Platform: first-class MouseScrollEvent for SDL2 and NaCl application.

The original implementation tried to mimic the behavior of GLUT, which
treats mouse wheel as a button. SDL2, GLFW and NaCl all treat scroll
event separately, so it was quite nastily hacked in, with horizontal
scrolling ignored and scrolling offset treated as cursor position.
Moreover, wheel up/down buttons were confused with extra mouse buttons
in SDL2.

Now there is a dedicated MouseScrollEvent, which has just the offset and
modifiers, no cursor position. The original way with WheelUp/WheelDown
buttons in mouse press event is still preserved, though it is marked as
deprecated and will be removed in future release. Sdl2Application had
WheelUp/WheelDown buttons also for mouse move event, which was
completely useless (try moving a mouse while the wheel is rotating, ha),
so it's removed.

Scroll event offset is now also consistently Vector2 across all toolkits
-- it was integer in SDL2, float in NaCl and double in GLFW.

The X1 and X2 buttons in Sdl2Application are not confused with wheel
up/down anymore and are a new Mouse*Event::Button::X1 and
Mouse*Event::Button::X2 enums -- on my mouse they are actually wheel
left and wheel right (though wheel left and wheel right is not treated
as horizontal scrolling, weird).

src/Magnum/Platform/GlfwApplication.cpp

@@ -187,13 +187,22 @@ void GlfwApplication::staticMouseEvent(GLFWwindow*, int button, int action, int
 }
 
 void GlfwApplication::staticMouseScrollEvent(GLFWwindow* window, double xoffset, double yoffset) {
-    MouseScrollEvent e(Vector2d{xoffset, yoffset}, KeyEvent::getCurrentGlfwModifiers(window));
+    MouseScrollEvent e(Vector2{Float(xoffset), Float(yoffset)}, KeyEvent::getCurrentGlfwModifiers(window));
     _instance->mouseScrollEvent(e);
 
+    #ifdef MAGNUM_BUILD_DEPRECATED
     if(yoffset != 0.0) {
+        #ifdef __GNUC__
+        #pragma GCC diagnostic push
+        #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+        #endif
         MouseEvent e1((yoffset > 0.0) ? MouseEvent::Button::WheelUp : MouseEvent::Button::WheelDown, KeyEvent::getCurrentGlfwModifiers(window));
+        #ifdef __GNUC__
+        #pragma GCC diagnostic pop
+        #endif
         _instance->mousePressEvent(e1);
     }
+    #endif
 }
 
 void GlfwApplication::staticErrorCallback(int, const char* description) {

src/Magnum/Platform/GlfwApplication.h

@@ -247,12 +247,7 @@ class GlfwApplication {
          */
         virtual void mouseMoveEvent(MouseMoveEvent& event);
 
-        /**
-         * @brief Mouse scroll event
-         *
-         * Called when a scrolling device is used (mouse wheel or scrolling
-         * area on touchpad). Default implementation does nothing.
-         */
+        /** @copydoc Sdl2Application::mouseScrollEvent() */
         virtual void mouseScrollEvent(MouseScrollEvent& event);
 
         /*@}*/
@@ -706,7 +701,8 @@ class GlfwApplication::KeyEvent: public GlfwApplication::InputEvent {
 /**
 @brief Mouse event
 
-@see @ref MouseMoveEvent, @ref MouseScrollEvent, @ref mousePressEvent(), @ref mouseReleaseEvent()
+@see @ref MouseMoveEvent, @ref MouseScrollEvent, @ref mousePressEvent(),
+    @ref mouseReleaseEvent()
 */
 class GlfwApplication::MouseEvent: public GlfwApplication::InputEvent {
     friend GlfwApplication;
@@ -730,8 +726,19 @@ class GlfwApplication::MouseEvent: public GlfwApplication::InputEvent {
             Button7 = GLFW_MOUSE_BUTTON_7,        /**< Mouse button 7 */
             Button8 = GLFW_MOUSE_BUTTON_8,        /**< Mouse button 8 */
 
