From 0238b98a03ef8c85cd6bdd1e942915b6527fb4de Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Mon, 10 Aug 2026 12:23:33 -0700
Subject: [PATCH 01/15] initial commit

---
 .../shader_lib/impeller/gradient.glsl         | 29 ++++++
 .../flutter/impeller/display_list/canvas.cc   | 89 +++++++++++++++----
 .../entity/contents/uber_sdf_contents.cc      | 58 +++++++++++-
 .../contents/uber_sdf_contents_unittests.cc   | 24 +++++
 .../entity/contents/uber_sdf_parameters.h     | 30 +++++++
 .../gradients/linear_gradient_fill.frag       | 13 +--
 .../gradients/radial_gradient_fill.frag       | 11 +--
 .../impeller/entity/shaders/uber_sdf.frag     | 39 +++++++-
 8 files changed, 256 insertions(+), 37 deletions(-)

diff --git a/engine/src/flutter/impeller/compiler/shader_lib/impeller/gradient.glsl b/engine/src/flutter/impeller/compiler/shader_lib/impeller/gradient.glsl
index 6f2b87f24a8f3..193dd6548feb0 100644
--- a/engine/src/flutter/impeller/compiler/shader_lib/impeller/gradient.glsl
+++ b/engine/src/flutter/impeller/compiler/shader_lib/impeller/gradient.glsl
@@ -149,4 +149,33 @@ vec3 IPComputeFixedGradientValues(float t, float colors_length) {
   return vec3(lower_index, upper_index, scale);
 }
 
+/// Samples a linear gradient from a 1D gradient ramp texture.
+vec4 IPSampleLinearGradient(sampler2D tex,
+                            vec2 start_point,
+                            vec2 end_point,
+                            vec2 pos,
+                            vec2 half_texel,
+                            float tile_mode,
+                            vec4 decal_border_color) {
+  vec2 start_to_end = end_point - start_point;
+  vec2 start_to_position = pos - start_point;
+  float t =
+      dot(start_to_position, start_to_end) / dot(start_to_end, start_to_end);
+  return IPSampleLinearWithTileMode(tex, vec2(t, 0.5), half_texel, tile_mode,
+                                    decal_border_color);
+}
+
+/// Samples a radial gradient from a 1D gradient ramp texture.
+vec4 IPSampleRadialGradient(sampler2D tex,
+                            vec2 center,
+                            float radius,
+                            vec2 pos,
+                            vec2 half_texel,
+                            float tile_mode,
+                            vec4 decal_border_color) {
+  float t = length(pos - center) / radius;
+  return IPSampleLinearWithTileMode(tex, vec2(t, 0.5), half_texel, tile_mode,
+                                    decal_border_color);
+}
+
 #endif
diff --git a/engine/src/flutter/impeller/display_list/canvas.cc b/engine/src/flutter/impeller/display_list/canvas.cc
index 02b6dd130c8dc..aa1a1ff12df08 100644
--- a/engine/src/flutter/impeller/display_list/canvas.cc
+++ b/engine/src/flutter/impeller/display_list/canvas.cc
@@ -34,6 +34,7 @@
 #include "impeller/entity/contents/content_context.h"
 #include "impeller/entity/contents/filters/filter_contents.h"
 #include "impeller/entity/contents/framebuffer_blend_contents.h"
+#include "impeller/entity/contents/gradient_generator.h"
 #include "impeller/entity/contents/shadow_vertices_contents.h"
 #include "impeller/entity/contents/solid_color_contents.h"
 #include "impeller/entity/contents/solid_rrect_blur_contents.h"
@@ -59,6 +60,7 @@
 #include "impeller/entity/save_layer_utils.h"
 #include "impeller/geometry/color.h"
 #include "impeller/geometry/constants.h"
+#include "impeller/geometry/gradient.h"
 #include "impeller/geometry/round_superellipse_param.h"
 #include "impeller/geometry/rounding_radii.h"
 #include "impeller/geometry/rstransform.h"
@@ -224,6 +226,59 @@ static std::pair<Rect, Color> ExpandRectToPixelMinimum(const Rect& rect,
   return {expanded.value(), color.WithAlpha(color.alpha * alpha_scaling)};
 }
 
+/// @brief  Attempts to populate `params` with the color source properties,
+///         if supported by UberSDF (e.g. for linear and radial gradients).
+///
+/// @return Whether the color source was successfully populated into `params`.
+static bool PopulateUberSDFColorSource(
+    const flutter::DlColorSource& color_source,
+    const ContentContext& renderer,
+    UberSDFParameters& params) {
+  if (color_source.isGradient()) {
+    UberSDFParameters::GradientParameters gradient;
+
+    std::vector<Color> colors;
+    std::vector<float> stops;
+
+    if (color_source.type() == flutter::DlColorSourceType::kLinearGradient) {
+      const auto* linear = color_source.asLinearGradient();
+      FML_DCHECK(linear);
+      Paint::ConvertStops(linear, colors, stops);
+      gradient.type = UberSDFParameters::GradientParameters::Type::kLinear;
+      gradient.start = linear->start_point();
+      gradient.end = linear->end_point();
+      gradient.tile_mode = static_cast<Entity::TileMode>(linear->tile_mode());
+    } else if (color_source.type() ==
+               flutter::DlColorSourceType::kRadialGradient) {
+      const auto* radial = color_source.asRadialGradient();
+      FML_DCHECK(radial);
+      Paint::ConvertStops(radial, colors, stops);
+      gradient.type = UberSDFParameters::GradientParameters::Type::kRadial;
+      gradient.start = radial->center();
+      // For radial gradients, gradient.end.x stores the radius.
+      gradient.end = Point(radial->radius(), 0.0f);
+      gradient.tile_mode = static_cast<Entity::TileMode>(radial->tile_mode());
+    } else {
+      // Gradient type not supported by UberSDF.
+      return false;
+    }
+
+    GradientData gradient_data = CreateGradientBuffer(colors, stops);
+    std::shared_ptr<Texture> texture =
+        CreateGradientTexture(gradient_data, renderer.GetContext());
+    if (!texture) {
+      return false;
+    }
+
+    gradient.texture = std::move(texture);
+    params.gradient = std::move(gradient);
+    return true;
+  }
+
+  // Color source not supported by UberSDF.
+  return false;
+}
+
 }  // namespace
 
 class Canvas::RRectBlurShape : public BlurShape {
@@ -2180,23 +2235,29 @@ void Canvas::AddRenderSDFEntityToCurrentPass(
   entity.SetTransform(transform);
   entity.SetBlendMode(paint.blend_mode);
 
-  if (paint.color_source) {
-    // Since we are going to use BlendMode::kSrcIn to implement the color_source
-    // the SDF portion of the blend should just be solid white to get the
-    // correct color from the color_source.
+  if (!paint.color_source ||
+      PopulateUberSDFColorSource(*paint.color_source, renderer_, params)) {
+    // No color source (solid paint color), or a supported color source was
+    // populated into UberSDFParams.
+    auto geometry = std::make_unique<UberSDFGeometry>(params);
+    auto contents = UberSDFContents::Make(params, std::move(geometry));
+    const Geometry* geom = contents->GetGeometry();
+    AddRenderEntityWithFiltersToCurrentPass(entity, geom, paint, reuse_depth,
+                                            /*override_contents=*/
+                                            std::move(contents));
+  } else {
+    // Color source not directly supported by UberSDF (e.g. image, runtime
+    // effect, or an unsupported gradient type). Render a solid white mask with
+    // UberSDF and blend with ColorSourceContents.
     params.color = Color::White();
-  }
-  auto geometry = std::make_unique<UberSDFGeometry>(params);
-  auto contents = UberSDFContents::Make(params, std::move(geometry));
-  const Geometry* geom = contents->GetGeometry();
+    auto geometry = std::make_unique<UberSDFGeometry>(params);
+    auto uber_sdf_contents = UberSDFContents::Make(params, std::move(geometry));
+    const Geometry* geom = uber_sdf_contents->GetGeometry();
 
-  if (paint.color_source) {
-    // UberSDF doesn't perform things like gradients so we blend the SDF
-    // with the color source.
     std::shared_ptr<ColorSourceContents> color_source_contents =
         paint.CreateContents(renderer_, geom, shape_transform);
     std::shared_ptr<Contents> final_contents = ColorFilterContents::MakeBlend(
-        BlendMode::kSrcIn, {FilterInput::Make(std::move(contents)),
+        BlendMode::kSrcIn, {FilterInput::Make(std::move(uber_sdf_contents)),
                             FilterInput::Make(color_source_contents)});
 
     Paint new_paint = paint;
@@ -2205,10 +2266,6 @@ void Canvas::AddRenderSDFEntityToCurrentPass(
                                             reuse_depth,
                                             /*override_contents=*/
                                             std::move(final_contents));
-  } else {
-    AddRenderEntityWithFiltersToCurrentPass(entity, geom, paint, reuse_depth,
-                                            /*override_contents=*/
-                                            std::move(contents));
   }
 }
 
diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
index 5bec7103c92b5..0d6a505c64525 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
@@ -4,6 +4,7 @@
 
 #include "impeller/entity/contents/uber_sdf_contents.h"
 
+#include "fml/logging.h"
 #include "impeller/entity/contents/color_source_contents.h"
 #include "impeller/entity/contents/content_context.h"
 #include "impeller/entity/contents/pipelines.h"
@@ -46,6 +47,44 @@ Scalar ToShaderStrokeJoin(Join join) {
   }
 }
 
