Auto merge of #23845 - paulrouget:cleanup, r=jdm

[hololens] More events, remove most of the statics, better shutdown

Depends on #23831

- Buttons are greyed out when necessary
- Reload, Stop, Back and Fwd are properly bound
- Servo.cpp rewritten in a much cleaner way
- Removed most of the statics
- Improved (but not full) shutdown

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---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23845)
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8 files changed, 343 insertions, 218 deletions

diff --git a/support/hololens/ServoApp/App.cpp b/support/hololens/ServoApp/App.cpp
index e373f05210d..9f6495c49e1 100644
--- a/support/hololens/ServoApp/App.cpp
+++ b/support/hololens/ServoApp/App.cpp
@@ -63,7 +63,12 @@ void App::OnLaunched(LaunchActivatedEventArgs const &e) {
 }
 
 void App::OnSuspending([[maybe_unused]] IInspectable const &sender,
-                       [[maybe_unused]] SuspendingEventArgs const &e) {}
+                       [[maybe_unused]] SuspendingEventArgs const &e) {
+  auto content = Window::Current().Content();
+  Frame rootFrame = content.try_as<Frame>();
+  auto page = rootFrame.Content().try_as<BrowserPage>();
+  page->Shutdown();
+}
 
 void App::OnNavigationFailed(IInspectable const &,
                              NavigationFailedEventArgs const &e) {
diff --git a/support/hololens/ServoApp/BrowserPage.cpp b/support/hololens/ServoApp/BrowserPage.cpp
index 2c2c6c6420b..c6fe3d9b969 100644
--- a/support/hololens/ServoApp/BrowserPage.cpp
+++ b/support/hololens/ServoApp/BrowserPage.cpp
@@ -16,96 +16,59 @@ using namespace winrt::Windows::UI::ViewManagement;
 using namespace winrt::Windows::Foundation;
 using namespace winrt::Windows::Graphics::Holographic;
 using namespace concurrency;
-
-static char sWakeupEvent[] = "SIGNAL_WAKEUP";
+using namespace servo;
 
 namespace winrt::ServoApp::implementation {
 BrowserPage::BrowserPage() {
-  InitializeComponent();
   log("BrowserPage::BrowserPage()");
+  InitializeComponent();
   Loaded(std::bind(&BrowserPage::OnPageLoaded, this, _1, _2));
   Window::Current().CoreWindow().VisibilityChanged(
       std::bind(&BrowserPage::OnVisibilityChanged, this, _1, _2));
 }
 
+void BrowserPage::Shutdown() {
+  log("BrowserPage::Shutdown()");
+
+  if (mServo != nullptr) {
+    if (!IsLoopRunning()) {
+      // FIXME: this should not happen. In that case, we can't send the
+      // shutdown event to Servo.
+    } else {
+      HANDLE hEvent = ::CreateEventA(nullptr, FALSE, FALSE, sShutdownEvent);
+      SendEventToServo({{Event::SHUTDOWN}});
+      log("Waiting for Servo to shutdown");
+      ::WaitForSingleObject(hEvent, INFINITE);
+      StopRenderLoop();
+      mServo.reset(); // will call servo::deinit
+    }
+  }
+}
+
 void BrowserPage::OnPageLoaded(IInspectable const &, RoutedEventArgs const &) {
   log("BrowserPage::OnPageLoaded()");
   CreateRenderSurface();
   StartRenderLoop();
-
   swapChainPanel().PointerReleased(
       std::bind(&BrowserPage::OnSurfaceClicked, this, _1, _2));
-
   swapChainPanel().ManipulationDelta(
       std::bind(&BrowserPage::OnSurfaceManipulationDelta, this, _1, _2));
 }
 