-            WheelUp = GLFW_MOUSE_BUTTON_LAST + 1,   /**< Mouse wheel up */
-            WheelDown = GLFW_MOUSE_BUTTON_LAST + 2  /**< Mouse wheel down */
+            #ifdef MAGNUM_BUILD_DEPRECATED
+            /**
+             * Wheel up
+             * @deprecated Use @ref MouseScrollEvent and @ref mouseScrollEvent() instead.
+             */
+            WheelUp CORRADE_DEPRECATED_ENUM("use mouseScrollEvent() and MouseScrollEvent instead") = GLFW_MOUSE_BUTTON_LAST + 1,
+
+            /**
+             * Wheel down
+             * @deprecated Use @ref MouseScrollEvent and @ref mouseScrollEvent() instead.
+             */
+            WheelDown CORRADE_DEPRECATED_ENUM("use mouseScrollEvent() and MouseScrollEvent instead") = GLFW_MOUSE_BUTTON_LAST + 2
+            #endif
         };
 
         /** @brief Button */
@@ -779,15 +786,15 @@ class GlfwApplication::MouseScrollEvent: public GlfwApplication::InputEvent {
 
     public:
         /** @brief Scroll offset */
-        constexpr Vector2d offset() const { return _offset; }
+        constexpr Vector2 offset() const { return _offset; }
 
         /** @brief Modifiers */
         constexpr Modifiers modifiers() const { return _modifiers; }
 
     private:
-        constexpr MouseScrollEvent(const Vector2d& offset, Modifiers modifiers): _offset(offset), _modifiers(modifiers) {}
+        constexpr MouseScrollEvent(const Vector2& offset, Modifiers modifiers): _offset(offset), _modifiers(modifiers) {}
 
-        const Vector2d _offset;
+        const Vector2 _offset;
         const Modifiers _modifiers;
 };
 

src/Magnum/Platform/NaClApplication.cpp

@@ -192,10 +192,17 @@ bool NaClApplication::HandleInputEvent(const pp::InputEvent& event) {
 
         case PP_INPUTEVENT_TYPE_WHEEL: {
             pp::WheelInputEvent wheelEvent(event);
-            if(Math::TypeTraits<Float>::equals(wheelEvent.GetDelta().y(), 0.0f)) return false;
-            MouseEvent e(wheelEvent.GetDelta().y() > 0 ? MouseEvent::Button::WheelUp : MouseEvent::Button::WheelDown, {}, static_cast<InputEvent::Modifier>(wheelEvent.GetModifiers()));
-            mousePressEvent(e);
+            MouseScrollEvent e{{wheelEvent.GetDelta().x(), wheelEvent.GetDelta().y()}, static_cast<InputEvent::Modifier>(wheelEvent.GetModifiers())};
+            mouseScrollEvent(e);
+            #ifdef MAGNUM_BUILD_DEPRECATED
+            if(!Math::TypeTraits<Float>::equals(wheelEvent.GetDelta().y(), 0.0f)) {
+                MouseEvent e2(wheelEvent.GetDelta().y() > 0 ? MouseEvent::Button::WheelUp : MouseEvent::Button::WheelDown, {}, static_cast<InputEvent::Modifier>(wheelEvent.GetModifiers()));
+                mousePressEvent(e2);
+                if(!e.isAccepted() && !e2.isAccepted()) return false;
+            } else if(!e.isAccepted()) return false;
+            #else
             if(!e.isAccepted()) return false;
+            #endif
             break;
         }
 
@@ -261,6 +268,7 @@ void NaClApplication::keyReleaseEvent(KeyEvent&) {}
 void NaClApplication::mousePressEvent(MouseEvent&) {}
 void NaClApplication::mouseReleaseEvent(MouseEvent&) {}
 void NaClApplication::mouseMoveEvent(MouseMoveEvent&) {}
+void NaClApplication::mouseScrollEvent(MouseScrollEvent&) {}
 
 template class BasicScreen<NaClApplication>;
 template class BasicScreenedApplication<NaClApplication>;

src/Magnum/Platform/NaClApplication.h

@@ -204,6 +204,7 @@ class NaClApplication: public pp::Instance, public pp::Graphics3DClient, public
         class KeyEvent;
         class MouseEvent;
         class MouseMoveEvent;
+        class MouseScrollEvent;
 
