JOGL: Proper handling of Read Drawable Support (if not supported), add query.

Read Drawable feature reflects the make context current API
having a seperate read drawable next to the write drawable (default).
  glXMakeContextCurrent(write, read, ..)

On X11 a ready drawable is only supported for GLX >= 1.3,
on Windows only if extension WGL_ARB_make_current_read is available,
on EGL it's always supported, on OSX not at all.

API cleanup GLContext:
  changes: setGLDrawableRead(GLDrawable) ->  setGLReadDrawable(GLDrawable)
  new:     isGLReadDrawableAvailable()
  new:     getGLExtensionsString();

Access qualifier cleanup.

GLContextImpl: GLVersionNumber moved out.

10 files changed, 363 insertions, 352 deletions

diff --git a/src/jogl/classes/com/jogamp/opengl/impl/GLContextImpl.java b/src/jogl/classes/com/jogamp/opengl/impl/GLContextImpl.java
index 4892303e3..cd121979a 100644
--- a/src/jogl/classes/com/jogamp/opengl/impl/GLContextImpl.java
+++ b/src/jogl/classes/com/jogamp/opengl/impl/GLContextImpl.java
@@ -62,7 +62,6 @@ import javax.media.opengl.GLProfile;
 
 public abstract class GLContextImpl extends GLContext {
   protected static final boolean DEBUG = Debug.debug("GLContext");
-  protected static final boolean VERBOSE = Debug.verbose();
 
   protected GLContextLock lock = new GLContextLock();
 
@@ -102,7 +101,7 @@ public abstract class GLContextImpl extends GLContext {
       mappedGLXProcAddress = new HashMap();
   }
 
-  public GLContextImpl(GLDrawableImpl drawable, GLDrawableImpl drawableRead, GLContext shareWith) {
+  public GLContextImpl(GLDrawableImpl drawable, GLContext shareWith) {
     super();
 
     if (shareWith != null) {
@@ -111,11 +110,7 @@ public abstract class GLContextImpl extends GLContext {
     GLContextShareSet.registerForBufferObjectSharing(shareWith, this);
 
     this.drawable = drawable;
-    setGLDrawableRead(drawableRead);
-  }
-
-  public GLContextImpl(GLDrawableImpl drawable, GLContext shareWith) {
-    this(drawable, null, shareWith);
+    this.drawableRead = drawable;
   }
 
   protected void resetStates() {
@@ -144,7 +139,10 @@ public abstract class GLContextImpl extends GLContext {
       super.resetStates();
   }
 
-  public void setGLDrawableRead(GLDrawable read) {
+  public final void setGLReadDrawable(GLDrawable read) {
+    if(null!=read && drawable!=read && !isGLReadDrawableAvailable()) {
+        throw new GLException("GL Read Drawable not available");
+    }
     boolean lockHeld = lock.isHeld();
     if(lockHeld) {
         release();
@@ -155,15 +153,15 @@ public abstract class GLContextImpl extends GLContext {
     }
   }
 
-  public GLDrawable getGLDrawable() {
-    return drawable;
+  public final GLDrawable getGLReadDrawable() {
+    return drawableRead;
   }
 
-  public GLDrawable getGLDrawableRead() {
-    return drawableRead;
+  public final GLDrawable getGLDrawable() {
+    return drawable;
   }
 
-  public GLDrawableImpl getDrawableImpl() {
+  public final GLDrawableImpl getDrawableImpl() {
     return (GLDrawableImpl) getGLDrawable();
   }
 
@@ -685,7 +683,7 @@ public abstract class GLContextImpl extends GLContext {
           ctxOptions = ctp;
 
           // Set version
-          Version version = new Version(versionStr);
+          GLVersionNumber version = new GLVersionNumber(versionStr);
           if (version.isValid()) {
             ctxMajorVersion = version.getMajor();
             ctxMinorVersion = version.getMinor();
@@ -980,14 +978,14 @@ public abstract class GLContextImpl extends GLContext {
       return null;
   }
 
-  public String getGLExtensions() {
+  public String getGLExtensionsString() {
       if(null!=extensionAvailability) {
-        return extensionAvailability.getGLExtensions();
+        return extensionAvailability.getGLExtensionsString();
       }
       return null;
   }
 
-  public boolean isExtensionCacheInitialized() {
+  public final boolean isExtensionCacheInitialized() {
       if(null!=extensionAvailability) {
         return extensionAvailability.isInitialized();
       }
@@ -1038,187 +1036,4 @@ public abstract class GLContextImpl extends GLContext {
     return lock.hasWaiters();
   }
 
