4 files changed, 52 insertions, 4 deletions
diff --git a/support/hololens/ServoApp/App.cpp b/support/hololens/ServoApp/App.cpp
index a505da34d5a..22b6f4586f4 100644
--- a/support/hololens/ServoApp/App.cpp
+++ b/support/hololens/ServoApp/App.cpp
@@ -103,10 +103,14 @@ void App::OnActivated(IActivatedEventArgs const &args) {
 }
 
 void App::OnSuspending(IInspectable const &, SuspendingEventArgs const &) {
-  auto content = Window::Current().Content();
+  // FIXME: Apps can be suspended for various reasons, not just closing them.
+  //        * Figure out how to save state like the current URL so it can be
+  //          restored if necessary.
+  //        * Determine if the user has actually closed the app and shutdown.
+  /*auto content = Window::Current().Content();
   Frame rootFrame = content.try_as<Frame>();
   auto page = rootFrame.Content().try_as<BrowserPage>();
-  page->Shutdown();
+  page->Shutdown();*/
 }
 
 void App::OnNavigationFailed(IInspectable const &,
diff --git a/support/hololens/ServoApp/Package.appxmanifest b/support/hololens/ServoApp/Package.appxmanifest
index 5ada19983d7..26091d47f0a 100644
--- a/support/hololens/ServoApp/Package.appxmanifest
+++ b/support/hololens/ServoApp/Package.appxmanifest
@@ -9,7 +9,7 @@
   </Properties>
   <Dependencies>
     <TargetDeviceFamily Name="Windows.Universal" MinVersion="10.0.0.0" MaxVersionTested="10.0.0.0" />
-    <PackageDependency Name="Microsoft.WindowsMixedReality.Runtime" Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US" MinVersion="0.0.1.0" />
+    <PackageDependency Name="Microsoft.WindowsMixedReality.Runtime" Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US" MinVersion="100.2004.3007.0"/>
   </Dependencies>
   <Resources>
     <Resource Language="x-generate" />
diff --git a/support/hololens/ServoApp/ServoControl/Servo.cpp b/support/hololens/ServoApp/ServoControl/Servo.cpp
index 76753d0758f..17c86f17271 100644
--- a/support/hololens/ServoApp/ServoControl/Servo.cpp
+++ b/support/hololens/ServoApp/ServoControl/Servo.cpp
@@ -36,6 +36,10 @@ void on_animating_changed(bool aAnimating) {
 }
 
 void on_panic(const char *backtrace) {
+  if (sLogHandle != INVALID_HANDLE_VALUE) {
+    CloseHandle(sLogHandle);
+    sLogHandle = INVALID_HANDLE_VALUE;
+  }
   throw hresult_error(E_FAIL, char2hstring(backtrace));
 }
 
@@ -86,6 +90,23 @@ void on_devtools_started(Servo::DevtoolsServerState result,
       result == Servo::DevtoolsServerState::Started, port);
 }
 
+void on_log_output(const char *buffer, uint32_t buffer_length) {
+  OutputDebugStringA(buffer);
+
+  if (sLogHandle == INVALID_HANDLE_VALUE) {
+    return;
+  }
+
+  DWORD bytesWritten;
+  auto writeResult =
+      WriteFile(sLogHandle, buffer, buffer_length, &bytesWritten, nullptr);
+
+  if (writeResult == FALSE || bytesWritten != buffer_length)
+    throw std::runtime_error(
+        "Failed to write log message to the log file: error code " +
+        std::to_string(GetLastError()));
+}
+
 Servo::PromptResult prompt_ok_cancel(const char *message, bool trusted) {
   return sServo->Delegate().OnServoPromptOkCancel(char2hstring(message),
                                                   trusted);
@@ -109,6 +130,7 @@ const char *prompt_input(const char *message, const char *default,
 Servo::Servo(hstring url, hstring args, GLsizei width, GLsizei height,
              float dpi, ServoDelegate &aDelegate)
     : mWindowHeight(height), mWindowWidth(width), mDelegate(aDelegate) {
+  SetEnvironmentVariableA("PreviewRuntimeEnabled", "1");
 
   capi::CInitOptions o;
   hstring defaultPrefs = L" --pref dom.webxr.enabled --devtools";
@@ -140,6 +162,22 @@ Servo::Servo(hstring url, hstring args, GLsizei width, GLsizei height,
 
   sServo = this; // FIXME;
 
+#ifdef _DEBUG
+  auto current = winrt::Windows::Storage::ApplicationData::Current();
+  auto filePath = std::wstring(current.LocalFolder().Path()) + L"\\stdout.txt";
+  sLogHandle =
+      CreateFile2(filePath.c_str(), GENERIC_WRITE, 0, CREATE_ALWAYS, nullptr);
+  if (sLogHandle == INVALID_HANDLE_VALUE)
+    throw std::runtime_error("Failed to open the log file: error code " +
+                             std::to_string(GetLastError()));
+
+  if (SetFilePointer(sLogHandle, 0, nullptr, FILE_END) ==
+      INVALID_SET_FILE_POINTER)
+    throw std::runtime_error(
+        "Failed to set file pointer to the end of file: error code " +
+        std::to_string(GetLastError()));
+#endif
+
   capi::CHostCallbacks c;
   c.flush = &flush;
   c.make_current = &make_current;
@@ -163,13 +201,18 @@ Servo::Servo(hstring url, hstring args, GLsizei width, GLsizei height,
   c.prompt_input = &prompt_input;
   c.on_devtools_started = &on_devtools_started;
   c.show_context_menu = &show_context_menu;
+  c.on_log_output = &on_log_output;
 
   capi::register_panic_handler(&on_panic);
 
   capi::init_with_egl(o, &wakeup, c);
 }
 
-Servo::~Servo() { sServo = nullptr; }
+Servo::~Servo() {
+  sServo = nullptr;
+  if (sLogHandle != INVALID_HANDLE_VALUE)
+    CloseHandle(sLogHandle);
+}
 
 winrt::hstring char2hstring(const char *c_str) {
   // FIXME: any better way of doing this?
diff --git a/support/hololens/ServoApp/ServoControl/Servo.h b/support/hololens/ServoApp/ServoControl/Servo.h
index 7b3b3b00ed3..ccc8c1efa06 100644
--- a/support/hololens/ServoApp/ServoControl/Servo.h
+++ b/support/hololens/ServoApp/ServoControl/Servo.h
@@ -119,5 +119,6 @@ protected:
 // 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;
+static HANDLE sLogHandle = INVALID_HANDLE_VALUE;
 
 } // namespace winrt::servo