         /** @copydoc Sdl2Application::Sdl2Application(const Arguments&, const Configuration&) */
         #ifdef DOXYGEN_GENERATING_OUTPUT
@@ -355,6 +356,16 @@ class NaClApplication: public pp::Instance, public pp::Graphics3DClient, public
          */
         virtual void mouseMoveEvent(MouseMoveEvent& event);
 
+        /**
+         * @brief Mouse scroll event
+         *
+         * Called when a scrolling device is used (mouse wheel or scrolling
+         * area on a touchpad). Default implementation does nothing. If you
+         * accept the event, call @ref InputEvent::setAccepted() "setAccepted()"
+         * on it, otherwise the event will be propagated to the browser.
+         */
+        virtual void mouseScrollEvent(MouseScrollEvent& event);
+
         /*@}*/
 
     private:
@@ -650,7 +661,8 @@ class NaClApplication::KeyEvent: public NaClApplication::InputEvent {
 @brief Mouse event
 
 See also @ref InputEvent for more information.
-@see @ref MouseMoveEvent, @ref mousePressEvent(), @ref mouseReleaseEvent()
+@see @ref MouseMoveEvent, @ref MouseScrollEvent, @ref mousePressEvent(),
+    @ref mouseReleaseEvent()
 */
 class NaClApplication::MouseEvent: public NaClApplication::InputEvent {
     friend NaClApplication;
@@ -665,8 +677,20 @@ class NaClApplication::MouseEvent: public NaClApplication::InputEvent {
             Left = PP_INPUTEVENT_MOUSEBUTTON_LEFT,      /**< Left button */
             Middle = PP_INPUTEVENT_MOUSEBUTTON_MIDDLE,  /**< Middle button */
             Right = PP_INPUTEVENT_MOUSEBUTTON_RIGHT,    /**< Right button */
-            WheelUp = 0xFFFF01,                         /**< Wheel up */
-            WheelDown = 0xFFFF02                        /**< Wheel down */
+
+            #ifdef MAGNUM_BUILD_DEPRECATED
+            /**
+             * Wheel up
+             * @deprecated Use @ref MouseScrollEvent and @ref mouseScrollEvent() instead.
+             */
+            WheelUp CORRADE_DEPRECATED_ENUM("use mouseScrollEvent() and MouseScrollEvent instead") = 0xFFFF01,
+
+            /**
+             * Wheel down
+             * @deprecated Use @ref MouseScrollEvent and @ref mouseScrollEvent() instead.
+             */
+            WheelDown CORRADE_DEPRECATED_ENUM("use mouseScrollEvent() and MouseScrollEvent instead") = 0xFFFF02
+            #endif
         };
 
         /** @brief Button */
@@ -692,7 +716,7 @@ class NaClApplication::MouseEvent: public NaClApplication::InputEvent {
 @brief Mouse move event
 
 See also @ref InputEvent for more information.
-@see @ref MouseEvent, @ref mouseMoveEvent()
+@see @ref MouseEvent, @ref MouseScrollEvent, @ref mouseMoveEvent()
 */
 class NaClApplication::MouseMoveEvent: public NaClApplication::InputEvent {
     friend NaClApplication;
@@ -714,6 +738,25 @@ class NaClApplication::MouseMoveEvent: public NaClApplication::InputEvent {
         const Vector2i _position, _relativePosition;
 };
 
+/**
+@brief Mouse scroll event
+
+See also @ref InputEvent for more information.
+@see @ref MouseEvent, @ref MouseMoveEvent, @ref mouseScrollEvent()
+*/
+class NaClApplication::MouseScrollEvent: public NaClApplication::InputEvent {
+    friend NaClApplication;
+
+    public:
+        /** @brief Scroll offset */
+        constexpr Vector2 offset() const { return _offset; }
+
+    private:
+        constexpr MouseScrollEvent(const Vector2& offset, Modifiers modifiers): InputEvent{modifiers}, _offset{offset} {}
+
+        const Vector2 _offset;
+};
+
 CORRADE_ENUMSET_OPERATORS(NaClApplication::Flags)
 
 namespace Implementation {

src/Magnum/Platform/Sdl2Application.cpp

@@ -384,15 +384,28 @@ void Sdl2Application::mainLoop() {
                 event.type == SDL_MOUSEBUTTONDOWN ? mousePressEvent(e) : mouseReleaseEvent(e);
             } break;
 
