Document the commands based Websocket interface

The old interface with ok|reply|stop tuples is deprecated.

doc/src/guide/ws_handlers.asciidoc

@@ -105,7 +105,7 @@ the upgrade:
 [source,erlang]
 ----
 websocket_init(State) ->
-    {reply, {text, <<"Hello!">>}, State}.
+    {[{text, <<"Hello!">>}], State}.
 ----
 
 === Receiving frames
@@ -122,7 +122,7 @@ ignores all others:
 [source,erlang]
 ----
 websocket_handle(Frame = {text, _}, State) ->
-    {reply, Frame, State};
+    {[Frame], State};
 websocket_handle(_Frame, State) ->
     {ok, State}.
 ----
@@ -145,7 +145,7 @@ and ignores all others:
 [source,erlang]
 ----
 websocket_info({log, Text}, State) ->
-    {reply, {text, Text}, State};
+    {[{text, Text}], State};
 websocket_info(_Info, State) ->
     {ok, State}.
 ----
@@ -167,24 +167,23 @@ websocket_info(_Info, State) ->
     {ok, State}.
 ----
 
-To send one frame, return a reply tuple with the frame to send:
+To send one frame, return the frame to be sent:
 
 [source,erlang]
 ----
 websocket_info(_Info, State) ->
-    {reply, {text, <<"Hello!">>}, State}.
+    {[{text, <<"Hello!">>}], State}.
 ----
 
 You can send frames of any type: text, binary, ping, pong
 or close frames.
 
-To send many frames at once, return a reply tuple with the
-list of frames to send:
+You can send many frames at the same time:
 
 [source,erlang]
 ----
 websocket_info(_Info, State) ->
-    {reply, [
+    {[
         {text, "Hello"},
         {text, <<"world!">>},
         {binary, <<0:8000>>}
@@ -246,18 +245,18 @@ Cowboy will have a more reasonable default.
 The Websocket connection process can be set to hibernate
 after the callback returns.
 
-Simply add an `hibernate` field to the ok or reply tuples:
+Simply add an `hibernate` field to the returned tuple:
 
 [source,erlang]
 ----
 websocket_init(State) ->
-    {ok, State, hibernate}.
+    {[], State, hibernate}.
 
 websocket_handle(_Frame, State) ->
-    {ok, State, hibernate}.
+    {[], State, hibernate}.
 
 websocket_info(_Info, State) ->
-    {reply, {text, <<"Hello!">>}, State, hibernate}.
+    {[{text, <<"Hello!">>}], State, hibernate}.
 ----
 
 It is highly recommended to write your handlers with
@@ -289,5 +288,5 @@ The following example sends a close frame with a reason message:
 [source,erlang]
 ----
 websocket_info(_Info, State) ->
-    {reply, {close, 1000, <<"some-reason">>}, State}.
+    {[{close, 1000, <<"some-reason">>}], State}.
 ----

doc/src/manual/cowboy_websocket.asciidoc

@@ -32,14 +32,18 @@ PartialReq :: map()
 State      :: any()
 Opts       :: cowboy_websocket:opts()
 InFrame    :: ping | pong | {text | binary | ping | pong, binary()}
-OutFrame   :: cow_ws:frame()                    %% see types below
 Info       :: any()
 
-CallResult :: {ok, State}
+CallResult :: {commands(), State}
+            | {commands(), State, hibernate}
+            | Deprecated
+
+Deprecated :: {ok, State}
             | {ok, State, hibernate}
             | {reply, OutFrame | [OutFrame], State}
             | {reply, OutFrame | [OutFrame], State, hibernate}
             | {stop, State}
+OutFrame   :: cow_ws:frame()                    %% see types below
 
 Reason     :: normal | stop | timeout
             | remote | {remote, cow_ws:close_code(), binary()}
@@ -69,9 +73,9 @@ frame received. The `websocket_info/2` callback will be
 called for every Erlang message received.
 
 All three Websocket callbacks may send one or more frames
-back to the client (by returning a `reply` tuple) or terminate
-the connection (by sending a `close` frame or returning a `stop`
-tuple).
+back to the client, including close frames to terminate
+the connection; enable/disable active mode; enable/disable
+compression for subsequent frames; or change Websocket options.
 
 The optional `terminate/3` callback will ultimately be called
 with the reason for the termination of the connection. This
@@ -128,6 +132,41 @@ timeout::
 
 == Types
 
+=== commands()
+
+[source,erlang]
+----
+commands() :: [Command]
+
+Command :: {active, boolean()}
+         | {deflate, boolean()}
+         | {set_options, #{idle_timeout => timeout()}}
+         | Frame :: cow_ws:frame()
+----
+
+Commands that may be returned from Websocket callbacks.
+
+The following commands are defined:
+
+active::
+
+Whether to disable or enable reading from the socket. This
+can be used to apply flow control to a Websocket connection.
+
+deflate::
+
+Whether the subsequent frames should be compressed. Has no
+effect on connections that did not negotiate compression.
+
+set_options::
+
+Set Websocket options. Currently only the option `idle_timeout`
+may be updated from a Websocket handler.
+
+Frame::
+
+Send the corresponding Websocket frame.
+
 === cow_ws:frame()
 
 [source,erlang]
@@ -224,6 +263,8 @@ normal circumstances if necessary.
 
 == Changelog
 
+* *2.7*: The commands based interface has been added. The old
+         interface is now deprecated.
 * *2.7*: The option `validate_utf8` has been added.
 * *2.6*: Deflate options can now be configured via `deflate_opts`.
 * *2.0*: The Req object is no longer passed to Websocket callbacks.