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

1 files changed, 4 insertions, 0 deletions

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 };