---
src/wayland-util.h | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/src/wayland-util.h b/src/wayland-util.h
index caeac82..b6cbe0e 100644
--- a/src/wayland-util.h
+++ b/src/wayland-util.h
@@ -78,12 +78,23 @@ extern "C" {
* wl_message is to a protocol message like a class is to an object.
*
* The `name` of a wl_message is the name of the corresponding protocol
message.
+ *
* The `signature` is an ordered list of symbols representing the data types
* of message arguments and, optionally, a protocol version and indicators for
* nullability. A leading integer in the `signature` indicates the _since_
* version of the protocol message. A `?` preceding a data type symbol
indicates
- * that the following argument type is nullable. When no arguments accompany a
- * message, `signature` is an empty string.
+ * that the following argument type is nullable. While it is a protocol
violation
+ * to send messages with non-nullable arguments set to `NULL`, event handlers
in
+ * clients might still get called with non-nullable object arguments set to
+ * `NULL`. This can happen when the client destroyed the object being used as
+ * argument on its side and an event referencing that object was sent before
the
+ * server knew about its destruction. As this race cannot be prevented, clients
+ * should - as a general rule - program their event handlers such that they can
+ * handle object arguments declared non-nullable being `NULL` gracefully.
+ *
+ * When no arguments accompany a message, `signature` is an empty string.
+ *
+ * Symbols:
*
* * `i`: int
* * `u`: uint
--
2.15.1
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