Document the GDK_VULKAN env var

This was not documented at all yet.

diff --git a/docs/reference/gtk/running.sgml b/docs/reference/gtk/running.sgml
index 3d042a01a1755a4dd850af42453d9942273d165c..b717d717c244c3cb03b157066f1e13d28712b20d 100644 (file)
--- a/docs/reference/gtk/running.sgml
+++ b/docs/reference/gtk/running.sgml
@@ -459,6 +459,28 @@ nevertheless.
   </para>
 </formalpara>
 
+<formalpara>
+  <title><envar>GDK_VULKAN</envar></title>
+
+  <para>
+    This variable can be set to a list of options that influence various aspects
+    of the Vulkan support in GTK+.
+  <variablelist>
+    <varlistentry>
+      <term>disable</term>
+      <listitem><para>Disable Vulkan support</para></listitem>
+    </varlistentry>
+    <varlistentry>
+      <term>validate </term>
+      <listitem><para>Enable the Vulkan validation layer</para></listitem>
+    </varlistentry>
+  </variablelist>
+  The special value <literal>all</literal> can be used to turn on all
+  options. The special value <literal>help</literal> can be used
+  to obtain a list of all supported options.
+  </para>
+</formalpara>
+
 <formalpara>
   <title><envar>GTK_CSD</envar></title>