LibWeb+LibWebView+WebContent: Add IPC to send drag-and-drop events

This adds the IPC and related hooks to allow the UI to send drag-and-
drop events from the UI process to the WebContent process.

Userland/Libraries/LibWeb/Page/InputEvent.cpp

@@ -76,3 +76,30 @@ ErrorOr<Web::MouseEvent> IPC::decode(Decoder& decoder)
 
     return Web::MouseEvent { type, position, screen_position, button, buttons, modifiers, wheel_delta_x, wheel_delta_y, nullptr };
 }
+
+template<>
+ErrorOr<void> IPC::encode(Encoder& encoder, Web::DragEvent const& event)
+{
+    TRY(encoder.encode(event.type));
+    TRY(encoder.encode(event.position));
+    TRY(encoder.encode(event.screen_position));
+    TRY(encoder.encode(event.button));
+    TRY(encoder.encode(event.buttons));
+    TRY(encoder.encode(event.modifiers));
+    TRY(encoder.encode(event.files));
+    return {};
+}
+
+template<>
+ErrorOr<Web::DragEvent> IPC::decode(Decoder& decoder)
+{
+    auto type = TRY(decoder.decode<Web::DragEvent::Type>());
+    auto position = TRY(decoder.decode<Web::DevicePixelPoint>());
+    auto screen_position = TRY(decoder.decode<Web::DevicePixelPoint>());
+    auto button = TRY(decoder.decode<Web::UIEvents::MouseButton>());
+    auto buttons = TRY(decoder.decode<Web::UIEvents::MouseButton>());
+    auto modifiers = TRY(decoder.decode<Web::UIEvents::KeyModifier>());
+    auto files = TRY(decoder.decode<Vector<Web::HTML::SelectedFile>>());
+
+    return Web::DragEvent { type, position, screen_position, button, buttons, modifiers, move(files), nullptr };
+}

Userland/Libraries/LibWeb/Page/InputEvent.h

@@ -82,7 +82,7 @@ struct DragEvent {
     OwnPtr<ChromeInputData> chrome_data;
 };
 
-using InputEvent = Variant<KeyEvent, MouseEvent>;
+using InputEvent = Variant<KeyEvent, MouseEvent, DragEvent>;
 
 }
 
@@ -100,4 +100,10 @@ ErrorOr<void> encode(Encoder&, Web::MouseEvent const&);
 template<>
 ErrorOr<Web::MouseEvent> decode(Decoder&);
 
+template<>
+ErrorOr<void> encode(Encoder&, Web::DragEvent const&);
+
+template<>
+ErrorOr<Web::DragEvent> decode(Decoder&);
+
 }

Userland/Libraries/LibWebView/ViewImplementation.cpp

@@ -137,6 +137,12 @@ void ViewImplementation::enqueue_input_event(Web::InputEvent event)
         },
         [this](Web::MouseEvent const& event) {
             client().async_mouse_event(m_client_state.page_index, event.clone_without_chrome_data());
+        },
+        [this](Web::DragEvent& event) {
+            auto cloned_event = event.clone_without_chrome_data();
+            cloned_event.files = move(event.files);
+
+            client().async_drag_event(m_client_state.page_index, move(cloned_event));
         });
 }
 
@@ -144,14 +150,21 @@ void ViewImplementation::did_finish_handling_input_event(Badge<WebContentClient>
 {
     auto event = m_pending_input_events.dequeue();
 
-    if (!event_was_accepted && event.has<Web::KeyEvent>()) {
-        auto const& key_event = event.get<Web::KeyEvent>();
+    if (event_was_accepted)
+        return;
 
-        // Here we handle events that were not consumed or cancelled by the WebContent. Propagate the event back
-        // to the concrete view implementation.
-        if (on_finish_handling_key_event)
-            on_finish_handling_key_event(key_event);
-    }
+    // Here we handle events that were not consumed or cancelled by the WebContent. Propagate the event back
+    // to the concrete view implementation.
+    event.visit(
+        [this](Web::KeyEvent const& event) {
+            if (on_finish_handling_key_event)
+                on_finish_handling_key_event(event);
+        },
+        [this](Web::DragEvent const& event) {
+            if (on_finish_handling_drag_event)
+                on_finish_handling_drag_event(event);
+        },
+        [](auto const&) {});
 }
 
 void ViewImplementation::set_preferred_color_scheme(Web::CSS::PreferredColorScheme color_scheme)

Userland/Libraries/LibWebView/ViewImplementation.h

@@ -203,6 +203,7 @@ public:
     Function<void(Web::HTML::FileFilter const& accepted_file_types, Web::HTML::AllowMultipleFiles)> on_request_file_picker;
     Function<void(Gfx::IntPoint content_position, i32 minimum_width, Vector<Web::HTML::SelectItem> items)> on_request_select_dropdown;
     Function<void(Web::KeyEvent const&)> on_finish_handling_key_event;
+    Function<void(Web::DragEvent const&)> on_finish_handling_drag_event;
     Function<void()> on_text_test_finish;
     Function<void(size_t current_match_index, Optional<size_t> const& total_match_count)> on_find_in_page;
     Function<void(Gfx::Color)> on_theme_color_change;

Userland/Services/WebContent/ConnectionFromClient.cpp

@@ -207,6 +207,9 @@ void ConnectionFromClient::process_next_input_event()
                 return page->page().handle_doubleclick(event.position, event.screen_position, event.button, event.buttons, event.modifiers);
             }
             VERIFY_NOT_REACHED();
+        },
+        [&](Web::DragEvent& event) {
+            return page->page().handle_drag_and_drop_event(event.type, event.position, event.screen_position, event.button, event.buttons, event.modifiers, move(event.files));
         });
 
     // We have to notify the client about coalesced events, so we do that by saying none of them were handled by the web page->
@@ -257,6 +260,11 @@ void ConnectionFromClient::mouse_event(u64 page_id, Web::MouseEvent const& event
     enqueue_input_event({ page_id, move(const_cast<Web::MouseEvent&>(event)), 0 });
 }
 
+void ConnectionFromClient::drag_event(u64 page_id, Web::DragEvent const& event)
+{
+    enqueue_input_event({ page_id, move(const_cast<Web::DragEvent&>(event)), 0 });
+}
+
 void ConnectionFromClient::enqueue_input_event(QueuedInputEvent event)
 {
     m_input_event_queue.enqueue(move(event));

Userland/Services/WebContent/ConnectionFromClient.h

@@ -67,6 +67,7 @@ private:
     virtual void set_viewport_size(u64 page_id, Web::DevicePixelSize const) override;
     virtual void key_event(u64 page_id, Web::KeyEvent const&) override;
     virtual void mouse_event(u64 page_id, Web::MouseEvent const&) override;
+    virtual void drag_event(u64 page_id, Web::DragEvent const&) override;
     virtual void ready_to_paint(u64 page_id) override;
     virtual void debug_request(u64 page_id, ByteString const&, ByteString const&) override;
     virtual void get_source(u64 page_id) override;

Userland/Services/WebContent/WebContentServer.ipc

@@ -35,6 +35,7 @@ endpoint WebContentServer
 
     key_event(u64 page_id, Web::KeyEvent event) =|
     mouse_event(u64 page_id, Web::MouseEvent event) =|
+    drag_event(u64 page_id, Web::DragEvent event) =|
 
     debug_request(u64 page_id, ByteString request, ByteString argument) =|
     get_source(u64 page_id) =|