+Scalar ToShaderColorSourceType(const UberSDFParameters& params) {
+  if (!params.gradient.has_value()) {
+    return 0.0f;
+  }
+  switch (params.gradient->type) {
+    case UberSDFParameters::GradientParameters::Type::kLinear:
+      return 1.0f;
+    case UberSDFParameters::GradientParameters::Type::kRadial:
+      return 2.0f;
+  }
+}
+
+struct SamplerBinding {
+  std::shared_ptr<Texture> texture;
+  raw_ptr<const Sampler> sampler;
+};
+
+/// @brief  Populates the gradient uniform fields in `frag_info` and returns
+///         the texture and sampler for the gradient.
+SamplerBinding SetupGradientParameters(
+    const UberSDFParameters::GradientParameters& gradient,
+    const ContentContext& renderer,
+    FS::FragInfo& frag_info) {
+  FML_DCHECK(gradient.texture);
+  frag_info.gradient_start = gradient.start;
+  frag_info.gradient_end = gradient.end;
+  frag_info.tile_mode = static_cast<Scalar>(gradient.tile_mode);
+  frag_info.half_texel = Point(0.5f, 0.5f) / gradient.texture->GetSize();
+
+  SamplerDescriptor sampler_desc;
+  sampler_desc.min_filter = MinMagFilter::kLinear;
+  sampler_desc.mag_filter = MinMagFilter::kLinear;
+  raw_ptr<const Sampler> sampler =
+      renderer.GetContext()->GetSamplerLibrary()->GetSampler(sampler_desc);
+
+  return {gradient.texture, sampler};
+}
+
 }  // namespace
 
 std::unique_ptr<UberSDFContents> UberSDFContents::Make(
@@ -69,6 +108,7 @@ bool UberSDFContents::Render(const ContentContext& renderer,
   VS::FrameInfo frame_info;
   FS::FragInfo frag_info;
   frag_info.type = ToShaderType(params_.type);
+  frag_info.color_source_type = ToShaderColorSourceType(params_);
   frag_info.color =
       params_.color.WithAlpha(params_.color.alpha * GetOpacityFactor());
   frag_info.center = params_.center;
@@ -87,6 +127,16 @@ bool UberSDFContents::Render(const ContentContext& renderer,
   frag_info.superellipse_scale = params_.superellipse_scale;
   frag_info.radii = params_.radii;
 
+  SamplerBinding sampler_binding;
+  if (params_.gradient) {
+    sampler_binding =
+        SetupGradientParameters(params_.gradient.value(), renderer, frag_info);
+  } else {
+    sampler_binding.texture = renderer.GetEmptyTexture();
+    sampler_binding.sampler =
+        renderer.GetContext()->GetSamplerLibrary()->GetSampler({});
+  }
+
   auto geometry_result =
       GetGeometry()->GetPositionBuffer(renderer, entity, pass);
 
@@ -99,7 +149,10 @@ bool UberSDFContents::Render(const ContentContext& renderer,
       this, GetGeometry(), renderer, entity, pass, pipeline_callback,
       frame_info,
       /*bind_fragment_callback=*/
-      [&frag_info, &data_host_buffer](RenderPass& pass) {
+      [&frag_info, &data_host_buffer,
+       sampler_binding = std::move(sampler_binding)](RenderPass& pass) {
+        FS::BindColorSourceSampler(pass, sampler_binding.texture,
+                                   sampler_binding.sampler);
         FS::BindFragInfo(pass, data_host_buffer.EmplaceUniform(frag_info));
         pass.SetCommandLabel("UberSDF");
         return true;
@@ -133,7 +186,8 @@ bool UberSDFContents::ApplyColorFilter(
 std::optional<Color> UberSDFContents::AsBackgroundColor(
     const Entity& entity,
     ISize target_size) const {
-  if (params_.type != UberSDFParameters::Type::kRect) {
+  if (params_.type != UberSDFParameters::Type::kRect ||
+      params_.gradient.has_value()) {
     return std::nullopt;
   }
   const Geometry* geometry = GetGeometry();
diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
index 00522e087d572..e862b42d8df34 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
@@ -100,5 +100,29 @@ TEST(UberSDFContentsTest, AsBackgroundColorStrokedRect) {
   EXPECT_FALSE(bg_color.has_value());
 }
 
+TEST(UberSDFContentsTest, AsBackgroundColorGradientReturnsNullopt) {
+  auto rect = Rect::MakeXYWH(-2, -2, 504, 504);
+  auto params =
+      UberSDFParameters::MakeRect(Color::Red(), rect, /*stroke=*/std::nullopt);
+
+  UberSDFParameters::GradientParameters gradient;
+  gradient.type = UberSDFParameters::GradientParameters::Type::kLinear;
+  gradient.start = Point(0, 0);
+  gradient.end = Point(500, 500);
+  gradient.tile_mode = Entity::TileMode::kClamp;
+  params.gradient = gradient;
+
+  auto geometry = std::make_unique<UberSDFGeometry>(params);
+  auto contents = UberSDFContents::Make(params, std::move(geometry));
+
+  Entity entity;
+  entity.SetTransform(Matrix());
+
+  // Even though the rect covers the entire area, a gradient is not a single
+  // solid background color, so AsBackgroundColor must return nullopt.
+  auto bg_color = contents->AsBackgroundColor(entity, ISize(500, 500));
+  EXPECT_FALSE(bg_color.has_value());
+}
+
 }  // namespace testing
 }  // namespace impeller
diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.h b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.h
index 942d6ccf5db3e..3e9520f9cc4fd 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.h
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.h
@@ -7,6 +7,8 @@
 
 #include <optional>
 
+#include "impeller/core/texture.h"
+#include "impeller/entity/entity.h"
 #include "impeller/geometry/color.h"
 #include "impeller/geometry/point.h"
 #include "impeller/geometry/rect.h"
@@ -32,6 +34,31 @@ struct UberSDFParameters {
     kRoundedSuperellipseSymmetric,
   };
 
+  /// The gradient properties applied to the shape.
+  struct GradientParameters {
+    enum class Type {
+      kLinear,
+      kRadial,
+    };
+
+    /// The type of gradient.
+    Type type;
+
+    /// Gradient start point (for linear gradients) or center (for radial
+    /// gradients).
+    Point start;
+
+    /// Gradient end point (for linear gradients) or `(radius, 0)` (for radial
+    /// gradients).
+    Point end;
+
+    /// Tile mode for the gradient.
+    Entity::TileMode tile_mode = Entity::TileMode::kClamp;
+
+    /// Texture for gradient ramp.
+    std::shared_ptr<Texture> texture;
+  };
+
   /// Creates UberSDFParameters for a rectangle.
   static UberSDFParameters MakeRect(Color color,
                                     const Rect& rect,
@@ -68,6 +95,9 @@ struct UberSDFParameters {
   /// The color used for filling or stroking the shape.
   Color color;
 
+  /// Gradient properties. Populated when using a gradient color source.
+  std::optional<GradientParameters> gradient;
+
   /// The center point of the shape in local coordinates.
   Point center;
 
diff --git a/engine/src/flutter/impeller/entity/shaders/gradients/linear_gradient_fill.frag b/engine/src/flutter/impeller/entity/shaders/gradients/linear_gradient_fill.frag
index 4c12983c34a1a..a62b77acf6f62 100644
--- a/engine/src/flutter/impeller/entity/shaders/gradients/linear_gradient_fill.frag
+++ b/engine/src/flutter/impeller/entity/shaders/gradients/linear_gradient_fill.frag
@@ -5,6 +5,7 @@
 precision mediump float;
 
 #include <impeller/color.glsl>
+#include <impeller/gradient.glsl>
 #include <impeller/texture.glsl>
 #include <impeller/types.glsl>
 
@@ -25,14 +26,8 @@ highp in vec2 v_position;
 out vec4 frag_color;
 
 void main() {
-  vec2 start_to_end = frag_info.end_point - frag_info.start_point;
-  vec2 start_to_position = v_position - frag_info.start_point;
-  float t =
-      dot(start_to_position, start_to_end) / dot(start_to_end, start_to_end);
-  frag_color = IPSampleLinearWithTileMode(texture_sampler,       //
-                                          vec2(t, 0.5),          //
-                                          frag_info.half_texel,  //
-                                          frag_info.tile_mode,   //
-                                          frag_info.decal_border_color);
+  frag_color = IPSampleLinearGradient(
+      texture_sampler, frag_info.start_point, frag_info.end_point, v_position,
+      frag_info.half_texel, frag_info.tile_mode, frag_info.decal_border_color);
   frag_color = IPPremultiply(frag_color) * frag_info.alpha;
 }
diff --git a/engine/src/flutter/impeller/entity/shaders/gradients/radial_gradient_fill.frag b/engine/src/flutter/impeller/entity/shaders/gradients/radial_gradient_fill.frag
index 866ebfaeeed26..596acfab6d42d 100644
--- a/engine/src/flutter/impeller/entity/shaders/gradients/radial_gradient_fill.frag
+++ b/engine/src/flutter/impeller/entity/shaders/gradients/radial_gradient_fill.frag
@@ -5,6 +5,7 @@
 precision mediump float;
 
 #include <impeller/color.glsl>
+#include <impeller/gradient.glsl>
 #include <impeller/texture.glsl>
 #include <impeller/types.glsl>
 
@@ -25,12 +26,8 @@ highp in vec2 v_position;
 out vec4 frag_color;
 
 void main() {
-  float len = length(v_position - frag_info.center);
-  float t = len / frag_info.radius;
-  frag_color = IPSampleLinearWithTileMode(texture_sampler,       //
-                                          vec2(t, 0.5),          //
-                                          frag_info.half_texel,  //
-                                          frag_info.tile_mode,   //
-                                          frag_info.decal_border_color);
+  frag_color = IPSampleRadialGradient(
+      texture_sampler, frag_info.center, frag_info.radius, v_position,
+      frag_info.half_texel, frag_info.tile_mode, frag_info.decal_border_color);
   frag_color = IPPremultiply(frag_color) * frag_info.alpha;
 }
diff --git a/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag b/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
index 97a5f5b715928..0ff413f14cc55 100644
--- a/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
+++ b/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
@@ -5,11 +5,15 @@
 precision mediump float;
 
 #include <impeller/color.glsl>
+#include <impeller/gradient.glsl>
+#include <impeller/texture.glsl>
 #include <impeller/types.glsl>
 
 #include "sdf_functions.glsl"
 #include "sdf_utils.glsl"
 
+uniform sampler2D color_source_sampler;
+
 uniform FragInfo {
   vec4 color;
   vec2 center;
@@ -27,6 +31,11 @@ uniform FragInfo {
   vec2 circle_center_right;
   vec2 superellipse_scale;
   vec4 radii;
+  vec2 gradient_start;
+  vec2 gradient_end;
+  vec2 half_texel;
+  float tile_mode;
+  float color_source_type;
 }
 frag_info;
 
@@ -34,6 +43,29 @@ out vec4 frag_color;
 
 highp in vec2 v_position;
 