-            case SDL_MOUSEWHEEL:
+            case SDL_MOUSEWHEEL: {
+                MouseScrollEvent e{{Float(event.wheel.x), Float(event.wheel.y)}};
+                mouseScrollEvent(e);
+
+                #ifdef MAGNUM_BUILD_DEPRECATED
                 if(event.wheel.y != 0) {
+                    #ifdef __GNUC__
+                    #pragma GCC diagnostic push
+                    #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+                    #endif
                     MouseEvent e(event.wheel.y > 0 ? MouseEvent::Button::WheelUp : MouseEvent::Button::WheelDown, {event.wheel.x, event.wheel.y}
                         #ifndef CORRADE_TARGET_EMSCRIPTEN
                         , 0
                         #endif
                         );
+                    #ifdef __GNUC__
+                    #pragma GCC diagnostic pop
+                    #endif
                     mousePressEvent(e);
-                } break;
+                }
+                #endif
+            } break;
 
             case SDL_MOUSEMOTION: {
                 MouseMoveEvent e({event.motion.x, event.motion.y}, {event.motion.xrel, event.motion.yrel}, static_cast<MouseMoveEvent::Button>(event.motion.state));
@@ -510,6 +523,7 @@ void Sdl2Application::keyReleaseEvent(KeyEvent&) {}
 void Sdl2Application::mousePressEvent(MouseEvent&) {}
 void Sdl2Application::mouseReleaseEvent(MouseEvent&) {}
 void Sdl2Application::mouseMoveEvent(MouseMoveEvent&) {}
+void Sdl2Application::mouseScrollEvent(MouseScrollEvent&) {}
 void Sdl2Application::multiGestureEvent(MultiGestureEvent&) {}
 void Sdl2Application::textInputEvent(TextInputEvent&) {}
 void Sdl2Application::textEditingEvent(TextEditingEvent&) {}
@@ -543,6 +557,12 @@ Sdl2Application::InputEvent::Modifiers Sdl2Application::MouseMoveEvent::modifier
     return _modifiers = fixedModifiers(Uint16(SDL_GetModState()));
 }
 
+Sdl2Application::InputEvent::Modifiers Sdl2Application::MouseScrollEvent::modifiers() {
+    if(_modifiersLoaded) return _modifiers;
+    _modifiersLoaded = true;
+    return _modifiers = fixedModifiers(Uint16(SDL_GetModState()));
+}
+
 template class BasicScreen<Sdl2Application>;
 template class BasicScreenedApplication<Sdl2Application>;
 

src/Magnum/Platform/Sdl2Application.h

@@ -331,6 +331,7 @@ class Sdl2Application {
         class KeyEvent;
         class MouseEvent;
         class MouseMoveEvent;
+        class MouseScrollEvent;
         class MultiGestureEvent;
         class TextInputEvent;
         class TextEditingEvent;
@@ -586,6 +587,14 @@ class Sdl2Application {
          */
         virtual void mouseMoveEvent(MouseMoveEvent& event);
 
+        /**
+         * @brief Mouse scroll event
+         *
+         * Called when a scrolling device is used (mouse wheel or scrolling
+         * area on a touchpad). Default implementation does nothing.
+         */
+        virtual void mouseScrollEvent(MouseScrollEvent& event);
+
         /*@}*/
 
         /** @{ @name Touch gesture handling */
@@ -1125,7 +1134,8 @@ class Sdl2Application::KeyEvent: public Sdl2Application::InputEvent {
 /**
 @brief Mouse event
 
