SDL: docs: Improved SDL_CommonEvent documentation.

SDL Commits
1 
From 179e66f1fe94311ef5c05bc15c90762a2be04571 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Wed, 24 Jun 2026 13:15:53 -0400
Subject: [PATCH] docs: Improved SDL_CommonEvent documentation.

---
 include/SDL3/SDL_events.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/SDL3/SDL_events.h b/include/SDL3/SDL_events.h
index 45181dbe0a015..3aced16fa6327 100644
--- a/include/SDL3/SDL_events.h
+++ b/include/SDL3/SDL_events.h
@@ -296,7 +296,13 @@ typedef enum SDL_EventType
 } SDL_EventType;
 
 /**
- * Fields shared by every event
+ * Fields shared by every event (event.common.*)
+ *
+ * All the individual structs that comprise the SDL_Event union start with
+ * these same fields, so you can access them from any struct directly.
+ *
+ * Event types that don't have further data in a specific struct will still
+ * have valid CommonEvent data, accessible via the event.common field.
  *
  * \since This struct is available since SDL 3.2.0.
  */