Merge pull request #279 from SceneTech/feature/css-accessibility-preferences-255

Add host CSS accessibility preference state

Author: wieslawsoltes

docs/validation/css-accessibility-preferences-255.md

@@ -0,0 +1,35 @@
+# CSS accessibility preference qualification
+
+This gate covers the product-neutral preference slice implemented for issue #255:
+
+- host publication of forced-colors, reduced-motion, and increased-contrast state;
+- live `forced-colors`, `prefers-reduced-motion`, and `prefers-contrast` media-query updates;
+- computed system colors plus inherited `color-scheme` and `accent-color` values;
+- a public managed host property and versioned native C ABI with unknown-flag rejection;
+- bounded refresh and cleanup across 4,096 controls and 100 enable/restore cycles.
+
+## Direct gates
+
+| Gate | Denominator | Result |
+| --- | ---: | --- |
+| Native WPT profile | 1 document / 10 subtests | 1/1 and 10/10 passed |
+| Chrome 153 oracle | 1 document / 10 subtests | 1/1 and 10/10 passed |
+| Native preference lifecycle/performance | 4,096 controls / 100 cycles / 200 states | passed in 8,394.38 ms; 8,194..8,198 fixture-node bound; at most 1 retained node |
+| Portable CSS tests | 364 tests / 2 target frameworks | 364/364 on net8.0 and 364/364 on net10.0 |
+| Managed host build | 1 target | 1/1 passed with 0 warnings and 0 errors |
+| Portable native build | 1 target | 1/1 passed |
+| V8 dedicated native target | 1 target / 1 CTest | 1/1 built and 1/1 passed |
+
+The native gate has a 15,000 ms ceiling, requires zero host animation-frame demand
+after the final settled state, waits for a completed low-memory notification, limits
+post-cleanup V8 heap growth to 32 MiB, and rejects unknown ABI flag bits. The two
+retained runner reports are bounded to 64 KiB each; their combined observed size is
+5,187 bytes.
+
+The monolithic native test executable is excluded from this change-related gate
+because it reaches the pre-existing four-engine resource-deduplication assertion.
+The dedicated `webscene_css_accessibility_preferences_tests` target isolates the
+#255 semantic, performance, memory, and lifecycle checks from that baseline failure.
+
+Machine-readable results and report digests are recorded in
+`docs/validation/evidence/css-accessibility-preferences-255-20260917.json`.

docs/validation/evidence/css-accessibility-preferences-255-20260917.json

@@ -0,0 +1,77 @@
+{
+  "schema": "webscene-css-accessibility-preferences-qualification-v1",
+  "recordedAt": "2026-09-17",
+  "baseCommit": "28d1d649e927c665ff05844197af44f223edf952",
+  "issue": 255,
+  "gates": {
+    "nativeWpt": {
+      "engineIdentity": "abi=3;sha256=524b39d85d81d84a2a05519b1d6ecfaeb64ee582237137bdd99172bd36ff02de",
+      "profileSha256": "c66cd93274676da6182295676a30780bae138c48e1fa402d3813e4973048fd74",
+      "documentsPassed": 1,
+      "documentsTotal": 1,
+      "subtestsPassed": 10,
+      "subtestsTotal": 10,
+      "durationSeconds": 0.091843,
+      "reportBytes": 2767,
+      "reportMaximumBytes": 65536,
+      "reportSha256": "ee64c9ff3fc8b847154c3709af914100cda909843883108a17c2a1a3a7abacb2"
+    },
+    "chromeOracle": {
+      "identity": "Google Chrome 153.0.8010.48",
+      "documentsPassed": 1,
+      "documentsTotal": 1,
+      "subtestsPassed": 10,
+      "subtestsTotal": 10,
+      "durationMilliseconds": 78,
+      "reportBytes": 2420,
+      "reportMaximumBytes": 65536,
+      "reportSha256": "762fca67035a191c38ff2102f36eff1284d5788ab06f4d3936a8dcebd164494e"
+    },
+    "nativeLifecycle": {
+      "controls": 4096,
+      "cycles": 100,
+      "states": 200,
+      "elapsedMilliseconds": 8394.38,
+      "maximumMilliseconds": 15000,
+      "minimumFixtureNodeDelta": 8194,
+      "maximumFixtureNodeDelta": 8198,
+      "maximumRetainedNodeDelta": 1,
+      "settledAnimationFrameDemand": 0,
+      "maximumPostCleanupHeapGrowthBytes": 33554432,
+      "unknownFlagSetsAccepted": 0
+    },
+    "portableCss": {
+      "net8TestsPassed": 364,
+      "net8TestsTotal": 364,
+      "net10TestsPassed": 364,
+      "net10TestsTotal": 364
+    },
+    "managedHostBuild": {
+      "targetsPassed": 1,
+      "targetsTotal": 1,
+      "warnings": 0,
+      "errors": 0
+    },
+    "portableNativeBuild": {
+      "targetsPassed": 1,
+      "targetsTotal": 1
+    },
+    "v8Native": {
+      "targetsBuilt": 1,
+      "targetsTotal": 1,
+      "ctestsPassed": 1,
+      "ctestsTotal": 1
+    }
+  },
+  "ownership": {
+    "pullRequest245Head": "c7859becc0f6799d206f0974534c0db3a589f950",
+    "pullRequest245Files": 52,
+    "overlappingFiles": 0
+  },
+  "knownBaselineFailure": {
+    "gate": "webscene_native_engine_tests",
+    "message": "identical resources (including warmup) were loaded more than once across four engines",
+    "changeRelated": false,
+    "excludedFromFocusedGate": true
+  }
+}

