Browser+LibWeb+WebContent: Show style for pseudo-elements :^)

This expands the InspectorWidget::Selection to include an optional
PseudoElement, which is then passed over IPC to request style
information for it.

As noted, this has some pretty big limitations because pseudo-elements
don't have DOM nodes:
- Declared style has to be recalculated when it's requested.
- We don't display the computed style.
- We don't display custom properties.

Userland/Applications/Browser/InspectorWidget.cpp

@@ -46,12 +46,19 @@ void InspectorWidget::set_selection(GUI::ModelIndex const index)
     auto* json = static_cast<JsonObject const*>(index.internal_data());
     VERIFY(json);
 
-    Selection selection { json->get("id").to_i32() };
+    Selection selection {};
+    if (json->has_u32("pseudo-element")) {
+        selection.dom_node_id = json->get("parent-id").to_i32();
+        selection.pseudo_element = static_cast<Web::CSS::Selector::PseudoElement>(json->get("pseudo-element").to_u32());
+    } else {
+        selection.dom_node_id = json->get("id").to_i32();
+    }
+
     if (selection == m_selection)
         return;
     m_selection = move(selection);
 
-    auto maybe_inspected_node_properties = m_web_view->inspect_dom_node(m_inspected_node_id);
+    auto maybe_inspected_node_properties = m_web_view->inspect_dom_node(m_selection.dom_node_id, m_selection.pseudo_element);
     if (maybe_inspected_node_properties.has_value()) {
         auto inspected_node_properties = maybe_inspected_node_properties.value();
         load_style_json(inspected_node_properties.specified_values_json, inspected_node_properties.computed_values_json, inspected_node_properties.custom_properties_json);

Userland/Applications/Browser/InspectorWidget.h

@@ -10,6 +10,7 @@
 
 #include "ElementSizePreviewWidget.h"
 #include <LibGUI/Widget.h>
+#include <LibWeb/CSS/Selector.h>
 #include <LibWeb/Forward.h>
 #include <LibWeb/Layout/BoxModelMetrics.h>
 
@@ -20,14 +21,17 @@ class InspectorWidget final : public GUI::Widget {
 public:
     struct Selection {
         i32 dom_node_id { 0 };
+        Optional<Web::CSS::Selector::PseudoElement> pseudo_element {};
 
         bool operator==(Selection const& other) const
         {
-            return dom_node_id == other.dom_node_id;
+            return dom_node_id == other.dom_node_id && pseudo_element == other.pseudo_element;
         }
 
         String to_string() const
         {
+            if (pseudo_element.has_value())
+                return String::formatted("id: {}, pseudo: {}", dom_node_id, Web::CSS::pseudo_element_name(pseudo_element.value()));
             return String::formatted("id: {}", dom_node_id);
         }
     };

Userland/Libraries/LibWeb/DOMTreeModel.cpp

@@ -182,22 +182,39 @@ void DOMTreeModel::map_dom_nodes_to_parent(JsonObject const* parent, JsonObject
     });
 }
 
-GUI::ModelIndex DOMTreeModel::index_for_node(i32 node_id) const
+GUI::ModelIndex DOMTreeModel::index_for_node(i32 node_id, Optional<Web::CSS::Selector::PseudoElement> pseudo_element) const
 {
     auto node = m_node_id_to_dom_node_map.get(node_id).value_or(nullptr);
     if (node) {
-        auto* parent = get_parent(*node);
+        if (pseudo_element.has_value()) {
-        if (!parent)
+            // Find pseudo-element child of the node.
-            return {};
+            auto node_children = get_children(*node);
-        auto parent_children = get_children(*parent);
+            for (size_t i = 0; i < node_children->size(); i++) {
-        for (size_t i = 0; i < parent_children->size(); i++) {
+                auto& child = node_children->at(i).as_object();
-            if (&parent_children->at(i).as_object() == node) {
+                if (!child.has("pseudo-element"))
-                return create_index(i, 0, node);
+                    continue;
+
+                auto child_pseudo_element = child.get("pseudo-element");
+                if (!child_pseudo_element.is_i32())
+                    continue;
+
+                if (child_pseudo_element.as_i32() == to_underlying(pseudo_element.value()))
+                    return create_index(i, 0, &child);
+            }
+        } else {
+            auto* parent = get_parent(*node);
+            if (!parent)
+                return {};
+            auto parent_children = get_children(*parent);
+            for (size_t i = 0; i < parent_children->size(); i++) {
+                if (&parent_children->at(i).as_object() == node) {
+                    return create_index(i, 0, node);
+                }
             }
         }
     }
 