-  /* FIXME: needed only by the Java 2D / JOGL bridge; refactor
-
-  public GLContextImpl(GLContext shareWith) {
-    this(shareWith, false);
-  }
-  
-  public GLContextImpl(GLContext shareWith, boolean dontShareWithJava2D) {
-    extensionAvailability = new ExtensionAvailabilityCache(this);
-    GLContext shareContext = shareWith;
-    if (!dontShareWithJava2D) {
-      shareContext = Java2D.filterShareContext(shareWith);
-    }
-    if (shareContext != null) {
-      GLContextShareSet.registerSharing(this, shareContext);
-    }
-    // Always indicate real behind-the-scenes sharing to track deleted objects
-    if (shareContext == null) {
-      shareContext = Java2D.filterShareContext(shareWith);
-    }
-    GLContextShareSet.registerForObjectTracking(shareWith, this, shareContext);
-    GLContextShareSet.registerForBufferObjectSharing(shareWith, this);
-    // This must occur after the above calls into the
-    // GLContextShareSet, which set up state needed by the GL object
-    setGL(createGL());
-  }
-
-  //---------------------------------------------------------------------------
-  // Helpers for integration with Java2D/OpenGL pipeline when FBOs are
-  // being used
-  //
-
-  public void setObjectTracker(GLObjectTracker tracker) {
-    this.tracker = tracker;
-  }
-  
-  public GLObjectTracker getObjectTracker() {
-    return tracker;
-  }
-
-  public void setDeletedObjectTracker(GLObjectTracker deletedObjectTracker) {
-    this.deletedObjectTracker = deletedObjectTracker;
-  }
-
-  public GLObjectTracker getDeletedObjectTracker() {
-    return deletedObjectTracker;
-  }
-
-  // Tracks creation and deletion of server-side OpenGL objects when
-  // the Java2D/OpenGL pipeline is active and using FBOs to render
-  private GLObjectTracker tracker;
-  // Supports deletion of these objects when no other context is
-  // current which can support immediate deletion of them
-  private GLObjectTracker deletedObjectTracker;
-
-  */
-
-  /**
-   * A class for storing and comparing OpenGL version numbers.
-   * This only works for desktop OpenGL at the moment.
-   */
-  private static class Version implements Comparable
-  {
-    private boolean valid;
-    private int major, minor, sub;
-    public Version(int majorRev, int minorRev, int subMinorRev)
-    {
-      major = majorRev;
-      minor = minorRev;
-      sub = subMinorRev;
-    }
-
-    /**
-     * @param versionString must be of the form "GL_VERSION_X" or
-     * "GL_VERSION_X_Y" or "GL_VERSION_X_Y_Z" or "X.Y", where X, Y,
-     * and Z are integers.
-     *
-     * @exception IllegalArgumentException if the argument is not a valid
-     * OpenGL version identifier
-     */
-    public Version(String versionString)
-    {
-      try 
-      {
-        if (versionString.startsWith("GL_VERSION_"))
-        {
-          StringTokenizer tok = new StringTokenizer(versionString, "_");
-
-          tok.nextToken(); // GL_
-          tok.nextToken(); // VERSION_ 
-          if (!tok.hasMoreTokens()) { major = 0; return; }
-          major = Integer.valueOf(tok.nextToken()).intValue();
-          if (!tok.hasMoreTokens()) { minor = 0; return; }
-          minor = Integer.valueOf(tok.nextToken()).intValue();
-          if (!tok.hasMoreTokens()) { sub = 0; return; }
-          sub = Integer.valueOf(tok.nextToken()).intValue();
-        }
-        else
-        {
-          int radix = 10;
-          if (versionString.length() > 2) {
-            if (Character.isDigit(versionString.charAt(0)) &&
-                versionString.charAt(1) == '.' &&
-                Character.isDigit(versionString.charAt(2))) {
-              major = Character.digit(versionString.charAt(0), radix);
-              minor = Character.digit(versionString.charAt(2), radix);
-
-              // See if there's version-specific information which might
-              // imply a more recent OpenGL version
-              StringTokenizer tok = new StringTokenizer(versionString, " ");
-              if (tok.hasMoreTokens()) {
-                tok.nextToken();
-                if (tok.hasMoreTokens()) {
-                  String token = tok.nextToken();
-                  int i = 0;
-                  while (i < token.length() && !Character.isDigit(token.charAt(i))) {
-                    i++;
-                  }
-                  if (i < token.length() - 2 &&
-                      Character.isDigit(token.charAt(i)) &&
-                      token.charAt(i+1) == '.' &&
-                      Character.isDigit(token.charAt(i+2))) {
-                    int altMajor = Character.digit(token.charAt(i), radix);
-                    int altMinor = Character.digit(token.charAt(i+2), radix);
-                    // Avoid possibly confusing situations by putting some
-                    // constraints on the upgrades we do to the major and
-                    // minor versions
-                    if ((altMajor == major && altMinor > minor) ||
-                        altMajor == major + 1) {
-                      major = altMajor;
-                      minor = altMinor;
-                    }
-                  }
-                }
-              }
-            }
-          }
-        }
-        valid = true;
-      }
-      catch (Exception e)
-      {
-        e.printStackTrace();
-        // FIXME: refactor desktop OpenGL dependencies and make this
-        // class work properly for OpenGL ES
-        System.err.println("Info: ExtensionAvailabilityCache: FunctionAvailabilityCache.Version.<init>: "+e);
-        major = 1;
-        minor = 0;
-        /*
-        throw (IllegalArgumentException)
-          new IllegalArgumentException(
-            "Illegally formatted version identifier: \"" + versionString + "\"")
-              .initCause(e);
-        */
-      }
-    }
-
-    public boolean isValid() {
-      return valid;
-    }
-
-    public int compareTo(Object o)
-    {
-      Version vo = (Version)o;
-      if (major > vo.major) return 1; 
-      else if (major < vo.major) return -1; 
-      else if (minor > vo.minor) return 1; 
-      else if (minor < vo.minor) return -1; 
-      else if (sub > vo.sub) return 1; 
-      else if (sub < vo.sub) return -1; 
-
-      return 0; // they are equal
-    }
-
-    public int getMajor() {
-      return major;
-    }
-
-    public int getMinor() {
-      return minor;
-    }
-    
-  } // end class Version
-
 }
diff --git a/src/jogl/classes/com/jogamp/opengl/impl/GLVersionNumber.java b/src/jogl/classes/com/jogamp/opengl/impl/GLVersionNumber.java
new file mode 100644
index 000000000..fa1c5c0c4
--- /dev/null
+++ b/src/jogl/classes/com/jogamp/opengl/impl/GLVersionNumber.java
@@ -0,0 +1,123 @@
+/**
+ * Copyright 2010 JogAmp Community. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification, are
+ * permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice, this list of
+ *       conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *       of conditions and the following disclaimer in the documentation and/or other materials
+ *       provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY JogAmp Community ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JogAmp Community OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * The views and conclusions contained in the software and documentation are those of the
+ * authors and should not be interpreted as representing official policies, either expressed
+ * or implied, of JogAmp Community.
+ */
+
+package com.jogamp.opengl.impl;
+
+import java.util.StringTokenizer;
+import com.jogamp.common.util.VersionNumber;
+
+/**
+ * A class for storing and comparing OpenGL version numbers.
+ * This only works for desktop OpenGL at the moment.
+ */
+class GLVersionNumber extends VersionNumber {
+
+    protected boolean valid;
+
+    public GLVersionNumber(int majorRev, int minorRev, int subMinorRev) {
+        super(majorRev, minorRev, subMinorRev);
+        valid = true;
+    }
+
+    public GLVersionNumber(String versionString) {
+        super();
+        valid = false;
+        try {
+            if (versionString.startsWith("GL_VERSION_")) {
+                StringTokenizer tok = new StringTokenizer(versionString, "_");
+                tok.nextToken(); // GL_
+                tok.nextToken(); // VERSION_
+                if (!tok.hasMoreTokens()) {
+                    major = 0;
+                    return;
+                }
+                major = Integer.valueOf(tok.nextToken()).intValue();
+                if (!tok.hasMoreTokens()) {
+                    minor = 0;
+                    return;
+                }
+                minor = Integer.valueOf(tok.nextToken()).intValue();
+                if (!tok.hasMoreTokens()) {
+                    sub = 0;
+                    return;
+                }
+                sub = Integer.valueOf(tok.nextToken()).intValue();
+            } else {
+                int radix = 10;
+                if (versionString.length() > 2) {
+                    if (Character.isDigit(versionString.charAt(0)) && versionString.charAt(1) == '.' && Character.isDigit(versionString.charAt(2))) {
+                        major = Character.digit(versionString.charAt(0), radix);
+                        minor = Character.digit(versionString.charAt(2), radix);
+                        // See if there's version-specific information which might
+                        // imply a more recent OpenGL version
+                        StringTokenizer tok = new StringTokenizer(versionString, " ");
+                        if (tok.hasMoreTokens()) {
+                            tok.nextToken();
+                            if (tok.hasMoreTokens()) {
+                                String token = tok.nextToken();
+                                int i = 0;
+                                while (i < token.length() && !Character.isDigit(token.charAt(i))) {
+                                    i++;
+                                }
+                                if (i < token.length() - 2 && Character.isDigit(token.charAt(i)) && token.charAt(i + 1) == '.' && Character.isDigit(token.charAt(i + 2))) {
+                                    int altMajor = Character.digit(token.charAt(i), radix);
+                                    int altMinor = Character.digit(token.charAt(i + 2), radix);
+                                    // Avoid possibly confusing situations by putting some
+                                    // constraints on the upgrades we do to the major and
+                                    // minor versions
+                                    if ((altMajor == major && altMinor > minor) || altMajor == major + 1) {
+                                        major = altMajor;
+                                        minor = altMinor;
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+            valid = true;
+        } catch (Exception e) {
+            e.printStackTrace();
+            // FIXME: refactor desktop OpenGL dependencies and make this
+            // class work properly for OpenGL ES
+            System.err.println("Info: ExtensionAvailabilityCache: FunctionAvailabilityCache.Version.<init>: " + e);
+            major = 1;
+            minor = 0;
+            /*
+            throw (IllegalArgumentException)
+            new IllegalArgumentException(
+            "Illegally formatted version identifier: \"" + versionString + "\"")
+            .initCause(e);
+             */
+        }
+    }
+
+    public final boolean isValid() {
+        return valid;
+    }
+}
diff --git a/src/jogl/classes/com/jogamp/opengl/impl/egl/EGLContext.java b/src/jogl/classes/com/jogamp/opengl/impl/egl/EGLContext.java
index d95a9e3ff..246814537 100644
--- a/src/jogl/classes/com/jogamp/opengl/impl/egl/EGLContext.java
+++ b/src/jogl/classes/com/jogamp/opengl/impl/egl/EGLContext.java
@@ -50,14 +50,9 @@ public abstract class EGLContext extends GLContextImpl {
     // EGL extension functions.
     private EGLExtProcAddressTable eglExtProcAddressTable;
 
