[gtkmm] Gtk::IconTheme, SelectionData: Add class documentation

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 9031ea0094e86bbeea6ce0932995df4d9377a758
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Jan 9 10:09:10 2018 +0100

    Gtk::IconTheme, SelectionData: Add class documentation

 gtk/src/icontheme.hg     |   21 +++++++++++++++++++++
 gtk/src/selectiondata.hg |   14 ++++++++++++++
 2 files changed, 35 insertions(+), 0 deletions(-)
---
diff --git a/gtk/src/icontheme.hg b/gtk/src/icontheme.hg
index d67643f..88375c1 100644
--- a/gtk/src/icontheme.hg
+++ b/gtk/src/icontheme.hg
@@ -35,6 +35,27 @@ _WRAP_ENUM(IconLookupFlags, GtkIconLookupFlags, NO_GTYPE)
  */
 _WRAP_GERROR(IconThemeError,GtkIconThemeError,GTK_ICON_THEME_ERROR)
 
+/** Looking up icons by name.
+ *
+ * %Gtk::IconTheme provides a facility for looking up icons by name
+ * and size. The main reason for using a name rather than simply
+ * providing a filename is to allow different icons to be used
+ * depending on what “icon theme” is selected by the user.
+ * The operation of icon themes on Linux and Unix follows the
+ * [Icon Theme Specification](http://www.freedesktop.org/Standards/icon-theme-spec).
+ * There is a fallback icon theme, named `hicolor`, where applications
+ * should install their icons, but additional icon themes can be installed
+ * as operating system vendors and users choose.
+ *
+ * In many cases, named themes are used indirectly, via Gtk::Image
+ * rather than directly, but looking up icons
+ * directly is also simple. The %Gtk::IconTheme object acts
+ * as a database of all the icons in the current theme. You
+ * can create new %Gtk::IconTheme objects, but it’s much more
+ * efficient to use the standard icon theme for the Gdk::Display
+ * so that the icon information is shared with other people
+ * looking up icons. Use get_default() or get_for_display().
+ */
 class IconTheme : public Glib::Object
 {
   _CLASS_GOBJECT(IconTheme, GtkIconTheme, GTK_ICON_THEME, Glib::Object, GObject)
diff --git a/gtk/src/selectiondata.hg b/gtk/src/selectiondata.hg
index 1e320a7..9573404 100644
--- a/gtk/src/selectiondata.hg
+++ b/gtk/src/selectiondata.hg
@@ -26,6 +26,20 @@ _DEFS(gtkmm,gtk)
 namespace Gtk
 {
 
+/** Functions for handling inter-process communication via selections.
+ *
+ * The selection mechanism provides the basis for different types
+ * of communication between processes. In particular, drag and drop
+ * works via selections. You will very seldom or
+ * never need to use most of the functions in this section directly.
+ *
+ * Some of the datatypes defined in this section are used in
+ * the drag-and-drop API as well. The Gdk::ContentFormats object represents
+ * lists of data types that are supported when sending or
+ * receiving data. The %Gtk::SelectionData object is used to
+ * store a chunk of data along with the data type and other
+ * associated information.
+ */
 class SelectionData
 {
   _CLASS_BOXEDTYPE(SelectionData, GtkSelectionData, NONE, gtk_selection_data_copy, gtk_selection_data_free)