Document, how return values of hooks are handled.

doc/api/api.md

@@ -1,6 +1,6 @@
-# API
 @include embed_parameters
 @include http_api
+@include hooks
 @include hooks_client-side
 @include hooks_server-side
 @include editorInfo

doc/api/hooks.md

@@ -0,0 +1,11 @@
+# Hooks
+All hooks are called with two arguments:
+
+1. name - the name of the hook being called
+2. context - an object with some relevant information about the context of the call
+
+## Return values
+A hook should always return a list or undefined. Returning undefined is equivalent to returning an empty list.
+All the returned lists are appended to each other, so if the return values where `[1, 2]`, `undefined`, `[3, 4,]`, `undefined` and `[5]`, the value returned by callHook would be `[1, 2, 3, 4, 5]`.
+
+This is, because it should never matter if you have one plugin or several plugins doing some work - a single plugin should be able to make callHook return the same value a set of plugins are able to return collectively. So, any plugin can return a list of values, of any length, not just one value.

doc/api/hooks_client-side.md

@@ -1,11 +1,6 @@
 # Client-side hooks
 Most of these hooks are called during or in order to set up the formatting process.
 
-All hooks registered to these events are called with two arguments:
-
-1. name - the name of the hook being called
-2. context - an object with some relevant information about the context of the call
-
 ## documentReady
 Called from: src/templates/pad.html
 

doc/api/hooks_server-side.md

@@ -1,11 +1,6 @@
 # Server-side hooks
 These hooks are called on server-side.
 
-All hooks registered to these events are called with two arguments:
-
-1. name - the name of the hook being called
-2. context - an object with some relevant information about the context of the call
-
 ## loadSettings
 Called from: src/node/server.js