[gtk+] Frame: Enhance CSS docs

[Daniel Boles <dboles src gnome org>]

commit 252b03c43eb984df6df399e140ecd75195fb1fb4
Author: Daniel Boles <dboles src gmail com>
Date:   Mon Oct 2 19:27:16 2017 +0100

    Frame: Enhance CSS docs
    
    Indicate how the old shadow types are replaced by CSS border-style et
    al., and quote the names of nodes and classes for easier readability.

 gtk/gtkframe.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)
---
diff --git a/gtk/gtkframe.c b/gtk/gtkframe.c
index 6f109ec..cb8225d 100644
--- a/gtk/gtkframe.c
+++ b/gtk/gtkframe.c
@@ -77,10 +77,14 @@
  * ╰── <child>
  * ]|
  *
- * GtkFrame has a main CSS node with name frame. This node can be given the
- * style class .flat, which is used by themes to disable drawing of the border.
- * To do this from code, call gtk_frame_set_shadow_type() with %GTK_SHADOW_NONE
- * to add the .flat class or any other shadow type to remove it.
+ * GtkFrame has a main CSS node with name “frame”, which is used to draw the
+ * visible border. You can set the appearance of the border using CSS properties
+ * like “border-style” on this node.
+ *
+ * The node can be given the style class “.flat”, which is used by themes to
+ * disable drawing of the border. To do this from code, call
+ * gtk_frame_set_shadow_type() with %GTK_SHADOW_NONE to add the “.flat” class or
+ * any other shadow type to remove it.
  */
 
 struct _GtkFramePrivate