[gimp] scrolledpreview: Add missing gir annotations

[Niels De Graef <nielsdg src gnome org>]

commit aa6079fe8a781abf7752b4b816688e9f67450acb
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Fri May 8 19:48:11 2020 +0200

    scrolledpreview: Add missing gir annotations

 libgimpwidgets/gimpscrolledpreview.c | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/libgimpwidgets/gimpscrolledpreview.c b/libgimpwidgets/gimpscrolledpreview.c
index 49ead8a1d3..cb63cf1163 100644
--- a/libgimpwidgets/gimpscrolledpreview.c
+++ b/libgimpwidgets/gimpscrolledpreview.c
@@ -930,6 +930,14 @@ gimp_scrolled_preview_thaw (GimpScrolledPreview *preview)
     }
 }
 
+/**
+ * gimp_scroll_adjustment_values:
+ * @sevent: A #GdkEventScroll
+ * @hadj: (nullable): Horizontal adjustment
+ * @vadj: (nullable): Vertical adjustment
+ * @hvalue: (out) (optional): Return location for horizontal value, or %NULL
+ * @vvalue: (out) (optional): Return location for vertical value, or %NULL
+ */
 void
 gimp_scroll_adjustment_values (GdkEventScroll *sevent,
                                GtkAdjustment  *hadj,