WindowServer+LibGUI: Handle mouse wheel deltas in the mouse event stream.

The wheel events will end up in GWidget::mousewheel_event(GMouseEvent&)
on the client-side. This patch also implements basic wheel scrolling in
GScrollableWidget via this mechanism. :^)

LibGUI/GEvent.h

@@ -19,6 +19,7 @@ public:
         MouseMove,
         MouseDown,
         MouseUp,
+        MouseWheel,
         Enter,
         Leave,
         KeyDown,
@@ -44,7 +45,6 @@ public:
     explicit GEvent(Type type) : CEvent(type) { }
     virtual ~GEvent() { }
 
-    bool is_mouse_event() const { return type() == MouseMove || type() == MouseDown || type() == MouseUp; }
     bool is_key_event() const { return type() == KeyUp || type() == KeyDown; }
     bool is_paint_event() const { return type() == Paint; }
 };
@@ -244,12 +244,13 @@ private:
 
 class GMouseEvent final : public GEvent {
 public:
-    GMouseEvent(Type type, const Point& position, unsigned buttons, GMouseButton button, unsigned modifiers)
+    GMouseEvent(Type type, const Point& position, unsigned buttons, GMouseButton button, unsigned modifiers, int wheel_delta)
         : GEvent(type)
         , m_position(position)
         , m_buttons(buttons)
         , m_button(button)
         , m_modifiers(modifiers)
+        , m_wheel_delta(wheel_delta)
     {
     }
 
@@ -259,10 +260,12 @@ public:
     GMouseButton button() const { return m_button; }
     unsigned buttons() const { return m_buttons; }
     unsigned modifiers() const { return m_modifiers; }
+    int wheel_delta() const { return m_wheel_delta; }
 
 private:
     Point m_position;
     unsigned m_buttons { 0 };
     GMouseButton m_button { GMouseButton::None };
     unsigned m_modifiers { 0 };
+    int m_wheel_delta { 0 };
 };

LibGUI/GEventLoop.cpp

@@ -152,13 +152,14 @@ void GEventLoop::handle_key_event(const WSAPI_ServerMessage& event, GWindow& win
 void GEventLoop::handle_mouse_event(const WSAPI_ServerMessage& event, GWindow& window)
 {
 #ifdef GEVENTLOOP_DEBUG
-    dbgprintf("WID=%x MouseEvent %d,%d\n", event.window_id, event.mouse.position.x, event.mouse.position.y);
+    dbgprintf("WID=%x MouseEvent %d,%d,%d\n", event.window_id, event.mouse.position.x, event.mouse.position.y, event.mouse.wheel_delta);
 #endif
     GMouseEvent::Type type;
     switch (event.type) {
     case WSAPI_ServerMessage::Type::MouseMove: type = GEvent::MouseMove; break;
     case WSAPI_ServerMessage::Type::MouseUp: type = GEvent::MouseUp; break;
     case WSAPI_ServerMessage::Type::MouseDown: type = GEvent::MouseDown; break;
+    case WSAPI_ServerMessage::Type::MouseWheel: type = GEvent::MouseWheel; break;
     default: ASSERT_NOT_REACHED(); break;
     }
     GMouseButton button { GMouseButton::None };
@@ -169,7 +170,7 @@ void GEventLoop::handle_mouse_event(const WSAPI_ServerMessage& event, GWindow& w
     case WSAPI_MouseButton::Middle: button = GMouseButton::Middle; break;
     default: ASSERT_NOT_REACHED(); break;
     }
-    post_event(window, make<GMouseEvent>(type, event.mouse.position, event.mouse.buttons, button, event.mouse.modifiers));
+    post_event(window, make<GMouseEvent>(type, event.mouse.position, event.mouse.buttons, button, event.mouse.modifiers, event.mouse.wheel_delta));
 }
 
 void GEventLoop::handle_menu_event(const WSAPI_ServerMessage& event)
@@ -276,6 +277,7 @@ void GEventLoop::process_unprocessed_bundles()
         case WSAPI_ServerMessage::Type::MouseDown:
         case WSAPI_ServerMessage::Type::MouseUp:
         case WSAPI_ServerMessage::Type::MouseMove:
+        case WSAPI_ServerMessage::Type::MouseWheel:
             handle_mouse_event(event, *window);
             break;
         case WSAPI_ServerMessage::Type::WindowActivated:

