⚡ Skip imperceptible shadows and simplify low-scale strokes (#11102)

* ⚡ Skip drop shadows that are imperceptible at current scale

Filter drop shadows by on-screen footprint (stricter for recursive
shapes) so overview HQ avoids expensive blur passes that barely show.

* ⚡ Simplify Path and Bool strokes at low scale

At overview zooms, Inner/Outer strokes fall back to Center and
dash/dotted styles become solid when the pattern is subpixel.
Strokes are never skipped so stroke-only icons stay visible.

* ⚡ Drain GPU work on partial render frames

Partial frames only flushed the Backbuffer, so tile GPU commands
queued until present_frame's flush_and_submit and stalled the
browser on large files. Submit the context each partial frame
without presenting Target or re-composing the tile atlas.

* ⚡ Prefer direct painting when effects are imperceptible

Skip the Fills/Strokes layered path when drop/inner shadows would
not paint at the current scale, and allow stroke-only shapes
(fills_none) on the direct path. Apply the same footprint LOD to
inner-shadow painting.

render-wasm/src/render.rs

@@ -935,10 +935,6 @@ impl RenderState {
         Ok(())
     }
 
-    pub fn flush(&mut self) {
-        self.surfaces.flush(SurfaceId::Backbuffer);
-    }
-
     pub fn flush_and_submit(&mut self) {
         self.surfaces.flush_and_submit(SurfaceId::Target);
     }
@@ -1229,11 +1225,16 @@ impl RenderState {
     }
 
     fn get_inherited_drop_shadows(&self) -> Option<Vec<skia_safe::Paint>> {
+        let scale = self.get_scale();
         let drop_shadows: Vec<&Shadow> = self
             .nested_shadows
             .iter()
             .flat_map(|shadows| shadows.iter())
-            .filter(|shadow| !shadow.hidden() && shadow.style() == crate::shapes::ShadowStyle::Drop)
+            .filter(|shadow| {
+                !shadow.hidden()
+                    && shadow.style() == crate::shapes::ShadowStyle::Drop
+                    && shadow.is_perceptible_at_scale(scale)
+            })
             .collect();
 
         if drop_shadows.is_empty() {
@@ -1337,6 +1338,7 @@ impl RenderState {
             | text_drop_shadows_surface_id as u32;
 
         let fast_mode = self.options.is_fast_mode();
+        let skip_drop_shadows = self.should_skip_drop_shadows();
         // Skip anti-aliasing entirely during fast_mode (interactive
         // gestures + pan/zoom). AA edge sampling is per-pixel and adds
         // up across many shapes; reverts to full quality on commit.
@@ -1367,11 +1369,25 @@ impl RenderState {
             return Ok(());
         }
 
+        // Only perceptible shadows need the layered Fills/Strokes path. Use the
+        // same footprint LOD as when painting drop and inner shadows.
+        let scale = self.get_scale();
+        let shadows_need_layered = !skip_drop_shadows
+            && (shape
+                .drop_shadows_visible()
+                .any(|s| s.is_perceptible_at_scale_for(scale, shape.is_recursive()))
+                || shape
+                    .inner_shadows_visible()
+                    .any(|s| s.is_perceptible_at_scale_for(scale, shape.is_recursive())));
+
         // Clip is allowed: we apply the same stack on Current after scale+translate.
         // Opacity < 1 with SrcOver is OK: render_shape_enter already opened a
         // save_layer on Current; painting fills/strokes into that layer matches
         // the layered path without Fills/Strokes blits.
         // Non-SrcOver blend, frame clip blur, and masked groups stay layered.
+        // Stroke-only (fills_none) can go direct: empty fills are a no-op and
+        // strokes paint into Current. Requires Partial GPU drain (dc1ab) so
+        // large SVG-icon files do not backlog commands until Full present.
         let can_render_directly = apply_to_current_surface
             && offset.is_none()
             && parent_shadows.is_none()
@@ -1381,20 +1397,15 @@ impl RenderState {
             && shape.blur.is_none()
             && shape.background_blur.is_none()
             && !has_inherited_blur
-            && shape.shadows.is_empty()
+            && !shadows_need_layered
             && matches!(
                 shape.shape_type,
                 Type::Rect(_) | Type::Circle | Type::Path(_) | Type::Bool(_) | Type::Frame(_)
             )
             && !(shape.fills.is_empty() && has_nested_fills)
-            && !shape
-                .svg_attrs
-                .as_ref()
-                .is_some_and(|attrs| attrs.fill_none)
             && target_surface != SurfaceId::Export;
 
