refactor(renderer): centralize layout invalidation and publication

moli-renderer-v8/src/native_bridge/context_host/host_environment.rs

@@ -2,6 +2,7 @@ use std::collections::HashSet;
 
 use super::{
     JsContextHost,
+    layout::LayoutInputChange,
     permissions::{permission_names_match, permission_override_name},
 };
 use crate::{
@@ -793,8 +794,7 @@ impl JsContextHost {
         overrides: &crate::protocol_types::EmulatedMediaOverrides,
     ) {
         if self.emulated_media != *overrides {
-            self.style_engine
-                .bump_target_context_epoch_for_document(self.document_handle());
+            self.invalidate_layout_inputs(LayoutInputChange::StyleEnvironment);
         }
         self.emulated_media = overrides.clone();
     }
@@ -809,8 +809,7 @@ impl JsContextHost {
     ) -> bool {
         let changed = self.viewport_surface != viewport_surface;
         if changed {
-            self.style_engine
-                .bump_target_context_epoch_for_document(self.document_handle());
+            self.invalidate_layout_inputs(LayoutInputChange::StyleEnvironment);
         }
         self.viewport_surface = viewport_surface;
         changed

moli-renderer-v8/src/native_bridge/context_host/layout.rs

@@ -14,6 +14,16 @@ use crate::{
     style_engine::{StyleViewport, StyloStyleEnvironment},
 };
 
+/// Invalidation required by a changed native input. Publication is a separate
+/// owner decision; these changes retain the last frozen layout for readers.
+#[derive(Clone, Copy)]
+pub(crate) enum LayoutInputChange {
+    /// Media and viewport changes invalidate computed styles through Stylo.
+    StyleEnvironment,
+    /// Scrollbar policy and interactions change future geometry/paint output.
+    UsedGeometry,
+}
+
 /// Resets the entry flag on every return path, including unwinding.
 ///
 /// This is a synchronous ownership guard, not a generation or a retry fence.
@@ -57,13 +67,26 @@ impl JsContextHost {
         self.layout_policy
     }
 
-    pub(crate) fn set_scrollbars_hidden(&mut self, hidden: bool) {
-        if self.scrollbars_hidden != hidden {
+    pub(crate) fn set_scrollbars_hidden(&mut self, hidden: bool) -> bool {
+        let changed = self.scrollbars_hidden != hidden;
+        if changed {
             self.scrollbars_hidden = hidden;
-            self.clear_layout_rect_cache();
-            self.document_layout_state
-                .get_mut()
-                .mark_visual_state_dirty();
+            self.invalidate_layout_inputs(LayoutInputChange::UsedGeometry);
+        }
+        changed
+    }
+
+    pub(crate) fn invalidate_layout_inputs(&self, change: LayoutInputChange) {
+        match change {
+            LayoutInputChange::StyleEnvironment => self
+                .style_engine
+                .bump_target_context_epoch_for_document(self.document_handle()),
+            LayoutInputChange::UsedGeometry => {
+                self.clear_layout_rect_cache();
+                self.document_layout_state
+                    .borrow_mut()
+                    .mark_visual_state_dirty();
+            }
         }
     }
 
@@ -519,12 +542,7 @@ impl JsContextHost {
     }
 
     pub(crate) fn invalidate_layout_after_interaction_state_change(&self) {
-        self.clear_layout_rect_cache();
-        // Interactions dirty future visual publication, while ordinary geometry
-        // and input keep consuming the last published frozen snapshot.
-        self.document_layout_state
-            .borrow_mut()
-            .mark_visual_state_dirty();
+        self.invalidate_layout_inputs(LayoutInputChange::UsedGeometry);
     }
 
     pub(crate) fn document_web_font_resources_are_current(

moli-renderer-v8/src/runtime/page_settings.rs

@@ -4,7 +4,7 @@ use crate::script_vm::{DocumentSetting, DocumentSettingEffect, DocumentSettingsA
 impl PageVm {
     fn apply_document_setting(&mut self, setting: DocumentSetting<'_>) -> anyhow::Result<()> {
         let layout = self.layout_configuration;
-        let effect = self.vm_mut().apply_document_setting(
+        let effect: DocumentSettingEffect = self.vm_mut().apply_document_setting(
             setting,
             layout,
             DocumentSettingsApplication::Live,
@@ -12,10 +12,8 @@ impl PageVm {
         // Retain the target value before publication. Even if publication
         // fails, a followed navigation must inherit the accepted native input.
         setting.retain_in(&mut self.document_settings);
-        if effect == DocumentSettingEffect::PublishLayout {
-            self.vm_mut().publish_layout()?;
-        }
-        Ok(())
+        self.vm_mut()
+            .complete_document_settings_application(DocumentSettingsApplication::Live, effect)
     }
 
     pub(crate) fn set_script_execution_disabled(&mut self, disabled: bool) -> anyhow::Result<()> {

moli-renderer-v8/src/script_vm/document_environment.rs

@@ -198,10 +198,10 @@ impl ScriptVm {
         self._context_host.borrow_mut().set_layout_policy(policy);
     }
 
-    pub(crate) fn set_scrollbars_hidden(&mut self, hidden: bool) {
+    pub(crate) fn set_scrollbars_hidden(&mut self, hidden: bool) -> bool {
         self._context_host
             .borrow_mut()
-            .set_scrollbars_hidden(hidden);
+            .set_scrollbars_hidden(hidden)
     }
 
     pub(super) fn sync_document_fonts_for_environment(&mut self) {

moli-renderer-v8/src/script_vm/document_settings.rs

@@ -12,7 +12,9 @@ pub(crate) enum DocumentSettingsApplication {
 
 #[derive(Clone, Copy, PartialEq, Eq)]
 pub(crate) enum DocumentSettingEffect {
+    /// Native values are installed; queued rendering updates publish later.
     Deferred,
+    /// Geometry must be current before a live setting command is acknowledged.
     PublishLayout,
 }
 
@@ -75,7 +77,9 @@ impl ScriptVm {
             DocumentSetting::DocumentActivity(*document_activity),
             DocumentSetting::ScrollbarsHidden(*scrollbars_hidden),
         ] {
-            self.apply_document_setting(setting, layout, DocumentSettingsApplication::Bootstrap)?;
+            let application = DocumentSettingsApplication::Bootstrap;
+            let effect = self.apply_document_setting(setting, layout, application)?;
+            self.complete_document_settings_application(application, effect)?;
         }
         Ok(())
     }
@@ -134,13 +138,27 @@ impl ScriptVm {
             }
             DocumentSetting::ScrollbarsHidden(value) => {
                 let hidden = layout.scrollbars_hidden_for(value);
-                let changed = self._context_host.borrow().scrollbars_hidden() != hidden;
-                self.set_scrollbars_hidden(hidden);
-                if live && changed {
+                if self.set_scrollbars_hidden(hidden) {
                     effect = DocumentSettingEffect::PublishLayout;
                 }
             }
         }
         Ok(effect)
     }
+
+    /// Initialization never publishes layout or runs rendering notifications.
+    /// Live commands publish only settings that require synchronous geometry.
+    pub(crate) fn complete_document_settings_application(
+        &mut self,
+        application: DocumentSettingsApplication,
+        effect: DocumentSettingEffect,
+    ) -> anyhow::Result<()> {
+        match (application, effect) {
+            (DocumentSettingsApplication::Bootstrap, _)
+            | (DocumentSettingsApplication::Live, DocumentSettingEffect::Deferred) => Ok(()),
+            (DocumentSettingsApplication::Live, DocumentSettingEffect::PublishLayout) => {
+                self.publish_layout()
+            }
+        }
+    }
 }