-void BrowserPage::OnSurfaceManipulationDelta(
-    IInspectable const &, Input::ManipulationDeltaRoutedEventArgs const &e) {
-  auto x = e.Position().X;
-  auto y = e.Position().Y;
-  auto dx = e.Delta().Translation.X;
-  auto dy = e.Delta().Translation.Y;
-  Event event = {{Event::SCROLL}};
-  event.scrollCoords = {dx, dy, x, y};
-  SendEventToServo(event);
-  e.Handled(true);
-}
-
-void BrowserPage::OnSurfaceClicked(IInspectable const &,
-                                   Input::PointerRoutedEventArgs const &e) {
-  auto coords = e.GetCurrentPoint(swapChainPanel());
-  auto x = coords.Position().X;
-  auto y = coords.Position().Y;
-
-  SendEventToServo({{Event::CLICK}, {x, y}});
-
-  e.Handled(true);
-}
-
-void BrowserPage::SendEventToServo(Event event) {
-  mEventsMutex.lock();
-  mEvents.push_back(event);
-  mEventsMutex.unlock();
-  Servo::sWakeUp();
-}
-
-void BrowserPage::OnBackButtonClicked(IInspectable const &,
-                                      RoutedEventArgs const &) {
-  SendEventToServo({{Event::BACK}});
-}
-
-void BrowserPage::OnForwardButtonClicked(IInspectable const &,
-                                         RoutedEventArgs const &) {
-  SendEventToServo({{Event::FORWARD}});
-}
-void BrowserPage::OnImmersiveButtonClicked(IInspectable const &,
-                                           RoutedEventArgs const &) {
-  if (HolographicSpace::IsAvailable()) {
-    log("Holographic space available");
-    auto v =
-        winrt::Windows::ApplicationModel::Core::CoreApplication::CreateNewView(
-            mImmersiveViewSource);
-    auto parentId = ApplicationView::GetForCurrentView().Id();
-    v.Dispatcher().RunAsync(CoreDispatcherPriority::Normal, [=]() {
-      auto winId = ApplicationView::GetForCurrentView().Id();
-      ApplicationViewSwitcher::SwitchAsync(winId, parentId);
-      log("Immersive view started");
-    });
-  } else {
-    log("Holographic space not available");
-  }
-}
-
 void BrowserPage::OnVisibilityChanged(CoreWindow const &,
                                       VisibilityChangedEventArgs const &args) {
   auto visible = args.Visible();
-  if (visible && !IsLoopRunning()) {
-    StartRenderLoop();
-  }
-  if (!visible && IsLoopRunning()) {
-    StopRenderLoop();
-  }
+
+  // FIXME: for now, this is disabled as we get this message before shutdown,
+  // stopping the event loop, which we can't recover from yet (see comment in
+  // Loop())
+
+  // if (visible && !IsLoopRunning()) {
+  //  StartRenderLoop();
+  //}
+  // if (!visible && IsLoopRunning()) {
+  //  StopRenderLoop();
+  //}
 }
 
 void BrowserPage::CreateRenderSurface() {
@@ -127,6 +90,8 @@ void BrowserPage::RecoverFromLostDevice() {
   StartRenderLoop();
 }
 
+/**** GL THREAD LOOP ****/
+
 bool BrowserPage::IsLoopRunning() {
   return mLoopTask != nullptr && !mLoopTask->is_done();
 }
@@ -136,65 +101,35 @@ void BrowserPage::Loop(cancellation_token cancel) {
 
   HANDLE hEvent = ::CreateEventA(nullptr, FALSE, FALSE, sWakeupEvent);
 
-  Servo::sOnAlert = [=](std::wstring message) {
-    // FIXME: make this sync
-    swapChainPanel().Dispatcher().RunAsync(
-        Windows::UI::Core::CoreDispatcherPriority::High, [=]() {
-          Windows::UI::Popups::MessageDialog msg{message};
-          msg.ShowAsync();
-        });
-  };
-
-  Servo::sOnTitleChanged = [=](std::wstring title) {
-    swapChainPanel().Dispatcher().RunAsync(CoreDispatcherPriority::High, [=]() {
-      ApplicationView::GetForCurrentView().Title(title);
-    });
-  };
-
-  Servo::sOnURLChanged = [=](std::wstring url) {
-    swapChainPanel().Dispatcher().RunAsync(CoreDispatcherPriority::High,
-                                           [=]() { urlTextbox().Text(url); });
-  };
-
-  Servo::sMakeCurrent = [=]() {
-    /* EGLint panelWidth = 0; */
-    /* EGLint panelHeight = 0; */
-    /* mOpenGLES->GetSurfaceDimensions(mRenderSurface, &panelWidth,
-     * &panelHeight); */
-    /* glViewport(0, 0, panelWidth, panelHeight); */
-    /* mServo->SetSize(panelWidth, panelHeight); */
-    mOpenGLES.MakeCurrent(mRenderSurface);
-  };
-
-  Servo::sFlush = [=]() {
-    if (mOpenGLES.SwapBuffers(mRenderSurface) != GL_TRUE) {
-      // The call to eglSwapBuffers might not be successful (i.e. due to Device
-      // Lost) If the call fails, then we must reinitialize EGL and the GL
-      // resources.
-      swapChainPanel().Dispatcher().RunAsync(
-          CoreDispatcherPriority::High, [this]() { RecoverFromLostDevice(); });
-    }
-  };
-
   mOpenGLES.MakeCurrent(mRenderSurface);
 
