update comments, etc related to Read/DrawBuffer state

1 files changed, 5 insertions, 2 deletions

diff --git a/src/mesa/main/buffers.c b/src/mesa/main/buffers.c
index 0e6ca8ea1c2..82dd059e4b2 100644
--- a/src/mesa/main/buffers.c
+++ b/src/mesa/main/buffers.c
@@ -479,9 +479,12 @@ set_color_output(GLcontext *ctx, GLuint output, GLenum buffer,
    /* not really needed, will be set later */
    fb->_NumColorDrawBuffers[output] = 0;
 
-   if (fb->Name == 0)
-   /* Set traditional state var */
+   if (fb->Name == 0) {
+      /* Only set the per-context DrawBuffer state if we're currently
+       * drawing to a window system framebuffer.
+       */
       ctx->Color.DrawBuffer[output] = buffer;
+   }
 }