From 2b3ec06ae79f6e66e16e782fd55a528aac1874bc Mon Sep 17 00:00:00 2001
From: MP <163126871+mp-freatic@users.noreply.github.com>
Date: Wed, 13 Nov 2024 10:59:50 +0100
Subject: [PATCH] Adding documentation for events discriminator

---
 docs/programs/anchor/idl.md | 53 +++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/docs/programs/anchor/idl.md b/docs/programs/anchor/idl.md
index 924980b42..2df2e37a3 100644
--- a/docs/programs/anchor/idl.md
+++ b/docs/programs/anchor/idl.md
@@ -459,5 +459,58 @@ Note that different programs using identical account names will generate the
 same discriminator. When deserializing account data, Anchor programs will also
 check an account is owned by the expected program for a specified account type.
 
+</Tab>
+<Tab value="Events">
+
+The event discriminator is used to identify the specific event type when
+deserializing on-chain data on event emission.
+
+```json filename="IDL"  {4}
+  "events": [
+    {
+      "name": "NewEvent",
+      "discriminator": [113, 21, 185, 70, 164, 99, 232, 201]
+    }
+  ]
+```
+
+The discriminator for an event is the first 8 bytes of the Sha256 hash of the
+prefix `event` plus the event name.
+
+For example:
+
+```
+sha256("event:NewEvent")
+```
+
+Hexadecimal output:
+
+```
+71 15 b9 46 a4 63 e8 c9 2a 3c 4d 83 87 16 cd 9b 66 28 cb e2 cb 7c 5d 70 59 f3 42 2b dc 35 03 53
+```
+
+The first 8 bytes are used as the discriminator for the account.
+
+Hex to decimal gives us:
+
+```
+71 = 113
+15 = 21
+b9 = 185
+46 = 70
+a4 = 164
+63 = 99
+e8 = 232
+c9 = 201
+```
+
+You can find the implementation of the discriminator generation in the Anchor
+codebase
+[here](https://github.com/coral-xyz/anchor/blob/v0.30.1/lang/attribute/event/src/lib.rs#L23-L27).
+
+Note that different programs using identical event names will generate the same
+discriminator. When deserializing event data, Anchor programs will also check an
+event is owned by the expected program for a specified event type.
+
 </Tab>
 </Tabs>