Honor word-break and overflow-wrap in retained text layout

docs/validation/code-oss-word-breaking-787.md

@@ -0,0 +1,42 @@
+# Code OSS retained word breaking (#787)
+
+Date: 2026-09-20
+
+## Source baseline
+
+- WebScene parent: `dd03421e180546c39aa4c272396b36af628d38c5`
+- unchanged Code OSS: `645f29cc3176500b4b5762ba887cf2a7f0ffdf2c`
+- tracking: WebScene #787, CSS epic #235
+
+## Reduced defect
+
+The retained inline formatter and fallback text painter wrapped only at whitespace. A token wider than its used content box stayed on one line even when author CSS requested `word-break: break-all`, `word-break: break-word`, `overflow-wrap: anywhere`, `overflow-wrap: break-word`, or the legacy `word-wrap` alias.
+
+The unchanged Code OSS inventory reaches this behavior in Markdown preview, dialogs, notifications, hover and parameter-hint content, quick input, suggestions, REPL/debug surfaces, editor placeholders, comments, and chat/session UI.
+
+## Implementation
+
+- Generated CSS property metadata now gives `word-break` and `overflow-wrap` stable native/managed identities. `word-wrap`, `wordWrap`, and compact CSSOM spellings resolve to `overflow-wrap`.
+- Both properties retain authored cascade values in the existing cold textual-style allocation and inherit through empty descendant sentinels. No hot `dom_node` field, timer, animation-frame participant, platform widget, document scan, or application CSS rewrite was added.
+- Inline assignment/removal, stylesheet application, custom-property resolution, global keywords, `all: unset`, CSSOM computed values, and managed mutation invalidation include the new properties.
+- Both retained inline fragments and fallback text lines use one UTF-8-boundary segmenter. It measures each code point once for the initial fit estimate, verifies the final shaped segment, never splits a multibyte sequence, and preserves source byte ranges used by selection/highlight paint.
+- `break-all` may use any code-point boundary. `break-word`/`anywhere` use emergency breaks for over-wide tokens. `normal`, `initial`, `revert`, and the currently bounded Latin `keep-all` path preserve whitespace wrapping.
+
+## Authored gates
+
+- `tests/WebPlatformSubset/contracts/css-word-breaking.html`: browser-referenced geometry, inheritance, CSSOM aliases, mutation/removal, and supplementary-plane text.
+- `test_word_break_and_overflow_wrap_layout`: native retained-layout regression for the same behavior.
+- `test_word_break_layout_performance_gate`: 4,096 nodes and ten forced style/layout transitions, with at most one layout pass per transition and a five-second wall-time ceiling.
+- The WPT-subset profile records the contract as candidate until direct Chromium/native evidence exists.
+
+## Evidence status
+
+No build, test, WPT run, benchmark, visual comparison, memory run, packaged-product run, or CI result was executed for this implementation. Evidence is zero. The gates above are source-authored and must be run during consolidated qualification.
+
+## Remaining qualification
+
+1. Run the focused native correctness and performance filters.
+2. Run the candidate contract in the pinned Chromium and native WPT lanes.
+3. Compare Markdown preview, dialog, notification, hover, parameter-hint, quick-input, suggestion, REPL, and editor-placeholder pixels and geometry with unchanged Chromium Code OSS.
+4. Record long-token, mixed-script, resize, mutation, lifecycle, CPU, allocation, scene-publication, and package evidence.
+5. Keep complete Unicode line-breaking, grapheme-cluster breaking, hyphenation, and international `keep-all` behavior outside the claim until separately implemented and qualified.

