Lerp HSVColor and HSLColor hue along the shortest arc by glitchfl · Pull Request #191186 · flutter/flutter

glitchfl · 2026-08-16T19:13:54Z

Hue is an angle but we lerped it like a plain number so anything crossing 0 took the long way round. 300 to 60 should be a 120 hop through red (it was doing 240 through cyan)

Added a _lerpHue helper that folds the delta into (-180, 180] first (used by both lerps)

Heads up - 0 -> 360 doesn't sweep the wheel anymore since its the same angle. Two tests relied on that so I moved them to 0 -> 180

fixes #138301

(I used antigravity to help with that fix) and I went over the checklist

gemini-code-assist

Code Review

This pull request introduces a private helper function _lerpHue in colors.dart to interpolate hue values along the shortest arc of a 360-degree circle. Both HSVColor.lerp and HSLColor.lerp are updated to use this helper function. Corresponding tests in colors_test.dart are updated and expanded to verify that hue interpolation correctly follows the shortest arc. There are no review comments, and I have no feedback to provide.

victorsanni

Mostly LGTM with 1 concern.

victorsanni · 2026-08-21T17:53:39Z

 }

+double _lerpHue(double a, double b, double t) {
+  double delta = (b - a) % 360.0;


delta will always be > 0, for example -180 % 360 and 180 % 360 both equal 180. Could this be a problem? Reversing the lerp should retrace the same path.

yea ur right (forgot that modulo is non-negative). dropped the modulo since hue is alris [0, 360] and fold with signed comparisons instead (so reversing retraces now) added tests for it but PTAL

victorsanni

Thanks for the fix!

justinmc

LGTM 👍

auto-submit · 2026-08-25T16:32:06Z

autosubmit label was removed for flutter/flutter/191186, because - The status or check suite ci.yaml validation has failed. Please fix the issues identified (or deflake) before re-applying this label.

…e arc

glitchfl · 2026-08-26T09:25:44Z

why merge and not rebase?