experiments/WebScene.NativeEngine.Probe/CMakeLists.txt

@@ -794,6 +794,16 @@ if(WEBSCENE_NATIVE_ENGINE_ENABLE_V8)
         set_tests_properties(webscene_css_containment_tests PROPERTIES
             TIMEOUT 30
             LABELS "native;css;containment;performance;lifecycle")
+        add_executable(webscene_css_accessibility_preferences_tests
+            tests/native_css_accessibility_preferences_tests.cpp)
+        target_compile_features(webscene_css_accessibility_preferences_tests PRIVATE cxx_std_20)
+        target_link_libraries(webscene_css_accessibility_preferences_tests PRIVATE
+            webscene_native_engine)
+        add_test(NAME webscene_css_accessibility_preferences_tests
+            COMMAND webscene_css_accessibility_preferences_tests)
+        set_tests_properties(webscene_css_accessibility_preferences_tests PROPERTIES
+            TIMEOUT 30
+            LABELS "native;css;accessibility;performance;lifecycle")
         add_test(NAME webscene_native_idle_v8_platform COMMAND webscene_native_engine_tests)
         add_test(NAME webscene_native_dom_punctuation_keyboard COMMAND webscene_native_engine_tests)
         add_test(NAME webscene_native_shortcut_activation COMMAND webscene_native_engine_tests)

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

@@ -0,0 +1,65 @@
+#pragma once
+
+#include <algorithm>
+#include <cctype>
+#include <cstdint>
+#include <optional>
+#include <string>
+#include <string_view>
+
+namespace webscene_native::css {
+
+struct accessibility_preferences final {
+    bool dark{false};
+    bool forced_colors{false};
+    bool reduced_motion{false};
+    bool contrast_more{false};
+};
+
+inline thread_local accessibility_preferences active_accessibility_preferences{};
+
+inline void set_active_accessibility_preferences(
+    accessibility_preferences preferences) noexcept
+{
+    active_accessibility_preferences = preferences;
+}
+
+inline accessibility_preferences get_active_accessibility_preferences() noexcept
+{
+    return active_accessibility_preferences;
+}
+
+inline std::optional<uint32_t> system_color_rgba(std::string_view input)
+{
+    auto name = std::string(input);
+    std::transform(name.begin(), name.end(), name.begin(), [](unsigned char value) {
+        return static_cast<char>(std::tolower(value));
+    });
+    const auto preferences = get_active_accessibility_preferences();
+    const auto dark = preferences.dark;
+    const auto forced = preferences.forced_colors;
+
+    if (name == "canvas") return dark ? 0x1e1e1effU : 0xffffffffU;
+    if (name == "canvastext") return dark ? 0xffffffffU : 0x000000ffU;
+    if (name == "buttonface" || name == "field") {
+        return forced ? (dark ? 0x000000ffU : 0xffffffffU)
+            : (dark ? 0x333333ffU : 0xefefefffU);
+    }
+    if (name == "buttontext" || name == "fieldtext") {
+        return dark ? 0xffffffffU : 0x000000ffU;
+    }
+    if (name == "graytext") return dark ? 0xaaaaaaffU : 0x6d6d6dffU;
+    if (name == "highlight" || name == "selecteditem" || name == "accentcolor") {
+        return dark ? 0x6aa9ffffU : 0x0067c0ffU;
+    }
+    if (name == "highlighttext" || name == "selecteditemtext"
+        || name == "accentcolortext") return 0xffffffffU;
+    if (name == "linktext") return dark ? 0x8ab4f8ffU : 0x0000eeffU;
+    if (name == "visitedtext") return dark ? 0xc58af9ffU : 0x551a8bffU;
+    if (name == "activetext") return 0xff0000ffU;
+    if (name == "mark") return 0xffff00ffU;
+    if (name == "marktext") return 0x000000ffU;
+    return std::nullopt;
+}
+
+} // namespace webscene_native::css