LibGUI/GScrollableWidget.cpp

@@ -27,6 +27,12 @@ GScrollableWidget::~GScrollableWidget()
 {
 }
 
+void GScrollableWidget::mousewheel_event(GMouseEvent& event)
+{
+    // FIXME: The wheel delta multiplier should probably come from... somewhere?
+    vertical_scrollbar().set_value(vertical_scrollbar().value() + event.wheel_delta() * 20);
+}
+
 void GScrollableWidget::resize_event(GResizeEvent& event)
 {
     auto inner_rect = frame_inner_rect_for_size(event.size());

LibGUI/GScrollableWidget.h

@@ -39,6 +39,7 @@ public:
 protected:
     explicit GScrollableWidget(GWidget* parent);
     virtual void resize_event(GResizeEvent&) override;
+    virtual void mousewheel_event(GMouseEvent&) override;
     virtual void did_scroll() { }
     void set_content_size(const Size&);
     void set_size_occupied_by_fixed_elements(const Size&);

LibGUI/GWidget.cpp

@@ -86,6 +86,8 @@ void GWidget::event(CEvent& event)
         return handle_mousedown_event(static_cast<GMouseEvent&>(event));
     case GEvent::MouseUp:
         return handle_mouseup_event(static_cast<GMouseEvent&>(event));
+    case GEvent::MouseWheel:
+        return mousewheel_event(static_cast<GMouseEvent&>(event));
     case GEvent::Enter:
         return handle_enter_event(event);
     case GEvent::Leave:
@@ -261,6 +263,10 @@ void GWidget::mousemove_event(GMouseEvent&)
 {
 }
 
+void GWidget::mousewheel_event(GMouseEvent&)
+{
+}
+
 void GWidget::context_menu_event(GContextMenuEvent&)
 {
 }

LibGUI/GWidget.h

@@ -58,6 +58,7 @@ public:
     virtual void mousemove_event(GMouseEvent&);
     virtual void mousedown_event(GMouseEvent&);
     virtual void mouseup_event(GMouseEvent&);
+    virtual void mousewheel_event(GMouseEvent&);
     virtual void click_event(GMouseEvent&);
     virtual void doubleclick_event(GMouseEvent&);
     virtual void context_menu_event(GContextMenuEvent&);

LibGUI/GWindow.cpp

@@ -170,19 +170,19 @@ void GWindow::set_override_cursor(GStandardCursor cursor)
 