-@see @ref MouseMoveEvent, @ref mousePressEvent(), @ref mouseReleaseEvent()
+@see @ref MouseMoveEvent, @ref MouseScrollEvent, @ref mousePressEvent(),
+    @ref mouseReleaseEvent()
 */
 class Sdl2Application::MouseEvent: public Sdl2Application::InputEvent {
     friend Sdl2Application;
@@ -1140,26 +1150,38 @@ class Sdl2Application::MouseEvent: public Sdl2Application::InputEvent {
             Left = SDL_BUTTON_LEFT,         /**< Left button */
             Middle = SDL_BUTTON_MIDDLE,     /**< Middle button */
             Right = SDL_BUTTON_RIGHT,       /**< Right button */
-            WheelUp = SDL_BUTTON_X1,        /**< Wheel up */
-            WheelDown = SDL_BUTTON_X2       /**< Wheel down */
+
+            /** First extra button (e.g. wheel left) */
+            X1 = SDL_BUTTON_X1,
+
+            /** Second extra button (e.g. wheel right) */
+            X2 = SDL_BUTTON_X2,
+
+            #ifdef MAGNUM_BUILD_DEPRECATED
+            /**
+             * Wheel up
+             * @deprecated Use @ref MouseScrollEvent and @ref mouseScrollEvent() instead.
+             */
+            WheelUp CORRADE_DEPRECATED_ENUM("use mouseScrollEvent() and MouseScrollEvent instead") = SDL_BUTTON_X2 + 1,
+
+            /**
+             * Wheel down
+             * @deprecated Use @ref MouseScrollEvent and @ref mouseScrollEvent() instead.
+             */
+            WheelDown CORRADE_DEPRECATED_ENUM("use mouseScrollEvent() and MouseScrollEvent instead") = SDL_BUTTON_X2 + 2
+            #endif
         };
 
         /** @brief Button */
         constexpr Button button() const { return _button; }
 
-        /**
-         * @brief Position
-         *
-         * For whell events this contains the horizontal and vertical scroll
-         * amount.
-         */
+        /** @brief Position */
         constexpr Vector2i position() const { return _position; }
 
         #ifndef CORRADE_TARGET_EMSCRIPTEN
         /**
          * @brief Click count
          *
-         * Ignored for wheel events.
          * @note Not available in @ref CORRADE_TARGET_EMSCRIPTEN "Emscripten".
          */
         constexpr Int clickCount() const { return _clickCount; }
@@ -1195,7 +1217,7 @@ class Sdl2Application::MouseEvent: public Sdl2Application::InputEvent {
 /**
 @brief Mouse move event
 
-@see @ref MouseEvent, @ref mouseMoveEvent()
+@see @ref MouseEvent, @ref MouseScrollEvent, @ref mouseMoveEvent()
 */
 class Sdl2Application::MouseMoveEvent: public Sdl2Application::InputEvent {
     friend Sdl2Application;
@@ -1210,8 +1232,12 @@ class Sdl2Application::MouseMoveEvent: public Sdl2Application::InputEvent {
             Left = SDL_BUTTON_LMASK,        /**< Left button */
             Middle = SDL_BUTTON_MMASK,      /**< Middle button */
             Right = SDL_BUTTON_RMASK,       /**< Right button */
-            WheelUp = SDL_BUTTON_X1MASK,    /**< Wheel up */
-            WheelDown = SDL_BUTTON_X2MASK   /**< Wheel down */
+
+            /** First extra button (e.g. wheel left) */
+            X1 = SDL_BUTTON_X1MASK,
+
+            /** Second extra button (e.g. wheel right) */
+            X2 = SDL_BUTTON_X2MASK
         };
 
         /**
@@ -1250,6 +1276,33 @@ class Sdl2Application::MouseMoveEvent: public Sdl2Application::InputEvent {
         Modifiers _modifiers;
 };
 
+/**
+@brief Mouse scroll event
+
+@see @ref MouseEvent, @ref MouseMoveEvent, @ref mouseScrollEvent()
+*/
+class Sdl2Application::MouseScrollEvent: public Sdl2Application::InputEvent {
+    friend Sdl2Application;
+
+    public:
+        /** @brief Scroll offset */
+        constexpr Vector2 offset() const { return _offset; }
+
+        /**
+         * @brief Modifiers
+         *
+         * Lazily populated on first request.
+         */
+        Modifiers modifiers();
+
+    private:
+        constexpr MouseScrollEvent(const Vector2& offset): _offset{offset}, _modifiersLoaded{false} {}
+
+        const Vector2 _offset;
+        bool _modifiersLoaded;
+        Modifiers _modifiers;
+};
+
 /**
 @brief Multi gesture event