   EGLint panelWidth = 0;
   EGLint panelHeight = 0;
   mOpenGLES.GetSurfaceDimensions(mRenderSurface, &panelWidth, &panelHeight);
   glViewport(0, 0, panelWidth, panelHeight);
-  mServo = std::make_unique<Servo>(panelWidth, panelHeight);
+
+  if (mServo == nullptr) {
+    log("Entering loop");
+    ServoDelegate *sd = static_cast<ServoDelegate *>(this);
+    mServo = std::make_unique<Servo>(panelWidth, panelHeight, *sd);
+  } else {
+    // FIXME: this will fail since create_task didn't pick the thread
+    // where Servo was running initially.
+    throw winrt::hresult_error(E_FAIL, L"Recovering loop unimplemented");
+  }
 
   // mServo->SetBatchMode(true);
-  // FIXME: ^ this should be necessary as call perform_update
+  // FIXME: ^ this should be necessary as we call perform_update
   // ourself. But enabling batch mode will make clicking a link
   // not working because during the click, this thread is not
   // waiting on the hEvent object. See the "wakeup" comment.
 
+  log("Entering loop");
   while (!cancel.is_canceled()) {
-    // Block until Servo::sWakeUp is called.
-    // Or run full speed if animating (see on_animating_changed),
-    // it will endup blocking on SwapBuffers to limit rendering to 60FPS
-    if (!Servo::sAnimating) {
+    // Block until wakeup is called.
+    // Or run full speed if animating (see OnAnimatingChanged),
+    // it will endup blocking on Flush to limit rendering to 60FPS
+    if (!mAnimating) {
       ::WaitForSingleObject(hEvent, INFINITE);
     }
     mEventsMutex.lock();
@@ -216,31 +151,36 @@ void BrowserPage::Loop(cancellation_token cancel) {
       case Event::BACK:
         mServo->GoBack();
         break;
+      case Event::RELOAD:
+        mServo->Reload();
+        break;
+      case Event::STOP:
+        mServo->Stop();
+        break;
+      case Event::SHUTDOWN:
+        log("Requesting Servo to shutdown");
+        mServo->RequestShutdown();
+        break;
       }
     }
     mEvents.clear();
     mEventsMutex.unlock();
     mServo->PerformUpdates();
   }
+  log("Leaving loop");
   cancel_current_task();
-}
+} // namespace winrt::ServoApp::implementation
 
 void BrowserPage::StartRenderLoop() {
   if (IsLoopRunning()) {
+#if defined _DEBUG
+    throw winrt::hresult_error(E_FAIL, L"GL thread is already looping");
+#else
     return;
+#endif
   }
-
-  auto token = mLoopCancel.get_token();
-
-  Servo::sWakeUp = []() {
-    // FIXME: this won't work if it's triggered while the thread is not
-    // waiting. We need a better looping logic.
-    HANDLE hEvent = ::OpenEventA(EVENT_ALL_ACCESS, FALSE, sWakeupEvent);
-    ::SetEvent(hEvent);
-  };
-
   log("BrowserPage::StartRenderLoop(). UI thread: %i", GetCurrentThreadId());
-
+  auto token = mLoopCancel.get_token();
   mLoopTask = std::make_unique<Concurrency::task<void>>(
       Concurrency::create_task([=] { Loop(token); }, token));
 }
@@ -253,4 +193,144 @@ void BrowserPage::StopRenderLoop() {
   }
 }
 