-    dbgln("Didn't find index for node {}!", node_id);
+    dbgln("Didn't find index for node {}, pseudo-element {}!", node_id, pseudo_element.has_value() ? CSS::pseudo_element_name(pseudo_element.value()) : "NONE");
     return {};
 }
 

Userland/Libraries/LibWeb/DOMTreeModel.h

@@ -10,6 +10,7 @@
 #include <AK/HashMap.h>
 #include <AK/JsonObject.h>
 #include <LibGUI/Model.h>
+#include <LibWeb/CSS/Selector.h>
 #include <LibWeb/Forward.h>
 
 namespace Web {
@@ -30,7 +31,7 @@ public:
     virtual GUI::ModelIndex index(int row, int column, const GUI::ModelIndex& parent = GUI::ModelIndex()) const override;
     virtual GUI::ModelIndex parent_index(const GUI::ModelIndex&) const override;
 
-    GUI::ModelIndex index_for_node(i32 node_id) const;
+    GUI::ModelIndex index_for_node(i32 node_id, Optional<Web::CSS::Selector::PseudoElement> pseudo_element) const;
 
 private:
     DOMTreeModel(JsonObject, GUI::TreeView&);

Userland/Libraries/LibWeb/OutOfProcessWebView.cpp

@@ -439,9 +439,9 @@ void OutOfProcessWebView::inspect_dom_tree()
     client().async_inspect_dom_tree();
 }
 
-Optional<OutOfProcessWebView::DOMNodeProperties> OutOfProcessWebView::inspect_dom_node(i32 node_id)
+Optional<OutOfProcessWebView::DOMNodeProperties> OutOfProcessWebView::inspect_dom_node(i32 node_id, Optional<CSS::Selector::PseudoElement> pseudo_element)
 {
-    auto response = client().inspect_dom_node(node_id);
+    auto response = client().inspect_dom_node(node_id, pseudo_element);
     if (!response.has_style())
         return {};
     return DOMNodeProperties {
@@ -454,7 +454,7 @@ Optional<OutOfProcessWebView::DOMNodeProperties> OutOfProcessWebView::inspect_do
 
 void OutOfProcessWebView::clear_inspected_dom_node()
 {
-    client().inspect_dom_node(0);
+    client().inspect_dom_node(0, {});
 }
 
 i32 OutOfProcessWebView::get_hovered_node_id()

Userland/Libraries/LibWeb/OutOfProcessWebView.h

@@ -9,6 +9,7 @@
 #include <AK/URL.h>
 #include <LibGUI/AbstractScrollableWidget.h>
 #include <LibGUI/Widget.h>
+#include <LibWeb/CSS/Selector.h>
 #include <LibWeb/Page/Page.h>
 #include <LibWeb/WebViewHooks.h>
 
@@ -40,7 +41,7 @@ public:
         String custom_properties_json;
         String node_box_sizing_json;
     };
-    Optional<DOMNodeProperties> inspect_dom_node(i32 node_id);
+    Optional<DOMNodeProperties> inspect_dom_node(i32 node_id, Optional<CSS::Selector::PseudoElement>);
     void clear_inspected_dom_node();
     i32 get_hovered_node_id();
 

