general: Use deducation guides for std::lock_guard and std::unique_lock

Since C++17, the introduction of deduction guides for locking facilities
means that we no longer need to hardcode the mutex type into the locks
themselves, making it easier to switch mutex types, should it ever be
necessary in the future.

src/input_common/sdl/sdl_impl.cpp

@@ -55,22 +55,22 @@ public:
         : guid{std::move(guid_)}, port{port_}, sdl_joystick{joystick, deleter} {}
 
     void SetButton(int button, bool value) {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::lock_guard lock{mutex};
         state.buttons[button] = value;
     }
 
     bool GetButton(int button) const {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::lock_guard lock{mutex};
         return state.buttons.at(button);
     }
 
     void SetAxis(int axis, Sint16 value) {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::lock_guard lock{mutex};
         state.axes[axis] = value;
     }
 
     float GetAxis(int axis) const {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::lock_guard lock{mutex};
         return state.axes.at(axis) / 32767.0f;
     }
 
@@ -92,12 +92,12 @@ public:
     }
 
     void SetHat(int hat, Uint8 direction) {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::lock_guard lock{mutex};
         state.hats[hat] = direction;
     }
 
     bool GetHatDirection(int hat, Uint8 direction) const {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::lock_guard lock{mutex};
         return (state.hats.at(hat) & direction) != 0;
     }
     /**
@@ -140,7 +140,7 @@ private:
  * Get the nth joystick with the corresponding GUID
  */
 std::shared_ptr<SDLJoystick> SDLState::GetSDLJoystickByGUID(const std::string& guid, int port) {
-    std::lock_guard<std::mutex> lock(joystick_map_mutex);
+    std::lock_guard lock{joystick_map_mutex};
     const auto it = joystick_map.find(guid);
     if (it != joystick_map.end()) {
         while (it->second.size() <= port) {
@@ -161,7 +161,8 @@ std::shared_ptr<SDLJoystick> SDLState::GetSDLJoystickByGUID(const std::string& g
 std::shared_ptr<SDLJoystick> SDLState::GetSDLJoystickBySDLID(SDL_JoystickID sdl_id) {
     auto sdl_joystick = SDL_JoystickFromInstanceID(sdl_id);
     const std::string guid = GetGUID(sdl_joystick);
-    std::lock_guard<std::mutex> lock(joystick_map_mutex);
+
+    std::lock_guard lock{joystick_map_mutex};
     auto map_it = joystick_map.find(guid);
     if (map_it != joystick_map.end()) {
         auto vec_it = std::find_if(map_it->second.begin(), map_it->second.end(),
@@ -198,8 +199,9 @@ void SDLState::InitJoystick(int joystick_index) {
         LOG_ERROR(Input, "failed to open joystick {}", joystick_index);
         return;
     }
-    std::string guid = GetGUID(sdl_joystick);
-    std::lock_guard<std::mutex> lock(joystick_map_mutex);
+    const std::string guid = GetGUID(sdl_joystick);
+
+    std::lock_guard lock{joystick_map_mutex};
     if (joystick_map.find(guid) == joystick_map.end()) {
         auto joystick = std::make_shared<SDLJoystick>(guid, 0, sdl_joystick);
         joystick_map[guid].emplace_back(std::move(joystick));
@@ -221,7 +223,7 @@ void SDLState::CloseJoystick(SDL_Joystick* sdl_joystick) {
     std::string guid = GetGUID(sdl_joystick);
     std::shared_ptr<SDLJoystick> joystick;
     {
-        std::lock_guard<std::mutex> lock(joystick_map_mutex);
+        std::lock_guard lock{joystick_map_mutex};
         // This call to guid is safe since the joystick is guaranteed to be in the map
         auto& joystick_guid_list = joystick_map[guid];
         const auto joystick_it =
@@ -274,7 +276,7 @@ void SDLState::HandleGameControllerEvent(const SDL_Event& event) {
 }
 
 void SDLState::CloseJoysticks() {
-    std::lock_guard<std::mutex> lock(joystick_map_mutex);
+    std::lock_guard lock{joystick_map_mutex};
     joystick_map.clear();
 }