         if can_render_directly {
-            let scale = self.get_scale();
             let translation = self
                 .surfaces
                 .get_render_context_translation(self.render_area, scale);
@@ -1661,10 +1672,25 @@ impl RenderState {
                         );
                     }
                 } else {
-                    let mut drop_shadows = shape.drop_shadow_paints();
+                    let shape_scale = self.get_scale();
+                    let mut drop_shadows = if skip_drop_shadows {
+                        Vec::new()
+                    } else {
+                        shape
+                            .drop_shadows_visible()
+                            .filter(|s| s.is_perceptible_at_scale(shape_scale))
+                            .map(|shadow| {
+                                let mut paint = skia_safe::Paint::default();
+                                paint.set_image_filter(shadow.get_drop_shadow_filter());
+                                paint
+                            })
+                            .collect()
+                    };
 
-                    if let Some(inherited_shadows) = self.get_inherited_drop_shadows() {
-                        drop_shadows.extend(inherited_shadows);
+                    if !skip_drop_shadows {
+                        if let Some(inherited_shadows) = self.get_inherited_drop_shadows() {
+                            drop_shadows.extend(inherited_shadows);
+                        }
                     }
 
                     let inner_shadows = shape.inner_shadow_paints();
@@ -1688,32 +1714,34 @@ impl RenderState {
                         .unzip();
 
                     if let Some(parent_shadows) = parent_shadows {
-                        if !shape.has_visible_strokes() {
-                            for shadow in parent_shadows {
-                                text::render(
-                                    Some(self),
-                                    None,
+                        if !skip_drop_shadows {
+                            if !shape.has_visible_strokes() {
+                                for shadow in parent_shadows {
+                                    text::render(
+                                        Some(self),
+                                        None,
+                                        &shape,
+                                        &mut paragraphs_with_shadows,
+                                        text_drop_shadows_surface_id.into(),
+                                        Some(&shadow),
+                                        blur_filter.as_ref(),
+                                        None,
+                                        None,
+                                    )?;
+                                }
+                            } else {
+                                shadows::render_text_shadows(
+                                    self,
                                     &shape,
                                     &mut paragraphs_with_shadows,
+                                    &mut stroke_paragraphs_with_shadows_list,
                                     text_drop_shadows_surface_id.into(),
-                                    Some(&shadow),
-                                    blur_filter.as_ref(),
-                                    None,
-                                    None,
+                                    &parent_shadows,
+                                    &blur_filter,
+                                    &stroke_kinds,
+                                    text_content,
                                 )?;
                             }
-                        } else {
-                            shadows::render_text_shadows(
-                                self,
-                                &shape,
-                                &mut paragraphs_with_shadows,
-                                &mut stroke_paragraphs_with_shadows_list,
-                                text_drop_shadows_surface_id.into(),
-                                &parent_shadows,
-                                &blur_filter,
-                                &stroke_kinds,
-                                text_content,
-                            )?;
                         }
                     } else {
                         // 1. Text drop shadows
@@ -2433,9 +2461,12 @@ impl RenderState {
                 panic!("FrameType::None");
             }
             FrameType::Partial => {
-                // Partial frame: just flush GPU work. The display shows the last
-                // fully submitted frame; no need to copy or draw UI overlays here.
-                self.flush();
+                // Drain tile GPU work (Current / tile atlas / cache) without
+                // presenting Target and without re-snapshotting the tile atlas —
+                // composition stays deferred to Full. A Backbuffer flush alone
+                // left commands queued until present_frame's flush_and_submit,
+                // which stalled the browser on large files.
+                crate::get_gpu_state().context.flush_and_submit();
             }
             FrameType::Full => {
                 // A full-quality frame is now complete. Rebuild the per-shape crop
@@ -2638,6 +2669,19 @@ impl RenderState {
         true
     }
 