+// Gets the color to use at v_position based on frag_info properties.
+vec4 getColor() {
+  vec4 color;
+  if (frag_info.color_source_type < 0.5) {
+    // Solid color
+    color = frag_info.color;
+  } else if (frag_info.color_source_type < 1.5) {
+    // Linear gradient
+    vec4 gradient_color = IPSampleLinearGradient(
+        color_source_sampler, frag_info.gradient_start, frag_info.gradient_end,
+        v_position, frag_info.half_texel, frag_info.tile_mode, vec4(0.0));
+    color = vec4(gradient_color.rgb, gradient_color.a * frag_info.color.a);
+  } else {
+    // Radial gradient
+    vec4 gradient_color = IPSampleRadialGradient(
+        color_source_sampler, frag_info.gradient_start,
+        frag_info.gradient_end.x, v_position, frag_info.half_texel,
+        frag_info.tile_mode, vec4(0.0));
+    color = vec4(gradient_color.rgb, gradient_color.a * frag_info.color.a);
+  }
+  return color;
+}
+
 float distanceFromCircle(vec2 p, float radius) {
   return length(p) - radius;
 }
@@ -276,8 +308,9 @@ float gammaCorrectedAlpha(float alpha, vec3 foreground_rgb) {
 }
 
 void main() {
-  vec2 p = v_position - frag_info.center;
+  vec4 color = getColor();
 
+  vec2 p = v_position - frag_info.center;
   vec2 sdf_and_pixel_size =
       (frag_info.stroked < 0.5) ? filledSDF(p) : strokedSDF(p);
   float sdf = sdf_and_pixel_size.x;
@@ -287,8 +320,8 @@ void main() {
   // Clamp alpha in case floating point precision errors cause it to be outside
   // [0.0, 1.0].
   alpha = clamp(alpha, 0.0, 1.0);
-  alpha = gammaCorrectedAlpha(alpha, frag_info.color.rgb);
+  alpha = gammaCorrectedAlpha(alpha, color.rgb);
 
-  frag_color = vec4(frag_info.color.rgb, frag_info.color.a * alpha);
+  frag_color = vec4(color.rgb, color.a * alpha);
   frag_color = IPPremultiply(frag_color);
 }

From 704e3985e7b2d5df7ee92a129f7a0f0b1d88632a Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Mon, 10 Aug 2026 13:31:49 -0700
Subject: [PATCH 02/15] gemini comments

---
 .../impeller/compiler/shader_lib/impeller/gradient.glsl  | 9 ++++++---
 .../impeller/entity/contents/uber_sdf_contents.cc        | 5 ++++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/engine/src/flutter/impeller/compiler/shader_lib/impeller/gradient.glsl b/engine/src/flutter/impeller/compiler/shader_lib/impeller/gradient.glsl
index 193dd6548feb0..f47bd9be4ed58 100644
--- a/engine/src/flutter/impeller/compiler/shader_lib/impeller/gradient.glsl
+++ b/engine/src/flutter/impeller/compiler/shader_lib/impeller/gradient.glsl
@@ -159,8 +159,11 @@ vec4 IPSampleLinearGradient(sampler2D tex,
                             vec4 decal_border_color) {
   vec2 start_to_end = end_point - start_point;
   vec2 start_to_position = pos - start_point;
-  float t =
-      dot(start_to_position, start_to_end) / dot(start_to_end, start_to_end);
+  float start_to_end_squared = dot(start_to_end, start_to_end);
+
+  float t = start_to_end_squared == 0.0
+                ? 0.0
+                : dot(start_to_position, start_to_end) / start_to_end_squared;
   return IPSampleLinearWithTileMode(tex, vec2(t, 0.5), half_texel, tile_mode,
                                     decal_border_color);
 }
@@ -173,7 +176,7 @@ vec4 IPSampleRadialGradient(sampler2D tex,
                             vec2 half_texel,
                             float tile_mode,
                             vec4 decal_border_color) {
-  float t = length(pos - center) / radius;
+  float t = radius == 0.0 ? 0.0 : length(pos - center) / radius;
   return IPSampleLinearWithTileMode(tex, vec2(t, 0.5), half_texel, tile_mode,
                                     decal_border_color);
 }
diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
index 0d6a505c64525..88f801c2a5693 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
@@ -74,7 +74,10 @@ SamplerBinding SetupGradientParameters(
   frag_info.gradient_start = gradient.start;
   frag_info.gradient_end = gradient.end;
   frag_info.tile_mode = static_cast<Scalar>(gradient.tile_mode);
-  frag_info.half_texel = Point(0.5f, 0.5f) / gradient.texture->GetSize();
+  auto texture_size = gradient.texture->GetSize();
+  FML_DCHECK(!texture_size.IsEmpty());
+  frag_info.half_texel =
+      Point(0.5f, 0.5f) / Point(texture_size.width, texture_size.height);
 
   SamplerDescriptor sampler_desc;
   sampler_desc.min_filter = MinMagFilter::kLinear;

From c4f1565b41e916271c77724d0915645c26526873 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Tue, 11 Aug 2026 13:40:49 -0700
Subject: [PATCH 03/15] malioc

---
 engine/src/flutter/impeller/tools/malioc.json | 164 +++++++++---------
 1 file changed, 83 insertions(+), 81 deletions(-)

diff --git a/engine/src/flutter/impeller/tools/malioc.json b/engine/src/flutter/impeller/tools/malioc.json
index d93c1e6ad6f2d..2539a10e56cdc 100644
--- a/engine/src/flutter/impeller/tools/malioc.json
+++ b/engine/src/flutter/impeller/tools/malioc.json
@@ -5067,7 +5067,7 @@
       "uses_late_zs_update": false,
       "variants": {
         "Main": {
-          "fp16_arithmetic": 0,
+          "fp16_arithmetic": 13,
           "has_stack_spilling": false,
           "performance": {
             "longest_path_bound_pipelines": [
@@ -5075,9 +5075,9 @@
               "arith_cvt"
             ],
             "longest_path_cycles": [
-              0.328125,
-              0.28125,
-              0.328125,
+              0.375,
+              0.265625,
+              0.375,
               0.125,
               0.0,
               0.25,
@@ -5096,9 +5096,9 @@
               "varying"
             ],
             "shortest_path_cycles": [
-              0.203125,
-              0.1875,
-              0.203125,
+              0.21875,
+              0.171875,
+              0.21875,
               0.125,
               0.0,
               0.25,
@@ -5109,9 +5109,9 @@
               "arith_cvt"
             ],
             "total_cycles": [
-              0.453125,
-              0.3125,
-              0.453125,
+              0.46875,
+              0.296875,
+              0.46875,
               0.125,
               0.0,
               0.25,
@@ -5120,7 +5120,7 @@
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
-          "uniform_registers_used": 18,
+          "uniform_registers_used": 16,
           "work_registers_used": 20
         }
       }
@@ -5138,7 +5138,7 @@
               "arithmetic"
             ],
             "longest_path_cycles": [
-              6.599999904632568,
+              6.929999828338623,
               1.0,
               1.0
             ],
@@ -5151,21 +5151,21 @@
               "arithmetic"
             ],
             "shortest_path_cycles": [
-              2.309999942779541,
-              1.0,
+              1.649999976158142,
+              0.0,
               0.0
             ],
             "total_bound_pipelines": [
               "arithmetic"
             ],
             "total_cycles": [
-              7.333333492279053,
+              7.666666507720947,
               1.0,
               1.0
             ]
           },
           "thread_occupancy": 100,
-          "uniform_registers_used": 4,
+          "uniform_registers_used": 3,
           "work_registers_used": 2
         }
       }
@@ -5809,7 +5809,7 @@
       "uses_late_zs_update": false,
       "variants": {
         "Main": {
-          "fp16_arithmetic": 0,
+          "fp16_arithmetic": 3,
           "has_stack_spilling": false,
           "performance": {
             "longest_path_bound_pipelines": [
@@ -5817,9 +5817,9 @@
               "arith_cvt"
             ],
             "longest_path_cycles": [
-              0.359375,
+              0.375,
               0.296875,
-              0.359375,
+              0.375,
               0.1875,
               0.0,
               0.25,
@@ -5835,15 +5835,16 @@
               "texture"
             ],
             "shortest_path_bound_pipelines": [
-              "varying"
+              "arith_total",
+              "arith_cvt"
             ],
             "shortest_path_cycles": [
               0.234375,
-              0.203125,
+              0.109375,
               0.234375,
-              0.1875,
+              0.125,
+              0.0,
               0.0,
-              0.25,
               0.0
             ],
             "total_bound_pipelines": [
@@ -5851,9 +5852,9 @@
               "arith_cvt"
             ],
             "total_cycles": [
-              0.484375,
+              0.5,
               0.328125,
-              0.484375,
+              0.5,
               0.1875,
               0.0,
               0.25,
@@ -5862,7 +5863,7 @@
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
-          "uniform_registers_used": 16,
+          "uniform_registers_used": 14,
           "work_registers_used": 20
         }
       }
@@ -5880,7 +5881,7 @@
               "arithmetic"
             ],
             "longest_path_cycles": [
-              6.599999904632568,
+              7.260000228881836,
               1.0,
               1.0
             ],
@@ -5893,15 +5894,15 @@
               "arithmetic"
             ],
             "shortest_path_cycles": [
-              2.309999942779541,
-              1.0,
+              1.649999976158142,
+              0.0,
               0.0
             ],
             "total_bound_pipelines": [
               "arithmetic"
             ],
             "total_cycles": [
-              7.333333492279053,
+              8.0,
               1.0,
               1.0
             ]
@@ -8597,7 +8598,7 @@
       "uses_late_zs_update": false,
       "variants": {
         "Main": {
-          "fp16_arithmetic": 32,
+          "fp16_arithmetic": 31,
           "has_stack_spilling": false,
           "performance": {
             "longest_path_bound_pipelines": [
@@ -8605,13 +8606,13 @@
               "arith_sfu"
             ],
             "longest_path_cycles": [
-              4.0,
-              3.875,
-              1.65625,
-              4.0,
+              4.1875,
+              4.125,
+              2.125,
+              4.1875,
               0.0,
               0.25,
-              0.0
+              0.25
             ],
             "pipelines": [
               "arith_total",
@@ -8627,9 +8628,9 @@
               "arith_fma"
             ],
             "shortest_path_cycles": [
-              0.53125,
-              0.53125,
-              0.15625,
+              0.578125,
+              0.578125,
+              0.234375,
               0.5,
               0.0,
               0.25,
@@ -8640,18 +8641,18 @@
               "arith_fma"
             ],
             "total_cycles": [
-              13.625,
-              13.625,
-              4.53125,
-              13.4375,
+              14.0625,
+              14.0625,
+              5.574999809265137,
+              13.75,
               0.0,
               0.25,
-              0.0
+              0.5
             ]
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
-          "uniform_registers_used": 46,
+          "uniform_registers_used": 62,
           "work_registers_used": 32
         }
       }
@@ -8669,9 +8670,9 @@
               "arithmetic"
             ],
             "longest_path_cycles": [
-              43.88999938964844,
-              3.0,
-              4.0
+              52.13999938964844,
+              6.0,
+              5.0
             ],
             "pipelines": [
               "arithmetic",
@@ -8682,21 +8683,21 @@
               "arithmetic"
             ],
             "shortest_path_cycles": [
-              6.269999980926514,
-              1.0,
+              6.929999828338623,
+              3.0,
               2.0
             ],
             "total_bound_pipelines": [
               "arithmetic"
             ],
             "total_cycles": [
-              105.66666412353516,
-              3.0,
-              24.0
+              122.33333587646484,
+              7.0,
+              26.0
             ]
           },
           "thread_occupancy": 100,
-          "uniform_registers_used": 7,
+          "uniform_registers_used": 9,
           "work_registers_used": 4
         }
       }
@@ -9361,17 +9362,17 @@
       "uses_late_zs_update": false,
       "variants": {
         "Main": {
-          "fp16_arithmetic": 28,
+          "fp16_arithmetic": 35,
           "has_stack_spilling": false,
           "performance": {
             "longest_path_bound_pipelines": [
-              "varying",
-              "texture"
+              "arith_total",
+              "arith_cvt"
             ],
             "longest_path_cycles": [
-              0.234375,
-              0.234375,
-              0.234375,
+              0.265625,
+              0.21875,
+              0.265625,
               0.0625,
               0.0,
               0.25,
@@ -9390,9 +9391,9 @@
               "varying"
             ],
             "shortest_path_cycles": [
-              0.171875,
-              0.140625,
-              0.171875,
+              0.203125,
+              0.125,
+              0.203125,
               0.0625,
               0.0,
               0.25,
@@ -9403,9 +9404,9 @@
               "arith_cvt"
             ],
             "total_cycles": [
-              0.328125,
-              0.265625,
-              0.328125,
+              0.359375,
+              0.25,
+              0.359375,
               0.0625,
               0.0,
               0.25,
@@ -9901,7 +9902,7 @@
       "uses_late_zs_update": false,
       "variants": {
         "Main": {
-          "fp16_arithmetic": 16,
+          "fp16_arithmetic": 21,
           "has_stack_spilling": false,
           "performance": {
             "longest_path_bound_pipelines": [
@@ -11823,7 +11824,7 @@
       "uses_late_zs_update": false,
       "variants": {
         "Main": {
-          "fp16_arithmetic": 35,
+          "fp16_arithmetic": 34,
           "has_stack_spilling": false,
           "performance": {
             "longest_path_bound_pipelines": [
@@ -11831,13 +11832,13 @@
               "arith_sfu"
             ],
             "longest_path_cycles": [
-              4.0,
-              3.387500047683716,
-              1.9375,
-              4.0,
+              4.125,
+              3.637500047683716,
+              2.299999952316284,
+              4.125,
               0.0,
               0.25,
-              0.0
+              0.25
             ],
             "pipelines": [
               "arith_total",
@@ -11850,12 +11851,13 @@
             ],
             "shortest_path_bound_pipelines": [
               "arith_total",
+              "arith_fma",
               "arith_sfu"
             ],
             "shortest_path_cycles": [
               0.5,
-              0.453125,
-              0.171875,
+              0.5,
+              0.25,
               0.5,
               0.0,
               0.25,
@@ -11866,18 +11868,18 @@
               "arith_sfu"
             ],
             "total_cycles": [
-              13.4375,
-              12.4375,
-              4.875,
-              13.4375,
+              13.625,
+              12.875,
+              5.65625,
+              13.625,
               0.0,
               0.25,
-              0.0
+              0.5
             ]
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
-          "uniform_registers_used": 48,
+          "uniform_registers_used": 66,
           "work_registers_used": 32
         }
       }

