Add mouse weel scroll signal

#463

library/phx/input/mouse.cpp

@@ -36,6 +36,8 @@ void Mouse::OnSDLEvent(const SDL_Event& event) {
   if (event.type == SDL_MOUSEMOTION) {
     move_signal_(static_cast<int>(event.motion.xrel),
                  static_cast<int>(event.motion.yrel));
+  } else if (event.type == SDL_MOUSEWHEEL) {
+    wheel_signal_(static_cast<int>(event.wheel.y));
   } else if (event.type == SDL_MOUSEBUTTONDOWN) {
     event_type = BUTTON_PRESSED;
   } else if (event.type == SDL_MOUSEBUTTONUP) {
@@ -75,4 +77,9 @@ boost::signals2::connection Mouse::RegisterMoveSignal(
   return move_signal_.connect(callback);
 }
 
+boost::signals2::connection Mouse::RegisterWheelSignal(
+    const std::function<void(int)>& callback) {
+  return wheel_signal_.connect(callback);
+}
+
 }  // namespace phx

library/phx/input/mouse.hpp

@@ -31,7 +31,6 @@
 #include "boost/signals2/signal.hpp"
 
 #include "phx/input/sdl_device.hpp"
-#include "phx/suppress_warnings.hpp"
 
 #include "phx/export.hpp"
 
@@ -57,10 +56,13 @@ class PHOENIX_EXPORT Mouse : public SDLDevice {
       const std::function<void(ButtonId, ButtonEvent)>& callback);
   boost::signals2::connection RegisterMoveSignal(
       const std::function<void(int, int)>& callback);
+  boost::signals2::connection RegisterWheelSignal(
+      const std::function<void(int)>& callback);
 
  private:
   boost::signals2::signal<void(ButtonId, ButtonEvent)> button_signal_;
   boost::signals2::signal<void(int, int)> move_signal_;
+  boost::signals2::signal<void(int)> wheel_signal_;
 };
 
 }  // namespace phx

tests/src/test_mouse.cpp

@@ -97,5 +97,29 @@ SCENARIO("Mouse signals received events.", "[phx][phx::Mouse]") {
         }
       }
     }
+
+    WHEN("a mouse scroll signal is registered") {
+      int y_delta_received = 0;
+      mouse.RegisterWheelSignal(
+          [&y_delta_received](int y_delta) { y_delta_received = y_delta; });
+      WHEN("A mouse scroll event is fired by SDL.") {
+        SDL_Event mouse_event;
+        mouse_event.type = SDL_MOUSEWHEEL;
+        mouse_event.wheel.y = 3;
+        auto first_call = std::make_shared<bool>(true);
+        ALLOW_CALL(sdl_mock.Get(), SDL_PollEvent(_))
+            .SIDE_EFFECT(*_1 = mouse_event)
+            .SIDE_EFFECT(*first_call = false)
+            .WITH(*first_call == true)
+            .RETURN(true);
+        ALLOW_CALL(sdl_mock.Get(), SDL_PollEvent(_))
+            .WITH(*first_call == false)
+            .RETURN(false);
+        THEN("I should receive a signal.") {
+          mouse.Update();
+          REQUIRE(y_delta_received == 3);
+        }
+      }
+    }
   }
 }