icons: Add section.

Author: flexibeast

src/SUMMARY.md

@@ -47,6 +47,7 @@
       - [Xorg](./config/graphical-session/xorg.md)
       - [Wayland](./config/graphical-session/wayland.md)
       - [Fonts](./config/graphical-session/fonts.md)
+      - [Icons](./config/graphical-session/icons.md)
       - [GNOME](./config/graphical-session/gnome.md)
       - [KDE](./config/graphical-session/kde.md)
    - [Multimedia](./config/media/index.md)

src/config/graphical-session/icons.md

@@ -0,0 +1,18 @@
+# Icons
+
+## GTK
+
+By default, GTK-based applications try to use the Adwaita icon theme for
+application icons. Consequently, installation of the `gtk+3` package will also
+install the `adwaita-icon-theme` package. If you wish to use a different theme,
+install the relevant package, then specify the theme in
+`/etc/gtk-3.0/settings.ini` or `~/.config/gtk-3.0/settings.ini`.
+`adwaita-icon-theme` can be removed after
+[ignoring](../../xbps/advanced-usage.md#ignoring-packages) the package.
+
+For information about how to specify a different GTK icon theme in
+`settings.ini`, refer to [the GtkSettings
+documentation](https://developer.gnome.org/gtk3/stable/GtkSettings.html#GtkSettings.properties),
+in particular the
+"[gtk-icon-theme-name](https://developer.gnome.org/gtk3/stable/GtkSettings.html#GtkSettings--gtk-icon-theme-name)"
+property.