBufferX11::PixelBufferX11(osg::GraphicsContext::Traits* traits)
   : _valid(false),
     _display(0),
-    _parent(0),
     _pbuffer(0),
     _visualInfo(0),
     _glxContext(0),
     _initialized(false),
-    _realized(false)
+    _realized(false),
+    _useGLX1_3(false)
 {
     _traits = traits;
 
@@ -85,7 +63,7 @@ PixelBufferX11::~PixelBufferX11()
     close(true);
 }
 
-#ifdef GLX_VERSION_1_3
+#if defined(GLX_VERSION_1_3) || defined(GLX_SGIX_pbuffer)
 bool PixelBufferX11::createVisualInfo()
 {
     typedef std::vector<int> Attributes;
@@ -153,7 +131,7 @@ void PixelBufferX11::init()
         return;
     }
 
-     // Query for GLX extension
+    // Query for GLX extension
     int errorBase, eventBase;
     if( glXQueryExtension( _display, &errorBase, &eventBase)  == False )
     {
@@ -178,16 +156,46 @@ void PixelBufferX11::init()
         return;
     }
 
-    // We need to have at least GLX 1.3 to use getFBConfigFromVisual and glXCreatePbuffer
+    // Just be paranoid, if we are older than 1.1, we cannot even call glxQueryExtensionString
-    if (major < 1 || (major == 1 && minor < 3))
+    if (1 < major || (1 == major && minor < 1))
     {
         osg::notify(osg::NOTICE) << "Error: " << XDisplayName(_traits->displayName().c_str())
-                                 << " GLX version " << major << "." << minor << " is too little." << std::endl;
+                                 << " GLX version " << major << "." << minor << " is too old." << std::endl;
         XCloseDisplay( _display );
         _display = 0;
         _valid = false;
         return;
     }
+
+    bool haveGLX1_3 = false;
+    bool haveSGIX_pbuffer = false;
+
+    // We need to have at least GLX 1.3 to use getFBConfigFromVisual and glXCreatePbuffer
+    if (1 < major || (1 == major && 3 <= minor))
+    {
+        haveGLX1_3 = true;
+    }
+
+#if defined(GLX_VERSION_1_1)
+    // We need at least GLX 1.1 for glXQueryExtensionsString
+    if (!haveGLX1_3 && 1 <= minor)
+    {
+        const char *extensions = glXQueryExtensionsString(_display, screen);
+        haveSGIX_pbuffer = osg::isExtensionInExtensionString("GLX_SGIX_pbuffer", extensions)
+           && osg::isExtensionInExtensionString("GLX_SGIX_fbconfig", extensions);
+    }
+#endif
+
+    if (!haveGLX1_3 && !haveSGIX_pbuffer)
+    {
+        osg::notify(osg::NOTICE) << "Error: " << XDisplayName(_traits->displayName().c_str())
+                                 << " no Pbuffer support in GLX available." << std::endl;
+        XCloseDisplay( _display );
+        _display = 0;
+        _valid = false;
+        return;
+    }
+
     
     if (!createVisualInfo())
     {
@@ -237,43 +245,53 @@ void PixelBufferX11::init()
         return;
     }
     
-    _parent = RootWindow( _display, screen );
+#ifdef GLX_VERSION_1_3
-
+    // First try the regular glx extension if we have a new enough version available.
-    XWindowAttributes watt;
+    if (haveGLX1_3)
-    XGetWindowAttributes( _display, _parent, &watt );
-    // unsigned int parentWindowHeight = watt.height;
-
-    XSetWindowAttributes swatt;
-    swatt.colormap = XCreateColormap( _display, _parent, _visualInfo->visual, AllocNone);
-    //swatt.colormap = DefaultColormap( _dpy, 10 );
-    swatt.background_pixel = 0;
-    swatt.border_pixel = 0;
-    swatt.event_mask =  0;
-    unsigned long mask = CWBackPixel | CWBorderPixel | CWEventMask | CWColormap;
-
-    bool overrideRedirect = false;
-    if (overrideRedirect)
     {
-        swatt.override_redirect = true;
+        int nelements;
-        mask |= CWOverrideRedirect;
+        GLXFBConfig *fbconfigs = glXGetFBConfigs( _display, screen, &nelements );
+        for ( int i = 0; i < nelements; ++i )
+        {
+            int visual_id;
+            if ( glXGetFBConfigAttrib( _display, fbconfigs[i], GLX_VISUAL_ID, &visual_id ) == 0 )
+            {
+                if ( !_pbuffer && (unsigned int)visual_id == _visualInfo->visualid )
+                {
+                    typedef std::vector <int> AttributeList;
+                   
+                    AttributeList attributes;
+                    attributes.push_back( GLX_PBUFFER_WIDTH );
+                    attributes.push_back( _traits->width );
+                    attributes.push_back( GLX_PBUFFER_HEIGHT );
+                    attributes.push_back( _traits->height );
+                    attributes.push_back( 0L );
+                    
+                    _pbuffer = glXCreatePbuffer(_display, fbconfigs[i], &attributes.front() );
+                    _useGLX1_3 = true;
+                }
+            }
+        }
+
+        XFree( fbconfigs );
     }
+#endif
 
-    GLXFBConfig fbconfig = getFBConfigFromVisual( _display, _visualInfo );
+#ifdef GLX_SGIX_pbuffer
+    // If we still have no pbuffer but a capable display with the SGIX extension, try to use that
+    if (!_pbuffer && haveSGIX_pbuffer)
+    {
+        GLXFBConfigSGIX fbconfig = glXGetFBConfigFromVisualSGIX( _display, _visualInfo );
 
-    typedef std::vector <int> AttributeList;
+        _pbuffer = glXCreateGLXPbufferSGIX(_display, fbconfig, _traits->width, _traits->height, 0 );
 
-    AttributeList attributes;
+        XFree( fbconfig );
-    attributes.push_back( GLX_PBUFFER_WIDTH );
+    }
-    attributes.push_back( _traits->width );
+#endif
-    attributes.push_back( GLX_PBUFFER_HEIGHT );
-    attributes.push_back( _traits->height );
-    attributes.push_back( 0L );
 
-    _pbuffer = glXCreatePbuffer(_display, fbconfig, &attributes.front() );
-                             
     if (!_pbuffer)
     {
-        osg::notify(osg::NOTICE)<<"Error: Unable to create Window."<<std::endl;
+        osg::notify(osg::NOTICE)<<"Error: Unable to create pbuffer."<<std::endl;
         XCloseDisplay( _display );
         _display = 0;
         _glxContext = 0;
@@ -301,16 +319,25 @@ void PixelBufferX11::closeImplementation()
     
         if (_pbuffer)
         {
-            glXDestroyPbuffer(_display, _pbuffer);
+            if (_useGLX1_3)
+            {
+#ifdef GLX_VERSION_1_3
+                glXDestroyPbuffer(_display, _pbuffer);
+#endif
+            }
+            else
+            {
+#ifdef GLX_SGIX_pbuffer
+                glXDestroyGLXPbufferSGIX(_display, _pbuffer);
+#endif
+            }
         }
 
         XFlush( _display );
         XSync( _display,0 );
-
     }
     
     _pbuffer = 0;
-    _parent = 0;
     _glxContext = 0;
 
     if (_visualInfo)
@@ -347,7 +374,6 @@ void PixelBufferX11::closeImplementation()
 {
     // osg::notify(osg::NOTICE)<<"Closing PixelBufferX11"<<std::endl;
     _pbuffer = 0;
-    _parent = 0;
     _glxContext = 0;
     _initialized = false;
     _realized = false;