[dia] Comment on apparently superfluous DDisplay::active_focus

[Hans Breuer <hans src gnome org>]

commit a14cf220e54813bb1a63560f041bdbf12afde7e4
Author: Hans Breuer <hans breuer org>
Date:   Sun Apr 17 13:40:34 2011 +0200

    Comment on apparently superfluous DDisplay::active_focus

 app/display.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/app/display.c b/app/display.c
index b8f2d98..ace42a5 100644
--- a/app/display.c
+++ b/app/display.c
@@ -1652,6 +1652,10 @@ ddisplay_im_context_preedit_reset(DDisplay *ddisp, Focus *focus)
 Focus *
 ddisplay_active_focus(DDisplay *ddisp)
 {
+  /* The functions doing the transition rely on this being slightly
+   * out of sync with get_active_focus(). But we would not need the
+   * pointer, because the return value is only checked being !=NULL
+   */
   return ddisp ? ddisp->active_focus : NULL;
 }