+/**** SERVO CALLBACKS ****/
+
+void BrowserPage::OnLoadStarted() {
+  RunOnUIThread([=] {
+    reloadButton().IsEnabled(false);
+    stopButton().IsEnabled(true);
+  });
+}
+
+void BrowserPage::OnLoadEnded() {
+  RunOnUIThread([=] {
+    reloadButton().IsEnabled(true);
+    stopButton().IsEnabled(false);
+  });
+}
+
+void BrowserPage::OnHistoryChanged(bool back, bool forward) {
+  RunOnUIThread([=] {
+    backButton().IsEnabled(back);
+    forwardButton().IsEnabled(forward);
+  });
+}
+
+void BrowserPage::OnShutdownComplete() {
+  log("Servo notified ShutdownComplete");
+  HANDLE hEvent = ::OpenEventA(EVENT_ALL_ACCESS, FALSE, sShutdownEvent);
+  ::SetEvent(hEvent);
+}
+
+void BrowserPage::OnAlert(std::wstring message) {
+  // FIXME: make this sync
+  RunOnUIThread([=] {
+    Windows::UI::Popups::MessageDialog msg{message};
+    msg.ShowAsync();
+  });
+}
+
+void BrowserPage::OnTitleChanged(std::wstring title) {
+  RunOnUIThread([=] { ApplicationView::GetForCurrentView().Title(title); });
+}
+
+void BrowserPage::OnURLChanged(std::wstring url) {
+  RunOnUIThread([=] { urlTextbox().Text(url); });
+}
+
+void BrowserPage::Flush() {
+  if (mOpenGLES.SwapBuffers(mRenderSurface) != GL_TRUE) {
+    // The call to eglSwapBuffers might not be successful (i.e. due to Device
+    // Lost) If the call fails, then we must reinitialize EGL and the GL
+    // resources.
+    RunOnUIThread([=] { RecoverFromLostDevice(); });
+  }
+}
+
+void BrowserPage::MakeCurrent() { mOpenGLES.MakeCurrent(mRenderSurface); }
+
+void BrowserPage::WakeUp() {
+  // FIXME: this won't work if it's triggered while the thread is not
+  // waiting. We need a better looping logic.
+  HANDLE hEvent = ::OpenEventA(EVENT_ALL_ACCESS, FALSE, sWakeupEvent);
+  ::SetEvent(hEvent);
+}
+
+bool BrowserPage::OnAllowNavigation(std::wstring) { return true; }
+
+void BrowserPage::OnAnimatingChanged(bool animating) { mAnimating = animating; }
+
+template <typename Callable> void BrowserPage::RunOnUIThread(Callable cb) {
+  swapChainPanel().Dispatcher().RunAsync(
+      Windows::UI::Core::CoreDispatcherPriority::High, cb);
+}
+
+/**** USER INTERACTIONS WITH UI ****/
+
+void BrowserPage::OnBackButtonClicked(IInspectable const &,
+                                      RoutedEventArgs const &) {
+  SendEventToServo({{Event::BACK}});
+}
+
+void BrowserPage::OnForwardButtonClicked(IInspectable const &,
+                                         RoutedEventArgs const &) {
+  SendEventToServo({{Event::FORWARD}});
+}
+
+void BrowserPage::OnReloadButtonClicked(IInspectable const &,
+                                        RoutedEventArgs const &) {
+  SendEventToServo({{Event::RELOAD}});
+}
+
+void BrowserPage::OnStopButtonClicked(IInspectable const &,
+                                      RoutedEventArgs const &) {
+  SendEventToServo({{Event::STOP}});
+}
+
+void BrowserPage::OnImmersiveButtonClicked(IInspectable const &,
+                                           RoutedEventArgs const &) {
+  if (HolographicSpace::IsAvailable()) {
+    log("Holographic space available");
+    auto v =
+        winrt::Windows::ApplicationModel::Core::CoreApplication::CreateNewView(
+            mImmersiveViewSource);
+    auto parentId = ApplicationView::GetForCurrentView().Id();
+    v.Dispatcher().RunAsync(CoreDispatcherPriority::Normal, [=] {
+      auto winId = ApplicationView::GetForCurrentView().Id();
+      ApplicationViewSwitcher::SwitchAsync(winId, parentId);
+      log("Immersive view started");
+    });
+  } else {
+    log("Holographic space not available");
+  }
+}
+
+void BrowserPage::OnSurfaceManipulationDelta(
+    IInspectable const &, Input::ManipulationDeltaRoutedEventArgs const &e) {
+  auto x = e.Position().X;
+  auto y = e.Position().Y;
+  auto dx = e.Delta().Translation.X;
+  auto dy = e.Delta().Translation.Y;
+  Event event = {{Event::SCROLL}};
+  event.scrollCoords = {dx, dy, x, y};
+  SendEventToServo(event);
+  e.Handled(true);
+}
+
+void BrowserPage::OnSurfaceClicked(IInspectable const &,
+                                   Input::PointerRoutedEventArgs const &e) {
+  auto coords = e.GetCurrentPoint(swapChainPanel());
+  auto x = coords.Position().X;
+  auto y = coords.Position().Y;
+  SendEventToServo({{Event::CLICK}, {x, y}});
+  e.Handled(true);
+}
+
+void BrowserPage::SendEventToServo(Event event) {
+  mEventsMutex.lock();
+  mEvents.push_back(event);
+  mEventsMutex.unlock();
+  WakeUp();
+}
+
 } // namespace winrt::ServoApp::implementation
diff --git a/support/hololens/ServoApp/BrowserPage.h b/support/hololens/ServoApp/BrowserPage.h
index 4eca25d363a..efa27ea4215 100644
--- a/support/hololens/ServoApp/BrowserPage.h
+++ b/support/hololens/ServoApp/BrowserPage.h
@@ -11,13 +11,17 @@
 
