LibWeb: Dispatch "wheel" event

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -405,6 +405,7 @@ set(SOURCES
     UIEvents/KeyboardEvent.cpp
     UIEvents/MouseEvent.cpp
     UIEvents/UIEvent.cpp
+    UIEvents/WheelEvent.cpp
     URL/URL.cpp
     URL/URLSearchParams.cpp
     URL/URLSearchParamsIterator.cpp

Userland/Libraries/LibWeb/Page/EventHandler.cpp

@@ -19,6 +19,7 @@
 #include <LibWeb/UIEvents/EventNames.h>
 #include <LibWeb/UIEvents/KeyboardEvent.h>
 #include <LibWeb/UIEvents/MouseEvent.h>
+#include <LibWeb/UIEvents/WheelEvent.h>
 
 namespace Web {
 
@@ -133,18 +134,51 @@ bool EventHandler::handle_mousewheel(Gfx::IntPoint const& position, unsigned int
     if (modifiers & KeyModifier::Mod_Shift)
         swap(wheel_delta_x, wheel_delta_y);
 
-    // FIXME: Support wheel events in nested browsing contexts.
+    bool handled_event = false;
 
-    auto result = paint_root()->hit_test(position.to_type<float>(), Painting::HitTestType::Exact);
-    if (result.has_value() && result->paintable->handle_mousewheel({}, position, buttons, modifiers, wheel_delta_x, wheel_delta_y))
-        return true;
-
-    if (auto* page = m_browsing_context.page()) {
-        page->client().page_did_request_scroll(wheel_delta_x * 20, wheel_delta_y * 20);
-        return true;
+    RefPtr<Painting::Paintable> paintable;
+    if (m_mouse_event_tracking_layout_node) {
+        paintable = m_mouse_event_tracking_layout_node->paintable();
+    } else {
+        if (auto result = paint_root()->hit_test(position.to_type<float>(), Painting::HitTestType::Exact); result.has_value())
+            paintable = result->paintable;
     }
 
-    return false;
+    if (paintable) {
+        paintable->handle_mousewheel({}, position, buttons, modifiers, wheel_delta_x, wheel_delta_y);
+
+        JS::GCPtr<DOM::Node> node = paintable->mouse_event_target();
+        if (!node)
+            node = paintable->dom_node();
+
+        if (node) {
+            // FIXME: Support wheel events in nested browsing contexts.
+            if (is<HTML::HTMLIFrameElement>(*node)) {
+                return false;
+            }
+
+            // Search for the first parent of the hit target that's an element.
+            auto* layout_node = &paintable->layout_node();
+            while (layout_node && node && !node->is_element() && layout_node->parent()) {
+                layout_node = layout_node->parent();
+                node = layout_node->dom_node();
+            }
+            if (!node || !layout_node) {
+                return false;
+            }
+
+            auto offset = compute_mouse_event_offset(position, *layout_node);
+            if (node->dispatch_event(*UIEvents::WheelEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::wheel, offset.x(), offset.y(), position.x(), position.y(), wheel_delta_x, wheel_delta_y))) {
+                if (auto* page = m_browsing_context.page()) {
+                    page->client().page_did_request_scroll(wheel_delta_x * 20, wheel_delta_y * 20);
+                }
+            }
+
+            handled_event = true;
+        }
+    }
+
+    return handled_event;
 }
 
 bool EventHandler::handle_mouseup(Gfx::IntPoint const& position, unsigned button, unsigned modifiers)

Userland/Libraries/LibWeb/UIEvents/EventNames.h

@@ -25,7 +25,8 @@ namespace Web::UIEvents::EventNames {
     __ENUMERATE_UI_EVENT(mouseout)   \
     __ENUMERATE_UI_EVENT(mouseover)  \
     __ENUMERATE_UI_EVENT(mouseup)    \
-    __ENUMERATE_UI_EVENT(resize)
+    __ENUMERATE_UI_EVENT(resize)     \
+    __ENUMERATE_UI_EVENT(wheel)
 
 #define __ENUMERATE_UI_EVENT(name) extern FlyString name;
 ENUMERATE_UI_EVENTS

Userland/Libraries/LibWeb/UIEvents/MouseEvent.h

@@ -21,7 +21,7 @@ struct MouseEventInit : public EventModifierInit {
     i16 button = 0;
 };
 
-class MouseEvent final : public UIEvent {
+class MouseEvent : public UIEvent {
     WEB_PLATFORM_OBJECT(MouseEvent, UIEvent);
 
 public:
@@ -43,9 +43,10 @@ public:
 
     virtual u32 which() const override { return m_button + 1; }
 
-private:
+protected:
     MouseEvent(JS::Realm&, FlyString const& event_name, MouseEventInit const& event_init);
 
+private:
     void set_event_characteristics();
 
     double m_offset_x { 0 };

