Add support for launching devtools server on random port

Assign random port to devtools server in case user does not specify a
port explicitly and report it to the embedding layer for display to user.

components/config/opts.rs

@@ -653,12 +653,7 @@ pub fn from_cmdline_args(mut opts: Options, args: &[String]) -> ArgumentParsingR
         "Start remote debugger server on port",
         "2794",
     );
-    opts.optflagopt(
-        "",
-        "devtools",
-        "Start remote devtools server on port",
-        "6000",
-    );
+    opts.optflagopt("", "devtools", "Start remote devtools server on port", "0");
     opts.optflagopt(
         "",
         "webdriver",
@@ -886,7 +881,8 @@ pub fn from_cmdline_args(mut opts: Options, args: &[String]) -> ArgumentParsingR
             })
         });
 
-    let devtools_port = opt_match.opt_default("devtools", "6000").map(|port| {
+    // Set default port 0 for a random port to be selected.
+    let devtools_port = opt_match.opt_default("devtools", "0").map(|port| {
         port.parse()
             .unwrap_or_else(|err| args_fail(&format!("Error parsing option: --devtools ({})", err)))
     });

components/devtools/lib.rs

@@ -154,7 +154,20 @@ fn run_server(
     port: u16,
     embedder: EmbedderProxy,
 ) {
-    let listener = TcpListener::bind(&("0.0.0.0", port)).unwrap();
+    let bound = TcpListener::bind(&("0.0.0.0", port)).ok().and_then(|l| {
+        l.local_addr()
+            .map(|addr| addr.port())
+            .ok()
+            .map(|port| (l, port))
+    });
+
+    let port = bound.as_ref().map(|(_, port)| *port).ok_or(());
+    embedder.send((None, EmbedderMsg::OnDevtoolsStarted(port)));
+
+    let listener = match bound {
+        Some((l, _)) => l,
+        None => return,
+    };
 
     let mut registry = ActorRegistry::new();
 

components/embedder_traits/lib.rs

@@ -198,6 +198,8 @@ pub enum EmbedderMsg {
     /// Notifies the embedder about media session events
     /// (i.e. when there is metadata for the active media session, playback state changes...).
     MediaSessionEvent(MediaSessionEvent),
+    /// Report the status of Devtools Server
+    OnDevtoolsStarted(Result<u16, ()>),
 }
 
 impl Debug for EmbedderMsg {
@@ -232,6 +234,7 @@ impl Debug for EmbedderMsg {
             EmbedderMsg::BrowserCreated(..) => write!(f, "BrowserCreated"),
             EmbedderMsg::ReportProfile(..) => write!(f, "ReportProfile"),
             EmbedderMsg::MediaSessionEvent(..) => write!(f, "MediaSessionEvent"),
+            EmbedderMsg::OnDevtoolsStarted(..) => write!(f, "OnDevtoolsStarted"),
         }
     }
 }

ports/glutin/browser.rs

@@ -515,6 +515,12 @@ where
                     debug!("MediaSessionEvent received");
                     // TODO(ferjm): MediaSession support for Glutin based browsers.
                 },
+                EmbedderMsg::OnDevtoolsStarted(port) => {
+                    match port {
+                        Ok(p) => info!("Devtools Server running on port {}", p),
+                        Err(()) => error!("Error running devtools server"),
+                    }
+                },
             }
         }
     }

ports/libmlservo/src/lib.rs

@@ -423,6 +423,13 @@ impl HostTrait for HostCallbacks {
     }
 
     fn set_clipboard_contents(&self, _contents: String) {}
+
+    fn on_devtools_started(&self, port: Result<u16, ()>) {
+        match port {
+            Ok(p) => info!("Devtools Server running on port {}", p),
+            Err(()) => error!("Error running Devtools server"),
+        }
+    }
 }
 
 pub struct ServoInstance {

ports/libsimpleservo/api/src/lib.rs

@@ -146,6 +146,8 @@ pub trait HostTrait {
     fn on_media_session_playback_state_change(&self, state: MediaSessionPlaybackState);
     /// Called when the media session position state is set.
     fn on_media_session_set_position_state(&self, duration: f64, position: f64, playback_rate: f64);
+    /// Called when devtools server is started
+    fn on_devtools_started(&self, port: Result<u16, ()>);
 }
 