 namespace winrt::ServoApp::implementation {
 
+static char sWakeupEvent[] = "SIGNAL_WAKEUP";
+static char sShutdownEvent[] = "SIGNAL_SHUTDOWN";
+
 struct Event {
-  enum { CLICK, SCROLL, BACK, FORWARD } type;
+  enum { CLICK, SCROLL, BACK, FORWARD, RELOAD, STOP, SHUTDOWN } type;
   std::tuple<float, float> clickCoords;
   std::tuple<float, float, float, float> scrollCoords;
 };
 
-struct BrowserPage : BrowserPageT<BrowserPage> {
+struct BrowserPage : BrowserPageT<BrowserPage>,
+                      public servo::ServoDelegate {
 public:
   BrowserPage();
 
@@ -27,7 +31,10 @@ public:
                               Windows::UI::Xaml::RoutedEventArgs const &);
   void OnBackButtonClicked(Windows::Foundation::IInspectable const &,
                            Windows::UI::Xaml::RoutedEventArgs const &);
-
+  void OnReloadButtonClicked(Windows::Foundation::IInspectable const &,
+                              Windows::UI::Xaml::RoutedEventArgs const &);
+  void OnStopButtonClicked(Windows::Foundation::IInspectable const &,
+                           Windows::UI::Xaml::RoutedEventArgs const &);
   void
   OnSurfaceClicked(Windows::Foundation::IInspectable const &,
                    Windows::UI::Xaml::Input::PointerRoutedEventArgs const &);
@@ -36,13 +43,28 @@ public:
       IInspectable const &,
       Windows::UI::Xaml::Input::ManipulationDeltaRoutedEventArgs const &e);
 