Userland/Libraries/LibWeb/UIEvents/WheelEvent.cpp

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2022, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/HTML/EventNames.h>
+#include <LibWeb/UIEvents/EventNames.h>
+#include <LibWeb/UIEvents/WheelEvent.h>
+
+namespace Web::UIEvents {
+
+WheelEvent::WheelEvent(JS::Realm& realm, FlyString const& event_name, WheelEventInit const& event_init)
+    : MouseEvent(realm, event_name, event_init)
+    , m_delta_x(event_init.delta_x)
+    , m_delta_y(event_init.delta_y)
+    , m_delta_mode(event_init.delta_mode)
+{
+    set_prototype(&Bindings::cached_web_prototype(realm, "WheelEvent"));
+    set_event_characteristics();
+}
+
+WheelEvent::~WheelEvent() = default;
+
+WheelEvent* WheelEvent::create(JS::Realm& realm, FlyString const& event_name, WheelEventInit const& event_init)
+{
+    return realm.heap().allocate<WheelEvent>(realm, realm, event_name, event_init);
+}
+
+WheelEvent* WheelEvent::create_from_platform_event(JS::Realm& realm, FlyString const& event_name, double offset_x, double offset_y, double client_x, double client_y, double delta_x, double delta_y)
+{
+    WheelEventInit event_init {};
+    event_init.offset_x = offset_x;
+    event_init.offset_y = offset_y;
+    event_init.client_x = client_x;
+    event_init.client_y = client_y;
+    event_init.delta_x = delta_x;
+    event_init.delta_y = delta_y;
+    event_init.delta_mode = WheelDeltaMode::DOM_DELTA_PIXEL;
+    return WheelEvent::create(realm, event_name, event_init);
+}
+
+void WheelEvent::set_event_characteristics()
+{
+    set_bubbles(true);
+    set_cancelable(true);
+    set_composed(true);
+}
+
+}

Userland/Libraries/LibWeb/UIEvents/WheelEvent.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2022, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/UIEvents/MouseEvent.h>
+#include <LibWeb/UIEvents/UIEvent.h>
+
+namespace Web::UIEvents {
+
+enum class WheelDeltaMode : unsigned long {
+    DOM_DELTA_PIXEL = 0,
+    DOM_DELTA_LINE = 1,
+    DOM_DELTA_PAGE = 2,
+};
+
+struct WheelEventInit : public MouseEventInit {
+    double delta_x = 0;
+    double delta_y = 0;
+    double delta_z = 0;
+
+    WheelDeltaMode delta_mode = WheelDeltaMode::DOM_DELTA_PIXEL;
+};
+
+class WheelEvent final : public MouseEvent {
+    WEB_PLATFORM_OBJECT(WheelEvent, MouseEvent);
+
+public:
+    static WheelEvent* create(JS::Realm&, FlyString const& event_name, WheelEventInit const& event_init = {});
+    static WheelEvent* create_from_platform_event(JS::Realm&, FlyString const& event_name, double offset_x, double offset_y, double client_x, double client_y, double delta_x, double delta_y);
+
+    virtual ~WheelEvent() override;
+
+    double delta_x() const { return m_delta_x; }
+    double delta_y() const { return m_delta_y; }
+    double delta_z() const { return m_delta_z; }
+    unsigned long delta_mode() const { return to_underlying(m_delta_mode); }
+
+private:
+    WheelEvent(JS::Realm&, FlyString const& event_name, WheelEventInit const& event_init);
+
+    void set_event_characteristics();
+
+    double m_delta_x { 0 };
+    double m_delta_y { 0 };
+    double m_delta_z { 0 };
+    WheelDeltaMode m_delta_mode { WheelDeltaMode::DOM_DELTA_PIXEL };
+};
+
+}

Userland/Libraries/LibWeb/UIEvents/WheelEvent.idl

@@ -0,0 +1,22 @@
+#import <UIEvents/MouseEvent.idl>
+
+// https://www.w3.org/TR/uievents/#idl-wheelevent
+[Exposed=Window]
+interface WheelEvent : MouseEvent {
+    // DeltaModeCode
+    const unsigned long DOM_DELTA_PIXEL = 0x00;
+    const unsigned long DOM_DELTA_LINE  = 0x01;
+    const unsigned long DOM_DELTA_PAGE  = 0x02;
+
+    readonly attribute double deltaX;
+    readonly attribute double deltaY;
+    readonly attribute double deltaZ;
+    readonly attribute unsigned long deltaMode;
+};
+
+dictionary WheelEventInit : MouseEventInit {
+    double deltaX = 0;
+    double deltaY = 0;
+    double deltaZ = 0;
+    unsigned long deltaMode = 0;
+};

Userland/Libraries/LibWeb/idl_files.cmake

@@ -184,6 +184,7 @@ libweb_js_bindings(UIEvents/FocusEvent)
 libweb_js_bindings(UIEvents/KeyboardEvent)
 libweb_js_bindings(UIEvents/MouseEvent)
 libweb_js_bindings(UIEvents/UIEvent)
+libweb_js_bindings(UIEvents/WheelEvent)
 libweb_js_bindings(URL/URL)
 libweb_js_bindings(URL/URLSearchParams ITERABLE)
 libweb_js_bindings(WebGL/WebGLContextEvent)