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

@@ -1,10 +1,36 @@
 #pragma once
 #include "webscene_css_container_queries.h"
 #include "webscene_css_matching.h"
+#include "webscene_accessibility_preferences.h"
 #include <cstdlib>
 
 namespace webscene_native::css {
-struct media_environment { float width; float height; bool dark=false; bool reduced_motion=false; };
+struct media_environment {
+    float width{};
+    float height{};
+    bool dark{false};
+    bool reduced_motion{false};
+    bool forced_colors{false};
+    bool contrast_more{false};
+
+    media_environment() = default;
+    media_environment(float width_value, float height_value)
+        : media_environment(width_value, height_value, false) {}
+    media_environment(float width_value, float height_value, bool dark_value)
+        : width(width_value), height(height_value), dark(dark_value)
+    {
+        const auto preferences = get_active_accessibility_preferences();
+        reduced_motion = preferences.reduced_motion;
+        forced_colors = preferences.forced_colors;
+        contrast_more = preferences.contrast_more;
+    }
+    media_environment(float width_value, float height_value, bool dark_value,
+        bool reduced_motion_value, bool forced_colors_value = false,
+        bool contrast_more_value = false)
+        : width(width_value), height(height_value), dark(dark_value),
+          reduced_motion(reduced_motion_value), forced_colors(forced_colors_value),
+          contrast_more(contrast_more_value) {}
+};
 inline bool media_matches(std::string query, const media_environment& environment)
 {
     if (is_container_query(query)) return true;
@@ -85,6 +111,10 @@ inline bool media_matches(std::string query, const media_environment& environmen
                         environment.dark
                             ? "dark"
                             : "light");
+                } else if (feature == "forced-colors") {
+                    matches = value == (environment.forced_colors ? "active" : "none");
+                } else if (feature == "prefers-contrast") {
+                    matches = value == (environment.contrast_more ? "more" : "no-preference");
                 } else {
                     matches = false;
                 }
@@ -152,7 +182,8 @@ bool inventory_media(std::string query, Record&& record_feature)
                 static const std::unordered_set<std::string> supported_features{
                     "max-width", "min-width", "max-height", "min-height", "orientation",
                     "hover", "any-hover", "pointer", "any-pointer",
-                    "prefers-reduced-motion", "prefers-color-scheme"};
+                    "prefers-reduced-motion", "prefers-color-scheme",
+                    "forced-colors", "prefers-contrast"};
                 const auto known = range_syntax || (separator != std::string::npos
                     && supported_features.contains(feature));
                 record_feature(

