Robostness FBObject / GLReadBufferUtil: Ignore pre-existing GL errors - remove GL error checking in FBObject bind/unbind.

- User GL code caused errors shall not fail impl.

- FBObject bind/unbind GL error checking is almost useless due to it's simple code,
  would only catch user GL code errors, which should be ignored here.

- MultisampleDemoES2: Only enable GL_MULTISAMPLE if available, i.e. validate passed multisample flag

2 files changed, 5 insertions, 3 deletions

diff --git a/src/jogl/classes/com/jogamp/opengl/FBObject.java b/src/jogl/classes/com/jogamp/opengl/FBObject.java
index 663b4fb9d..8a6495e6b 100644
--- a/src/jogl/classes/com/jogamp/opengl/FBObject.java
+++ b/src/jogl/classes/com/jogamp/opengl/FBObject.java
@@ -725,7 +725,7 @@ public class FBObject {
         
         glerr = gl.glGetError();
         if(DEBUG && GL.GL_NO_ERROR != glerr) {
-            System.err.println("FBObject.init-preexisting.1 GL Error 0x"+Integer.toHexString(glerr));
+            System.err.println("Info: FBObject.init: pre-existing GL error 0x"+Integer.toHexString(glerr));
         }
         
         this.width = width;
@@ -1741,7 +1741,6 @@ public class FBObject {
                 gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, getWriteFramebuffer());                
             }
 
-            checkNoError(null, gl.glGetError(), "FBObject post-bind"); // throws GLException if error
             bound = true;
             samplesSinkDirty = true;
         }
@@ -1766,7 +1765,6 @@ public class FBObject {
             } else {
                 gl.glBindFramebuffer(GL.GL_FRAMEBUFFER, 0); // default draw buffer                
             }
-            checkNoError(null, gl.glGetError(), "FBObject post-unbind"); // throws GLException if error
             bound = false;
         }
     }
diff --git a/src/jogl/classes/com/jogamp/opengl/util/GLReadBufferUtil.java b/src/jogl/classes/com/jogamp/opengl/util/GLReadBufferUtil.java
index b0fae8a6d..34cc0eb07 100644
--- a/src/jogl/classes/com/jogamp/opengl/util/GLReadBufferUtil.java
+++ b/src/jogl/classes/com/jogamp/opengl/util/GLReadBufferUtil.java
@@ -116,6 +116,10 @@ public class GLReadBufferUtil {
      * @see #GLReadBufferUtil(boolean, boolean)
      */
     public boolean readPixels(GL gl, boolean flip) {
+        final int glerr0 = gl.glGetError();
+        if(GL.GL_NO_ERROR != glerr0) {
+            System.err.println("Info: GLReadBufferUtil.readPixels: pre-exisiting GL error 0x"+Integer.toHexString(glerr0));
+        }
         final GLDrawable drawable = gl.getContext().getGLReadDrawable();
         final int textureInternalFormat, textureDataFormat, textureDataType;
         final int[] glImplColorReadVals = new int[] { 0, 0 };