+    /// Skip all drop/inner shadows in fast mode, or when even a large design-space
+    /// shadow would be subpixel. Otherwise filter per shadow via
+    /// [`Shadow::is_perceptible_at_scale_for`] (stricter for recursive shapes).
+    #[inline]
+    pub(crate) fn should_skip_drop_shadows(&self) -> bool {
+        if self.options.is_fast_mode() {
+            return true;
+        }
+        let scale = self.get_scale();
+        scale * crate::shapes::DROP_SHADOW_LARGE_DESIGN_PX
+            < crate::shapes::DROP_SHADOW_MIN_DEVICE_PX
+    }
+
     #[inline]
     fn clip_target_surface_to_stack(
         &mut self,
@@ -3185,10 +3229,15 @@ impl RenderState {
         node_render_state: &NodeRenderState,
         target_surface: SurfaceId,
     ) -> Result<bool> {
-        // Avoid a blank DropShadows→Current blit + clear on every shape without
-        // shadows. Callers must still touch DropShadows once per tile when this
-        // returns false (see `drop_shadows_ops_warmed`).
-        if element.drop_shadows_visible().next().is_none() {
+        // Avoid a blank DropShadows→Current blit + clear when nothing will paint
+        // (no shadows, fast/overview skip, or all footprints subpixel). Callers
+        // must still touch DropShadows once per tile when this returns false
+        // (see `drop_shadows_ops_warmed`).
+        if self.should_skip_drop_shadows()
+            || !element
+                .drop_shadows_visible()
+                .any(|s| s.is_perceptible_at_scale_for(scale, element.is_recursive()))
+        {
             return Ok(false);
         }
 
@@ -3198,7 +3247,13 @@ impl RenderState {
             _ => None,
         };
 
+        let recursive = element.is_recursive();
+        let mut rendered_any = false;
         for shadow in element.drop_shadows_visible() {
+            if !shadow.is_perceptible_at_scale_for(scale, recursive) {
+                continue;
+            }
+            rendered_any = true;
             let paint = skia::Paint::default();
             let layer_rec = skia::canvas::SaveLayerRec::default().paint(&paint);
             self.surfaces
@@ -3290,6 +3345,10 @@ impl RenderState {
             self.surfaces.canvas(SurfaceId::DropShadows).restore();
         }
 
+        if !rendered_any {
+            return Ok(false);
+        }
+
         if let Some(clips) = clip_bounds.as_ref() {
             let antialias = !self.options.is_fast_mode()
                 && element.should_use_antialias(scale, self.options.antialias_threshold);
@@ -3541,10 +3600,12 @@ impl RenderState {
                 // the layer blur (which would make it more diffused than without clipping)
                 let shadow_before_layer = !node_render_state.is_root()
                     && self.focus_mode.is_active()
-                    && !self.options.is_fast_mode()
+                    && !self.should_skip_drop_shadows()
                     && !matches!(element.shape_type, Type::Text(_))
                     && Self::frame_clip_layer_blur(element).is_some()
-                    && element.drop_shadows_visible().next().is_some();
+                    && element
+                        .drop_shadows_visible()
+                        .any(|s| s.is_perceptible_at_scale_for(scale, element.is_recursive()));
 
                 if shadow_before_layer
                     && self.render_element_drop_shadows_and_composite(
@@ -3570,8 +3631,8 @@ impl RenderState {
             }
 
             if !node_render_state.is_root() && self.focus_mode.is_active() {
-                // Skip expensive drop shadow rendering in fast mode (during pan/zoom).
-                let skip_shadows = self.options.is_fast_mode();
+                // Skip expensive drop shadows in fast mode and at overview zooms.
+                let skip_shadows = self.should_skip_drop_shadows();
 
                 // Skip shadow block when already rendered before the layer (frame_clip_layer_blur)
                 let shadows_already_rendered = Self::frame_clip_layer_blur(element).is_some();

render-wasm/src/render/shadows.rs

@@ -13,10 +13,16 @@ pub fn render_fill_inner_shadows(
     antialias: bool,
     surface_id: SurfaceId,
 ) {
-    if shape.has_fills() {
-        for shadow in shape.inner_shadows_visible() {
-            render_fill_inner_shadow(render_state, shape, shadow, antialias, surface_id);
+    if !shape.has_fills() || render_state.should_skip_drop_shadows() {
+        return;
+    }
+    let scale = render_state.get_scale();
+    let recursive = shape.is_recursive();
+    for shadow in shape.inner_shadows_visible() {
+        if !shadow.is_perceptible_at_scale_for(scale, recursive) {
+            continue;
         }
+        render_fill_inner_shadow(render_state, shape, shadow, antialias, surface_id);
     }
 }
 