-    public EGLContext(GLDrawableImpl drawable, GLDrawableImpl drawableRead,
-                      GLContext shareWith) {
-        super(drawable, drawableRead, shareWith);
-    }
-
-    public EGLContext(GLDrawableImpl drawable,
-                      GLContext shareWith) {
-        this(drawable, null, shareWith);
+    EGLContext(GLDrawableImpl drawable,
+               GLContext shareWith) {
+        super(drawable, shareWith);
     }
 
     public Object getPlatformGLExtensions() {
@@ -83,6 +78,10 @@ public abstract class EGLContext extends GLContextImpl {
 
     protected Map/*<String, String>*/ getExtensionNameMap() { return null; }
 
+    public final boolean isGLReadDrawableAvailable() {
+        return true;
+    }
+
     protected void makeCurrentImpl(boolean newCreated) throws GLException {
         if(EGL.EGL_NO_DISPLAY==((EGLDrawable)drawable).getDisplay() ) {
             throw new GLException("drawable not properly initialized, NO DISPLAY: "+drawable);
diff --git a/src/jogl/classes/com/jogamp/opengl/impl/macosx/cgl/MacOSXCGLContext.java b/src/jogl/classes/com/jogamp/opengl/impl/macosx/cgl/MacOSXCGLContext.java
index 3cd2aa650..6a916765a 100644
--- a/src/jogl/classes/com/jogamp/opengl/impl/macosx/cgl/MacOSXCGLContext.java
+++ b/src/jogl/classes/com/jogamp/opengl/impl/macosx/cgl/MacOSXCGLContext.java
@@ -56,14 +56,9 @@ public abstract class MacOSXCGLContext extends GLContextImpl
   // CGL extension functions.
   private CGLExtProcAddressTable cglExtProcAddressTable;
   
-  public MacOSXCGLContext(GLDrawableImpl drawable, GLDrawableImpl drawableRead,
-                          GLContext shareWith) {
-    super(drawable, drawableRead, shareWith);
-  }
-
-  public MacOSXCGLContext(GLDrawableImpl drawable,
-                          GLContext shareWith) {
-    this(drawable, null, shareWith);
+  protected MacOSXCGLContext(GLDrawableImpl drawable,
+                   GLContext shareWith) {
+    super(drawable, shareWith);
   }
   
   public Object getPlatformGLExtensions() {
@@ -99,6 +94,10 @@ public abstract class MacOSXCGLContext extends GLContextImpl
       // FIXME
   }
 
+  public final boolean isGLReadDrawableAvailable() {
+    return false;
+  }
+
   /**
    * Creates and initializes an appropriate OpenGl Context (NS). Should only be
    * called by {@link makeCurrentImpl()}.
@@ -292,11 +291,6 @@ public abstract class MacOSXCGLContext extends GLContextImpl
     throw new GLException("Not yet implemented");
   }
 
-  public boolean isFunctionAvailable(String glFunctionName)
-  {
-    return super.isFunctionAvailable(glFunctionName);
-  }
-  
   public boolean isExtensionAvailable(String glExtensionName) {
     if (glExtensionName.equals("GL_ARB_pbuffer") ||
         glExtensionName.equals("GL_ARB_pixel_format")) {
diff --git a/src/jogl/classes/com/jogamp/opengl/impl/macosx/cgl/awt/MacOSXJava2DCGLContext.java b/src/jogl/classes/com/jogamp/opengl/impl/macosx/cgl/awt/MacOSXJava2DCGLContext.java
index b42f1132c..f19fbcf6b 100644
--- a/src/jogl/classes/com/jogamp/opengl/impl/macosx/cgl/awt/MacOSXJava2DCGLContext.java
+++ b/src/jogl/classes/com/jogamp/opengl/impl/macosx/cgl/awt/MacOSXJava2DCGLContext.java
@@ -62,7 +62,7 @@ public class MacOSXJava2DCGLContext extends MacOSXCGLContext implements Java2DGL
   // rethink this in particular if using FBOs to implement the
   // Java2D/OpenGL pipeline on Mac OS X
 
-  public MacOSXJava2DCGLContext(GLContext shareWith) {
+  MacOSXJava2DCGLContext(GLContext shareWith) {
     super(null, shareWith);
   }
 
diff --git a/src/jogl/classes/com/jogamp/opengl/impl/windows/wgl/WindowsWGLContext.java b/src/jogl/classes/com/jogamp/opengl/impl/windows/wgl/WindowsWGLContext.java
index 2735389e8..53badb25e 100644
--- a/src/jogl/classes/com/jogamp/opengl/impl/windows/wgl/WindowsWGLContext.java
+++ b/src/jogl/classes/com/jogamp/opengl/impl/windows/wgl/WindowsWGLContext.java
@@ -59,8 +59,8 @@ import javax.media.opengl.GLCapabilitiesImmutable;
 
 
 public class WindowsWGLContext extends GLContextImpl {
-  private static final Map/*<String, String>*/ functionNameMap;
-  private static final Map/*<String, String>*/ extensionNameMap;
+  static final Map/*<String, String>*/ functionNameMap;
+  static final Map/*<String, String>*/ extensionNameMap;
   private boolean wglGetExtensionsStringEXTInitialized;
   private boolean wglGetExtensionsStringEXTAvailable;
   private boolean wglMakeContextCurrentInitialized;
@@ -81,14 +81,9 @@ public class WindowsWGLContext extends GLContextImpl {
   }
 