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

@@ -67,6 +67,7 @@ enum inline_style_property : uint64_t {
     inline_scrollbar_color = 1ULL << 59U,
     inline_svg_stroke_width = 1ULL << 60U,
     inline_align_content = 1ULL << 61U,
+    inline_accessibility_colors = 1ULL << 62U,
     inline_containment_features = 1ULL << 63U,
     inline_transition = inline_transition_property | inline_transition_duration
         | inline_transition_delay | inline_transition_timing
@@ -134,6 +135,9 @@ inline uint64_t property_mask(std::string_view name)
         if (name == "visibility") return inline_visibility;
         if (name == "pointer-events") return inline_pointer_events;
         if (name == "color") return inline_color;
+        if (name == "color-scheme" || name == "accent-color") {
+            return inline_accessibility_colors;
+        }
         if (name == "fill") return inline_svg_fill;
         if (name == "stroke") return inline_svg_stroke;
         if (name == "text-anchor") return inline_svg_text_anchor;

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

@@ -58,6 +58,10 @@ inline void apply_all_unset(dom_node& node)
         textual.contain_intrinsic_size = previous.textual().contain_intrinsic_size;
         reset.content_visibility_hidden = previous.content_visibility_hidden;
     }
+    if (is_inline(inline_accessibility_colors)) {
+        reset.mutable_textual().color_scheme = previous.textual().color_scheme;
+        reset.mutable_textual().accent_color = previous.textual().accent_color;
+    }
     if (is_inline(inline_padding)) {
         reset.padding_left = previous.padding_left;
         reset.padding_top = previous.padding_top;

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

@@ -263,6 +263,32 @@ bool apply_text_value(dom_node& node,const std::string& name,const std::string&
             } else if (value == "inherit" || value == "unset") {
                 node.style.mutable_textual().svg_text_anchor.clear();
             }
+        } else if (name == "color-scheme" && !is_inline(inline_accessibility_colors)) {
+            const auto normalized = value == "inherit" || value == "unset"
+                ? std::string{} : value == "initial" ? std::string{"normal"} : value;
+            if (normalized.empty() || normalized == "normal" || normalized == "light"
+                || normalized == "dark" || normalized == "light dark"
+                || normalized == "dark light" || normalized == "only light"
+                || normalized == "only dark") {
+                node.style.mutable_textual().color_scheme = normalized;
+            } else {
+                decision.classification = "unsupported";
+                decision.semantic_slice = "normal, light, dark, only, and inheritance";
+            }
+        } else if (name == "accent-color" && !is_inline(inline_accessibility_colors)) {
+            if (value == "inherit" || value == "unset") {
+                node.style.mutable_textual().accent_color.clear();
+            } else if (value == "initial" || value == "auto") {
+                node.style.mutable_textual().accent_color = "auto";
+            } else {
+                const auto parsed = native_document::parse_color(value);
+                if (is_explicit_color_token(value, parsed)) {
+                    node.style.mutable_textual().accent_color = value;
+                } else {
+                    decision.classification = "unsupported";
+                    decision.semantic_slice = "auto, CSS colors, system colors, and inheritance";
+                }
+            }
         } else if (name == "cursor" && !is_inline(inline_cursor)) {
             node.style.mutable_textual().cursor =
                 value == "initial" ? "auto" : value;

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

@@ -2,6 +2,7 @@
 
 #include "webscene_native_engine.h"
 #include "webscene_named_colors.h"
+#include "webscene_accessibility_preferences.h"
 #include "graphics/canvas_backing.h"
 #include "graphics/image_lease_abi.h"
 
@@ -575,6 +576,9 @@ struct node_style final {
         std::string container_name{"none"};
         std::string content_visibility{"visible"};
         css_length contain_intrinsic_size{};
+        // Empty means inherit; computed CSSOM supplies the initial root value.
+        std::string color_scheme;
+        std::string accent_color;
         // Authored cursor token. Cursor is inherited, so an empty value means
         // the host projection resolves the nearest declaration or `auto`.
         std::string cursor;

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

@@ -254,6 +254,7 @@ uint32_t native_document::parse_color(const std::string& value)
             return static_cast<char>(std::tolower(character));
         });
 
+    if (const auto system = css::system_color_rgba(normalized)) return *system;
     if (const auto named = named_color_rgba(normalized)) return *named;
     if ((normalized.starts_with("hsl(") || normalized.starts_with("hsla("))
         && normalized.ends_with(')')) {