experiments/WebScene.NativeEngine.Probe/native/css_property_metadata.json

@@ -137,6 +137,8 @@
     {"id": "text_align", "name": "text-align", "aliases": ["textalign"]},
     {"id": "text_transform", "name": "text-transform", "aliases": ["texttransform"]},
     {"id": "white_space", "name": "white-space", "aliases": ["whitespace"]},
+    {"id": "word_break", "name": "word-break", "aliases": ["wordbreak"]},
+    {"id": "overflow_wrap", "name": "overflow-wrap", "aliases": ["word-wrap", "overflowwrap", "wordwrap"]},
     {"id": "list_style", "name": "list-style"},
     {"id": "list_style_position", "name": "list-style-position"},
     {"id": "list_style_type", "name": "list-style-type"},
@@ -167,7 +169,7 @@
     "keyword": [
       "all", "display", "position", "floating", "flex_direction", "flex_wrap", "align_items", "align_self",
       "justify_content", "box_sizing", "vertical_align", "grid_auto_flow", "border_collapse", "table_layout", "border_style", "background_repeat",
-      "visibility", "pointer_events", "text_anchor", "font_smoothing", "text_align", "text_transform", "white_space", "list_style_position",
+      "visibility", "pointer_events", "text_anchor", "font_smoothing", "text_align", "text_transform", "white_space", "word_break", "overflow_wrap", "list_style_position",
       "list_style_type", "scrollbar_width", "container", "container_type", "content_visibility"
     ],
     "componentList": [
@@ -205,13 +207,13 @@
   "nativeInheritedProperties": [
     "all", "color", "cursor", "direction", "font", "font-family", "font-size", "font-style",
     "font-weight", "letter-spacing", "line-height", "list-style", "list-style-position", "list-style-type",
-    "text-align", "text-transform", "visibility", "white-space", "word-spacing", "-webkit-font-smoothing"
+    "text-align", "text-transform", "visibility", "white-space", "word-break", "overflow-wrap", "word-spacing", "-webkit-font-smoothing"
   ],
   "nativeMasklessPropertyIds": [
     "content", "aspect_ratio", "vertical_align", "grid_auto_columns", "grid_auto_flow", "table_layout", "border_inline", "border_block",
     "outline", "outline_width", "outline_color", "animation", "animation_name", "animation_duration", "animation_delay",
     "animation_timing_function", "animation_iteration_count", "background_repeat", "background_position", "background_size",
-    "font", "text_transform", "list_style", "list_style_position", "list_style_type"
+    "font", "text_transform", "word_break", "overflow_wrap", "list_style", "list_style_position", "list_style_type"
   ],
   "managedKnownProperties": [
     "align-content", "align-items", "align-self", "all", "background", "background-color",
@@ -230,7 +232,7 @@
     "order", "overflow", "overflow-x", "overflow-y", "padding", "padding-bottom", "padding-left",
     "padding-right", "padding-top", "pointer-events", "position", "right", "row-gap", "stroke",
     "stroke-linecap", "stroke-linejoin", "stroke-width", "text-align", "text-indent", "text-transform",
-    "top", "transform", "visibility", "white-space", "width", "word-spacing", "z-index",
+    "top", "transform", "visibility", "white-space", "word-break", "overflow-wrap", "width", "word-spacing", "z-index",
     "outline", "outline-color", "outline-offset", "outline-style", "outline-width",
     "grid-template-areas", "aspect-ratio"
   ],
@@ -255,7 +257,7 @@
     "moz-transform", "-webkit-transform", "webkit-transform", "-webkit-font-smoothing", "webkit-font-smoothing", "orphans", "resize",
     "scrollbar-color", "scrollbar-width", "table-layout", "text-anchor", "text-decoration", "text-overflow", "vertical-align", "transition", "transition-delay",
     "transition-duration", "transition-property", "transition-timing-function", "transform-origin",
-    "widows", "zoom"
+    "widows", "word-wrap", "zoom"
   ],
   "properties": [
     {"name": "border-block-color", "mask": ["inline_border"], "expansion": ["border-top-color", "border-bottom-color"], "applyExpansion": true},

experiments/WebScene.NativeEngine.Probe/native/generated/webscene_css_property_identity.inc

@@ -196,6 +196,12 @@ inline constexpr std::array native_typed_property_identity_catalog{
     native_typed_property_identity{"texttransform", css_property_id::text_transform},
     native_typed_property_identity{"white-space", css_property_id::white_space},
     native_typed_property_identity{"whitespace", css_property_id::white_space},
+    native_typed_property_identity{"word-break", css_property_id::word_break},
+    native_typed_property_identity{"wordbreak", css_property_id::word_break},
+    native_typed_property_identity{"overflow-wrap", css_property_id::overflow_wrap},
+    native_typed_property_identity{"word-wrap", css_property_id::overflow_wrap},
+    native_typed_property_identity{"overflowwrap", css_property_id::overflow_wrap},
+    native_typed_property_identity{"wordwrap", css_property_id::overflow_wrap},
     native_typed_property_identity{"list-style", css_property_id::list_style},
     native_typed_property_identity{"list-style-position", css_property_id::list_style_position},
     native_typed_property_identity{"list-style-type", css_property_id::list_style_type},
@@ -414,6 +420,8 @@ inline constexpr std::array native_modeled_property_mask_catalog{
     false,
     false,
     false,
+    false,
+    false,
     true,
     true,
     true,
@@ -432,7 +440,7 @@ inline constexpr bool generated_property_has_modeled_mask(
         && native_modeled_property_mask_catalog[index];
 }
 