   // FIXME: figure out how to hook back in the Java 2D / JOGL bridge
-  public WindowsWGLContext(GLDrawableImpl drawable, GLDrawableImpl drawableRead,
-                           GLContext shareWith) {
-    super(drawable, drawableRead, shareWith);
-  }
-
-  public WindowsWGLContext(GLDrawableImpl drawable,
-                           GLContext shareWith) {
-    this(drawable, null, shareWith);
+  WindowsWGLContext(GLDrawableImpl drawable,
+                    GLContext shareWith) {
+    super(drawable, shareWith);
   }
 
   protected void resetState() {
@@ -111,20 +106,30 @@ public class WindowsWGLContext extends GLContextImpl {
     return wglExt;
   }
 
+  public final boolean isGLReadDrawableAvailable() {
+    if(!wglMakeContextCurrentInitialized && null != getWGLExtProcAddressTable()) {
+        WindowsWGLDrawableFactory factory = (WindowsWGLDrawableFactory)drawable.getFactoryImpl();
+        AbstractGraphicsConfiguration config = drawable.getNativeSurface().getGraphicsConfiguration().getNativeGraphicsConfiguration();
+        AbstractGraphicsDevice device = config.getScreen().getDevice();
+        WindowsWGLDrawableFactory.SharedResource sr = factory.getOrCreateShared(device);
+        if(null != sr) {
+            wglMakeContextCurrentAvailable = factory.isReadDrawableAvailable(device);
+            wglMakeContextCurrentInitialized=true;
+        }
+    }
+    return wglMakeContextCurrentAvailable;
+  }
+
   private final boolean wglMakeContextCurrent(long hDrawDC, long hReadDC, long ctx) {
     boolean ok = false;
-    WGLExt _wglExt = getWGLExt();
-    if (!wglMakeContextCurrentInitialized) {
-      wglMakeContextCurrentAvailable = isFunctionAvailable("wglMakeContextCurrent");
-      wglMakeContextCurrentInitialized = true;
-      if(DEBUG) {
-          System.err.println("WindowsWGLContext.wglMakeContextCurrent: "+wglMakeContextCurrentAvailable);
-      }
-    }
     if(wglMakeContextCurrentAvailable) {
-        ok = _wglExt.wglMakeContextCurrent(hDrawDC, hReadDC, ctx);
-    } else {
+        // needs initilized WGL ProcAddress table
+        ok = getWGLExt().wglMakeContextCurrent(hDrawDC, hReadDC, ctx);
+    } else if ( hDrawDC == hReadDC ) {
         ok = WGL.wglMakeCurrent(hDrawDC, ctx);
+    } else {
+        // should not happen due to 'isGLReadDrawableAvailable()' query in GLContextImpl
+        throw new InternalError("Given readDrawable but no driver support");
     }
     if(!ok && 0==hDrawDC && 0==hReadDC) {
         // Some GPU's falsely fails with a zero error code (success),
@@ -147,7 +152,7 @@ public class WindowsWGLContext extends GLContextImpl {
   protected Map/*<String, String>*/ getExtensionNameMap() { return extensionNameMap; }
 
   protected void destroyContextARBImpl(long context) {
-    wglMakeContextCurrent(0, 0, 0);
+    WGL.wglMakeCurrent(0, 0);
     WGL.wglDeleteContext(context);
   }
 
@@ -156,11 +161,11 @@ public class WindowsWGLContext extends GLContextImpl {
     AbstractGraphicsConfiguration config = drawable.getNativeSurface().getGraphicsConfiguration().getNativeGraphicsConfiguration();
     AbstractGraphicsDevice device = config.getScreen().getDevice();
     WindowsWGLContext sharedContext = (WindowsWGLContext) factory.getOrCreateSharedContextImpl(device);
-    WGLExt wglExt;
+    WGLExt _wglExt;
     if(null==sharedContext) {
-        wglExt = getWGLExt();
+        _wglExt = getWGLExt();
     } else {
-        wglExt = sharedContext.getWGLExt();
+        _wglExt = sharedContext.getWGLExt();
     }
 
     boolean ctBwdCompat = 0 != ( CTX_PROFILE_COMPAT & ctp ) ;
@@ -202,7 +207,7 @@ public class WindowsWGLContext extends GLContextImpl {
     }
 
     try {
-        ctx = wglExt.wglCreateContextAttribsARB(drawable.getHandle(), share, attribs, 0);
+        ctx = _wglExt.wglCreateContextAttribsARB(drawable.getHandle(), share, attribs, 0);
     } catch (RuntimeException re) {
         if(DEBUG) {
           Throwable t = new Throwable("Info: WindowWGLContext.createContextARBImpl wglCreateContextAttribsARB failed with "+getGLVersion(major, minor, ctp, "@creation"), re);
@@ -211,7 +216,8 @@ public class WindowsWGLContext extends GLContextImpl {
     }
 
     if(0!=ctx) {
-        if (!wglMakeContextCurrent(drawable.getHandle(), drawableRead.getHandle(), ctx)) {
+        // cannot use wglMakeContextCurrent since WGLExt ProcAddressTable is not ready yet.
+        if( !WGL.wglMakeCurrent(drawable.getHandle(), ctx) ) {
             if(DEBUG) {
               System.err.println("WindowsWGLContext.createContextARB couldn't make current "+getGLVersion(major, minor, ctp, "@creation"));
             }
@@ -242,6 +248,8 @@ public class WindowsWGLContext extends GLContextImpl {
     WindowsWGLContext sharedContext = (WindowsWGLContext) factory.getOrCreateSharedContextImpl(device);
     GLCapabilitiesImmutable glCaps = drawable.getChosenGLCapabilities();
 