From 1096e810653d90b8d0bc557e89ec5209debfa41f Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Tue, 11 Aug 2026 13:41:12 -0700
Subject: [PATCH 04/15] Fix incorrect ending coord check in
 IPSampleLinearWithTileMode for decal mode

---
 .../impeller/compiler/shader_lib/impeller/texture.glsl    | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/engine/src/flutter/impeller/compiler/shader_lib/impeller/texture.glsl b/engine/src/flutter/impeller/compiler/shader_lib/impeller/texture.glsl
index bab5a65e45ba2..6e4ef63d03401 100644
--- a/engine/src/flutter/impeller/compiler/shader_lib/impeller/texture.glsl
+++ b/engine/src/flutter/impeller/compiler/shader_lib/impeller/texture.glsl
@@ -98,8 +98,12 @@ vec4 IPSampleLinearWithTileMode(sampler2D tex,
                                 float x_tile_mode,
                                 float y_tile_mode,
                                 vec4 decal_border_color) {
-  if (x_tile_mode == kTileModeDecal && (coords.x < 0 || coords.x >= 1) ||
-      y_tile_mode == kTileModeDecal && (coords.y < 0 || coords.y >= 1)) {
+  // Unlike 2D image sampling which uses a half-open interval [0, 1) where 1.0
+  // is outside the texture boundary, linear sampling uses a closed interval
+  // [0, 1]. Therefore, decal mode checks the ending coordinate using > 1 rather
+  // than >= 1.
+  if (x_tile_mode == kTileModeDecal && (coords.x < 0.0 || coords.x > 1.0) ||
+      y_tile_mode == kTileModeDecal && (coords.y < 0.0 || coords.y > 1.0)) {
     return decal_border_color;
   }
 

From 8bb2c2a62c54b49370d43ff040b90262a52e9069 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Tue, 11 Aug 2026 13:42:12 -0700
Subject: [PATCH 05/15] UberSDFContents::ApplyColorFilter does not work with
 gradients

---
 .../entity/contents/uber_sdf_contents.cc      |  3 +++
 .../contents/uber_sdf_contents_unittests.cc   | 23 +++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
index 88f801c2a5693..407729fbe8b7a 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
@@ -182,6 +182,9 @@ Color UberSDFContents::GetColor() const {
 
 bool UberSDFContents::ApplyColorFilter(
     const ColorFilterProc& color_filter_proc) {
+  if (params_.gradient.has_value()) {
+    return false;
+  }
   params_.color = color_filter_proc(params_.color);
   return true;
 }
diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
index e862b42d8df34..b1a057f0a277a 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
@@ -29,6 +29,29 @@ TEST(UberSDFContentsTest, ApplyColorFilter) {
   EXPECT_EQ(contents->GetColor(), Color::Blue());
 }
 
+TEST(UberSDFContentsTest, ApplyColorFilterWithGradient) {
+  auto rect = Rect::MakeXYWH(100, 100, 200, 200);
+  auto params =
+      UberSDFParameters::MakeRect(Color::Red(), rect, /*stroke=*/std::nullopt);
+  UberSDFParameters::GradientParameters gradient;
+  gradient.type = UberSDFParameters::GradientParameters::Type::kLinear;
+  gradient.start = Point(0, 0);
+  gradient.end = Point(200, 200);
+  params.gradient = gradient;
+
+  auto geometry = std::make_unique<UberSDFGeometry>(params);
+  auto contents = UberSDFContents::Make(params, std::move(geometry));
+
+  // Color filters cannot be applied on CPU to pre-baked gradients in UberSDFContents,
+  // so ApplyColorFilter must return false to trigger GPU filter wrapping.
+  bool result =
+      contents->ApplyColorFilter([](Color color) { return Color::Blue(); });
+
+  EXPECT_FALSE(result);
+  // The color should remain unchanged.
+  EXPECT_EQ(contents->GetColor(), Color::Red());
+}
+
 TEST(UberSDFContentsTest, AsBackgroundColor) {
   auto rect = Rect::MakeXYWH(-2, -2, 504, 504);
   auto params =

From 69cda7b8e2cf551dbb0cf1eed17c446996ea8299 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Tue, 11 Aug 2026 13:43:27 -0700
Subject: [PATCH 06/15] Make CreateGradientBuffer compatible with overlapping
 color stops

---
 .../impeller/geometry/geometry_unittests.cc   | 19 ++++++++--
 .../src/flutter/impeller/geometry/gradient.cc | 36 +++++++++----------
 2 files changed, 35 insertions(+), 20 deletions(-)

diff --git a/engine/src/flutter/impeller/geometry/geometry_unittests.cc b/engine/src/flutter/impeller/geometry/geometry_unittests.cc
index 0e85fb6c6fc20..d805a595f6207 100644
--- a/engine/src/flutter/impeller/geometry/geometry_unittests.cc
+++ b/engine/src/flutter/impeller/geometry/geometry_unittests.cc
@@ -1834,13 +1834,28 @@ TEST(GeometryTest, Gradient) {
   }
 
   {
-    // Gradient with duplicate stops does not create an empty texture.
+    // Gradient with duplicate stops creates a 1024 texture.
     std::vector<Color> colors = {Color::Red(), Color::Yellow(), Color::Black(),
                                  Color::Blue()};
     std::vector<Scalar> stops = {0.0, 0.25, 0.25, 1.0};
 
     auto gradient = CreateGradientBuffer(colors, stops);
-    ASSERT_EQ(gradient.texture_size, 5u);
+    ASSERT_EQ(gradient.texture_size, 1024u);
+
+    std::vector<Color> expected_colors(1024);
+    for (size_t i = 0; i < 1024; i++) {
+      double t = i / 1023.0;
+      if (i < 256) {
+        // Interval 1: texels 0 to 255 (stop interval 0 to 0.25)
+        expected_colors[i] =
+            Color::Lerp(Color::Red(), Color::Yellow(), t / 0.25);
+      } else {
+        // Interval 2: texels 256 to 1023 (stop interval 0.25 to 1.0)
+        expected_colors[i] =
+            Color::Lerp(Color::Black(), Color::Blue(), (t - 0.25) / 0.75);
+      }
+    }
+    ASSERT_COLOR_BUFFER_NEAR(gradient.color_bytes, expected_colors);
   }
 
