Handle symmetric rectangular and elliptical round super ellipses in the uber SDF renderer by walley892 · Pull Request #185695 · flutter/flutter

walley892 · 2026-04-28T17:51:18Z

Adds support for drawing rectangular (non-square) and elliptical (two corner radii) round superellipses in the UberSDF renderer.

Doesn't support non-symmetric corners.

Should be covered by existing golden tests.

Pre-launch Checklist

gemini-code-assist

Code Review

This pull request enhances the RoundSuperellipse implementation in Impeller to support non-square bounds and non-circular corners. It updates the Canvas class, UberSDFParameters, and the uber_sdf.frag shader to handle separate parameters for the top and right octants of the superellipse, including degrees, semi-axes, and circular arc spans. I have no feedback to provide.

gaaclarke · 2026-04-28T18:25:36Z

+        paint.color, round_superellipse.GetBounds(),
+        Point(octant_top.se_n, octant_right.se_n),
+        Point(octant_top.se_a, octant_right.se_a), adjusted_radii,
+        Point(octant_top.circle_max_angle.radians,
+              octant_right.circle_max_angle.radians),
+        octant_top.circle_center, octant_right.circle_center,
+        octant_top.se_a - octant_right.se_a,
+        Point(round_superellipse_params.top_right.signed_scale.Abs()),


argument comments would be nice at this point

I see your Point. Added

gaaclarke · 2026-04-28T18:26:44Z

+    const Point& superellipse_degree,
+    const Point& superellipse_a,


Sometimes you are passing points by reference and sometimes by value. I'd just pass them by value since they are small and unlikely to grow.

gaaclarke · 2026-04-28T18:28:44Z

 float distanceFromRoundedSuperellipse(vec2 p,
-                                      vec2 ab,
-                                      float n,
-                                      float angle_span,
-                                      vec2 circle_center,
-                                      float radius) {
+                                      vec2 degree,
+                                      vec2 se_a,
+                                      vec4 radii_top,
+                                      vec2 angle_span,
+                                      vec2 circle_center_top,
+                                      vec4 radii_right,
+                                      vec2 circle_center_right,
+                                      float c,
+                                      vec2 scale) {


I'd be interested to see the malioc results here. I have concerns about register pressure when we have so many arguments to the function. I wonder if we can make it easier with a struct?

Malioc'd.

The work_registers haven't changed which is surprising to me. The superellipses have such specialized params that both this signature and the uniform block are u-g-l-y.

Adding the non-uniform case will add even more uniforms and arguments here 😢. Maybe we can hold off on any optimizations until that's done?

It may even end up being worth making a more opaque uniform block with packing and unpacking logic everywhere to reduce CPU<->GPU overhead.

gaaclarke · 2026-04-28T18:29:26Z

-    p = p.yx;
+  vec2 p_norm = p / scale;
+
+  float n, span, r, a, s;


Can the names be more descriptive or add a comment here?

Yes and yes. Hopefully the variables are clearer now

gaaclarke · 2026-04-28T18:30:25Z

I have no feedback to provide.

It's speechless, bravo.

gaaclarke

This looks good to me, i checked out the goldens too and there's no problems to report.

dkwingsmt

LGTM. Thank you very much!

dkwingsmt · 2026-04-29T19:38:06Z

-                                      float radius) {
+                                      vec2 degree,
+                                      vec2 se_a,
+                                      vec4 radii_top,


It seems that radii_top only has its x used?

Yeah, if you look at the caller, it was passing in radii.x. The uniform is reused from the round rect implementation. I bumped the unpacking x here to get the arguments ready for RSEs with different corner parameters

flutter-dashboard · 2026-04-30T20:20:24Z

Golden file changes have been found for this pull request. Click here to view and triage (e.g. because this is an intentional change).

If you are still iterating on this change and are not ready to resolve the images on the Flutter Gold dashboard, consider marking this PR as a draft pull request above. You will still be able to view image results on the dashboard, commenting will be silenced, and the check will not try to resolve itself until marked ready for review.

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Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

