Document GSEAL_ENABLE with other preprocessor symbols.

diff --git a/docs/reference/gtk/compiling.sgml b/docs/reference/gtk/compiling.sgml
index a9a3632a91bee60272fa12cd9ee638574c76aa1a..c5e58b79c52cb56158ebf4065fc8f568fb6c39fb 100644 (file)
--- a/docs/reference/gtk/compiling.sgml
+++ b/docs/reference/gtk/compiling.sgml
@@ -81,5 +81,14 @@ The same for <filename>gtkunixprint.h</filename> if you use the non-portable
 <link linkend="GtkPrintUnixDialog">GtkPrintUnixDialog</link> API.
 </para>
 
+<para>
+The next major version, GTK+ 3,  will remove many implementation details and
+struct members from its public headers. To ensure that your application will
+not have problems with this, you can define the preprocessor symbol
+GSEAL_ENABLE. This will make the compiler catch all uses of direct access to
+struct fields so that you can go through them one by one and replace them with
+a call to an accessor function instead.
+</para>
+
 </refsect1>
 </refentry>