+    isGLReadDrawableAvailable(); // trigger setup wglMakeContextCurrentAvailable
+
     // Windows can set up sharing of display lists after creation time
     WindowsWGLContext other = (WindowsWGLContext) GLContextShareSet.getShareContext(this);
     long share = 0;
@@ -302,12 +310,12 @@ public class WindowsWGLContext extends GLContextImpl {
     
     if(0!=contextHandle) {
         share = 0; // mark as shared thx to the ARB create method
-        if(0!=temp_ctx) {
-            WGL.wglMakeCurrent(0, 0);
+        WGL.wglMakeCurrent(0, 0); // the ARB create method used WGL.wglMakeCurrent(0, 0)
+        if(0!=temp_ctx) {            
             WGL.wglDeleteContext(temp_ctx);
-            if (!wglMakeContextCurrent(drawable.getHandle(), drawableRead.getHandle(), contextHandle)) {
-                throw new GLException("Cannot make previous verified context current: 0x" + toHexString(contextHandle) + ", werr: " + GDI.GetLastError());
-            }
+        }
+        if (!wglMakeContextCurrent(drawable.getHandle(), drawableRead.getHandle(), contextHandle)) {
+            throw new GLException("Cannot make previous verified context current: 0x" + toHexString(contextHandle) + ", werr: " + GDI.GetLastError());
         }
     } else {
         if(glCaps.getGLProfile().isGL3()) {
@@ -345,7 +353,7 @@ public class WindowsWGLContext extends GLContextImpl {
       if (!wglMakeContextCurrent(drawable.getHandle(), drawableRead.getHandle(), contextHandle)) {
         throw new GLException("Error making context current: 0x" + toHexString(contextHandle) + ", werr: " + GDI.GetLastError() + ", " + this);
       } else {
-        if (DEBUG && (VERBOSE || newCreated)) {
+        if (DEBUG && newCreated) {
           System.err.println(getThreadName() + ": wglMakeCurrent(hdc " + toHexString(drawable.getHandle()) +
                              ", contextHandle " + toHexString(contextHandle) + ") succeeded");
         }
diff --git a/src/jogl/classes/com/jogamp/opengl/impl/windows/wgl/WindowsWGLDrawableFactory.java b/src/jogl/classes/com/jogamp/opengl/impl/windows/wgl/WindowsWGLDrawableFactory.java
index 0180b6c87..99e78b184 100644
--- a/src/jogl/classes/com/jogamp/opengl/impl/windows/wgl/WindowsWGLDrawableFactory.java
+++ b/src/jogl/classes/com/jogamp/opengl/impl/windows/wgl/WindowsWGLDrawableFactory.java
@@ -113,12 +113,18 @@ public class WindowsWGLDrawableFactory extends GLDrawableFactoryImpl {
       private WindowsDummyWGLDrawable drawable;
       private WindowsWGLContext context;
       private boolean canCreateGLPbuffer;
+      private boolean readDrawableAvailable;
 
-      SharedResource(WindowsDummyWGLDrawable draw, WindowsWGLContext ctx, boolean canPbuffer) {
+      SharedResource(WindowsDummyWGLDrawable draw, WindowsWGLContext ctx, boolean readBufferAvail, boolean canPbuffer) {
           drawable = draw;
           context = ctx;
           canCreateGLPbuffer = canPbuffer;
+          readDrawableAvailable = readBufferAvail;
       }
+      WindowsWGLContext getContext() { return context; }
+      boolean canCreateGLPbuffer() { return canCreateGLPbuffer; }
+      boolean isReadDrawableAvailable() { return readDrawableAvailable; }
+
   }
   HashMap/*<connection, SharedResource>*/ sharedMap = new HashMap();
   WindowsGraphicsDevice defaultDevice;
@@ -146,7 +152,11 @@ public class WindowsWGLDrawableFactory extends GLDrawableFactoryImpl {
       }
   }
 
-  private final SharedResource getOrCreateShared(AbstractGraphicsDevice device) {
+  final static String GL_ARB_pbuffer = "GL_ARB_pbuffer";
+  final static String WGL_ARB_make_current_read = "WGL_ARB_make_current_read";
+  final static String wglMakeContextCurrent = "wglMakeContextCurrent";
+
+  protected final SharedResource getOrCreateShared(AbstractGraphicsDevice device) {
     String connection = device.getConnection();
     SharedResource sr;
     synchronized(sharedMap) {
@@ -159,14 +169,17 @@ public class WindowsWGLDrawableFactory extends GLDrawableFactoryImpl {
             WindowsDummyWGLDrawable sharedDrawable = WindowsDummyWGLDrawable.create(this, null);
             WindowsWGLContext ctx  = (WindowsWGLContext) sharedDrawable.createContext(null);
             ctx.makeCurrent();
-            boolean canCreateGLPbuffer = ctx.getGL().isExtensionAvailable("GL_ARB_pbuffer");
+            boolean canCreateGLPbuffer = ctx.getGL().isExtensionAvailable(GL_ARB_pbuffer);
+            boolean readDrawableAvailable = ctx.isExtensionAvailable(WGL_ARB_make_current_read) &&
+                                                     ctx.isFunctionAvailable(wglMakeContextCurrent);
             ctx.release();
-            sr = new SharedResource(sharedDrawable, ctx, canCreateGLPbuffer);
+            sr = new SharedResource(sharedDrawable, ctx, readDrawableAvailable, canCreateGLPbuffer);
             synchronized(sharedMap) {
                 sharedMap.put(device.getConnection(), sr);
             }
             if (DEBUG) {
-              System.err.println("!!! SharedContext: "+ctx+", pbuffer supported "+canCreateGLPbuffer);
+              System.err.println("!!! SharedContext: "+ctx+", pbuffer supported "+canCreateGLPbuffer+
+                                 ", readDrawable supported "+readDrawableAvailable);
             }
 
         } catch (Throwable t) {
@@ -181,7 +194,7 @@ public class WindowsWGLDrawableFactory extends GLDrawableFactoryImpl {
   protected final GLContext getOrCreateSharedContextImpl(AbstractGraphicsDevice device) {
     SharedResource sr = getOrCreateShared(device);
     if(null!=sr) {
-      return sr.context;
+      return sr.getContext();
     }
     return null;
   }
@@ -232,10 +245,18 @@ public class WindowsWGLDrawableFactory extends GLDrawableFactoryImpl {
     return new WindowsOffscreenWGLDrawable(this, target);
   }
 
+  public final boolean isReadDrawableAvailable(AbstractGraphicsDevice device) {
+    SharedResource sr = getOrCreateShared((null!=device)?device:defaultDevice);
+    if(null!=sr) {
+        return sr.isReadDrawableAvailable();
+    }
+    return false;
+  }
+
   public final boolean canCreateGLPbuffer(AbstractGraphicsDevice device) {
     SharedResource sr = getOrCreateShared((null!=device)?device:defaultDevice);
     if(null!=sr) {
-        return sr.canCreateGLPbuffer;
+        return sr.canCreateGLPbuffer();
     }
     return false;
   }
diff --git a/src/jogl/classes/com/jogamp/opengl/impl/x11/glx/X11GLXContext.java b/src/jogl/classes/com/jogamp/opengl/impl/x11/glx/X11GLXContext.java
index 1dadc2edf..fddfb4cd1 100644
--- a/src/jogl/classes/com/jogamp/opengl/impl/x11/glx/X11GLXContext.java
+++ b/src/jogl/classes/com/jogamp/opengl/impl/x11/glx/X11GLXContext.java
@@ -40,6 +40,7 @@
 
 package com.jogamp.opengl.impl.x11.glx;
 