@@ -38,19 +44,25 @@ pub fn render_stroke_inner_shadows(
     antialias: bool,
     surface_id: SurfaceId,
 ) -> Result<()> {
-    if !shape.has_fills() {
-        for shadow in shape.inner_shadows_visible() {
-            let filter = shadow.get_inner_shadow_filter();
-            strokes::render_single(
-                render_state,
-                shape,
-                stroke,
-                Some(surface_id),
-                filter.as_ref(),
-                antialias,
-                None, // Inner shadows don't use spread
-            )?;
+    if shape.has_fills() || render_state.should_skip_drop_shadows() {
+        return Ok(());
+    }
+    let scale = render_state.get_scale();
+    let recursive = shape.is_recursive();
+    for shadow in shape.inner_shadows_visible() {
+        if !shadow.is_perceptible_at_scale_for(scale, recursive) {
+            continue;
         }
+        let filter = shadow.get_inner_shadow_filter();
+        strokes::render_single(
+            render_state,
+            shape,
+            stroke,
+            Some(surface_id),
+            filter.as_ref(),
+            antialias,
+            None, // Inner shadows don't use spread
+        )?;
     }
     Ok(())
 }

render-wasm/src/render/strokes.rs

@@ -561,6 +561,13 @@ fn draw_image_stroke_in_container(
     surface_id: SurfaceId,
 ) -> Result<()> {
     let scale = render_state.get_scale();
+    let lod_stroke;
+    let stroke = if matches!(shape.shape_type, Type::Path(_) | Type::Bool(_)) {
+        lod_stroke = stroke.path_lod_at_scale(shape.is_open(), scale);
+        &lod_stroke
+    } else {
+        stroke
+    };
     let Some(image) = get_resources().images.get(&image_fill.id()) else {
         return Ok(());
     };
@@ -938,12 +945,13 @@ fn render_merged(
         shape_type @ (Type::Path(_) | Type::Bool(_)) => {
             if let Some(path) = shape_type.path() {
                 let is_open = path.is_open();
+                let lod_stroke = representative.path_lod_at_scale(is_open, scale);
                 let mut paint =
-                    representative.to_stroked_paint(is_open, &selrect, svg_attrs, antialias);
+                    lod_stroke.to_stroked_paint(is_open, &selrect, svg_attrs, antialias);
                 paint.set_shader(merged.shader());
                 draw_stroke_on_path(
                     canvas,
-                    representative,
+                    &lod_stroke,
                     path,
                     &paint,
                     path_transform.as_ref(),
@@ -1097,6 +1105,8 @@ fn render_single_internal(
             shape_type @ (Type::Path(_) | Type::Bool(_)) => {
                 if let Some(path) = shape_type.path() {
                     let is_open = path.is_open();
+                    let lod_stroke = stroke.path_lod_at_scale(is_open, scale);
+                    let stroke = &lod_stroke;
                     let mut paint =
                         stroke.to_stroked_paint(is_open, &selrect, svg_attrs, antialias);
                     // Apply outset by increasing stroke width

render-wasm/src/shapes/shadows.rs

@@ -4,6 +4,18 @@ use super::blurs::radius_to_sigma;
 use super::Color;
 use crate::render::filters::compose_filters;
 
+/// Soft visibility floor in device pixels for leaf shapes. Below this, a drop
+/// shadow is visual noise relative to its blur cost.
+pub const DROP_SHADOW_MIN_DEVICE_PX: f32 = 2.0;
+
+/// Recursive shapes (frames/groups) redraw children into the shadow layer; they
+/// need a clearer on-screen footprint before that cost is worthwhile.
+pub const DROP_SHADOW_RECURSIVE_MIN_DEVICE_PX: f32 = 4.0;
+
+/// Generous design-space shadow budget used with [`DROP_SHADOW_MIN_DEVICE_PX`]
+/// for a hard global early-out (subpixel even for huge shadows).
+pub const DROP_SHADOW_LARGE_DESIGN_PX: f32 = 64.0;
+
 #[derive(Debug, Default, Clone, Copy, PartialEq)]
 pub enum ShadowStyle {
     #[default]
@@ -48,6 +60,32 @@ impl Shadow {
         self.hidden
     }
 