   {
diff --git a/engine/src/flutter/impeller/geometry/gradient.cc b/engine/src/flutter/impeller/geometry/gradient.cc
index 8bdfbe2cb2507..13967ebfd03d2 100644
--- a/engine/src/flutter/impeller/geometry/gradient.cc
+++ b/engine/src/flutter/impeller/geometry/gradient.cc
@@ -9,6 +9,9 @@
 
 namespace impeller {
 
+// TODO(b-luk): this should use a platform specific max texture size.
+static constexpr uint32_t kMaxGradientTextureSize = 1024;
+
 static void AppendColor(const Color& color, GradientData* data) {
   auto converted = color.ToR8G8B8A8();
   data->color_bytes.push_back(converted[0]);
@@ -26,22 +29,21 @@ GradientData CreateGradientBuffer(const std::vector<Color>& colors,
     texture_size = colors.size();
   } else {
     auto minimum_delta = 1.0;
+    // Avoid creating textures that are absurdly large due to stops that are
+    // very close together.
+    auto minimum_allowable_delta = 1.0 / (kMaxGradientTextureSize - 1.0);
     for (size_t i = 1; i < stops.size(); i++) {
       auto value = stops[i] - stops[i - 1];
-      // Smaller than kEhCloseEnough
-      if (value < 0.0001) {
-        continue;
+      if (value <= minimum_allowable_delta) {
+        minimum_delta = minimum_allowable_delta;
+        break;
       }
       if (value < minimum_delta) {
         minimum_delta = value;
       }
     }
-    // Avoid creating textures that are absurdly large due to stops that are
-    // very close together.
-    // TODO(jonahwilliams): this should use a platform specific max texture
-    // size.
-    texture_size = std::min(
-        static_cast<uint32_t>(std::round(1.0 / minimum_delta)) + 1, 1024u);
+    texture_size =
+        static_cast<uint32_t>(std::round(1.0 / minimum_delta)) + 1;
   }
   GradientData data = {
       .color_bytes = {},
@@ -49,7 +51,8 @@ GradientData CreateGradientBuffer(const std::vector<Color>& colors,
   };
   data.color_bytes.reserve(texture_size * 4);
 
-  if (texture_size == colors.size() && colors.size() <= 1024) {
+  if (texture_size == colors.size() &&
+      colors.size() <= kMaxGradientTextureSize) {
     for (auto i = 0u; i < colors.size(); i++) {
       AppendColor(colors[i], &data);
     }
@@ -79,17 +82,14 @@ GradientData CreateGradientBuffer(const std::vector<Color>& colors,
 
         AppendColor(mixed_color, &data);
       } else {
-        // We've slightly overshot the previous stop.
+        // We've passed the next stop. Advance to the next stop interval.
+        // Decrement `i` to re-evaluate the current texel against the new
+        // interval. When there are overlapping or zero-delta stops, this branch
+        // evaluates repeatedly until the overlap is passed.
         previous_color = next_color;
         previous_stop = next_stop;
         previous_color_index += 1;
-        next_color = colors[previous_color_index + 1];
-        auto next_stop = stops[previous_color_index + 1];
-
-        auto t = (scaled_i - previous_stop) / (next_stop - previous_stop);
-        auto mixed_color = Color::Lerp(previous_color, next_color, t);
-
-        AppendColor(mixed_color, &data);
+        i--;
       }
     }
     // The last index is always equal to the last color, exactly.

From 5b5fcdc07b0fe9585be8b525e5ecfab1530bef69 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Tue, 11 Aug 2026 13:44:21 -0700
Subject: [PATCH 07/15] Make PopulateUberSDFColorSource account for matrix
 transformations

---
 .../flutter/impeller/display_list/canvas.cc   | 37 ++++++++++++++++---
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/engine/src/flutter/impeller/display_list/canvas.cc b/engine/src/flutter/impeller/display_list/canvas.cc
index aa1a1ff12df08..8e77d72cd826c 100644
--- a/engine/src/flutter/impeller/display_list/canvas.cc
+++ b/engine/src/flutter/impeller/display_list/canvas.cc
@@ -231,8 +231,9 @@ static std::pair<Rect, Color> ExpandRectToPixelMinimum(const Rect& rect,
 ///
 /// @return Whether the color source was successfully populated into `params`.
 static bool PopulateUberSDFColorSource(
-    const flutter::DlColorSource& color_source,
     const ContentContext& renderer,
+    const flutter::DlColorSource& color_source,
+    const std::optional<Matrix>& shape_transform,
     UberSDFParameters& params) {
   if (color_source.isGradient()) {
     UberSDFParameters::GradientParameters gradient;
@@ -240,23 +241,46 @@ static bool PopulateUberSDFColorSource(
     std::vector<Color> colors;
     std::vector<float> stops;
 
+    // When a shape transform is applied to transform the SDF shape from local
+    // space into canvas space, the gradient parameters must be mapped from
+    // canvas space into local space via the inverse shape transform.
+    Matrix inverted_shape_transform =
+        shape_transform.has_value() ? shape_transform->Invert() : Matrix();
+
     if (color_source.type() == flutter::DlColorSourceType::kLinearGradient) {
       const auto* linear = color_source.asLinearGradient();
       FML_DCHECK(linear);
+      Matrix gradient_transform = inverted_shape_transform * linear->matrix();
+      if (!gradient_transform.IsAffine()) {
+        // Non-affine matrix transformation not supported by UberSDF.
+        return false;
+      }
       Paint::ConvertStops(linear, colors, stops);
       gradient.type = UberSDFParameters::GradientParameters::Type::kLinear;
-      gradient.start = linear->start_point();
-      gradient.end = linear->end_point();
+      gradient.start = gradient_transform * linear->start_point();
+      gradient.end = gradient_transform * linear->end_point();
       gradient.tile_mode = static_cast<Entity::TileMode>(linear->tile_mode());
     } else if (color_source.type() ==
                flutter::DlColorSourceType::kRadialGradient) {
       const auto* radial = color_source.asRadialGradient();
       FML_DCHECK(radial);
+      Matrix gradient_transform = inverted_shape_transform * radial->matrix();
+      if (!gradient_transform.IsAffine()) {
+        // Non-affine matrix transformation not supported by UberSDF.
+        return false;
+      }
+      auto scales = gradient_transform.GetScales2D();
+      if (!scales.has_value() ||
+          !ScalarNearlyEqual(scales->first, scales->second)) {
+        // Non-uniform scaling on a radial gradient creates an ellipse, which is
+        // not supported by UberSDF.
+        return false;
+      }
       Paint::ConvertStops(radial, colors, stops);
       gradient.type = UberSDFParameters::GradientParameters::Type::kRadial;
-      gradient.start = radial->center();
+      gradient.start = gradient_transform * radial->center();
       // For radial gradients, gradient.end.x stores the radius.
-      gradient.end = Point(radial->radius(), 0.0f);
+      gradient.end = Point(radial->radius() * scales->first, 0.0f);
       gradient.tile_mode = static_cast<Entity::TileMode>(radial->tile_mode());
     } else {
       // Gradient type not supported by UberSDF.
@@ -2236,7 +2260,8 @@ void Canvas::AddRenderSDFEntityToCurrentPass(
   entity.SetBlendMode(paint.blend_mode);
 
   if (!paint.color_source ||
-      PopulateUberSDFColorSource(*paint.color_source, renderer_, params)) {
+      PopulateUberSDFColorSource(renderer_, *paint.color_source,
+                                 shape_transform, params)) {
     // No color source (solid paint color), or a supported color source was
     // populated into UberSDFParams.
     auto geometry = std::make_unique<UberSDFGeometry>(params);

From ab93ec4cb08cc973a6c048f505fc133cf6965249 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Tue, 11 Aug 2026 13:45:25 -0700
Subject: [PATCH 08/15] et format

---
 .../impeller/entity/contents/uber_sdf_contents_unittests.cc  | 5 +++--
 engine/src/flutter/impeller/geometry/gradient.cc             | 3 +--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
index b1a057f0a277a..fd82167da8e88 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents_unittests.cc
@@ -42,8 +42,9 @@ TEST(UberSDFContentsTest, ApplyColorFilterWithGradient) {
   auto geometry = std::make_unique<UberSDFGeometry>(params);
   auto contents = UberSDFContents::Make(params, std::move(geometry));
 
-  // Color filters cannot be applied on CPU to pre-baked gradients in UberSDFContents,
-  // so ApplyColorFilter must return false to trigger GPU filter wrapping.
+  // Color filters cannot be applied on CPU to pre-baked gradients in
+  // UberSDFContents, so ApplyColorFilter must return false to trigger GPU
+  // filter wrapping.
   bool result =
       contents->ApplyColorFilter([](Color color) { return Color::Blue(); });
 
diff --git a/engine/src/flutter/impeller/geometry/gradient.cc b/engine/src/flutter/impeller/geometry/gradient.cc
index 13967ebfd03d2..3ed83d6cb5a6a 100644
--- a/engine/src/flutter/impeller/geometry/gradient.cc
+++ b/engine/src/flutter/impeller/geometry/gradient.cc
@@ -42,8 +42,7 @@ GradientData CreateGradientBuffer(const std::vector<Color>& colors,
         minimum_delta = value;
       }
     }
-    texture_size =
-        static_cast<uint32_t>(std::round(1.0 / minimum_delta)) + 1;
+    texture_size = static_cast<uint32_t>(std::round(1.0 / minimum_delta)) + 1;
   }
   GradientData data = {
       .color_bytes = {},

From cef74280cb700eae0418f9d6a298a943380d3436 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Tue, 11 Aug 2026 14:58:06 -0700
Subject: [PATCH 09/15] malioc