Changes reported for pull request #185695 at sha 1c64890

Roll Flutter from 81bc3d69535f to 707dbc0420a3 (85 revisions) flutter/flutter@81bc3d6...707dbc0 2026-05-01 [email protected] Removing TODOs from the WebParagraph code and addressing technical debts. (flutter/flutter#185168) 2026-05-01 [email protected] Ensure that vulkan_interface.h gets included before vk_mem_alloc.h (flutter/flutter#185777) 2026-05-01 [email protected] [flutter_tools] Bump dwds dependency to v27.1.1 (flutter/flutter#185357) 2026-05-01 [email protected] Roll Dart SDK from 6d4a319cbdac to 9aa7097f2e3e (3 revisions) (flutter/flutter#185888) 2026-05-01 [email protected] Roll Skia from fa1dcb289709 to 7ac6d42f2fd0 (1 revision) (flutter/flutter#185887) 2026-05-01 [email protected] Roll Skia from 54cc00adde38 to fa1dcb289709 (3 revisions) (flutter/flutter#185880) 2026-05-01 [email protected] [iOS] Migrate to FlutterFMLTaskRunner(s) (flutter/flutter#185815) 2026-05-01 [email protected] Remove material imports from navigator_on_did_remove_page_test and scrollable_in_overlay_test (flutter/flutter#182546) 2026-05-01 [email protected] Roll Skia from 2e279266f06a to 54cc00adde38 (3 revisions) (flutter/flutter#185872) 2026-05-01 [email protected] dev: Remove unused parameters (flutter/flutter#185345) 2026-05-01 [email protected] Roll Fuchsia Linux SDK from HN5VYzftnf_B8T-n9... to VnzuUefDQR0UhQ1L1... (flutter/flutter#185870) 2026-05-01 [email protected] Use g_free when using glib memory allocation (flutter/flutter#185519) 2026-05-01 [email protected] Roll Dart SDK from d30df3428f2e to 6d4a319cbdac (2 revisions) (flutter/flutter#185862) 2026-05-01 [email protected] Remove trivial test utility cross-imports from material and cupertino… (flutter/flutter#184295) 2026-05-01 [email protected] Inline test callback painter in tab scaffold test (flutter/flutter#184851) 2026-05-01 [email protected] [a11y] Add support for high contrast themes in the a11y assessments app (flutter/flutter#185801) 2026-05-01 [email protected] [a11y assessment app] Use default color for banner (flutter/flutter#185804) 2026-04-30 [email protected] Added name to AUTHORS (flutter/flutter#185586) 2026-04-30 [email protected] Remove semantics_tester import from raw_material_button_test.dart (flutter/flutter#184806) 2026-04-30 [email protected] Remove semantics_tester import from user_accounts_drawer_header_test.dart (flutter/flutter#184809) 2026-04-30 [email protected] Roll Skia from 7b88c5c281e5 to 2e279266f06a (5 revisions) (flutter/flutter#185854) 2026-04-30 [email protected] Handle symmetric rectangular and elliptical round super ellipses in the uber SDF renderer (flutter/flutter#185695) 2026-04-30 [email protected] Match on process name before killing for SwiftPM (flutter/flutter#185774) 2026-04-30 [email protected] Sync CHANGELOG.md from stable (flutter/flutter#185838) 2026-04-30 [email protected] Roll Dart SDK from 25910e31a6d2 to d30df3428f2e (5 revisions) (flutter/flutter#185839) 2026-04-30 [email protected] Check cross imports test subfolders (flutter/flutter#185493) 2026-04-30 [email protected] test: inline TestCallbackPainter in cupertino/picker_test.dart (flutter/flutter#185398) 2026-04-30 [email protected] Update customer testing version (flutter/flutter#185830) 2026-04-30 [email protected] Adapt the Metal shader library output list for debug versus release mode (flutter/flutter#185798) 2026-04-30 [email protected] [Impeller] Port a recent Vulkan swapchain fence waiting fix to the AHB version of the swapchain (flutter/flutter#185763) 2026-04-30 [email protected] Roll Skia from 26a59aa71eff to 7b88c5c281e5 (1 revision) (flutter/flutter#185821) 2026-04-30 [email protected] Roll Skia from 6b4167b4e204 to 26a59aa71eff (4 revisions) (flutter/flutter#185808) 2026-04-30 [email protected] [a11y] Mark SemanticsNode dirty when customSemanticsActions change (flutter/flutter#185707) 2026-04-30 [email protected] Roll Skia from 1bd2f1cc2746 to 6b4167b4e204 (8 revisions) (flutter/flutter#185799) 2026-04-30 [email protected] [iOS] Extract FlutterVSyncClient from vsync_waiter_ios (flutter/flutter#185737) 2026-04-30 [email protected] Roll Fuchsia Linux SDK from nnv8-SSam6yE8dw4z... to HN5VYzftnf_B8T-n9... 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walley892 added 4 commits April 27, 2026 14:32

handle non-square RSEs

39c7003

fix diffbase conflicts

20e9790

Merge remote-tracking branch 'upstream/master' into sdf-rect-se

ff5306d

consolidate params

0408ece

flutter-dashboard Bot added the CICD Run CI/CD label Apr 28, 2026

github-actions Bot added engine flutter/engine related. See also e: labels. e: impeller Impeller rendering backend issues and features requests labels Apr 28, 2026

walley892 requested a review from gaaclarke April 28, 2026 17:52

gaaclarke marked this pull request as ready for review April 28, 2026 18:24

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lint error rip

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walley892 dismissed stale reviews from dkwingsmt and gaaclarke via ea43da5 April 29, 2026 23:54

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Merge remote-tracking branch 'upstream/master' into sdf-rect-se

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Merged via the queue into flutter:master with commit 1047c96 Apr 30, 2026
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Flutter Notable Commits - 2026 #181433

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		const Point& superellipse_degree,
		const Point& superellipse_a,

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walley892 commented Apr 28, 2026

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gaaclarke commented Apr 28, 2026

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