Add {GL, GLContext}.getDefaultDrawBuffer() to complement getDefaultReadBuffer()

3 files changed, 18 insertions, 0 deletions

diff --git a/src/jogl/classes/jogamp/opengl/GLContextImpl.java b/src/jogl/classes/jogamp/opengl/GLContextImpl.java
index 88b746df6..8154dec31 100644
--- a/src/jogl/classes/jogamp/opengl/GLContextImpl.java
+++ b/src/jogl/classes/jogamp/opengl/GLContextImpl.java
@@ -2938,6 +2938,8 @@ public abstract class GLContextImpl extends GLContext {
   @Override
   public final int getDefaultReadFramebuffer() { return drawable.getDefaultReadFramebuffer(); }
   @Override
+  public final int getDefaultDrawBuffer() { return drawable.getDefaultDrawBuffer(gl); }
+  @Override
   public final int getDefaultReadBuffer() { return drawable.getDefaultReadBuffer(gl, drawableRead != drawable); }
 
   //---------------------------------------------------------------------------
diff --git a/src/jogl/classes/jogamp/opengl/GLDrawableImpl.java b/src/jogl/classes/jogamp/opengl/GLDrawableImpl.java
index 98a0a0948..4e0f5eaca 100644
--- a/src/jogl/classes/jogamp/opengl/GLDrawableImpl.java
+++ b/src/jogl/classes/jogamp/opengl/GLDrawableImpl.java
@@ -257,6 +257,17 @@ public abstract class GLDrawableImpl implements GLDrawable {
   protected int getDefaultDrawFramebuffer() { return 0; }
   /** Callback for special implementations, allowing GLContext to fetch a custom default read framebuffer. Defaults to zero. */
   protected int getDefaultReadFramebuffer() { return 0; }
+
+  /** Callback for special implementations, allowing GLContext to fetch a custom default draw buffer of current framebuffer. */
+  protected int getDefaultDrawBuffer(final GL gl) {
+      if( gl.isGLES() || getChosenGLCapabilities().getDoubleBuffered() ) {
+          // Note-1: Neither ES1 nor ES2 supports selecting the read buffer via glDrawBuffer
+          // Note-2: ES3 only supports GL_BACK, GL_NONE or GL_COLOR_ATTACHMENT0+i
+          return GL.GL_BACK;
+      }
+      return GL.GL_FRONT;
+  }
+
   /** Callback for special implementations, allowing GLContext to fetch a custom default read buffer of current framebuffer. */
   protected int getDefaultReadBuffer(final GL gl, final boolean hasDedicatedDrawableRead) {
       if( gl.isGLES() || hasDedicatedDrawableRead || getChosenGLCapabilities().getDoubleBuffered() ) {
diff --git a/src/jogl/classes/jogamp/opengl/GLFBODrawableImpl.java b/src/jogl/classes/jogamp/opengl/GLFBODrawableImpl.java
index 8ec3c0dd9..2bc682324 100644
--- a/src/jogl/classes/jogamp/opengl/GLFBODrawableImpl.java
+++ b/src/jogl/classes/jogamp/opengl/GLFBODrawableImpl.java
@@ -411,6 +411,11 @@ public class GLFBODrawableImpl extends GLDrawableImpl implements GLFBODrawable {
     protected final int getDefaultReadFramebuffer() { return initialized ? fbos[fboIFront].getReadFramebuffer() : 0; }
 
     @Override
+    protected final int getDefaultDrawBuffer(final GL gl) {
+        return initialized ? fbos[fboIBack].getDefaultDrawBuffer() : GL.GL_COLOR_ATTACHMENT0 ;
+    }
+
+    @Override
     protected final int getDefaultReadBuffer(final GL gl, final boolean hasDedicatedDrawableRead) {
         return initialized ? fbos[fboIFront].getDefaultReadBuffer() : GL.GL_COLOR_ATTACHMENT0 ;
     }