GLCapabilities Native Aquisition: Set alpha bits at last - due to it's auto setting by setSampleBuffers(true) and setBackgroundOpaque(false)

This bug lead to X11 GLCapabilities rgba: 8/8/8/1 - which ofc is invalid. Sideeffect was a bad selected GLXFB configuration
and the GLContext couldn't be made current.

Patch sets alpha bits reflecting reality carefully after opaque/samples. Added API doc note.

2 files changed, 23 insertions, 22 deletions

diff --git a/src/jogl/classes/jogamp/opengl/egl/EGLGraphicsConfiguration.java b/src/jogl/classes/jogamp/opengl/egl/EGLGraphicsConfiguration.java
index 214b36493..73867fb40 100644
--- a/src/jogl/classes/jogamp/opengl/egl/EGLGraphicsConfiguration.java
+++ b/src/jogl/classes/jogamp/opengl/egl/EGLGraphicsConfiguration.java
@@ -209,24 +209,6 @@ public class EGLGraphicsConfiguration extends MutableGraphicsConfiguration imple
             return false;
         }        
                 
-        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_RED_SIZE, val)) {
-            caps.setRedBits(val.get(0));
-        }
-        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_GREEN_SIZE, val)) {
-            caps.setGreenBits(val.get(0));
-        }
-        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_BLUE_SIZE, val)) {
-            caps.setBlueBits(val.get(0));
-        }
-        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_ALPHA_SIZE, val)) {
-            caps.setAlphaBits(val.get(0));
-        }
-        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_STENCIL_SIZE, val)) {
-            caps.setStencilBits(val.get(0));
-        }
-        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_DEPTH_SIZE, val)) {
-            caps.setDepthBits(val.get(0));
-        }
         if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_SAMPLES, val)) {
             caps.setSampleBuffers(val.get(0)>0?true:false);
             caps.setNumSamples(val.get(0));
@@ -262,6 +244,25 @@ public class EGLGraphicsConfiguration extends MutableGraphicsConfiguration imple
                 caps.setTransparentAlphaValue(val.get(0)==EGL.EGL_DONT_CARE?-1:val.get(0));
             } */
         }
+        // ALPHA shall be set at last - due to it's auto setting by the above (!opaque / samples)
+        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_RED_SIZE, val)) {
+            caps.setRedBits(val.get(0));
+        }
+        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_GREEN_SIZE, val)) {
+            caps.setGreenBits(val.get(0));
+        }
+        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_BLUE_SIZE, val)) {
+            caps.setBlueBits(val.get(0));
+        }
+        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_ALPHA_SIZE, val)) {
+            caps.setAlphaBits(val.get(0));
+        }
+        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_STENCIL_SIZE, val)) {
+            caps.setStencilBits(val.get(0));
+        }
+        if(EGL.eglGetConfigAttrib(display, config, EGL.EGL_DEPTH_SIZE, val)) {
+            caps.setDepthBits(val.get(0));
+        }
         return GLGraphicsConfigurationUtil.addGLCapabilitiesPermutations(capsBucket, caps, drawableTypeBits );
     }
 
diff --git a/src/jogl/classes/jogamp/opengl/egl/EGLGraphicsConfigurationFactory.java b/src/jogl/classes/jogamp/opengl/egl/EGLGraphicsConfigurationFactory.java
index 6be9cb547..d79c351a0 100644
--- a/src/jogl/classes/jogamp/opengl/egl/EGLGraphicsConfigurationFactory.java
+++ b/src/jogl/classes/jogamp/opengl/egl/EGLGraphicsConfigurationFactory.java
@@ -253,12 +253,12 @@ public class EGLGraphicsConfigurationFactory extends GLGraphicsConfigurationFact
             //
             // rgb888 - d16, s4
             final GLCapabilities fixedCaps = new GLCapabilities(glp);
+            fixedCaps.setSampleBuffers(true);
+            fixedCaps.setNumSamples(4);
             fixedCaps.setRedBits(8);
             fixedCaps.setGreenBits(8);
             fixedCaps.setBlueBits(8);
             fixedCaps.setDepthBits(16);
-            fixedCaps.setSampleBuffers(true);
-            fixedCaps.setNumSamples(4);
             if( !capsChosen.isOnscreen() ) {
                 fixedCaps.setOnscreen(false);
                 fixedCaps.setPBuffer(capsChosen.isPBuffer());
@@ -291,12 +291,12 @@ public class EGLGraphicsConfigurationFactory extends GLGraphicsConfigurationFact
             //
             // rgb565 - d16, s4
             final GLCapabilities fixedCaps = new GLCapabilities(glp);
+            fixedCaps.setSampleBuffers(true);
+            fixedCaps.setNumSamples(4);
             fixedCaps.setRedBits(5);
             fixedCaps.setGreenBits(6);
             fixedCaps.setBlueBits(5);
             fixedCaps.setDepthBits(16);
-            fixedCaps.setSampleBuffers(true);
-            fixedCaps.setNumSamples(4);
             if( !capsChosen.isOnscreen() ) {
                 fixedCaps.setOnscreen(false);
                 fixedCaps.setPBuffer(capsChosen.isPBuffer());