+    /// Approximate on-screen footprint (blur/spread + offset) at `scale` (zoom×dpr).
+    #[inline]
+    pub fn device_extent(&self, scale: f32) -> f32 {
+        let soft = self.blur.max(self.spread);
+        let offset = self.offset.0.abs().max(self.offset.1.abs());
+        (soft + offset) * scale
+    }
+
+    /// True when this shadow still has a perceptible footprint at `scale`.
+    /// Recursive shapes use a higher floor because compositing children into
+    /// the shadow layer is far more expensive than a leaf silhouette.
+    #[inline]
+    pub fn is_perceptible_at_scale(&self, scale: f32) -> bool {
+        self.is_perceptible_at_scale_for(scale, false)
+    }
+
+    #[inline]
+    pub fn is_perceptible_at_scale_for(&self, scale: f32, recursive: bool) -> bool {
+        let min = if recursive {
+            DROP_SHADOW_RECURSIVE_MIN_DEVICE_PX
+        } else {
+            DROP_SHADOW_MIN_DEVICE_PX
+        };
+        self.device_extent(scale) >= min
+    }
+
     pub fn get_drop_shadow_filter(&self) -> Option<ImageFilter> {
         let sigma = radius_to_sigma(self.blur);
         let mut filter = image_filters::drop_shadow_only(
@@ -112,3 +150,44 @@ impl Shadow {
         self.offset.1 *= value;
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn shadow(blur: f32, spread: f32, ox: f32, oy: f32) -> Shadow {
+        Shadow::new(
+            skia::Color::BLACK,
+            blur,
+            spread,
+            (ox, oy),
+            ShadowStyle::Drop,
+            false,
+        )
+    }
+
+    #[test]
+    fn leaf_floor_at_moderate_zoom() {
+        // blur 16 @ 0.13 ≈ 2.08px → keep leaf
+        assert!(shadow(16.0, 0.0, 0.0, 0.0).is_perceptible_at_scale_for(0.13, false));
+        // blur 8 @ 0.13 ≈ 1.04px → skip leaf (below 2px)
+        assert!(!shadow(8.0, 0.0, 0.0, 0.0).is_perceptible_at_scale_for(0.13, false));
+    }
+
+    #[test]
+    fn recursive_floor_is_stricter() {
+        // blur 24 @ 0.13 ≈ 3.12px → keep leaf, skip recursive (needs 4px)
+        let s = shadow(24.0, 0.0, 0.0, 0.0);
+        assert!(s.is_perceptible_at_scale_for(0.13, false));
+        assert!(!s.is_perceptible_at_scale_for(0.13, true));
+        // blur 32 @ 0.13 ≈ 4.16px → keep recursive
+        assert!(shadow(32.0, 0.0, 0.0, 0.0).is_perceptible_at_scale_for(0.13, true));
+    }
+
+    #[test]
+    fn overview_scale_vs_extent() {
+        // At 0.038 even blur 50 is only ~1.9px — below leaf floor.
+        assert!(!shadow(50.0, 0.0, 0.0, 0.0).is_perceptible_at_scale_for(0.038, false));
+        assert!(shadow(60.0, 0.0, 0.0, 0.0).is_perceptible_at_scale_for(0.038, false));
+    }
+}

render-wasm/src/shapes/strokes.rs

@@ -7,6 +7,14 @@ use super::StrokeLineCap;
 use super::StrokeLineJoin;
 use super::SvgAttrs;
 
+/// Soft floor in device pixels for dropping dash/dotted PathEffects when the
+/// pattern period is effectively invisible.
+pub const STROKE_MIN_DEVICE_PX: f32 = 0.75;
+
+/// When Inner/Outer doubled-width footprint is below this (device px), paint
+/// as Center to avoid save_layer / Clear paths.
+pub const STROKE_INNER_OUTER_SIMPLIFY_DEVICE_PX: f32 = 2.0;
+
 #[derive(Debug, Clone, PartialEq, Copy)]
 pub enum StrokeStyle {
     Solid,
@@ -69,6 +77,62 @@ impl Stroke {
         }
     }
 