 void GWindow::event(CEvent& event)
 {
-    if (event.type() == GEvent::MouseUp || event.type() == GEvent::MouseDown || event.type() == GEvent::MouseMove) {
+    if (event.type() == GEvent::MouseUp || event.type() == GEvent::MouseDown || event.type() == GEvent::MouseMove || event.type() == GEvent::MouseWheel) {
         auto& mouse_event = static_cast<GMouseEvent&>(event);
         if (m_global_cursor_tracking_widget) {
             auto window_relative_rect = m_global_cursor_tracking_widget->window_relative_rect();
             Point local_point { mouse_event.x() - window_relative_rect.x(), mouse_event.y() - window_relative_rect.y() };
-            auto local_event = make<GMouseEvent>((GEvent::Type)event.type(), local_point, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers());
+            auto local_event = make<GMouseEvent>((GEvent::Type)event.type(), local_point, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers(), mouse_event.wheel_delta());
             m_global_cursor_tracking_widget->event(*local_event);
             return;
         }
         if (m_automatic_cursor_tracking_widget) {
             auto window_relative_rect = m_automatic_cursor_tracking_widget->window_relative_rect();
             Point local_point { mouse_event.x() - window_relative_rect.x(), mouse_event.y() - window_relative_rect.y() };
-            auto local_event = make<GMouseEvent>((GEvent::Type)event.type(), local_point, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers());
+            auto local_event = make<GMouseEvent>((GEvent::Type)event.type(), local_point, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers(), mouse_event.wheel_delta());
             m_automatic_cursor_tracking_widget->event(*local_event);
             if (mouse_event.buttons() == 0)
                 m_automatic_cursor_tracking_widget = nullptr;
@@ -190,16 +190,14 @@ void GWindow::event(CEvent& event)
         }
         if (!m_main_widget)
             return;
-        if (m_main_widget) {
+        auto result = m_main_widget->hit_test(mouse_event.position());
-            auto result = m_main_widget->hit_test(mouse_event.position());
+        auto local_event = make<GMouseEvent>((GEvent::Type)event.type(), result.local_position, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers(), mouse_event.wheel_delta());
-            auto local_event = make<GMouseEvent>((GEvent::Type)event.type(), result.local_position, mouse_event.buttons(), mouse_event.button(), mouse_event.modifiers());
+        ASSERT(result.widget);
-            ASSERT(result.widget);
+        set_hovered_widget(result.widget);
-            set_hovered_widget(result.widget);
+        if (mouse_event.buttons() != 0 && !m_automatic_cursor_tracking_widget)
-            if (mouse_event.buttons() != 0 && !m_automatic_cursor_tracking_widget)
+            m_automatic_cursor_tracking_widget = result.widget->make_weak_ptr();
-                m_automatic_cursor_tracking_widget = result.widget->make_weak_ptr();
+        if (result.widget != m_global_cursor_tracking_widget.ptr())
-            if (result.widget != m_global_cursor_tracking_widget.ptr())
+            return result.widget->event(*local_event);
-                return result.widget->event(*local_event);
-        }
         return;
     }
 

Servers/WindowServer/WSAPITypes.h

@@ -74,6 +74,7 @@ struct WSAPI_ServerMessage {
         MouseMove,
         MouseDown,
         MouseUp,
+        MouseWheel,
         WindowEntered,
         WindowLeft,
         KeyDown,
@@ -155,6 +156,7 @@ struct WSAPI_ServerMessage {
             WSAPI_MouseButton button;
             unsigned buttons;
             byte modifiers;
+            int wheel_delta;
         } mouse;
         struct {
             char character;

Servers/WindowServer/WSEvent.h

@@ -18,6 +18,7 @@ public:
         MouseMove,
         MouseDown,
         MouseUp,
+        MouseWheel,
         WindowEntered,
         WindowLeft,
         KeyDown,
@@ -74,7 +75,7 @@ public:
     virtual ~WSEvent() { }
 
     bool is_client_request() const { return type() > __Begin_API_Client_Requests && type() < __End_API_Client_Requests; }
-    bool is_mouse_event() const { return type() == MouseMove || type() == MouseDown || type() == MouseUp; }
+    bool is_mouse_event() const { return type() == MouseMove || type() == MouseDown || type() == MouseUp || type() == MouseWheel; }
     bool is_key_event() const { return type() == KeyUp || type() == KeyDown; }
 };
 
@@ -718,12 +719,13 @@ private:
 
 class WSMouseEvent final : public WSEvent {
 public:
-    WSMouseEvent(Type type, const Point& position, unsigned buttons, MouseButton button, unsigned modifiers)
+    WSMouseEvent(Type type, const Point& position, unsigned buttons, MouseButton button, unsigned modifiers, int wheel_delta = 0)
         : WSEvent(type)
         , m_position(position)
         , m_buttons(buttons)
         , m_button(button)
         , m_modifiers(modifiers)
+        , m_wheel_delta(wheel_delta)
     {
     }
 
@@ -733,14 +735,16 @@ public:
     MouseButton button() const { return m_button; }
     unsigned buttons() const { return m_buttons; }
     unsigned modifiers() const { return m_modifiers; }
+    int wheel_delta() const { return m_wheel_delta; }
 
