[gtk+/scrollable-indicator] Add a gtk_scrollable_get_border

[Matthias Clasen <matthiasc src gnome org>]

commit 0ca42c9881dcb33bcad3c6b77d09ff3af1f3f3bf
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Dec 10 06:45:21 2014 -0500

    Add a gtk_scrollable_get_border
    
    Add a vfunc to return a non-scrollable border around scrollables.
    This would be nicer as a property, but we can't add properties
    to an interface without breaking 3rd party implementations, so
    make this an optional vfunc, and handle it not being set.

 docs/reference/gtk/gtk3-sections.txt |    2 +-
 gtk/gtkscrollable.c                  |   28 ++++++++++++++++++++++++++++
 gtk/gtkscrollable.h                  |    8 ++++++++
 3 files changed, 37 insertions(+), 1 deletions(-)
---
diff --git a/docs/reference/gtk/gtk3-sections.txt b/docs/reference/gtk/gtk3-sections.txt
index 6c34734..702a741 100644
--- a/docs/reference/gtk/gtk3-sections.txt
+++ b/docs/reference/gtk/gtk3-sections.txt
@@ -3096,7 +3096,7 @@ gtk_scrollable_get_hscroll_policy
 gtk_scrollable_set_hscroll_policy
 gtk_scrollable_get_vscroll_policy
 gtk_scrollable_set_vscroll_policy
-
+gtk_scrollable_get_border
 
 <SUBSECTION Standard>
 GtkScrollableInterface
diff --git a/gtk/gtkscrollable.c b/gtk/gtkscrollable.c
index 2002878..1ac26b6 100644
--- a/gtk/gtkscrollable.c
+++ b/gtk/gtkscrollable.c
@@ -312,3 +312,31 @@ gtk_scrollable_set_vscroll_policy (GtkScrollable       *scrollable,
 
   g_object_set (scrollable, "vscroll-policy", policy, NULL);
 }
+
+/**
+ * gtk_scrollable_get_border:
+ * @scrollable: a #GtkScrollable
+ * @border: return location for the results
+ *
+ * Returns the size of a non-scrolling border around the
+ * outside of the scrollable. An example for this would
+ * be treeview headers. GTK+ can use this information to
+ * display overlayed graphics, like the overshoot indication,
+ * at the right position.
+ *
+ * Returns: %TRUE if @border has been set
+ *
+ * Since: 3.16
+ */
+gboolean
+gtk_scrollable_get_border (GtkScrollable *scrollable,
+                           GtkBorder     *border)
+{
+  g_return_val_if_fail (GTK_IS_SCROLLABLE (scrollable), FALSE);
+  g_return_val_if_fail (border != NULL, FALSE);
+
+  if (GTK_SCROLLABLE_GET_IFACE (scrollable)->get_border)
+    return GTK_SCROLLABLE_GET_IFACE (scrollable)->get_border (scrollable, border);
+
+  return FALSE;
+}
diff --git a/gtk/gtkscrollable.h b/gtk/gtkscrollable.h
index 112301f..a4e0af1 100644
--- a/gtk/gtkscrollable.h
+++ b/gtk/gtkscrollable.h
@@ -25,6 +25,7 @@
 #include <gdk/gdk.h>
 #include <gtk/gtkenums.h>
 #include <gtk/gtktypes.h>
+#include <gtk/gtkborder.h>
 
 G_BEGIN_DECLS
 
@@ -39,6 +40,9 @@ typedef struct _GtkScrollableInterface GtkScrollableInterface;
 struct _GtkScrollableInterface
 {
   GTypeInterface base_iface;
+
+  gboolean (* get_border) (GtkScrollable *scrollable,
+                           GtkBorder     *border);
 };
 
 /* Public API */
@@ -65,6 +69,10 @@ GDK_AVAILABLE_IN_ALL
 void                 gtk_scrollable_set_vscroll_policy     (GtkScrollable       *scrollable,
                                                            GtkScrollablePolicy  policy);
 
+GDK_AVAILABLE_IN_3_16
+gboolean             gtk_scrollable_get_border             (GtkScrollable       *scrollable,
+                                                            GtkBorder           *border);
+
 G_END_DECLS
 
 #endif /* __GTK_SCROLLABLE_H__ */