LibWeb+LibWebView+WebContent: Inform the UI about DOM mutations

This will allow our DevTools server to inform the Firefox DevTools
client about DOM mutations.

Libraries/LibWebView/CMakeLists.txt

@@ -9,6 +9,7 @@ set(SOURCES
     Database.cpp
     HelperProcess.cpp
     InspectorClient.cpp
+    Mutation.cpp
     Plugins/FontPlugin.cpp
     Plugins/ImageCodecPlugin.cpp
     Process.cpp

Libraries/LibWebView/Forward.h

@@ -21,6 +21,7 @@ class WebContentClient;
 struct Attribute;
 struct ConsoleOutput;
 struct CookieStorageKey;
+struct Mutation;
 struct ProcessHandle;
 struct SearchEngine;
 

Libraries/LibWebView/Mutation.cpp

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2025, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibIPC/Decoder.h>
+#include <LibIPC/Encoder.h>
+#include <LibWebView/Mutation.h>
+
+template<>
+ErrorOr<void> IPC::encode(Encoder& encoder, WebView::AttributeMutation const& mutation)
+{
+    TRY(encoder.encode(mutation.attribute_name));
+    TRY(encoder.encode(mutation.new_value));
+    return {};
+}
+
+template<>
+ErrorOr<WebView::AttributeMutation> IPC::decode(Decoder& decoder)
+{
+    auto attribute_name = TRY(decoder.decode<String>());
+    auto new_value = TRY(decoder.decode<Optional<String>>());
+
+    return WebView::AttributeMutation { move(attribute_name), move(new_value) };
+}
+
+template<>
+ErrorOr<void> IPC::encode(Encoder& encoder, WebView::CharacterDataMutation const& mutation)
+{
+    TRY(encoder.encode(mutation.new_value));
+    return {};
+}
+
+template<>
+ErrorOr<WebView::CharacterDataMutation> IPC::decode(Decoder& decoder)
+{
+    auto new_value = TRY(decoder.decode<String>());
+
+    return WebView::CharacterDataMutation { move(new_value) };
+}
+
+template<>
+ErrorOr<void> IPC::encode(Encoder& encoder, WebView::ChildListMutation const& mutation)
+{
+    TRY(encoder.encode(mutation.added));
+    TRY(encoder.encode(mutation.removed));
+    TRY(encoder.encode(mutation.target_child_count));
+    return {};
+}
+
+template<>
+ErrorOr<WebView::ChildListMutation> IPC::decode(Decoder& decoder)
+{
+    auto added = TRY(decoder.decode<Vector<Web::UniqueNodeID>>());
+    auto removed = TRY(decoder.decode<Vector<Web::UniqueNodeID>>());
+    auto target_child_count = TRY(decoder.decode<size_t>());
+
+    return WebView::ChildListMutation { move(added), move(removed), target_child_count };
+}
+
+template<>
+ErrorOr<void> IPC::encode(Encoder& encoder, WebView::Mutation const& mutation)
+{
+    TRY(encoder.encode(mutation.type));
+    TRY(encoder.encode(mutation.target));
+    TRY(encoder.encode(mutation.serialized_target));
+    TRY(encoder.encode(mutation.mutation));
+    return {};
+}
+
+template<>
+ErrorOr<WebView::Mutation> IPC::decode(Decoder& decoder)
+{
+    auto type = TRY(decoder.decode<String>());
+    auto target = TRY(decoder.decode<Web::UniqueNodeID>());
+    auto serialized_target = TRY(decoder.decode<String>());
+    auto mutation = TRY(decoder.decode<WebView::Mutation::Type>());
+
+    return WebView::Mutation { move(type), target, move(serialized_target), move(mutation) };
+}