+  template <typename Callable> void RunOnUIThread(Callable);
+  void Shutdown();
+
+  virtual void WakeUp();
+  virtual void OnLoadStarted();
+  virtual void OnLoadEnded();
+  virtual void OnHistoryChanged(bool, bool);
+  virtual void OnShutdownComplete();
+  virtual void OnTitleChanged(std::wstring);
+  virtual void OnAlert(std::wstring);
+  virtual void OnURLChanged(std::wstring);
+  virtual void Flush();
+  virtual void MakeCurrent();
+  virtual bool OnAllowNavigation(std::wstring);
+  virtual void OnAnimatingChanged(bool);
+
 private:
   void OnVisibilityChanged(
       Windows::UI::Core::CoreWindow const &,
       Windows::UI::Core::VisibilityChangedEventArgs const &args);
   void OnPageLoaded(Windows::Foundation::IInspectable const &,
                     Windows::UI::Xaml::RoutedEventArgs const &);
-
   void CreateRenderSurface();
   void DestroyRenderSurface();
   void RecoverFromLostDevice();
@@ -56,13 +78,15 @@ private:
   std::unique_ptr<Concurrency::task<void>> mLoopTask;
   winrt::ServoApp::ImmersiveViewSource mImmersiveViewSource;
   EGLSurface mRenderSurface{EGL_NO_SURFACE};
-  std::unique_ptr<Servo> mServo;
+  std::unique_ptr<servo::Servo> mServo;
 
   void BrowserPage::SendEventToServo(Event event);
   std::vector<Event> mEvents;
   std::mutex mEventsMutex;
 
   OpenGLES mOpenGLES; // FIXME: shared pointer
+
+  bool mAnimating;
 };
 } // namespace winrt::ServoApp::implementation
 
diff --git a/support/hololens/ServoApp/BrowserPage.xaml b/support/hololens/ServoApp/BrowserPage.xaml
index 4247c9a1f68..f6e6e227318 100644
--- a/support/hololens/ServoApp/BrowserPage.xaml
+++ b/support/hololens/ServoApp/BrowserPage.xaml
@@ -20,8 +20,10 @@
         <ColumnDefinition Width="auto"/>
       </Grid.ColumnDefinitions>
       <StackPanel Orientation="Horizontal" Grid.Column="0">
-        <Button Content="Back" Click="OnBackButtonClicked"/>
-        <Button Content="Forward" Click="OnForwardButtonClicked"/>
+        <Button x:Name="backButton" IsEnabled="false" Content="Back" Click="OnBackButtonClicked"/>
+        <Button x:Name="forwardButton" IsEnabled="false" Content="Forward" Click="OnForwardButtonClicked"/>
+        <Button x:Name="reloadButton" IsEnabled="false" Content="reload" Click="OnReloadButtonClicked"/>
+        <Button x:Name="stopButton" IsEnabled="false" Content="stop" Click="OnStopButtonClicked"/>
       </StackPanel>
       <TextBox Text="" AcceptsReturn="True" PlaceholderText="Type a URL" x:Name="urlTextbox" Grid.Column="1" IsReadOnly="True"/>
       <StackPanel Orientation="Horizontal" Grid.Column="2">
diff --git a/support/hololens/ServoApp/Common/DeviceResources.h b/support/hololens/ServoApp/Common/DeviceResources.h
index ff0248b221d..f4bb4a0030f 100644
--- a/support/hololens/ServoApp/Common/DeviceResources.h
+++ b/support/hololens/ServoApp/Common/DeviceResources.h
@@ -1,5 +1,4 @@
-
-#pragma once
+#pragma once
 
 #include "CameraResources.h"
 
diff --git a/support/hololens/ServoApp/Servo.cpp b/support/hololens/ServoApp/Servo.cpp
index b262d420819..4283b66bc11 100644
--- a/support/hololens/ServoApp/Servo.cpp
+++ b/support/hololens/ServoApp/Servo.cpp
@@ -1,55 +1,38 @@
 #include "pch.h"
 #include "Servo.h"
 
-void on_load_started() {}
-void on_load_ended() {}
-void on_history_changed(bool, bool) {}
-void on_shutdown_complete() {}
+// FIXME: rename mozilla to something else
+namespace servo {
 