---
 engine/src/flutter/impeller/tools/malioc.json | 93 ++++++++++---------
 1 file changed, 48 insertions(+), 45 deletions(-)

diff --git a/engine/src/flutter/impeller/tools/malioc.json b/engine/src/flutter/impeller/tools/malioc.json
index 2539a10e56cdc..a16d8ac41a980 100644
--- a/engine/src/flutter/impeller/tools/malioc.json
+++ b/engine/src/flutter/impeller/tools/malioc.json
@@ -744,7 +744,7 @@
             ],
             "longest_path_cycles": [
               0.675000011920929,
-              0.46875,
+              0.484375,
               0.675000011920929,
               0.1875,
               0.0,
@@ -778,9 +778,9 @@
               "arith_cvt"
             ],
             "total_cycles": [
-              0.862500011920929,
+              0.84375,
               0.59375,
-              0.862500011920929,
+              0.84375,
               0.3125,
               0.0,
               0.25,
@@ -816,8 +816,8 @@
               "arith_fma"
             ],
             "longest_path_cycles": [
-              0.328125,
-              0.328125,
+              0.34375,
+              0.34375,
               0.296875,
               0.125,
               0.0,
@@ -834,12 +834,14 @@
               "texture"
             ],
             "shortest_path_bound_pipelines": [
+              "arith_total",
+              "arith_fma",
               "varying"
             ],
             "shortest_path_cycles": [
-              0.234375,
-              0.234375,
-              0.203125,
+              0.25,
+              0.25,
+              0.1875,
               0.125,
               0.0,
               0.25,
@@ -850,9 +852,9 @@
               "arith_cvt"
             ],
             "total_cycles": [
-              0.421875,
+              0.40625,
               0.359375,
-              0.421875,
+              0.40625,
               0.125,
               0.0,
               0.25,
@@ -889,7 +891,7 @@
             ],
             "longest_path_cycles": [
               0.421875,
-              0.328125,
+              0.34375,
               0.421875,
               0.125,
               0.0,
@@ -922,9 +924,9 @@
               "arith_cvt"
             ],
             "total_cycles": [
-              0.546875,
+              0.53125,
               0.359375,
-              0.546875,
+              0.53125,
               0.125,
               0.0,
               0.25,
@@ -9367,12 +9369,14 @@
           "performance": {
             "longest_path_bound_pipelines": [
               "arith_total",
-              "arith_cvt"
+              "arith_cvt",
+              "varying",
+              "texture"
             ],
             "longest_path_cycles": [
-              0.265625,
-              0.21875,
-              0.265625,
+              0.25,
+              0.234375,
+              0.25,
               0.0625,
               0.0,
               0.25,
@@ -9391,9 +9395,9 @@
               "varying"
             ],
             "shortest_path_cycles": [
-              0.203125,
-              0.125,
-              0.203125,
+              0.1875,
+              0.140625,
+              0.1875,
               0.0625,
               0.0,
               0.25,
@@ -9404,9 +9408,9 @@
               "arith_cvt"
             ],
             "total_cycles": [
-              0.359375,
-              0.25,
-              0.359375,
+              0.34375,
+              0.265625,
+              0.34375,
               0.0625,
               0.0,
               0.25,
@@ -9907,12 +9911,12 @@
           "performance": {
             "longest_path_bound_pipelines": [
               "arith_total",
-              "arith_cvt"
+              "arith_fma"
             ],
             "longest_path_cycles": [
               0.265625,
-              0.25,
               0.265625,
+              0.25,
               0.125,
               0.0,
               0.25,
@@ -9931,9 +9935,9 @@
               "varying"
             ],
             "shortest_path_cycles": [
-              0.203125,
-              0.15625,
-              0.203125,
+              0.1875,
+              0.171875,
+              0.1875,
               0.125,
               0.0,
               0.25,
@@ -9944,9 +9948,9 @@
               "arith_cvt"
             ],
             "total_cycles": [
-              0.359375,
-              0.28125,
-              0.359375,
+              0.34375,
+              0.296875,
+              0.34375,
               0.125,
               0.0,
               0.25,
@@ -10885,9 +10889,9 @@
               "arith_fma"
             ],
             "longest_path_cycles": [
-              0.40625,
-              0.40625,
-              0.296875,
+              0.421875,
+              0.421875,
+              0.28125,
               0.3125,
               0.0,
               0.25,
@@ -10904,13 +10908,12 @@
             ],
             "shortest_path_bound_pipelines": [
               "arith_total",
-              "arith_fma",
-              "arith_sfu"
+              "arith_fma"
             ],
             "shortest_path_cycles": [
-              0.3125,
-              0.3125,
-              0.234375,
+              0.328125,
+              0.328125,
+              0.21875,
               0.3125,
               0.0,
               0.25,
@@ -10921,9 +10924,9 @@
               "arith_fma"
             ],
             "total_cycles": [
-              0.4375,
-              0.4375,
-              0.390625,
+              0.453125,
+              0.453125,
+              0.375,
               0.3125,
               0.0,
               0.25,
@@ -11833,8 +11836,8 @@
             ],
             "longest_path_cycles": [
               4.125,
-              3.637500047683716,
-              2.299999952316284,
+              3.65625,
+              2.28125,
               4.125,
               0.0,
               0.25,
@@ -11870,7 +11873,7 @@
             "total_cycles": [
               13.625,
               12.875,
-              5.65625,
+              5.625,
               13.625,
               0.0,
               0.25,

From 2770ec3486ee4dae308546b03b14ea708d4e1b78 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Wed, 12 Aug 2026 10:50:19 -0700
Subject: [PATCH 10/15] Reorder and document UberSDF FragInfo fields

---
 .../impeller/entity/shaders/uber_sdf.frag     | 92 +++++++++++++++++--
 1 file changed, 83 insertions(+), 9 deletions(-)

diff --git a/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag b/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
index 0ff413f14cc55..af1162ac30e45 100644
--- a/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
+++ b/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
@@ -15,27 +15,101 @@ precision mediump float;
 uniform sampler2D color_source_sampler;
 
 uniform FragInfo {
+  // FragInfo fields are sorted by size (vec4 -> vec2 -> float) to optimize
+  // uniform register usage.
+
+  // ===========================================================================
+  // vec4 fields
+  // ===========================================================================
+
+  /// The RGBA color of the shape (or paint opacity in color.a for gradients).
   vec4 color;
+  /// Corner radii for rounded rects (top-left, top-right, bottom-left,
+  /// bottom-right) or rounded superellipses (xy).
+  vec4 radii;
+
+  // ===========================================================================
+  // vec2 fields
+  // ===========================================================================
+
+  // --- General Shape Geometry ---
+  /// The center position of the shape in local coordinates.
   vec2 center;
+  /// The half-dimensions of the shape (half-width, half-height).
   vec2 size;
-  float stroke_width;
-  float stroke_join;
-  float aa_pixels;
-  float stroked;
-  float type;
+
+  // --- Superellipse Parameters ---
+  /// The exponent degree (n_x, n_y) of the superellipse curvature.
   vec2 superellipse_degree;
+  /// The semi-axis lengths (a, b) of the superellipse.
   vec2 superellipse_semi_axis;
+  /// Normalization scale factor mapping the superellipse quadrant to a unit
+  /// square.
+  vec2 superellipse_scale;
+  /// The angular span of the corner circular arc transitions for rounded
+  /// superellipses.
   vec2 angle_span;
-  float octant_offset_c;
+  /// The center of the corner transition circle for the top octant of a
+  /// rounded superellipse.
   vec2 circle_center_top;
+  /// The center of the corner transition circle for the right octant of a
+  /// rounded superellipse.
   vec2 circle_center_right;
-  vec2 superellipse_scale;
-  vec4 radii;
+
+  // --- Gradient Parameters ---
+  /// The starting point of a linear gradient, or the center point of a radial
+  /// gradient.
   vec2 gradient_start;
+  /// The ending point of a linear gradient, or (radius, 0.0) for a radial
+  /// gradient.
   vec2 gradient_end;
+  /// Half the size of a single gradient texel in normalized texture
+  /// coordinates.
   vec2 half_texel;
-  float tile_mode;
+
+  // ===========================================================================
+  // float fields
+  // ===========================================================================
+
+  // --- General Configuration ---
+  /// The shape type:
+  ///   0: Circle
+  ///   1: Rect
+  ///   2: Oval
+  ///   3: RoundRect
+  ///   4: Superellipse
+  float type;
+  /// The type of color source:
+  ///   0: Solid color
+  ///   1: Linear gradient
+  ///   2: Radial gradient
   float color_source_type;
+  /// The width in device pixels over which to apply antialiasing.
+  float aa_pixels;
+
+  // --- Stroke Parameters ---
+  /// Whether the shape is stroked (1.0) or filled (0.0).
+  float stroked;
+  /// The width of the stroke.
+  float stroke_width;
+  /// The join style for the stroke:
+  ///   0: Miter
+  ///   1: Bevel
+  ///   2: Round
+  float stroke_join;
+
+  // --- Superellipse Parameters ---
+  /// Transition line offset dividing top and right octants for rounded
+  /// superellipses.
+  float octant_offset_c;
+
+  // --- Gradient Parameters ---
+  /// The tile mode for gradient sampling:
+  ///   0: Clamp
+  ///   1: Repeat
+  ///   2: Mirror
+  ///   3: Decal
+  float tile_mode;
 }
 frag_info;
 

From 228eebd85491adc956c6964c86fc8e8399848318 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Wed, 12 Aug 2026 18:03:05 +0000
Subject: [PATCH 11/15] malioc

---
 engine/src/flutter/impeller/tools/malioc.json | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/engine/src/flutter/impeller/tools/malioc.json b/engine/src/flutter/impeller/tools/malioc.json
index a16d8ac41a980..4f8480ed4321e 100644
--- a/engine/src/flutter/impeller/tools/malioc.json
+++ b/engine/src/flutter/impeller/tools/malioc.json
@@ -8672,7 +8672,7 @@
               "arithmetic"
             ],
             "longest_path_cycles": [
-              52.13999938964844,
+              51.47999954223633,
               6.0,
               5.0
             ],
@@ -8685,7 +8685,7 @@
               "arithmetic"
             ],
             "shortest_path_cycles": [
-              6.929999828338623,
+              6.599999904632568,
               3.0,
               2.0
             ],
@@ -8693,7 +8693,7 @@
               "arithmetic"
             ],
             "total_cycles": [
-              122.33333587646484,
+              121.0,
               7.0,
               26.0
             ]

From 7f4eae884d1f26a4c02601259ad3dc4bf31117d9 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Mon, 24 Aug 2026 17:50:39 +0000
Subject: [PATCH 12/15] malioc

