Honor hidden details marker pseudo

docs/validation/css-placeholder-pseudo-paint-237-235.md

@@ -46,8 +46,7 @@ The remaining core pseudo-element inventory is:
   discrete transition behavior remain open;
 - two functional `::highlight()` rules, which require named Highlight ranges,
   functional pseudo parsing, range paint, mutation, and teardown;
-- two `::-webkit-details-marker` rules and six internal form-control part
-  rules (`::-webkit-inner-spin-button`, `::-webkit-outer-spin-button`,
+- six internal form-control part rules (`::-webkit-inner-spin-button`, `::-webkit-outer-spin-button`,
   `::-ms-clear`, and `::-webkit-search-cancel-button`), which require bounded
   native control-part ownership before their declarations can have an
   observable effect.
@@ -63,6 +62,12 @@ highlights and one `::marker`; shadow-only `::part`/`::slotted`, complete marker
 styling, first-line/first-letter layout, and cumulative browser/package/
 performance evidence remain outside this slice. No Code OSS source changes.
 
+The two Code OSS `::-webkit-details-marker { display:none }` rules are now a
+separate bounded follow-up. They reuse the retained list marker and store one
+hidden bit only when the pseudo matches; internal form-control parts remain the
+only reachable vendor pseudo inventory without an observable WebScene control
+part to style.
+
 The remaining parser-recognized but runtime-unmaterialized pseudo-elements are
 `::first-letter`, `::first-line`, `::marker`, `::file-selector-button`, `::cue`,
 `::cue-region`, `::grammar-error`, `::spelling-error`, and `::target-text`.

docs/validation/css-webkit-details-marker-783.md

@@ -0,0 +1,28 @@
+# Hidden retained details markers
+
+Issues: WebScene #783, #237, and #235
+
+Pinned unchanged Code OSS `645f29cc3176500b4b5762ba887cf2a7f0ffdf2c`
+authors two `::-webkit-details-marker { display:none }` rules for Chat
+disclosures. WebScene already represents `<summary>` as a list item and retains
+one marker geometry/paint path. The selector was previously classified as an
+ordinary unsupported pseudo and its declaration never reached that path.
+
+The selector now has a dedicated pseudo kind. Its bounded cascade accepts the
+observed `display:none` value and restores the initial marker for
+`initial`/`unset`/`revert`/visible display values. A hidden bit lives inside the
+existing copy-on-write pseudo allocation only for a matching summary. Marker
+text, geometry, intrinsic contribution, and scene paint all consume the same
+existing `list_marker_text` decision; no second marker representation exists.
+
+Layout-style equality includes the hidden bit, so a winning-value mutation
+invalidates layout once while unrelated recascades remain paint-only. A
+non-summary selector match returns before allocating pseudo state. The authored
+native contract covers classification, initial visibility, hiding, restoration,
+and the non-summary allocation guard. The browser/native reftest compares the
+pseudo-hidden result with the established `list-style:none` reference.
+
+No tests, builds, pixels, or performance gates were executed under the current
+implementation-throughput direction. Dynamic mutation, 4,096-summary scaling,
+teardown, exact Code OSS Chat pixels, and cross-platform package evidence remain
+zero until run.

experiments/WebScene.NativeEngine.Probe/native/webscene_css_cascade_finalization.h

@@ -196,6 +196,7 @@ inline bool computed_layout_style_equal(
                 right_table.border_spacing_vertical)
             && left_table.border_collapsed == right_table.border_collapsed
             && grid_layout_equal(left.grid(), right.grid())
+            && left.details_marker_hidden() == right.details_marker_hidden()
             && pseudo_layout_equal(left.before_pseudo(), right.before_pseudo())
             && pseudo_layout_equal(left.after_pseudo(), right.after_pseudo());
     }

experiments/WebScene.NativeEngine.Probe/native/webscene_css_native_cascade.h

@@ -160,6 +160,12 @@ bool apply_native_cascade(native_document& document,dom_node& node,
                         variables,result,[](bool) {});
                     observe(declaration,result);
                 }
+                else if(kind==10) {
+                    property_result result;
+                    apply_details_marker_declaration(
+                        node,declaration,variables,result);
+                    observe(declaration,result);
+                }
                 else if(kind>=3) apply_scrollbar_declaration(node,kind,declaration,variables);
                 else {
                     auto& pseudo=kind==1?node.style.mutable_before_pseudo():node.style.mutable_after_pseudo();

experiments/WebScene.NativeEngine.Probe/native/webscene_css_pseudo_application.h

@@ -36,6 +36,7 @@ inline int split_pseudo_element_selector(const std::string& selector, std::strin
         if (const auto kind = split_suffix("::-moz-placeholder", 8); kind != 0) return kind;
         if (const auto kind = split_suffix("::placeholder", 8); kind != 0) return kind;
         if (const auto kind = split_suffix("::details-content", 9); kind != 0) return kind;
+        if (const auto kind = split_suffix("::-webkit-details-marker", 10); kind != 0) return kind;
         if (const auto kind = split_suffix("::backdrop", 7); kind != 0) return kind;
         if (const auto kind = split_suffix("::-webkit-scrollbar-thumb", 4); kind != 0) return kind;
         if (const auto kind = split_suffix("::-webkit-scrollbar-track", 5); kind != 0) return kind;
@@ -71,6 +72,35 @@ inline bool split_custom_highlight_selector(
     return true;
 }
 