-inline constexpr std::array<std::string_view, 20> native_inherited_property_catalog{
+inline constexpr std::array<std::string_view, 22> native_inherited_property_catalog{
     "-webkit-font-smoothing",
     "all",
     "color",
@@ -448,10 +456,12 @@ inline constexpr std::array<std::string_view, 20> native_inherited_property_cata
     "list-style",
     "list-style-position",
     "list-style-type",
+    "overflow-wrap",
     "text-align",
     "text-transform",
     "visibility",
     "white-space",
+    "word-break",
     "word-spacing",
 };
 
@@ -603,6 +613,8 @@ inline constexpr std::array native_property_grammar_catalog{
     native_property_grammar::keyword,
     native_property_grammar::keyword,
     native_property_grammar::keyword,
+    native_property_grammar::keyword,
+    native_property_grammar::keyword,
     native_property_grammar::complex,
     native_property_grammar::keyword,
     native_property_grammar::keyword,
@@ -818,6 +830,12 @@ inline css_property_id generated_property_id_lowercase(std::string_view name) no
     if (name == "texttransform") return css_property_id::text_transform;
     if (name == "white-space") return css_property_id::white_space;
     if (name == "whitespace") return css_property_id::white_space;
+    if (name == "word-break") return css_property_id::word_break;
+    if (name == "wordbreak") return css_property_id::word_break;
+    if (name == "overflow-wrap") return css_property_id::overflow_wrap;
+    if (name == "word-wrap") return css_property_id::overflow_wrap;
+    if (name == "overflowwrap") return css_property_id::overflow_wrap;
+    if (name == "wordwrap") return css_property_id::overflow_wrap;
     if (name == "list-style") return css_property_id::list_style;
     if (name == "list-style-position") return css_property_id::list_style_position;
     if (name == "list-style-type") return css_property_id::list_style_type;

experiments/WebScene.NativeEngine.Probe/native/generated/webscene_css_property_ids.inc

@@ -135,6 +135,8 @@ line_height,
 text_align,
 text_transform,
 white_space,
+word_break,
+overflow_wrap,
 list_style,
 list_style_position,
 list_style_type,

experiments/WebScene.NativeEngine.Probe/native/generated/webscene_css_supported_properties.inc

@@ -195,6 +195,7 @@ inline constexpr std::array cssom_supported_property_catalog{
     cssom_supported_property_metadata{"outline-style", "outlineStyle"},
     cssom_supported_property_metadata{"outline-width", "outlineWidth"},
     cssom_supported_property_metadata{"overflow", "overflow"},
+    cssom_supported_property_metadata{"overflow-wrap", "overflowWrap"},
     cssom_supported_property_metadata{"overflow-x", "overflowX"},
     cssom_supported_property_metadata{"overflow-y", "overflowY"},
     cssom_supported_property_metadata{"padding", "padding"},
@@ -241,9 +242,11 @@ inline constexpr std::array cssom_supported_property_catalog{
     cssom_supported_property_metadata{"white-space", "whiteSpace"},
     cssom_supported_property_metadata{"widows", "widows"},
     cssom_supported_property_metadata{"width", "width"},
+    cssom_supported_property_metadata{"word-break", "wordBreak"},
     cssom_supported_property_metadata{"word-spacing", "wordSpacing"},
+    cssom_supported_property_metadata{"word-wrap", "wordWrap"},
     cssom_supported_property_metadata{"z-index", "zIndex"},
     cssom_supported_property_metadata{"zoom", "zoom"},
 };
 
-inline constexpr auto cssom_style_template_property_accessor_count = 435U;
+inline constexpr auto cssom_style_template_property_accessor_count = 441U;

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

@@ -280,6 +280,9 @@ void apply_declaration(native_document& document,dom_node& node,
         normalized=authored;normalized->name="transform";
     } else if(authored.name=="grid-gap" || authored.name=="grid-row-gap" || authored.name=="grid-column-gap") {
         normalized=authored;normalized->name=canonical_property_name(authored.name);
+    } else if (authored.name == "word-wrap") {
+        normalized = authored;
+        normalized->name = "overflow-wrap";
     }
     const auto& declaration=normalized?*normalized:authored;
     if(declaration.name.starts_with("--")) {

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

@@ -224,6 +224,8 @@ inline void reset_cascaded_style(dom_node& node,
             if ((node.style.inline_property_mask & inline_white_space) == 0U) {
                 textual->white_space.clear();
             }
+            textual->word_break.clear();
+            textual->overflow_wrap.clear();
         }
         if ((node.style.inline_property_mask & inline_font_weight) == 0U) node.style.font_weight = 0;
         if ((node.style.inline_property_mask & inline_line_height) == 0U) node.style.line_height = -1;

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

@@ -223,6 +223,14 @@ inline void apply_all_unset(
         reset.mutable_textual().white_space =
             previous.textual().white_space;
     }
+    if (has_inline({"word-break"})) {
+        reset.mutable_textual().word_break =
+            previous.textual().word_break;
+    }
+    if (has_inline({"overflow-wrap", "word-wrap"})) {
+        reset.mutable_textual().overflow_wrap =
+            previous.textual().overflow_wrap;
+    }
 
     // These modeled properties do not yet have dedicated inline-mask
     // bits, so preserve their applied values by authored declaration.