Userland/Services/WebContent/ConnectionFromClient.cpp

@@ -245,7 +245,7 @@ void ConnectionFromClient::inspect_dom_tree()
     }
 }
 
-Messages::WebContentServer::InspectDomNodeResponse ConnectionFromClient::inspect_dom_node(i32 node_id)
+Messages::WebContentServer::InspectDomNodeResponse ConnectionFromClient::inspect_dom_node(i32 node_id, Optional<Web::CSS::Selector::PseudoElement> const& pseudo_element)
 {
     auto& top_context = page().top_level_browsing_context();
 
@@ -261,6 +261,7 @@ Messages::WebContentServer::InspectDomNodeResponse ConnectionFromClient::inspect
         return { false, "", "", "", "" };
     }
 
+    // FIXME: Pass the pseudo-element here.
     node->document().set_inspected_node(node);
 
     if (node->is_element()) {
@@ -326,6 +327,23 @@ Messages::WebContentServer::InspectDomNodeResponse ConnectionFromClient::inspect
             MUST(serializer.finish());
             return builder.to_string();
         };
+
+        if (pseudo_element.has_value()) {
+            auto pseudo_element_node = element.get_pseudo_element_node(pseudo_element.value());
+            if (pseudo_element_node.is_null())
+                return { false, "", "", "", "" };
+
+            // FIXME: Pseudo-elements only exist as Layout::Nodes, which don't have style information
+            //        in a format we can use. So, we run the StyleComputer again to get the specified
+            //        values, and have to ignore the computed values and custom properties.
+            auto pseudo_element_style = page().focused_context().active_document()->style_computer().compute_style(element, pseudo_element);
+            String specified_values_json = serialize_json(pseudo_element_style);
+            String computed_values_json = "{}";
+            String custom_properties_json = "{}";
+            String node_box_sizing_json = "{}";
+            return { true, specified_values_json, computed_values_json, custom_properties_json, node_box_sizing_json };
+        }
+
         String specified_values_json = serialize_json(*element.specified_css_values());
         String computed_values_json = serialize_json(element.computed_style());
         String custom_properties_json = serialize_custom_properties_json(element);

Userland/Services/WebContent/ConnectionFromClient.h

@@ -55,7 +55,7 @@ private:
     virtual void debug_request(String const&, String const&) override;
     virtual void get_source() override;
     virtual void inspect_dom_tree() override;
-    virtual Messages::WebContentServer::InspectDomNodeResponse inspect_dom_node(i32) override;
+    virtual Messages::WebContentServer::InspectDomNodeResponse inspect_dom_node(i32 node_id, Optional<Web::CSS::Selector::PseudoElement> const& pseudo_element) override;
     virtual Messages::WebContentServer::GetHoveredNodeIdResponse get_hovered_node_id() override;
     virtual Messages::WebContentServer::DumpLayoutTreeResponse dump_layout_tree() override;
     virtual void set_content_filters(Vector<String> const&) override;

Userland/Services/WebContent/WebContentServer.ipc

@@ -2,6 +2,7 @@
 #include <LibCore/AnonymousBuffer.h>
 #include <LibGfx/ShareableBitmap.h>
 #include <LibWeb/CSS/PreferredColorScheme.h>
+#include <LibWeb/CSS/Selector.h>
 
 endpoint WebContentServer
 {
@@ -29,7 +30,7 @@ endpoint WebContentServer
     debug_request(String request, String argument) =|
     get_source() =|
     inspect_dom_tree() =|
-    inspect_dom_node(i32 node_id) => (bool has_style, String specified_style, String computed_style, String custom_properties, String node_box_sizing)
+    inspect_dom_node(i32 node_id, Optional<Web::CSS::Selector::PseudoElement> pseudo_element) => (bool has_style, String specified_style, String computed_style, String custom_properties, String node_box_sizing)
     get_hovered_node_id() => (i32 node_id)
     js_console_input(String js_source) =|
     js_console_request_messages(i32 start_index) =|