 pub struct ServoGlue {
@@ -670,6 +672,9 @@ impl ServoGlue {
                             ),
                     };
                 },
+                EmbedderMsg::OnDevtoolsStarted(port) => {
+                    self.callbacks.host_callbacks.on_devtools_started(port);
+                },
                 EmbedderMsg::Status(..) |
                 EmbedderMsg::SelectFiles(..) |
                 EmbedderMsg::MoveTo(..) |

ports/libsimpleservo/capi/src/lib.rs

@@ -23,7 +23,7 @@ use simpleservo::{
 use std::ffi::{CStr, CString};
 #[cfg(target_os = "windows")]
 use std::mem;
-use std::os::raw::{c_char, c_void};
+use std::os::raw::{c_char, c_uint, c_void};
 use std::panic::{self, UnwindSafe};
 use std::slice;
 use std::str::FromStr;
@@ -229,6 +229,7 @@ pub struct CHostCallbacks {
         default: *const c_char,
         trusted: bool,
     ) -> *const c_char,
+    pub on_devtools_started: extern "C" fn(result: CDevtoolsServerState, port: c_uint),
 }
 
 /// Servo options
@@ -286,6 +287,12 @@ pub enum CMediaSessionPlaybackState {
     Paused,
 }
 
+#[repr(C)]
+pub enum CDevtoolsServerState {
+    Started,
+    Error,
+}
+
 impl From<MediaSessionPlaybackState> for CMediaSessionPlaybackState {
     fn from(state: MediaSessionPlaybackState) -> Self {
         match state {
@@ -854,4 +861,17 @@ impl HostTrait for HostCallbacks {
         let contents_str = c_str.to_str().expect("Can't create str");
         Some(contents_str.to_owned())
     }
+
+    fn on_devtools_started(&self, port: Result<u16, ()>) {
+        match port {
+            Ok(p) => {
+                info!("Devtools Server running on port {}", p);
+                (self.0.on_devtools_started)(CDevtoolsServerState::Started, p.into());
+            },
+            Err(()) => {
+                error!("Error running devtools server");
+                (self.0.on_devtools_started)(CDevtoolsServerState::Error, 0);
+            },
+        }
+    }
 }

ports/libsimpleservo/jniapi/src/lib.rs

@@ -603,6 +603,13 @@ impl HostTrait for HostCallbacks {
         )
         .unwrap();
     }
+
+    fn on_devtools_started(&self, port: Result<u16, ()>) {
+        match port {
+            Ok(p) => info!("Devtools Server running on port {}", p),
+            Err(()) => error!("Error running devtools server"),
+        }
+    }
 }
 
 fn initialize_android_glue(env: &JNIEnv, activity: JObject) {

support/hololens/ServoApp/ServoControl/Servo.cpp

@@ -87,6 +87,11 @@ const char *prompt_input(const char *message, const char *default,
   }
 }
 
+void on_devtools_started(Servo::DevtoolsServerState result,
+                         const unsigned int port) {
+  // FIXME
+}
+
 Servo::Servo(hstring url, hstring args, GLsizei width, GLsizei height,
              float dpi, ServoDelegate &aDelegate)
     : mWindowHeight(height), mWindowWidth(width), mDelegate(aDelegate) {
@@ -147,6 +152,7 @@ Servo::Servo(hstring url, hstring args, GLsizei width, GLsizei height,
   c.prompt_ok_cancel = &prompt_ok_cancel;
   c.prompt_yes_no = &prompt_yes_no;
   c.prompt_input = &prompt_input;
+  c.on_devtools_started = &on_devtools_started;
 
   capi::register_panic_handler(&on_panic);
 

support/hololens/ServoApp/ServoControl/Servo.h

@@ -31,6 +31,7 @@ public:
   typedef capi::CPromptResult PromptResult;
   typedef capi::CMediaSessionActionType MediaSessionActionType;
   typedef capi::CMediaSessionPlaybackState MediaSessionPlaybackState;
+  typedef capi::CDevtoolsServerState DevtoolsServerState;
 
   void PerformUpdates() { capi::perform_updates(); }
   void DeInit() { capi::deinit(); }