-    WSMouseEvent translated(const Point& delta) const { return WSMouseEvent((Type)type(), m_position.translated(delta), m_buttons, m_button, m_modifiers); }
+    WSMouseEvent translated(const Point& delta) const { return WSMouseEvent((Type)type(), m_position.translated(delta), m_buttons, m_button, m_modifiers, m_wheel_delta); }
 
 private:
     Point m_position;
     unsigned m_buttons { 0 };
     MouseButton m_button { MouseButton::None };
     unsigned m_modifiers { 0 };
+    int m_wheel_delta { 0 };
 };
 
 class WSResizeEvent final : public WSEvent {

Servers/WindowServer/WSEventLoop.cpp

@@ -62,6 +62,7 @@ void WSEventLoop::drain_mouse()
     unsigned prev_buttons = screen.mouse_button_state();
     int dx = 0;
     int dy = 0;
+    int dz = 0;
     unsigned buttons = prev_buttons;
     for (;;) {
         MousePacket packet;
@@ -73,15 +74,17 @@ void WSEventLoop::drain_mouse()
 
         dx += packet.dx;
         dy += -packet.dy;
+        dz += packet.dz;
         if (buttons != prev_buttons) {
-            screen.on_receive_mouse_data(dx, dy, buttons);
+            screen.on_receive_mouse_data(dx, dy, dz, buttons);
             dx = 0;
             dy = 0;
+            dz = 0;
             prev_buttons = buttons;
         }
     }
-    if (dx || dy)
+    if (dx || dy || dz)
-        screen.on_receive_mouse_data(dx, dy, buttons);
+        screen.on_receive_mouse_data(dx, dy, dz, buttons);
 }
 
 void WSEventLoop::drain_keyboard()

Servers/WindowServer/WSScreen.cpp

@@ -58,7 +58,7 @@ void WSScreen::set_resolution(int width, int height)
     m_cursor_location.constrain(rect());
 }
 
-void WSScreen::on_receive_mouse_data(int dx, int dy, unsigned buttons)
+void WSScreen::on_receive_mouse_data(int dx, int dy, int dz, unsigned buttons)
 {
     auto prev_location = m_cursor_location;
     m_cursor_location.move_by(dx, dy);
@@ -80,6 +80,11 @@ void WSScreen::on_receive_mouse_data(int dx, int dy, unsigned buttons)
         WSEventLoop::the().post_event(WSWindowManager::the(), move(message));
     }
 
+    if (dz) {
+        auto message = make<WSMouseEvent>(WSEvent::MouseWheel, m_cursor_location, buttons, MouseButton::None, m_modifiers, dz);
+        WSEventLoop::the().post_event(WSWindowManager::the(), move(message));
+    }
+
     if (m_cursor_location != prev_location)
         WSWindowManager::the().invalidate_cursor();
 }

Servers/WindowServer/WSScreen.h

@@ -26,7 +26,7 @@ public:
     Point cursor_location() const { return m_cursor_location; }
     unsigned mouse_button_state() const { return m_mouse_button_state; }
 
-    void on_receive_mouse_data(int dx, int dy, unsigned buttons);
+    void on_receive_mouse_data(int dx, int dy, int dz, unsigned buttons);
     void on_receive_keyboard_data(KeyEvent);
 
 private:

Servers/WindowServer/WSWindow.cpp

@@ -95,6 +95,7 @@ void WSWindow::handle_mouse_event(const WSMouseEvent& event)
     case WSEvent::MouseMove: server_message.type = WSAPI_ServerMessage::Type::MouseMove; break;
     case WSEvent::MouseDown: server_message.type = WSAPI_ServerMessage::Type::MouseDown; break;
     case WSEvent::MouseUp: server_message.type = WSAPI_ServerMessage::Type::MouseUp; break;
+    case WSEvent::MouseWheel: server_message.type = WSAPI_ServerMessage::Type::MouseWheel; break;
     default: ASSERT_NOT_REACHED();
     }
 
@@ -102,6 +103,7 @@ void WSWindow::handle_mouse_event(const WSMouseEvent& event)
     server_message.mouse.button = to_api(event.button());
     server_message.mouse.buttons = event.buttons();
     server_message.mouse.modifiers = event.modifiers();
+    server_message.mouse.wheel_delta = event.wheel_delta();
 
     m_client->post_message(server_message);
 }