From 4a0cd0b7ce6cd020be7d61362dc12abbf4e54dd9 Mon Sep 17 00:00:00 2001
From: Elena Torro <elenatorro@gmail.com>
Date: Tue, 5 May 2026 14:16:40 +0200
Subject: [PATCH] :zap: Translation-only fast paths for Shape and Path
 transforms

---
 render-wasm/src/shapes.rs       | 40 ++++++++++++++++++++++++++++-----
 render-wasm/src/shapes/fills.rs | 14 ++++++++----
 render-wasm/src/shapes/paths.rs | 22 ++++++++++++++++++
 3 files changed, 67 insertions(+), 9 deletions(-)

diff --git a/render-wasm/src/shapes.rs b/render-wasm/src/shapes.rs
index a122b1d8f6..ec99e7fef0 100644
--- a/render-wasm/src/shapes.rs
+++ b/render-wasm/src/shapes.rs
@@ -1015,6 +1015,7 @@ impl Shape {
     }
 
     pub fn calculate_extrect(&self, shapes_pool: ShapesPoolRef, scale: f32) -> math::Rect {
+        // `scale` is forwarded to children but intentionally NOT part of the cache key.
         if let Some(cached_extrect) = *self.extrect_cache.borrow() {
             return cached_extrect;
         }
@@ -1346,8 +1347,10 @@ impl Shape {
     pub fn get_skia_path(&self) -> Option<skia::Path> {
         if let Some(path) = self.shape_type.path() {
             let mut skia_path = path.to_skia_path(self.svg_attrs.as_ref());
-            if let Some(path_transform) = self.to_path_transform() {
-                skia_path = skia_path.make_transform(&path_transform);
+            if !math::identitish(&self.transform) {
+                if let Some(path_transform) = self.to_path_transform() {
+                    skia_path = skia_path.make_transform(&path_transform);
+                }
             }
             Some(skia_path)
         } else {
@@ -1356,6 +1359,19 @@ impl Shape {
     }
 
     fn transform_selrect(&mut self, transform: &Matrix) {
+        if math::is_move_only_matrix(transform) {
+            let tx = transform.translate_x();
+            let ty = transform.translate_y();
+            // `self.transform` (rotation/scale around center) is unchanged by translation.
+            self.selrect = math::Rect::from_xywh(
+                self.selrect.left + tx,
+                self.selrect.top + ty,
+                self.selrect.width(),
+                self.selrect.height(),
+            );
+            return;
+        }
+
         let mut center = self.selrect.center();
         center = transform.map_point(center);
 
@@ -1377,9 +1393,23 @@ impl Shape {
     pub fn apply_transform(&mut self, transform: &Matrix) {
         self.transform_selrect(transform);
 
-        // TODO: See if we can change this invalidation to a transformation
-        self.invalidate_extrect();
-        self.invalidate_bounds();
+        // Outsets (strokes, shadows, blur, children) are translation-invariant,
+        // so the cached extrect can be shifted instead of invalidated.
+        if math::is_move_only_matrix(transform) {
+            let tx = transform.translate_x();
+            let ty = transform.translate_y();
+            if let Some(rect) = self.extrect_cache.borrow_mut().as_mut() {
+                *rect = math::Rect::from_xywh(
+                    rect.left + tx,
+                    rect.top + ty,
+                    rect.width(),
+                    rect.height(),
+                );
+            }
+        } else {
+            self.invalidate_extrect();
+            self.invalidate_bounds();
+        }
 
         if let shape_type @ (Type::Path(_) | Type::Bool(_)) = &mut self.shape_type {
             if let Some(path) = shape_type.path_mut() {
diff --git a/render-wasm/src/shapes/fills.rs b/render-wasm/src/shapes/fills.rs
index 5b61b3ee2a..87da3881bf 100644
--- a/render-wasm/src/shapes/fills.rs
+++ b/render-wasm/src/shapes/fills.rs
@@ -259,15 +259,21 @@ pub fn get_fill_shader(fill: &Fill, bounding_box: &Rect) -> Option<skia::Shader>
 }
 
 pub fn merge_fills(fills: &[Fill], bounding_box: Rect) -> skia::Paint {
-    let mut combined_shader: Option<skia::Shader> = None;
     let mut fills_paint = skia::Paint::default();
 
     if fills.is_empty() {
-        combined_shader = Some(skia::shaders::color(skia::Color::TRANSPARENT));
-        fills_paint.set_shader(combined_shader);
+        fills_paint.set_color(skia::Color::TRANSPARENT);
         return fills_paint;
     }
 
+    if fills.len() == 1 {
+        if let Fill::Solid(SolidColor(color)) = &fills[0] {
+            fills_paint.set_color(*color);
+            return fills_paint;
+        }
+    }
+
+    let mut combined_shader: Option<skia::Shader> = None;
     for fill in fills {
         let shader = get_fill_shader(fill, &bounding_box);
 
@@ -287,7 +293,7 @@ pub fn merge_fills(fills: &[Fill], bounding_box: Rect) -> skia::Paint {
         }
     }
 
-    fills_paint.set_shader(combined_shader.clone());
+    fills_paint.set_shader(combined_shader);
     fills_paint
 }
 
diff --git a/render-wasm/src/shapes/paths.rs b/render-wasm/src/shapes/paths.rs
index ab7dc5acbf..aa14953341 100644
--- a/render-wasm/src/shapes/paths.rs
+++ b/render-wasm/src/shapes/paths.rs
@@ -236,6 +236,28 @@ impl Path {
     }
 
     pub fn transform(&mut self, mtx: &Matrix) {
+        if math::is_move_only_matrix(mtx) {
+            let tx = mtx.translate_x();
+            let ty = mtx.translate_y();
+            self.segments.iter_mut().for_each(|s| match s {
+                Segment::MoveTo(p) | Segment::LineTo(p) => {
+                    p.0 += tx;
+                    p.1 += ty;
+                }
+                Segment::CurveTo((c1, c2, p)) => {
+                    c1.0 += tx;
+                    c1.1 += ty;
+                    c2.0 += tx;
+                    c2.1 += ty;
+                    p.0 += tx;
+                    p.1 += ty;
+                }
+                _ => {}
+            });
+            self.skia_path = self.skia_path.with_offset((tx, ty));
+            return;
+        }
+
         self.segments.iter_mut().for_each(|s| match s {
             Segment::MoveTo(p) => {
                 let np = mtx.map_point(skia::Point::new(p.0, p.1));