---
 engine/src/flutter/impeller/tools/malioc.json | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/engine/src/flutter/impeller/tools/malioc.json b/engine/src/flutter/impeller/tools/malioc.json
index fedd4d4c89985..46ecb48e49508 100644
--- a/engine/src/flutter/impeller/tools/malioc.json
+++ b/engine/src/flutter/impeller/tools/malioc.json
@@ -8654,7 +8654,7 @@
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
-          "uniform_registers_used": 44,
+          "uniform_registers_used": 60,
           "work_registers_used": 32
         }
       }
@@ -8693,13 +8693,13 @@
               "arithmetic"
             ],
             "total_cycles": [
-              121.0,
+              121.33333587646484,
               7.0,
               26.0
             ]
           },
           "thread_occupancy": 100,
-          "uniform_registers_used": 5,
+          "uniform_registers_used": 9,
           "work_registers_used": 4
         }
       }

From e877b1b9aeb4d97d1f88ee4f9292de85495e9e2b Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Mon, 24 Aug 2026 18:02:43 +0000
Subject: [PATCH 13/15] Remove octant_offset_c uniform from ubersdf

---
 .../impeller/entity/contents/uber_sdf_contents.cc   |  1 -
 .../impeller/entity/contents/uber_sdf_parameters.cc |  1 -
 .../impeller/entity/contents/uber_sdf_parameters.h  |  3 ---
 .../contents/uber_sdf_parameters_unittests.cc       |  6 ------
 .../flutter/impeller/entity/shaders/uber_sdf.frag   | 13 +++++--------
 engine/src/flutter/impeller/tools/malioc.json       | 12 ++++++------
 6 files changed, 11 insertions(+), 25 deletions(-)

diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
index 20913fca7d722..be7b69fb962f5 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_contents.cc
@@ -123,7 +123,6 @@ bool UberSDFContents::Render(const ContentContext& renderer,
   frag_info.aa_pixels = UberSDFParameters::kAntialiasPixels;
   frag_info.superellipse_degree = params_.superellipse_degree;
   frag_info.angle_span = params_.angle_span;
-  frag_info.octant_offset_c = params_.octant_offset_c;
   frag_info.circle_center_top = params_.circle_center_top;
   frag_info.circle_center_right = params_.circle_center_right;
   frag_info.radii = params_.radii;
diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.cc
index f349bb74fa277..6569c6c1cd8ab 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.cc
@@ -105,7 +105,6 @@ std::optional<UberSDFParameters> UberSDFParameters::MakeRoundedSuperellipse(
       .superellipse_degree = Point(top_right.top.se_n, top_right.right.se_n),
       .angle_span = Point(top_right.top.circle_max_angle.radians,
                           top_right.right.circle_max_angle.radians),
-      .octant_offset_c = top_right.top.se_a - top_right.right.se_a,
       .circle_center_top = top_right.top.circle_center,
       .circle_center_right = top_right.right.circle_center,
       .radii = Vector4(top_right.top.circle_radius,
diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.h b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.h
index d09ede41a7e02..16fa2bef01b0d 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.h
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters.h
@@ -116,9 +116,6 @@ struct UberSDFParameters {
   /// The angular span of the circular cap for the top and right octants.
   Point angle_span;
 
-  /// The geometric offset 'c' used to connect the two octants of each quadrant.
-  float octant_offset_c;
-
   /// The circular cap center for the top octant of each
   /// quadrant.
   Point circle_center_top;
diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters_unittests.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters_unittests.cc
index 1e906a30be451..c470cf863a500 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters_unittests.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters_unittests.cc
@@ -169,10 +169,6 @@ TEST(UberSDFParametersTest, MakeRoundedSuperellipse) {
         params.angle_span.y,
         round_superellipse_params.top_right.right.circle_max_angle.radians);
 
-    EXPECT_EQ(params.octant_offset_c,
-              round_superellipse_params.top_right.top.se_a -
-                  round_superellipse_params.top_right.right.se_a);
-
     EXPECT_EQ(params.circle_center_top,
               round_superellipse_params.top_right.top.circle_center);
     EXPECT_EQ(params.circle_center_right,
@@ -204,8 +200,6 @@ TEST(UberSDFParametersTest, MakeRectangularRoundedSuperellipse) {
     EXPECT_EQ(params.center, Point(60, 120));
     EXPECT_EQ(params.size, Point(50, 100));
     EXPECT_FALSE(params.stroke.has_value());
-
-    EXPECT_EQ(params.octant_offset_c, -50.0f);
   }
 }
 
diff --git a/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag b/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
index 38b59b10315c4..a67679dcadbb1 100644
--- a/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
+++ b/engine/src/flutter/impeller/entity/shaders/uber_sdf.frag
@@ -95,11 +95,6 @@ uniform FragInfo {
   ///   2: Round
   float stroke_join;
 
-  // --- Superellipse Parameters ---
-  /// Transition line offset dividing top and right octants for rounded
-  /// superellipses.
-  float octant_offset_c;
-
   // --- Gradient Parameters ---
   /// The tile mode for gradient sampling:
   ///   0: Clamp
@@ -181,11 +176,13 @@ float distanceFromRoundedSuperellipse(vec2 p,
                                       vec2 radii,
                                       vec2 angle_span,
                                       vec2 circle_center_top,
-                                      vec2 circle_center_right,
-                                      float c) {
+                                      vec2 circle_center_right) {
   // Do work in the first quadrant to simply things.
   p = abs(p);
 
+  // Transition line offset dividing top and right octants.
+  float c = size.x - size.y;
+
   // Declare all RSE params for a single octant.
   float se_degree, span, radius, axis_length;
   vec2 circle_center;
@@ -299,7 +296,7 @@ vec2 filledSDF(vec2 p) {
     sdf = distanceFromRoundedSuperellipse(
         p, frag_info.superellipse_degree, frag_info.size, frag_info.radii.xy,
         frag_info.angle_span, frag_info.circle_center_top,
-        frag_info.circle_center_right, frag_info.octant_offset_c);
+        frag_info.circle_center_right);
     pixel_size = pixelSize(sdf);
   }
   return vec2(sdf, pixel_size);
diff --git a/engine/src/flutter/impeller/tools/malioc.json b/engine/src/flutter/impeller/tools/malioc.json
index 46ecb48e49508..5674d6d3d3ac9 100644
--- a/engine/src/flutter/impeller/tools/malioc.json
+++ b/engine/src/flutter/impeller/tools/malioc.json
@@ -8645,7 +8645,7 @@
             "total_cycles": [
               14.0625,
               14.0625,
-              5.574999809265137,
+              5.550000190734863,
               13.75,
               0.0,
               0.25,
@@ -8654,7 +8654,7 @@
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
-          "uniform_registers_used": 60,
+          "uniform_registers_used": 62,
           "work_registers_used": 32
         }
       }
@@ -8672,7 +8672,7 @@
               "arithmetic"
             ],
             "longest_path_cycles": [
-              51.47999954223633,
+              52.13999938964844,
               6.0,
               5.0
             ],
@@ -8693,7 +8693,7 @@
               "arithmetic"
             ],
             "total_cycles": [
-              121.33333587646484,
+              122.0,
               7.0,
               26.0
             ]
@@ -11873,7 +11873,7 @@
             "total_cycles": [
               13.625,
               12.875,
-              5.625,
+              5.59375,
               13.625,
               0.0,
               0.25,
@@ -11882,7 +11882,7 @@
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
-          "uniform_registers_used": 66,
+          "uniform_registers_used": 64,
           "work_registers_used": 32
         }
       }

From a0363dcdd3200e0f5cb1c0b1a558654250ae4cd9 Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Tue, 25 Aug 2026 11:26:09 -0700
Subject: [PATCH 14/15] Don't use auto for non-obvious types, and use a const
 reference to address clang-tidy warning

---
 .../contents/uber_sdf_parameters_unittests.cc | 32 +++++++++++--------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters_unittests.cc b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters_unittests.cc
index c470cf863a500..69223cfff4fd3 100644
--- a/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters_unittests.cc
+++ b/engine/src/flutter/impeller/entity/contents/uber_sdf_parameters_unittests.cc
@@ -137,14 +137,15 @@ TEST(UberSDFParametersTest, MakeRoundedSuperellipse) {
   auto round_superellipse = RoundSuperellipse::MakeRectRadii(rect, radii);
   auto round_superellipse_params =
       RoundSuperellipseParam::MakeBoundsRadii(rect, radii);
-  auto maybe_params = UberSDFParameters::MakeRoundedSuperellipse(
-      /*color=*/Color::Red(), /*round_superellipse=*/round_superellipse,
-      /*stroke=*/std::nullopt);
+  std::optional<UberSDFParameters> maybe_params =
+      UberSDFParameters::MakeRoundedSuperellipse(
+          /*color=*/Color::Red(), /*round_superellipse=*/round_superellipse,
+          /*stroke=*/std::nullopt);
 
   ASSERT_TRUE(maybe_params.has_value());
 
   if (maybe_params.has_value()) {
-    auto params = maybe_params.value();
+    const UberSDFParameters& params = maybe_params.value();
 
     EXPECT_EQ(params.type,
               UberSDFParameters::Type::kRoundedSuperellipseSymmetric);
@@ -185,14 +186,15 @@ TEST(UberSDFParametersTest, MakeRectangularRoundedSuperellipse) {
       .bottom_right = Size(10.0f, 10.0f),
   };
   auto round_superellipse = RoundSuperellipse::MakeRectRadii(rect, radii);
-  auto maybe_params = UberSDFParameters::MakeRoundedSuperellipse(
-      /*color=*/Color::Red(), /*round_superellipse=*/round_superellipse,
-      /*stroke=*/std::nullopt);
+  std::optional<UberSDFParameters> maybe_params =
+      UberSDFParameters::MakeRoundedSuperellipse(
+          /*color=*/Color::Red(), /*round_superellipse=*/round_superellipse,
+          /*stroke=*/std::nullopt);
 
   ASSERT_TRUE(maybe_params.has_value());
 
   if (maybe_params.has_value()) {
-    auto params = maybe_params.value();
+    const UberSDFParameters& params = maybe_params.value();
 
     EXPECT_EQ(params.type,
               UberSDFParameters::Type::kRoundedSuperellipseSymmetric);
@@ -212,9 +214,10 @@ TEST(UberSDFParametersTest, MakeRoundedSuperellipseRejectsNonSymmetric) {
       .bottom_right = Size(10.0f, 10.0f),
   };
   auto round_superellipse = RoundSuperellipse::MakeRectRadii(rect, radii);
-  auto params = UberSDFParameters::MakeRoundedSuperellipse(
-      /*color=*/Color::Red(), /*round_superellipse=*/round_superellipse,
-      /*stroke=*/std::nullopt);
+  std::optional<UberSDFParameters> params =
+      UberSDFParameters::MakeRoundedSuperellipse(
+          /*color=*/Color::Red(), /*round_superellipse=*/round_superellipse,
+          /*stroke=*/std::nullopt);
 
