protocol: improve set_keymap docs

 protocol/river-xkb-config-v1.xml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/protocol/river-xkb-config-v1.xml b/protocol/river-xkb-config-v1.xml
index eb57b91..2e3b8dd 100644
--- a/protocol/river-xkb-config-v1.xml
+++ b/protocol/river-xkb-config-v1.xml
@@ -178,6 +178,8 @@
       <description summary="set the keymap">
         Set the keymap for the keyboard.
 
+        Setting a keymap will reset all layout/modifier state.
+
         It is a protocol error to pass a keymap object for which the
         river_xkb_keymap_v1.success event was not received.
       </description>