+import com.jogamp.common.util.VersionNumber;
 import java.nio.*;
 import java.util.*;
 import javax.media.opengl.*;
@@ -48,13 +49,14 @@ import com.jogamp.opengl.impl.*;
 import com.jogamp.gluegen.runtime.ProcAddressTable;
 import com.jogamp.gluegen.runtime.opengl.GLProcAddressResolver;
 import com.jogamp.nativewindow.impl.x11.X11Util;
-import javax.media.nativewindow.x11.X11GraphicsDevice;
 
 public abstract class X11GLXContext extends GLContextImpl {
   protected static final boolean TRACE_CONTEXT_CURRENT = false; // true;
 
   private static final Map/*<String, String>*/ functionNameMap;
   private static final Map/*<String, String>*/ extensionNameMap;
+  private VersionNumber glXVersion;
+  private boolean glXVersionOneThreeCapable;
   private boolean glXQueryExtensionsStringInitialized;
   private boolean glXQueryExtensionsStringAvailable;
   private GLXExt glXExt;
@@ -78,17 +80,14 @@ public abstract class X11GLXContext extends GLContextImpl {
     extensionNameMap.put("GL_ARB_pixel_format", "GLX_SGIX_pbuffer"); // good enough
   }
 
-  public X11GLXContext(GLDrawableImpl drawable, GLDrawableImpl drawableRead,
-                      GLContext shareWith) {
-    super(drawable, drawableRead, shareWith);
-  }
-
-  public X11GLXContext(GLDrawableImpl drawable,
-                      GLContext shareWith) {
-    this(drawable, null, shareWith);
+  X11GLXContext(GLDrawableImpl drawable,
+                GLContext shareWith) {
+    super(drawable, shareWith);
   }
   
   protected void resetState() {
+    glXVersion = null;
+    glXVersionOneThreeCapable = false;
     glXQueryExtensionsStringInitialized=false;
     glXQueryExtensionsStringAvailable=false;
     // no inner state glXExt=null;
@@ -120,16 +119,38 @@ public abstract class X11GLXContext extends GLContextImpl {
 
   protected Map/*<String, String>*/ getExtensionNameMap() { return extensionNameMap; }
 
-  protected boolean glXMakeContextCurrent(long dpy, long writeDrawable, long readDrawable, long ctx) {
+  public final boolean isGLReadDrawableAvailable() {
+    if(null == glXVersion) {
+        X11GLXDrawableFactory factory = (X11GLXDrawableFactory)drawable.getFactoryImpl();
+
+        X11GLXGraphicsConfiguration config = (X11GLXGraphicsConfiguration)drawable.getNativeSurface().getGraphicsConfiguration().getNativeGraphicsConfiguration();
+        AbstractGraphicsDevice device = config.getScreen().getDevice();
+
+        glXVersion = factory.getGLXVersion(device);
+        if( null != glXVersion ) {
+            glXVersionOneThreeCapable = glXVersion.compareTo(factory.versionOneThree)>=0;
+        }
+    }
+    return glXVersionOneThreeCapable;
+  }
+
+  private final boolean glXMakeContextCurrent(long dpy, long writeDrawable, long readDrawable, long ctx) {
     boolean res = false;
 
     try {
         if(TRACE_CONTEXT_CURRENT) {
             Throwable t = new Throwable(Thread.currentThread()+" - glXMakeContextCurrent("+toHexString(dpy)+", "+
-                    toHexString(writeDrawable)+", "+toHexString(readDrawable)+", "+toHexString(ctx)+")");
+                    toHexString(writeDrawable)+", "+toHexString(readDrawable)+", "+toHexString(ctx)+") - GLX >= 1.3 "+ glXVersionOneThreeCapable);
             t.printStackTrace();
         }
-        res = GLX.glXMakeContextCurrent(dpy, writeDrawable, readDrawable, ctx);
+        if ( glXVersionOneThreeCapable ) {
+            res = GLX.glXMakeContextCurrent(dpy, writeDrawable, readDrawable, ctx);
+        } else if ( writeDrawable == readDrawable ) {
+            res = GLX.glXMakeCurrent(dpy, writeDrawable, ctx);
+        } else {
+            // should not happen due to 'isGLReadDrawableAvailable()' query in GLContextImpl
+            throw new InternalError("Given readDrawable but no driver support");
+        }
     } catch (RuntimeException re) {
         if(DEBUG) {
           System.err.println("Warning: X11GLXContext.glXMakeContextCurrent failed: "+re+", with "+
@@ -258,6 +279,8 @@ public abstract class X11GLXContext extends GLContextImpl {
     X11GLXContext sharedContext = (X11GLXContext) factory.getOrCreateSharedContextImpl(device);
     long display = device.getHandle();
 
+    isGLReadDrawableAvailable(); // trigger setup glXVersionOneThreeCapable
+
     X11GLXContext other = (X11GLXContext) GLContextShareSet.getShareContext(this);
     long share = 0;
     if (other != null) {
@@ -270,7 +293,7 @@ public abstract class X11GLXContext extends GLContextImpl {
 
     GLCapabilitiesImmutable glCaps = (GLCapabilitiesImmutable) config.getChosenCapabilities();
     GLProfile glp = glCaps.getGLProfile();
-    isVendorATI = factory.isVendorATI(device);
+    isVendorATI = factory.isGLXVendorATI(device);
 
     if(config.getFBConfigID()<0) {
         // not able to use FBConfig
@@ -388,7 +411,7 @@ public abstract class X11GLXContext extends GLContextImpl {
         } finally {
             X11Util.setX11ErrorHandler(false, false);
         }
-        if (DEBUG && (VERBOSE || newCreated)) {
+        if (DEBUG && newCreated) {
             System.err.println(getThreadName() + ": glXMakeCurrent(display " + 
                                toHexString(dpy)+
                                ", drawable " + toHexString(drawable.getHandle()) +
diff --git a/src/jogl/classes/com/jogamp/opengl/impl/x11/glx/X11GLXDrawableFactory.java b/src/jogl/classes/com/jogamp/opengl/impl/x11/glx/X11GLXDrawableFactory.java
index 4412a7a1c..c8b656e9f 100644
--- a/src/jogl/classes/com/jogamp/opengl/impl/x11/glx/X11GLXDrawableFactory.java
+++ b/src/jogl/classes/com/jogamp/opengl/impl/x11/glx/X11GLXDrawableFactory.java
@@ -55,6 +55,7 @@ import java.util.Iterator;
 public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
   
   private static final DesktopGLDynamicLookupHelper x11GLXDynamicLookupHelper;
+  static final VersionNumber versionOneThree = new VersionNumber(1, 3, 0);
 