+    /// Inner/Outer use a doubled-width Center stroke plus clip/clear. When that
+    /// footprint is thin on screen, fall back to a plain Center stroke.
+    #[inline]
+    pub fn simplified_kind_at_scale(&self, is_open: bool, scale: f32) -> StrokeKind {
+        let kind = self.render_kind(is_open);
+        match kind {
+            StrokeKind::Inner | StrokeKind::Outer
+                if 2.0 * self.max_width() * scale < STROKE_INNER_OUTER_SIMPLIFY_DEVICE_PX =>
+            {
+                StrokeKind::Center
+            }
+            other => other,
+        }
+    }
+
+    /// Drop dash/dotted PathEffects when the pattern period is subpixel.
+    #[inline]
+    pub fn style_at_scale(&self, scale: f32) -> StrokeStyle {
+        if self.style == StrokeStyle::Solid {
+            return StrokeStyle::Solid;
+        }
+        let period = match self.style {
+            StrokeStyle::Dotted => self.width + 5.0,
+            StrokeStyle::Dashed => {
+                let dash = self.dash.unwrap_or(self.width + 10.);
+                let gap = self.gap.unwrap_or(self.width + 10.);
+                dash.min(gap)
+            }
+            StrokeStyle::Mixed => self.width + 1.0,
+            StrokeStyle::Solid => return StrokeStyle::Solid,
+        };
+        if period * scale < STROKE_MIN_DEVICE_PX {
+            StrokeStyle::Solid
+        } else {
+            self.style
+        }
+    }
+
+    /// Path/Bool overview LOD: simplify Inner/Outer and dash/dotted at low
+    /// scale. Never skips painting; stroke-only icons would otherwise go blank.
+    pub fn path_lod_at_scale(&self, is_open: bool, scale: f32) -> Stroke {
+        let kind = self.simplified_kind_at_scale(is_open, scale);
+        let style = self.style_at_scale(scale);
+        let kind_unchanged = kind == self.render_kind(is_open);
+        let style_unchanged = style == self.style;
+        if kind_unchanged && style_unchanged {
+            return self.clone();
+        }
+        let mut stroke = self.clone();
+        if !is_open {
+            stroke.kind = kind;
+        }
+        stroke.style = style;
+        stroke
+    }
+
     /// Per-side widths [top, right, bottom, left] when they actually differ.
     /// Returns `None` when unset or when all sides are equal, so the uniform
     /// render path (which supports dashed/dotted styles) keeps handling that
@@ -493,4 +557,48 @@ mod tests {
         assert_eq!(stroke.widths, Some([2.0, 4.0, 6.0, 8.0]));
         assert_eq!(stroke.width, 4.0);
     }
+
+    fn solid_center(width: f32) -> Stroke {
+        Stroke::new_center_stroke(width, StrokeStyle::Solid, None, None, None, None)
+    }
+
+    #[test]
+    fn inner_outer_simplify_to_center_when_thin() {
+        let inner = Stroke::new_inner_stroke(8.0, StrokeStyle::Solid, None, None, None, None);
+        // 2 * 8 * 0.1 = 1.6 < 2.0, simplify to Center
+        assert_eq!(
+            inner.simplified_kind_at_scale(false, 0.1),
+            StrokeKind::Center
+        );
+        // 2 * 8 * 0.2 = 3.2 >= 2.0, keep Inner
+        assert_eq!(
+            inner.simplified_kind_at_scale(false, 0.2),
+            StrokeKind::Inner
+        );
+    }
+
+    #[test]
+    fn dash_becomes_solid_when_period_subpixel() {
+        let dashed =
+            Stroke::new_center_stroke(2.0, StrokeStyle::Dashed, None, None, Some(20.0), Some(20.0));
+        // period 20 * 0.03 = 0.6 < 0.75, solid
+        assert_eq!(dashed.style_at_scale(0.03), StrokeStyle::Solid);
+        // period 20 * 0.05 = 1.0 >= 0.75, keep dashed
+        assert_eq!(dashed.style_at_scale(0.05), StrokeStyle::Dashed);
+    }
+
+    #[test]
+    fn path_lod_never_drops_thin_stroke() {
+        // Hairline strokes must still paint (stroke-only icons).
+        let thin = solid_center(1.0).path_lod_at_scale(false, 0.5);
+        assert_eq!(thin.width, 1.0);
+        assert_eq!(thin.kind, StrokeKind::Center);
+    }
+
+    #[test]
+    fn path_lod_simplifies_inner_at_overview() {
+        let inner = Stroke::new_inner_stroke(8.0, StrokeStyle::Solid, None, None, None, None);
+        let lod = inner.path_lod_at_scale(false, 0.1);
+        assert_eq!(lod.kind, StrokeKind::Center);
+    }
 }