-std::function<void()> Servo::sFlush = []() {};
-std::function<void()> Servo::sMakeCurrent = []() {};
-std::function<void()> Servo::sWakeUp = []() {};
-std::function<void(std::wstring const &)> Servo::sOnAlert =
-    [](std::wstring const &) {};
-std::function<void(std::wstring const &)> Servo::sOnTitleChanged =
-    [](std::wstring const &) {};
-std::function<void(std::wstring const &)> Servo::sOnURLChanged =
-    [](std::wstring const &) {};
-
-bool Servo::sAnimating = false;
-
-std::wstring char2w(const char *c_str) {
-  auto str = std::string(c_str);
-  int size_needed =
-      MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), NULL, 0);
-  std::wstring str2(size_needed, 0);
-  MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), &str2[0],
-                      size_needed);
-  return str2;
+void on_load_started() { sServo->Delegate().OnLoadStarted(); }
+void on_load_ended() { sServo->Delegate().OnLoadEnded(); }
+void on_history_changed(bool back, bool forward) {
+  sServo->Delegate().OnHistoryChanged(back, forward);
+}
+void on_shutdown_complete() { sServo->Delegate().OnShutdownComplete(); }
+void on_alert(const char *message) {
+  sServo->Delegate().OnAlert(char2w(message));
 }
-
-void on_alert(const char *message) { Servo::sOnAlert(char2w(message)); }
-
 void on_title_changed(const char *title) {
-  Servo::sOnTitleChanged(char2w(title));
+  sServo->Delegate().OnTitleChanged(char2w(title));
+}
+void on_url_changed(const char *url) {
+  sServo->Delegate().OnURLChanged(char2w(url));
+}
+void flush() { sServo->Delegate().Flush(); }
+void make_current() { sServo->Delegate().MakeCurrent(); }
+void wakeup() { sServo->Delegate().WakeUp(); }
+bool on_allow_navigation(const char *url) {
+ return sServo->Delegate().OnAllowNavigation(char2w(url));
+};
+void on_animating_changed(bool aAnimating) {
+  sServo->Delegate().OnAnimatingChanged(aAnimating);
 }
 
-void on_url_changed(const char *url) { Servo::sOnURLChanged(char2w(url)); }
-
-void flush() { Servo::sFlush(); }
-
-void make_current() { Servo::sMakeCurrent(); }
-
-void wakeup() { Servo::sWakeUp(); }
-
-bool on_allow_navigation(const char *url) { return true; };
-
-void on_animating_changed(bool aAnimating) { Servo::sAnimating = aAnimating; }
-
-Servo::Servo(GLsizei width, GLsizei height)
-    : mAnimating(false), mWindowHeight(height), mWindowWidth(width) {
+Servo::Servo(GLsizei width, GLsizei height, ServoDelegate &aDelegate)
+    : mWindowHeight(height), mWindowWidth(width), mDelegate(aDelegate) {
 
-  CInitOptions o;
+  capi::CInitOptions o;
   o.args = NULL;
   o.url = "https://servo.org";
   o.width = mWindowWidth;
@@ -58,7 +41,9 @@ Servo::Servo(GLsizei width, GLsizei height)
   o.enable_subpixel_text_antialiasing = false;
   o.vr_pointer = NULL;
 
-  CHostCallbacks c;
+  sServo = this; // FIXME;
+
+  capi::CHostCallbacks c;
   c.flush = &flush;
   c.make_current = &make_current;
   c.on_alert = &on_alert;
@@ -74,23 +59,16 @@ Servo::Servo(GLsizei width, GLsizei height)
   init_with_egl(o, &wakeup, c);
 }
 
-Servo::~Servo() { deinit(); }
-
-void Servo::PerformUpdates() { perform_updates(); }
-
-void Servo::SetBatchMode(bool mode) { set_batch_mode(mode); }
-
-void Servo::GoForward() { go_forward(); }
-
-void Servo::GoBack() { go_back(); }
+Servo::~Servo() { capi::deinit(); }
 
-void Servo::SetSize(GLsizei width, GLsizei height) {
-  if (width != mWindowWidth || height != mWindowHeight) {
-    mWindowWidth = width;
-    mWindowHeight = height;
-    resize(mWindowWidth, mWindowHeight);
-  }
+std::wstring char2w(const char *c_str) {
+  auto str = std::string(c_str);
+  int size_needed =
+      MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), NULL, 0);
+  std::wstring str2(size_needed, 0);
+  MultiByteToWideChar(CP_UTF8, 0, &str[0], (int)str.size(), &str2[0],
+                      size_needed);
+  return str2;
 }
 
