Replace std::lock_guard and std::lock with std::scoped_lock (#1758)

std::scoped_lock was introduced in C++17 and is strictly better than
std::lock_guard as it supports locking any number of mutexes safely.
It's also easier to use than std::lock for locking multiple mutexes at
once.

cscore/src/main/native/cpp/SourceImpl.cpp

@@ -44,13 +44,13 @@ SourceImpl::~SourceImpl() {
 }
 
 void SourceImpl::SetDescription(const wpi::Twine& description) {
-  std::lock_guard lock(m_mutex);
+  std::scoped_lock lock(m_mutex);
   m_description = description.str();
 }
 
 wpi::StringRef SourceImpl::GetDescription(
     wpi::SmallVectorImpl<char>& buf) const {
-  std::lock_guard lock(m_mutex);
+  std::scoped_lock lock(m_mutex);
   buf.append(m_description.begin(), m_description.end());
   return wpi::StringRef{buf.data(), buf.size()};
 }
@@ -93,7 +93,7 @@ Frame SourceImpl::GetNextFrame(double timeout) {
 
 void SourceImpl::Wakeup() {
   {
-    std::lock_guard lock{m_frameMutex};
+    std::scoped_lock lock{m_frameMutex};
     m_frame = Frame{*this, wpi::StringRef{}, 0};
   }
   m_frameCv.notify_all();
@@ -134,7 +134,7 @@ void SourceImpl::SetExposureManual(int value, CS_Status* status) {
 
 VideoMode SourceImpl::GetVideoMode(CS_Status* status) const {
   if (!m_properties_cached && !CacheProperties(status)) return VideoMode{};
-  std::lock_guard lock(m_mutex);
+  std::scoped_lock lock(m_mutex);
   return m_mode;
 }
 
@@ -380,7 +380,7 @@ std::vector<VideoMode> SourceImpl::EnumerateVideoModes(
     CS_Status* status) const {
   if (!m_properties_cached && !CacheProperties(status))
     return std::vector<VideoMode>{};
-  std::lock_guard lock(m_mutex);
+  std::scoped_lock lock(m_mutex);
   return m_videoModes;
 }
 
@@ -388,7 +388,7 @@ std::unique_ptr<Image> SourceImpl::AllocImage(
     VideoMode::PixelFormat pixelFormat, int width, int height, size_t size) {
   std::unique_ptr<Image> image;
   {
-    std::lock_guard lock{m_poolMutex};
+    std::scoped_lock lock{m_poolMutex};
     // find the smallest existing frame that is at least big enough.
     int found = -1;
     for (size_t i = 0; i < m_imagesAvail.size(); ++i) {
@@ -440,7 +440,7 @@ void SourceImpl::PutFrame(std::unique_ptr<Image> image, Frame::Time time) {
 
   // Update frame
   {
-    std::lock_guard lock{m_frameMutex};
+    std::scoped_lock lock{m_frameMutex};
     m_frame = Frame{*this, std::move(image), time};
   }
 
@@ -451,7 +451,7 @@ void SourceImpl::PutFrame(std::unique_ptr<Image> image, Frame::Time time) {
 void SourceImpl::PutError(const wpi::Twine& msg, Frame::Time time) {
   // Update frame
   {
-    std::lock_guard lock{m_frameMutex};
+    std::scoped_lock lock{m_frameMutex};
     m_frame = Frame{*this, msg, time};
   }
 
@@ -489,7 +489,7 @@ void SourceImpl::UpdatePropertyValue(int property, bool setString, int value,
 }
 
 void SourceImpl::ReleaseImage(std::unique_ptr<Image> image) {
-  std::lock_guard lock{m_poolMutex};
+  std::scoped_lock lock{m_poolMutex};
   if (m_destroyFrames) return;
   // Return the frame to the pool.  First try to find an empty slot, otherwise
   // add it to the end.
@@ -511,7 +511,7 @@ void SourceImpl::ReleaseImage(std::unique_ptr<Image> image) {
 }
 
 std::unique_ptr<Frame::Impl> SourceImpl::AllocFrameImpl() {
-  std::lock_guard lock{m_poolMutex};
+  std::scoped_lock lock{m_poolMutex};
 
   if (m_framesAvail.empty()) return std::make_unique<Frame::Impl>(*this);
 
@@ -521,7 +521,7 @@ std::unique_ptr<Frame::Impl> SourceImpl::AllocFrameImpl() {
 }
 
 void SourceImpl::ReleaseFrameImpl(std::unique_ptr<Frame::Impl> impl) {
-  std::lock_guard lock{m_poolMutex};
+  std::scoped_lock lock{m_poolMutex};
   if (m_destroyFrames) return;
   m_framesAvail.push_back(std::move(impl));
 }