+template<typename Decision>
+void apply_details_marker_declaration(
+    dom_node& node,
+    const css_declaration& declaration,
+    const std::unordered_map<std::string,std::string>& variables,
+    Decision& decision)
+{
+    decision.classification = "unsupported";
+    if (node.tag != "summary" || declaration.name != "display") return;
+    const auto contains_variable = declaration.value.find("var(") != std::string::npos;
+    auto resolved_value = std::string{};
+    const auto& value = contains_variable
+        ? (resolved_value = resolve_value(node, declaration.value, variables))
+        : declaration.value;
+    if (value.empty() && contains_variable) {
+        decision.classification = "invalid-authoring";
+        return;
+    }
+    const auto lower = ascii_lower(trim_value(value));
+    if (lower == "none") {
+        node.style.mutable_details_marker_hidden() = true;
+        decision.classification = "supported";
+    } else if (lower == "initial" || lower == "unset" || lower == "revert"
+        || lower == "inline" || lower == "list-item") {
+        node.style.mutable_details_marker_hidden() = false;
+        decision.classification = "supported";
+    }
+}
+
 inline bool split_selection_selector(
     std::string_view selector,
     std::string& origin)

experiments/WebScene.NativeEngine.Probe/native/webscene_css_rule_operations.h

@@ -310,7 +310,7 @@ void for_each_cascaded_pseudo_declaration(
         // kind prevents a high-priority ::before declaration from affecting
         // ::after while reusing the same layer/importance/rollback machinery
         // as the originating element.
-        std::array<std::vector<const css_rule*>, 10> rules_by_kind;
+        std::array<std::vector<const css_rule*>, 11> rules_by_kind;
         for (const auto& [kind, rule] : matched_rules) {
             if (kind > 0 && static_cast<size_t>(kind) < rules_by_kind.size())
                 rules_by_kind[static_cast<size_t>(kind)].push_back(rule);

experiments/WebScene.NativeEngine.Probe/native/webscene_native_dom.cpp

@@ -73,6 +73,7 @@ std::string list_marker_text(const dom_node& node)
     if (node.tag != "li" && node.style.display != display_mode::list_item) {
         return {};
     }
+    if (node.tag == "summary" && node.style.details_marker_hidden()) return {};
     const auto type = resolved_list_style(node, false);
     if (type == "none") return {};
     if (type != "decimal" && type != "decimal-leading-zero") {

experiments/WebScene.NativeEngine.Probe/native/webscene_native_dom.h

@@ -617,6 +617,7 @@ struct node_style final {
         pseudo_element after;
         placeholder_element placeholder;
         details_content_element details_content;
+        bool details_marker_hidden{false};
     };
 
     const pseudo_element& before_pseudo() const noexcept
@@ -667,6 +668,17 @@ struct node_style final {
         return pseudo_elements->details_content;
     }
 
+    bool details_marker_hidden() const noexcept
+    {
+        return pseudo_elements != nullptr && pseudo_elements->details_marker_hidden;
+    }
+
+    bool& mutable_details_marker_hidden()
+    {
+        ensure_unique_pseudo_elements();
+        return pseudo_elements->details_marker_hidden;
+    }
+
     void clear_pseudo_elements() noexcept
     {
         pseudo_elements.reset();

experiments/WebScene.NativeEngine.Probe/native/webscene_v8_runtime_css_cascade.inc

@@ -503,6 +503,12 @@
                     node,node.style.mutable_details_content_pseudo(),declaration);
                 return;
             }
+            if (pseudo_kind == 10) {
+                css::property_result result;
+                css::apply_details_marker_declaration(
+                    node,declaration,css_variables,result);
+                return;
+            }
             if (pseudo_kind >= 3 && pseudo_kind <= 6) {
                 apply_scrollbar_css_declaration(node, pseudo_kind, declaration);
                 return;
@@ -734,6 +740,12 @@
                     node,node.style.mutable_details_content_pseudo(),declaration);
                 return;
             }
+            if (pseudo_kind == 10) {
+                css::property_result result;
+                css::apply_details_marker_declaration(
+                    node,declaration,css_variables,result);
+                return;
+            }
             if (pseudo_kind >= 3 && pseudo_kind <= 6) {
                 apply_scrollbar_css_declaration(node, pseudo_kind, declaration);
                 return;

experiments/WebScene.NativeEngine.Probe/native/webscene_v8_runtime_css_parsing.inc