   static {
     DesktopGLDynamicLookupHelper tmp = null;
@@ -208,7 +209,7 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
           sharedDevice.setCloseDisplay(true);
           X11Util.lockDefaultToolkit(sharedDevice.getHandle()); // OK
           try {
-              String vendorName = GLXUtil.getVendorName(sharedDevice.getHandle());
+              String glXVendorName = GLXUtil.getVendorName(sharedDevice.getHandle());
               X11GraphicsScreen sharedScreen = new X11GraphicsScreen(sharedDevice, 0);
               X11DummyGLXDrawable sharedDrawable = X11DummyGLXDrawable.create(sharedScreen, X11GLXDrawableFactory.this,
                                                                               GLProfile.getDefault(sharedDevice));
@@ -216,9 +217,16 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
                   throw new GLException("Couldn't init shared screen(" + sharedScreen + ")/drawable(" + sharedDrawable + ")");
               }
               X11GLXContext sharedContext;
+              VersionNumber glXVersion;
               try {
                   X11GLXContext ctx = (X11GLXContext) sharedDrawable.createContext(null);
                   ctx.makeCurrent();
+                  {
+                      int[] major = new int[1];
+                      int[] minor = new int[1];
+                      GLXUtil.getGLXVersion(sharedDevice.getHandle(), major, minor);
+                      glXVersion = new VersionNumber(major[0], minor[0], 0);
+                  }
                   ctx.release();
                   sharedContext = ctx;
               } catch (Throwable t) {
@@ -228,12 +236,14 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
                   throw new GLException("X11GLXDrawableFactory - Shared Context is null");
               }
               if (DEBUG) {
-                  System.err.println("!!! SharedDevice: "+sharedDevice);
-                  System.err.println("!!! SharedScreen: "+sharedScreen);
+                  System.err.println("!!! SharedDevice:  "+sharedDevice);
+                  System.err.println("!!! SharedScreen:  "+sharedScreen);
                   System.err.println("!!! SharedContext: "+sharedContext);
-                  System.err.println("!!! Vendor: "+vendorName);
+                  System.err.println("!!! GLX Vendor:    "+glXVendorName);
+                  System.err.println("!!! GLX Version:   "+glXVersion + 
+                                     " >= 1.3: " + ( glXVersion.compareTo(versionOneThree) >= 0 ) );
               }
-              return new SharedResource(sharedDevice, sharedScreen, sharedDrawable, sharedContext, vendorName);
+              return new SharedResource(sharedDevice, sharedScreen, sharedDrawable, sharedContext, glXVersion, glXVendorName);
           } finally {
               X11Util.unlockDefaultToolkit(sharedDevice.getHandle()); // OK
           }
@@ -246,10 +256,10 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
 
               if (DEBUG) {
                   System.err.println("!!! Shutdown Shared:");
-                  System.err.println("!!!          Device  : "+sr.device);
-                  System.err.println("!!!          Screen  : "+sr.screen);
-                  System.err.println("!!!          Drawable: "+sr.drawable);
-                  System.err.println("!!!          CTX     : "+sr.context);
+                  System.err.println("!!!   Device  : "+sr.device);
+                  System.err.println("!!!   Screen  : "+sr.screen);
+                  System.err.println("!!!   Drawable: "+sr.drawable);
+                  System.err.println("!!!   CTX     : "+sr.context);
               }
 
               if (null != sr.context) {
@@ -278,23 +288,34 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
   SharedResourcesRunner sharedResourcesRunner=null;
 
   static class SharedResource {
-      private X11GraphicsDevice device;
-      private X11GraphicsScreen screen;
-      private X11DummyGLXDrawable drawable;
-      private X11GLXContext context;
-      private String vendorName;
-      private boolean isVendorATI;
-      private boolean isVendorNVIDIA;
-      
-      SharedResource(X11GraphicsDevice dev, X11GraphicsScreen scrn, X11DummyGLXDrawable draw, X11GLXContext ctx, String vendor) {
+      X11GraphicsDevice device;
+      X11GraphicsScreen screen;
+      X11DummyGLXDrawable drawable;
+      X11GLXContext context;
+      String glXVendorName;
+      boolean isGLXVendorATI;
+      boolean isGLXVendorNVIDIA;
+      VersionNumber glXVersion;
+
+      SharedResource(X11GraphicsDevice dev, X11GraphicsScreen scrn, 
+                     X11DummyGLXDrawable draw, X11GLXContext ctx,
+                     VersionNumber glXVer, String glXVendor) {
           device = dev;
           screen = scrn;
           drawable = draw;
           context = ctx;
-          vendorName = vendor;
-          isVendorATI = GLXUtil.isVendorATI(vendorName);
-          isVendorNVIDIA = GLXUtil.isVendorNVIDIA(vendorName);          
+          glXVersion = glXVer;
+          glXVendorName = glXVendor;
+          isGLXVendorATI = GLXUtil.isVendorATI(glXVendorName);
+          isGLXVendorNVIDIA = GLXUtil.isVendorNVIDIA(glXVendorName);
       }
+      X11GraphicsDevice getDevice() { return device; }
+      X11GraphicsScreen getScreen() { return screen; }
+      X11GLXContext getContext() { return context; }
+      String getGLXVendorName() { return glXVendorName; }
+      boolean isGLXVendorATI() { return isGLXVendorATI; }
+      boolean isGLXVendorNVIDIA() { return isGLXVendorNVIDIA; }
+      VersionNumber getGLXVersion() { return glXVersion; }
   }
   HashMap/*<connection, SharedResource>*/ sharedMap = new HashMap();
   X11GraphicsDevice defaultDevice;
@@ -354,7 +375,7 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
   protected final GLContext getOrCreateSharedContextImpl(AbstractGraphicsDevice device) {
     SharedResource sr = getOrCreateShared(device);
     if(null!=sr) {
-      return sr.context;
+      return sr.getContext();
     }
     return null;
   }
@@ -362,31 +383,39 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
   protected final long getOrCreateSharedDpy(AbstractGraphicsDevice device) {
     SharedResource sr = getOrCreateShared(device);
     if(null!=sr) {
-        return sr.device.getHandle();
+        return sr.getDevice().getHandle();
     }
     return 0;
   }
 
-  protected final String getVendorName(AbstractGraphicsDevice device) {
+  protected final VersionNumber getGLXVersion(AbstractGraphicsDevice device) {
     SharedResource sr = getOrCreateShared(device);
     if(null!=sr) {
-      return sr.vendorName;
+      return sr.getGLXVersion();
+    }
+    return null;
+  }
+
+  protected final String getGLXVendorName(AbstractGraphicsDevice device) {
+    SharedResource sr = getOrCreateShared(device);
+    if(null!=sr) {
+      return sr.getGLXVendorName();
     }
     return GLXUtil.getVendorName(device.getHandle());
   }
 
-  protected final boolean isVendorATI(AbstractGraphicsDevice device) {
+  protected final boolean isGLXVendorATI(AbstractGraphicsDevice device) {
     SharedResource sr = getOrCreateShared(device);
     if(null!=sr) {
-      return sr.isVendorATI;
+      return sr.isGLXVendorATI();
     }
     return GLXUtil.isVendorATI(device.getHandle());
   }
 