   EXPECT_FALSE(params.has_value());
 }
@@ -228,9 +231,10 @@ TEST(UberSDFParametersTest, MakeRoundedSuperellipseRejectsNonCircular) {
       .bottom_right = Size(9.0f, 10.0f),
   };
   auto round_superellipse = RoundSuperellipse::MakeRectRadii(rect, radii);
-  auto params = UberSDFParameters::MakeRoundedSuperellipse(
-      /*color=*/Color::Red(), /*round_superellipse=*/round_superellipse,
-      /*stroke=*/std::nullopt);
+  std::optional<UberSDFParameters> params =
+      UberSDFParameters::MakeRoundedSuperellipse(
+          /*color=*/Color::Red(), /*round_superellipse=*/round_superellipse,
+          /*stroke=*/std::nullopt);
 
   EXPECT_FALSE(params.has_value());
 }

From 643f07dcd838eb47cf2b1a2b5f25653351a95dab Mon Sep 17 00:00:00 2001
From: Benson Luk <97480502+b-luk@users.noreply.github.com>
Date: Wed, 26 Aug 2026 10:28:12 -0700
Subject: [PATCH 15/15] address comments

---
 .../flutter/impeller/display_list/canvas.cc   | 148 +++++++++---------
 .../src/flutter/impeller/geometry/gradient.cc |   1 +
 2 files changed, 76 insertions(+), 73 deletions(-)

diff --git a/engine/src/flutter/impeller/display_list/canvas.cc b/engine/src/flutter/impeller/display_list/canvas.cc
index 010182108da36..fda9f88c4b351 100644
--- a/engine/src/flutter/impeller/display_list/canvas.cc
+++ b/engine/src/flutter/impeller/display_list/canvas.cc
@@ -268,81 +268,80 @@ static std::pair<Rect, Color> ExpandRectToPixelMinimum(const Rect& rect,
   return {expanded.value(), color.WithAlpha(color.alpha * alpha_scaling)};
 }
 
-/// @brief  Attempts to populate `params` with the color source properties,
+/// @brief  Attempts to create UberSDF GradientParameters from a DlColorSource,
 ///         if supported by UberSDF (e.g. for linear and radial gradients).
 ///
-/// @return Whether the color source was successfully populated into `params`.
-static bool PopulateUberSDFColorSource(
-    const ContentContext& renderer,
-    const flutter::DlColorSource& color_source,
-    const std::optional<Matrix>& shape_transform,
-    UberSDFParameters& params) {
-  if (color_source.isGradient()) {
-    UberSDFParameters::GradientParameters gradient;
-
-    std::vector<Color> colors;
-    std::vector<float> stops;
-
-    // When a shape transform is applied to transform the SDF shape from local
-    // space into canvas space, the gradient parameters must be mapped from
-    // canvas space into local space via the inverse shape transform.
-    Matrix inverted_shape_transform =
-        shape_transform.has_value() ? shape_transform->Invert() : Matrix();
-
-    if (color_source.type() == flutter::DlColorSourceType::kLinearGradient) {
-      const auto* linear = color_source.asLinearGradient();
-      FML_DCHECK(linear);
-      Matrix gradient_transform = inverted_shape_transform * linear->matrix();
-      if (!gradient_transform.IsAffine()) {
-        // Non-affine matrix transformation not supported by UberSDF.
-        return false;
-      }
-      Paint::ConvertStops(linear, colors, stops);
-      gradient.type = UberSDFParameters::GradientParameters::Type::kLinear;
-      gradient.start = gradient_transform * linear->start_point();
-      gradient.end = gradient_transform * linear->end_point();
-      gradient.tile_mode = static_cast<Entity::TileMode>(linear->tile_mode());
-    } else if (color_source.type() ==
-               flutter::DlColorSourceType::kRadialGradient) {
-      const auto* radial = color_source.asRadialGradient();
-      FML_DCHECK(radial);
-      Matrix gradient_transform = inverted_shape_transform * radial->matrix();
-      if (!gradient_transform.IsAffine()) {
-        // Non-affine matrix transformation not supported by UberSDF.
-        return false;
-      }
-      auto scales = gradient_transform.GetScales2D();
-      if (!scales.has_value() ||
-          !ScalarNearlyEqual(scales->first, scales->second)) {
-        // Non-uniform scaling on a radial gradient creates an ellipse, which is
-        // not supported by UberSDF.
-        return false;
-      }
-      Paint::ConvertStops(radial, colors, stops);
-      gradient.type = UberSDFParameters::GradientParameters::Type::kRadial;
-      gradient.start = gradient_transform * radial->center();
-      // For radial gradients, gradient.end.x stores the radius.
-      gradient.end = Point(radial->radius() * scales->first, 0.0f);
-      gradient.tile_mode = static_cast<Entity::TileMode>(radial->tile_mode());
-    } else {
-      // Gradient type not supported by UberSDF.
-      return false;
-    }
+/// @return The GradientParameters if the color source is a supported gradient,
+///         otherwise std::nullopt.
+static std::optional<UberSDFParameters::GradientParameters>
+CreateUberSDFGradientParameters(const ContentContext& renderer,
+                                const flutter::DlColorSource& color_source,
+                                const std::optional<Matrix>& shape_transform) {
+  if (!color_source.isGradient()) {
+    // Color source not supported by UberSDF.
+    return std::nullopt;
+  }
 
-    GradientData gradient_data = CreateGradientBuffer(colors, stops);
-    std::shared_ptr<Texture> texture =
-        CreateGradientTexture(gradient_data, renderer.GetContext());
-    if (!texture) {
-      return false;
+  UberSDFParameters::GradientParameters gradient;
+
+  std::vector<Color> colors;
+  std::vector<float> stops;
+
+  // When a shape transform is applied to transform the SDF shape from local
+  // space into canvas space, the gradient parameters must be mapped from
+  // canvas space into local space via the inverse shape transform.
+  Matrix inverted_shape_transform =
+      shape_transform.has_value() ? shape_transform->Invert() : Matrix();
+
+  if (color_source.type() == flutter::DlColorSourceType::kLinearGradient) {
+    const auto* linear = color_source.asLinearGradient();
+    FML_DCHECK(linear);
+    Matrix gradient_transform = inverted_shape_transform * linear->matrix();
+    if (!gradient_transform.IsAffine()) {
+      // Non-affine matrix transformation not supported by UberSDF.
+      return std::nullopt;
+    }
+    Paint::ConvertStops(linear, colors, stops);
+    gradient.type = UberSDFParameters::GradientParameters::Type::kLinear;
+    gradient.start = gradient_transform * linear->start_point();
+    gradient.end = gradient_transform * linear->end_point();
+    gradient.tile_mode = static_cast<Entity::TileMode>(linear->tile_mode());
+  } else if (color_source.type() ==
+             flutter::DlColorSourceType::kRadialGradient) {
+    const auto* radial = color_source.asRadialGradient();
+    FML_DCHECK(radial);
+    Matrix gradient_transform = inverted_shape_transform * radial->matrix();
+    if (!gradient_transform.IsAffine()) {
+      // Non-affine matrix transformation not supported by UberSDF.
+      return std::nullopt;
+    }
+    auto scales = gradient_transform.GetScales2D();
+    if (!scales.has_value() ||
+        !ScalarNearlyEqual(scales->first, scales->second)) {
+      // Non-uniform scaling on a radial gradient creates an ellipse, which is
+      // not supported by UberSDF.
+      return std::nullopt;
     }
+    Paint::ConvertStops(radial, colors, stops);
+    gradient.type = UberSDFParameters::GradientParameters::Type::kRadial;
+    gradient.start = gradient_transform * radial->center();
+    // For radial gradients, gradient.end.x stores the radius.
+    gradient.end = Point(radial->radius() * scales->first, 0.0f);
+    gradient.tile_mode = static_cast<Entity::TileMode>(radial->tile_mode());
+  } else {
+    // Gradient type not supported by UberSDF.
+    return std::nullopt;
+  }
 
-    gradient.texture = std::move(texture);
-    params.gradient = std::move(gradient);
-    return true;
+  GradientData gradient_data = CreateGradientBuffer(colors, stops);
+  std::shared_ptr<Texture> texture =
+      CreateGradientTexture(gradient_data, renderer.GetContext());
+  if (!texture) {
+    return std::nullopt;
   }
 
-  // Color source not supported by UberSDF.
-  return false;
+  gradient.texture = std::move(texture);
+  return gradient;
 }
 
 }  // namespace
@@ -2292,11 +2291,14 @@ void Canvas::AddRenderSDFEntityToCurrentPass(
   entity.SetTransform(transform);
   entity.SetBlendMode(paint.blend_mode);
 
-  if (!paint.color_source ||
-      PopulateUberSDFColorSource(renderer_, *paint.color_source,
-                                 shape_transform, params)) {
-    // No color source (solid paint color), or a supported color source was
-    // populated into UberSDFParams.
+  if (paint.color_source) {
+    params.gradient = CreateUberSDFGradientParameters(
+        renderer_, *paint.color_source, shape_transform);
+  }
+
+  if (!paint.color_source || params.gradient.has_value()) {
+    // No color source (solid paint color), or a supported gradient color
+    // source.
     auto geometry = std::make_unique<UberSDFGeometry>(params);
     auto contents = UberSDFContents::Make(params, std::move(geometry));
     const Geometry* geom = contents->GetGeometry();
diff --git a/engine/src/flutter/impeller/geometry/gradient.cc b/engine/src/flutter/impeller/geometry/gradient.cc
index 3ed83d6cb5a6a..9aabf8bdc9170 100644
--- a/engine/src/flutter/impeller/geometry/gradient.cc
+++ b/engine/src/flutter/impeller/geometry/gradient.cc
@@ -10,6 +10,7 @@
 namespace impeller {
 
 // TODO(b-luk): this should use a platform specific max texture size.
+// https://github.com/flutter/flutter/issues/191820
 static constexpr uint32_t kMaxGradientTextureSize = 1024;
 
 static void AppendColor(const Color& color, GradientData* data) {