@@ -863,8 +863,11 @@
                 if (pseudo_element) {
                     const auto supported = name == "before" || name == "after"
                         || name == "selection" || name == "placeholder"
+                        || name == "-webkit-input-placeholder"
+                        || name == "-moz-placeholder"
                         || name == "highlight"
                         || name == "details-content"
+                        || name == "-webkit-details-marker"
                         || name == "backdrop" || name == "-webkit-scrollbar"
                         || name == "-webkit-scrollbar-thumb"
                         || name == "-webkit-scrollbar-track"

tests/NativeWeb/css_service.cpp

@@ -723,6 +723,7 @@ int main(int argc,char** argv) {
         {".base::backdrop",7},{".base::placeholder",8},
         {".base::-webkit-input-placeholder",8},{".base::-moz-placeholder",8},
         {".base::details-content",9},
+        {".base::-webkit-details-marker",10},
         {".base[data-label='::before']",0}
     };
     for(const auto& [selector,kind]:classified_selectors) {
@@ -1105,6 +1106,21 @@ int main(int argc,char** argv) {
     if(!details_content.present || !details_content.block_size_zero
         || details_content.opacity!=.4F
         || details_content.padding_inline_start.value!=12.0F) return 180;
+    auto& summary=ordered_document.create_element("summary");
+    summary.style.display=webscene_native::display_mode::list_item;
+    if(webscene_native::list_marker_text(summary).empty()) return 194;
+    webscene_native::css::apply_details_marker_declaration(
+        summary,{"display","none",false},variable_root,pseudo_result);
+    if(!summary.style.details_marker_hidden()
+        || !webscene_native::list_marker_text(summary).empty()) return 195;
+    webscene_native::css::apply_details_marker_declaration(
+        summary,{"display","initial",false},variable_root,pseudo_result);
+    if(summary.style.details_marker_hidden()
+        || webscene_native::list_marker_text(summary).empty()) return 196;
+    auto& marker_miss=ordered_document.create_element("div");
+    webscene_native::css::apply_details_marker_declaration(
+        marker_miss,{"display","none",false},variable_root,pseudo_result);
+    if(marker_miss.style.has_pseudo_elements()) return 197;
     webscene_native::css::apply_scrollbar_declaration(ordered_node,3,{"display","none",true},variable_root);
     webscene_native::css::apply_scrollbar_declaration(ordered_node,3,{"display","block",false},variable_root);
     if(!ordered_node.style.scrollbar_hidden || ordered_node.style.display==webscene_native::display_mode::none) return 131;

tests/WebPlatformSubset/contracts/css-webkit-details-marker-display-ref.html

@@ -0,0 +1,12 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Reference without a disclosure marker</title>
+<style>
+  body { margin: 0; background: white; color: #202124; }
+  details { width: 260px; margin: 20px; font: 16px/24px sans-serif; }
+  summary { padding: 4px 8px; border: 1px solid #7b8190; list-style: none; }
+</style>
+<details open>
+  <summary>Completed response</summary>
+  <div>Retained details content</div>
+</details>

tests/WebPlatformSubset/contracts/css-webkit-details-marker-display.html

@@ -0,0 +1,14 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>WebKit details marker display none hides the retained disclosure marker</title>
+<link rel="match" href="css-webkit-details-marker-display-ref.html">
+<style>
+  body { margin: 0; background: white; color: #202124; }
+  details { width: 260px; margin: 20px; font: 16px/24px sans-serif; }
+  summary { padding: 4px 8px; border: 1px solid #7b8190; }
+  summary::-webkit-details-marker { display: none; }
+</style>
+<details open>
+  <summary>Completed response</summary>
+  <div>Retained details content</div>
+</details>

tests/WebPlatformSubset/webscene-component-profile.json

@@ -1381,6 +1381,13 @@
       "evidence": ["css-pseudo-elements-4-placeholder", "native-retained-scene-contract", "vscode-oss-645f29c-placeholder-ledger"],
       "reason": "Implementation-first WebScene #237/#781 slice for standard and legacy placeholder selectors in unchanged Code OSS core CSS. The browser-shaped contract adds the Chromium-reachable ::-webkit-input-placeholder alias; the native companion covers both WebKit and Mozilla aliases with distinct colors/opacities, class recascade, live-value suppression, and empty-value restoration. All aliases reuse the standard retained paint path without layout, generated nodes, or frame demand. Direct browser/native profile execution remains validation debt; additional placeholder properties remain outside this bounded candidate."
     },
+    {
+      "path": "contracts/css-webkit-details-marker-display.html",
+      "type": "reftest",
+      "capabilities": ["webkit-details-marker-display-none", "retained-summary-marker-suppression", "details-marker-layout-invalidation"],
+      "evidence": ["css-pseudo-elements-derived", "native-retained-list-marker-contract", "vscode-oss-645f29c-details-marker-ledger"],
+      "reason": "Implementation-first WebScene #783 slice for the two unchanged Code OSS Chat disclosure rules. The pseudo-hidden result matches the established list-style:none reference while reusing one retained marker representation. Native companion coverage requires initial visibility, hide/restore, classifier origin, layout equality, and a non-summary zero-allocation guard. Direct browser/native pixels, dynamic mutation, 4,096-summary performance/lifecycle, and package execution remain validation debt."
+    },
     {
       "path": "contracts/css-checkbox-required-validity.html",
       "type": "testharness",