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

@@ -56,7 +56,8 @@ inline constexpr auto specified_property_samples = std::to_array<specified_prope
     {"font","700 16px/1.5 system-ui"},{"font-size","16px"},{"font-family","system-ui, sans-serif"},
     {"-webkit-font-smoothing","antialiased"},{"font-weight","700"},{"letter-spacing",".2px"},
     {"word-spacing","1px"},{"line-height","1.5"},{"text-align","center"},{"text-transform","uppercase"},
-    {"white-space","nowrap"},{"list-style","inside square"},{"list-style-position","outside"},{"list-style-type","decimal"},
+    {"white-space","nowrap"},{"word-break","break-all"},{"overflow-wrap","anywhere"},
+    {"list-style","inside square"},{"list-style-position","outside"},{"list-style-type","decimal"},
     {"scrollbar-width","thin"},{"scrollbar-color","#777 transparent"},
     {"container","sidebar / inline-size"},{"container-type","inline-size"},
     {"container-name","sidebar"},{"content-visibility","auto"},

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

@@ -406,6 +406,14 @@ bool apply_text_value(dom_node& node,const std::string& name,const std::string&
             node.style.mutable_textual().white_space =
                 value == "inherit" || value == "unset"
                 ? std::string{} : value;
+        } else if (name == "word-break") {
+            node.style.mutable_textual().word_break =
+                value == "inherit" || value == "unset"
+                ? std::string{} : value;
+        } else if (name == "overflow-wrap") {
+            node.style.mutable_textual().overflow_wrap =
+                value == "inherit" || value == "unset"
+                ? std::string{} : value;
         } else if (name == "list-style-position") {
             node.style.mutable_textual().list_style_position = value;
         } else if (name == "list-style-type") {

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

@@ -1027,6 +1027,37 @@ bool resolved_white_space_wraps(const dom_node& node)
     return true;
 }
 
+std::string_view resolved_word_break(const dom_node& node)
+{
+    for (auto* current = &node; current != nullptr; current = current->parent) {
+        const auto& value = current->style.textual().word_break;
+        if (value.empty() || value == "inherit" || value == "unset") continue;
+        return value == "initial" || value == "revert"
+            ? std::string_view{"normal"} : std::string_view{value};
+    }
+    return "normal";
+}
+
+std::string_view resolved_overflow_wrap(const dom_node& node)
+{
+    for (auto* current = &node; current != nullptr; current = current->parent) {
+        const auto& value = current->style.textual().overflow_wrap;
+        if (value.empty() || value == "inherit" || value == "unset") continue;
+        return value == "initial" || value == "revert"
+            ? std::string_view{"normal"} : std::string_view{value};
+    }
+    return "normal";
+}
+
+bool breaks_inside_words(const dom_node& node, bool token_exceeds_line)
+{
+    const auto word_break = resolved_word_break(node);
+    if (word_break == "break-all" || word_break == "break-word") return true;
+    const auto overflow_wrap = resolved_overflow_wrap(node);
+    return token_exceeds_line
+        && (overflow_wrap == "anywhere" || overflow_wrap == "break-word");
+}
+
 bool has_visible_text(const std::string& value)
 {
     return std::any_of(value.begin(), value.end(), [](unsigned char character) {

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

@@ -785,6 +785,10 @@ struct node_style final {
         std::string vertical_align;
         std::string text_transform;
         std::string white_space;
+        // Inherited line-breaking policy. Empty values inherit without adding
+        // state to descendants; the root resolves both properties to normal.
+        std::string word_break;
+        std::string overflow_wrap;
         std::string contain_value;
         std::string container_type{"normal"};
         std::string container_name{"none"};
@@ -2733,6 +2737,10 @@ class native_document final {
         float available_width,
         const dom_node& node,
         bool allow_wrap) const;
+    std::vector<std::pair<size_t, size_t>> break_text_segments(
+        std::string_view value,
+        float available_width,
+        const dom_node& node) const;
     float resolve_length(
         const dom_node& context,
         css_length value,