Libraries/LibWebView/Mutation.h

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2025, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <AK/Variant.h>
+#include <AK/Vector.h>
+#include <LibIPC/Forward.h>
+#include <LibWeb/Forward.h>
+
+namespace WebView {
+
+struct AttributeMutation {
+    String attribute_name;
+    Optional<String> new_value;
+};
+
+struct CharacterDataMutation {
+    String new_value;
+};
+
+struct ChildListMutation {
+    Vector<Web::UniqueNodeID> added;
+    Vector<Web::UniqueNodeID> removed;
+    size_t target_child_count { 0 };
+};
+
+struct Mutation {
+    using Type = Variant<AttributeMutation, CharacterDataMutation, ChildListMutation>;
+
+    String type;
+    Web::UniqueNodeID target { 0 };
+    String serialized_target;
+    Type mutation;
+};
+
+}
+
+namespace IPC {
+
+template<>
+ErrorOr<void> encode(Encoder&, WebView::AttributeMutation const&);
+
+template<>
+ErrorOr<WebView::AttributeMutation> decode(Decoder&);
+
+template<>
+ErrorOr<void> encode(Encoder&, WebView::CharacterDataMutation const&);
+
+template<>
+ErrorOr<WebView::CharacterDataMutation> decode(Decoder&);
+
+template<>
+ErrorOr<void> encode(Encoder&, WebView::ChildListMutation const&);
+
+template<>
+ErrorOr<WebView::ChildListMutation> decode(Decoder&);
+
+template<>
+ErrorOr<void> encode(Encoder&, WebView::Mutation const&);
+
+template<>
+ErrorOr<WebView::Mutation> decode(Decoder&);
+
+}

Libraries/LibWebView/ViewImplementation.cpp

@@ -333,6 +333,11 @@ void ViewImplementation::clear_highlighted_dom_node()
     highlight_dom_node(0, {});
 }
 
+void ViewImplementation::set_listen_for_dom_mutations(bool listen_for_dom_mutations)
+{
+    client().async_set_listen_for_dom_mutations(page_id(), listen_for_dom_mutations);
+}
+
 void ViewImplementation::set_dom_node_text(Web::UniqueNodeID node_id, String text)
 {
     client().async_set_dom_node_text(page_id(), node_id, move(text));

Libraries/LibWebView/ViewImplementation.h

@@ -112,6 +112,7 @@ public:
     void highlight_dom_node(Web::UniqueNodeID node_id, Optional<Web::CSS::Selector::PseudoElement::Type> pseudo_element);
     void clear_highlighted_dom_node();
 
+    void set_listen_for_dom_mutations(bool);
     void set_dom_node_text(Web::UniqueNodeID node_id, String text);
     void set_dom_node_tag(Web::UniqueNodeID node_id, String name);
     void add_dom_node_attributes(Web::UniqueNodeID node_id, Vector<Attribute> attributes);
@@ -213,6 +214,7 @@ public:
     Function<void(Web::CSS::StyleSheetIdentifier const&)> on_inspector_requested_style_sheet_source;
     Function<void(Web::CSS::StyleSheetIdentifier const&, URL::URL const&, String const&)> on_received_style_sheet_source;
     Function<void(Web::UniqueNodeID)> on_received_hovered_node_id;
+    Function<void(Mutation)> on_dom_mutation_received;
     Function<void(Optional<Web::UniqueNodeID> const& node_id)> on_finshed_editing_dom_node;
     Function<void(String const&)> on_received_dom_node_html;
     Function<void(JsonValue)> on_received_js_console_result;

Libraries/LibWebView/WebContentClient.cpp

@@ -341,6 +341,14 @@ void WebContentClient::did_finish_editing_dom_node(u64 page_id, Optional<Web::Un
     }
 }
 
+void WebContentClient::did_mutate_dom(u64 page_id, Mutation const& mutation)
+{
+    if (auto view = view_for_page_id(page_id); view.has_value()) {
+        if (view->on_dom_mutation_received)
+            view->on_dom_mutation_received(move(const_cast<Mutation&>(mutation)));
+    }
+}
+
 void WebContentClient::did_get_dom_node_html(u64 page_id, String const& html)
 {
     if (auto view = view_for_page_id(page_id); view.has_value()) {

Libraries/LibWebView/WebContentClient.h

@@ -76,6 +76,7 @@ private:
     virtual void did_inspect_accessibility_tree(u64 page_id, String const&) override;
     virtual void did_get_hovered_node_id(u64 page_id, Web::UniqueNodeID const& node_id) override;
     virtual void did_finish_editing_dom_node(u64 page_id, Optional<Web::UniqueNodeID> const& node_id) override;
+    virtual void did_mutate_dom(u64 page_id, Mutation const&) override;
     virtual void did_get_dom_node_html(u64 page_id, String const& html) override;
     virtual void did_take_screenshot(u64 page_id, Gfx::ShareableBitmap const& screenshot) override;
     virtual void did_get_internal_page_info(u64 page_id, PageInfoType, String const&) override;