-void Servo::Click(float x, float y) { click(x, y); }
-void Servo::Scroll(float dx, float dy, float x, float y) { scroll(dx, dy, x, y); }
+} // namespace mozilla
diff --git a/support/hololens/ServoApp/Servo.h b/support/hololens/ServoApp/Servo.h
index 2772d5ea20b..17f283cdf56 100644
--- a/support/hololens/ServoApp/Servo.h
+++ b/support/hololens/ServoApp/Servo.h
@@ -5,37 +5,73 @@
 #pragma once
 
 #include "pch.h"
+#include "logs.h"
 
+namespace servo {
+
+namespace capi {
 extern "C" {
 #include <simpleservo.h>
 }
+} // namespace capi
+
+class ServoDelegate {
+public:
+  // Called from any thread
+  virtual void WakeUp() = 0;
+  // Called from GL thread
+  virtual void OnLoadStarted() = 0;
+  virtual void OnLoadEnded() = 0;
+  virtual void OnHistoryChanged(bool, bool) = 0;
+  virtual void OnShutdownComplete() = 0;
+  virtual void OnTitleChanged(std::wstring) = 0;
+  virtual void OnAlert(std::wstring) = 0;
+  virtual void OnURLChanged(std::wstring) = 0;
+  virtual void Flush() = 0;
+  virtual void MakeCurrent() = 0;
+  virtual bool OnAllowNavigation(std::wstring) = 0;
+  virtual void OnAnimatingChanged(bool) = 0;
+
+protected:
+  virtual ~ServoDelegate(){log("A1");};
+};
 
 class Servo {
 public:
-  Servo(GLsizei width, GLsizei height);
+  Servo(GLsizei, GLsizei, ServoDelegate &);
   ~Servo();
-  void PerformUpdates();
-  void Click(float, float);
-  void Scroll(float dx, float dy, float x, float y);
-  void SetSize(GLsizei width, GLsizei height);
-  void SetBatchMode(bool);
-  void GoBack();
-  void GoForward();
-
-  // Static lambas called by Servo callbacks.
-
-  // Will be called from any thead
-  static std::function<void()> sWakeUp;
-  // Will be called from GL thread
-  static std::function<void()> sFlush;
-  static std::function<void()> sMakeCurrent;
-  static std::function<void(std::wstring const &)> sOnAlert;
-  static std::function<void(std::wstring const &)> sOnTitleChanged;
-  static std::function<void(std::wstring const &)> sOnURLChanged;
-  static bool sAnimating;
+  ServoDelegate &Delegate() { return mDelegate; }
+
+  void PerformUpdates() { capi::perform_updates(); }
+  void RequestShutdown() { capi::request_shutdown(); }
+  void SetBatchMode(bool mode) { capi::set_batch_mode(mode); }
+  void GoForward() { capi::go_forward(); }
+  void GoBack() { capi::go_back(); }
+  void Click(float x, float y) { capi::click(x, y); }
+  void Reload() { capi::reload(); }
+  void Stop() { capi::stop(); }
+  void Scroll(float dx, float dy, float x, float y) {
+    capi::scroll(dx, dy, x, y);
+  }
+  void SetSize(GLsizei width, GLsizei height) {
+    if (width != mWindowWidth || height != mWindowHeight) {
+      mWindowWidth = width;
+      mWindowHeight = height;
+      capi::resize(mWindowWidth, mWindowHeight);
+    }
+  }
 
 private:
+  ServoDelegate &mDelegate;
   GLsizei mWindowWidth;
   GLsizei mWindowHeight;
-  bool mAnimating;
 };
+
+// This is sad. We need a static pointer to Servo because we use function
+// pointer as callback in Servo, and these functions need a way to get
+// the Servo instance. See https://github.com/servo/servo/issues/22967
+static Servo *sServo = nullptr;
+
+std::wstring char2w(const char *c_str);
+
+} // namespace servo
diff --git a/support/hololens/ServoApp/pch.h b/support/hololens/ServoApp/pch.h
index c8689fab90e..0b8e6047454 100644
--- a/support/hololens/ServoApp/pch.h
+++ b/support/hololens/ServoApp/pch.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <functional>
 #include <future>
 #include <hstring.h>
 #include <map>