-  protected final boolean isVendorNVIDIA(AbstractGraphicsDevice device) {
+  protected final boolean isGLXVendorNVIDIA(AbstractGraphicsDevice device) {
     SharedResource sr = getOrCreateShared(device);
     if(null!=sr) {
-      return sr.isVendorNVIDIA;
+      return sr.isGLXVendorNVIDIA();
     }
     return GLXUtil.isVendorNVIDIA(device.getHandle());
   }
@@ -413,43 +442,19 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
     return new X11OffscreenGLXDrawable(this, target);
   }
 
-  public final boolean canCreateGLPbuffer(AbstractGraphicsDevice device) {
-      return glxVersionGreaterEqualThan(device, 1, 3); 
+  public final boolean glXVersionGreaterEqualOneThree(AbstractGraphicsDevice device) {
+      VersionNumber glXVersion = getGLXVersion(device);
+      return ( null != glXVersion ) ? glXVersion.compareTo(versionOneThree) >= 0 : false ;
   }
 
-  private boolean glxVersionsQueried = false;
-  private int     glxVersionMajor=0, glxVersionMinor=0;
-  protected final boolean glxVersionGreaterEqualThan(AbstractGraphicsDevice device, int majorReq, int minorReq) {
-    if (!glxVersionsQueried) {
-        if(null == device) {
-            SharedResource sr = getOrCreateShared(defaultDevice);
-            if(null!=sr) {
-                device = sr.device;
-            }
-        }
-        if(null == device) {
-            throw new GLException("FIXME: No AbstractGraphicsDevice (passed or shared-device");
-        }
-        device.lock(); // OK
-        try {
-            long display = device.getHandle();
-            int[] major = new int[1];
-            int[] minor = new int[1];
-
-            GLXUtil.getGLXVersion(display, major, minor);
-            if (DEBUG) {
-              System.err.println("!!! GLX version: major " + major[0] +
-                                 ", minor " + minor[0]);
-            }
-
-            glxVersionMajor = major[0];
-            glxVersionMinor = minor[0];
-            glxVersionsQueried = true;
-        } finally {
-            device.unlock(); // OK
+  public final boolean canCreateGLPbuffer(AbstractGraphicsDevice device) {
+      if(null == device) {
+        SharedResource sr = getOrCreateShared(defaultDevice);
+        if(null!=sr) {
+            device = sr.getDevice();
         }
-    }
-    return ( glxVersionMajor > majorReq ) || ( glxVersionMajor == majorReq && glxVersionMinor >= minorReq ) ;
+      }
+      return glXVersionGreaterEqualOneThree(device);
   }
 
   protected final GLDrawableImpl createGLPbufferDrawableImpl(final NativeSurface target) {
@@ -469,7 +474,7 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
      * since switching Display in this regard is another ATI bug.
      */
     SharedResource sr = getOrCreateShared(device);
-    if( null!=sr && sr.isVendorATI && null == GLContext.getCurrent() ) {
+    if( null!=sr && sr.isGLXVendorATI() && null == GLContext.getCurrent() ) {
         synchronized(sr.context) {
             sr.context.makeCurrent();
             try {
@@ -490,7 +495,7 @@ public class X11GLXDrawableFactory extends GLDrawableFactoryImpl {
     X11GraphicsScreen screen = null;
     SharedResource sr = getOrCreateShared(defaultDevice);
     if(null!=sr) {
-        screen = sr.screen;
+        screen = sr.getScreen();
     }
     if(null==screen) {
         return null;
diff --git a/src/jogl/classes/javax/media/opengl/GLContext.java b/src/jogl/classes/javax/media/opengl/GLContext.java
index 45e1361fb..f76f2b664 100644
--- a/src/jogl/classes/javax/media/opengl/GLContext.java
+++ b/src/jogl/classes/javax/media/opengl/GLContext.java
@@ -116,17 +116,32 @@ public abstract class GLContext {
   public abstract GLDrawable getGLDrawable();
 
   /**
-   * Set the GLDrawable from which this context may be used to
-   * read.<br>
-   * If read is null, the default write drawable will be used.
+   * Return availability of GL read drawable.
+   * @return true if a GL read drawable is supported with your driver, otherwise false.
    */
-  public abstract void setGLDrawableRead(GLDrawable read);
+  public abstract boolean isGLReadDrawableAvailable();
 
   /**
-   * Returns the GLDrawable from which this context may be used to
-   * read.
+   * Set the read GLDrawable for read framebuffer operations.<br>
+   * The caller should query if this feature is supported via {@link #isGLReadDrawableAvailable()}.
+   *
+   * @param read the read GLDrawable for read framebuffer operations.
+   * If null is passed, the default write drawable will be set.
+   *
+   * @throws GLException in case a read drawable is not supported
+   *         and the given drawable is not null and not equal to the internal write drawable.
+   *
+   * @see #isGLReadDrawableAvailable()
+   * @see #getGLReadDrawable()
    */
-  public abstract GLDrawable getGLDrawableRead();
+  public abstract void setGLReadDrawable(GLDrawable read);
+
+  /**
+   * Returns the read GLDrawable this context uses for read framebuffer operations.
+   * @see #isGLReadDrawableAvailable()
+   * @see #setGLReadDrawable(javax.media.opengl.GLDrawable)
+   */
+  public abstract GLDrawable getGLReadDrawable();
 
   /**
    * Makes this GLContext current on the calling thread.
@@ -341,13 +356,13 @@ public abstract class GLContext {
     sb.append(toHexString(contextHandle));
     sb.append(", ");
     sb.append(getGL());
-    if(getGLDrawable()!=getGLDrawableRead()) {
-        sb.append(",\n\tDrawable Read : ");
-        sb.append(getGLDrawableRead());
-        sb.append(",\n\tDrawable Write: ");
+    if(getGLDrawable()!=getGLReadDrawable()) {
+        sb.append(",\n\tRead Drawable : ");
+        sb.append(getGLReadDrawable());
+        sb.append(",\n\tWrite Drawable: ");
         sb.append(getGLDrawable());
     } else {
-        sb.append(",\n\tDrawable Read/Write: ");
+        sb.append(",\n\tDrawable: ");
         sb.append(getGLDrawable());
     }
     return sb;
@@ -359,6 +374,14 @@ public abstract class GLContext {
       current. */
   public abstract String getPlatformExtensionsString();
 
+  /** Returns a non-null (but possibly empty) string containing the
+      space-separated list of available extensions.
+      Can only be called while this context is current.
+      This is equivalent to
+      {@link javax.media.opengl.GL#glGetString(int) glGetString}({@link javax.media.opengl.GL#GL_EXTENSIONS GL_EXTENSIONS})
+   */
+  public abstract String getGLExtensionsString();
+
   public final int getGLVersionMajor() { return ctxMajorVersion; }
   public final int getGLVersionMinor() { return ctxMinorVersion; }
   public final boolean isGLCompatibilityProfile() { return ( 0 != ( CTX_PROFILE_COMPAT & ctxOptions ) ); }