Roll Flutter from 15d8908addf6 to e8dca90ec9e0 (58 revisions) flutter/flutter@15d8908...e8dca90 2026-08-27 [email protected] Terminate existing process before launching with devicectl (flutter/flutter#191885) 2026-08-27 [email protected] Roll Fuchsia Linux SDK from qjOQi-zAgu_tADorh... to dDxH8G5cDBP602eyG... (flutter/flutter#191889) 2026-08-27 [email protected] [flutter_tools] Verify native assets tree-shaking during linking (flutter/flutter#191637) 2026-08-27 [email protected] Denylists b-series powervr from vulkan (flutter/flutter#191808) 2026-08-27 [email protected] Handle linear and radial gradients in UberSDF (flutter/flutter#190874) 2026-08-27 [email protected] Roll Packages from 740f093 to bd3cbc1 (7 revisions) (flutter/flutter#191886) 2026-08-27 [email protected] Disable more Windows tests that have been causing CI flakes (flutter/flutter#191822) 2026-08-27 [email protected] Roll Skia from d32721369bd8 to 82e972ea84b1 (2 revisions) (flutter/flutter#191880) 2026-08-27 [email protected] Roll Skia from 3640b8edd16c to d32721369bd8 (10 revisions) (flutter/flutter#191858) 2026-08-27 [email protected] Revert: [AGP 9] Update remaining tests to AGP 9 (flutter/flutter#191863) 2026-08-27 [email protected] Roll Fuchsia Test Scripts from 0iCv10IlKfiilEBOU... to 6SXRz6wsA2Zm_rAqP... (flutter/flutter#191852) 2026-08-27 [email protected] Roll pub packages (flutter/flutter#191851) 2026-08-27 [email protected] Refactor FormField build wrappers (flutter/flutter#185795) 2026-08-27 [email protected] Make ScrollPhysics reactive by introducing shouldUpdate (flutter/flutter#189664) 2026-08-27 [email protected] macOS: Fix crash on out-of-bounds text input ranges (flutter/flutter#191780) 2026-08-27 [email protected] Add HCPP feature flag, and turn it on by default in beta/master (flutter/flutter#190623) 2026-08-27 [email protected] [tool] Migrate CleanCommand to modular dependency injection (flutter/flutter#190742) 2026-08-26 [email protected] Update triage docs for ecosystem and codelab changes (flutter/flutter#191809) 2026-08-26 [email protected] [AGP 9] Update remaining tests to AGP 9 (flutter/flutter#191824) 2026-08-26 [email protected] [UIScene] Migrate dev/benchmarks/complex_layout to UIScene lifecycle (flutter/flutter#191619) 2026-08-26 [email protected] Add SliverAppBar showOnScreen semantics test coverage (flutter/flutter#190410) 2026-08-26 [email protected] Add prompt_suggestion icon to list of RTL mirroring icons. (flutter/flutter#191741) 2026-08-26 [email protected] Remove bringup for batch 3 (flutter/flutter#191750) 2026-08-26 [email protected] Roll Skia from b5465d7b0b77 to 3640b8edd16c (6 revisions) (flutter/flutter#191835) 2026-08-26 [email protected] Uiscene migrate custom channels views (flutter/flutter#191817) 2026-08-26 [email protected] Support --[no-]adb-log-filtering CLI option (flutter/flutter#187252) 2026-08-26 [email protected] Roll Dart SDK from cb8a4e1a0fbb to cb4c39d067f3 (2 revisions) (flutter/flutter#191825) 2026-08-26 [email protected] Fix `Navigator.pushNamed<T>()` type checking (flutter/flutter#188148) 2026-08-26 [email protected] Handle the case where a window doesn't have a title set (flutter/flutter#191767) 2026-08-26 [email protected] [Android] Remove old `InputType` constructor from embedding (flutter/flutter#191244) 2026-08-26 [email protected] Roll Skia from 244a6a0f8f92 to b5465d7b0b77 (19 revisions) (flutter/flutter#191810) 2026-08-26 [email protected] Tolerate floating-point rounding in paintImage centerSlice assertion (flutter/flutter#185789) 2026-08-26 [email protected] Fixes translated bounded blurs (flutter/flutter#191615) 2026-08-26 [email protected] Roll Fuchsia Linux SDK from MstTWE1RDOT-RnrtH... to qjOQi-zAgu_tADorh... (flutter/flutter#191769) 2026-08-26 [email protected] Lerp HSVColor and HSLColor hue along the shortest arc (flutter/flutter#191186) 2026-08-26 [email protected] Fix enum instances comparison to use `equality ==` since dart has the correct behavior now (flutter/flutter#191537) 2026-08-26 [email protected] Switches windows to opengles 3 (flutter/flutter#191516) 2026-08-26 [email protected] Roll Dart SDK from 7739e8602bc1 to cb8a4e1a0fbb (1 revision) (flutter/flutter#191784) 2026-08-26 [email protected] iOS,macOS: Check viewType before creating a platform view (flutter/flutter#191777) 2026-08-26 [email protected] Revert: [tool_tests] Remove bringup from Windows tool_tests_commands_2_2 (flutter/flutter#191793) 2026-08-26 [email protected] refactor(flutter_tools): clean up dead unreferenced declarations (flutter/flutter#191163) 2026-08-26 [email protected] Roll Fuchsia GN SDK from a87CbQSWEjkPUK1ZY... to ZsxUUK2SfA-TrNvb8... (flutter/flutter#191763) 2026-08-26 [email protected] [tool_tests] Remove bringup from Windows tool_tests_commands_2_2 (flutter/flutter#191732) 2026-08-25 [email protected] Remove legacy gen_defaults analyze checks (flutter/flutter#191629) 2026-08-25 [email protected] Refactors `try` to avoid `unawaited_return_in_try_block` case (flutter/flutter#191129) 2026-08-25 [email protected] Roll Dart SDK from 8996935d3d0a to 7739e8602bc1 (1 revision) (flutter/flutter#191754) ...

…r#12660) Roll Flutter from 15d8908addf6 to e8dca90ec9e0 (58 revisions) flutter/flutter@15d8908...e8dca90 2026-08-27 [email protected] Terminate existing process before launching with devicectl (flutter/flutter#191885) 2026-08-27 [email protected] Roll Fuchsia Linux SDK from qjOQi-zAgu_tADorh... to dDxH8G5cDBP602eyG... (flutter/flutter#191889) 2026-08-27 [email protected] [flutter_tools] Verify native assets tree-shaking during linking (flutter/flutter#191637) 2026-08-27 [email protected] Denylists b-series powervr from vulkan (flutter/flutter#191808) 2026-08-27 [email protected] Handle linear and radial gradients in UberSDF (flutter/flutter#190874) 2026-08-27 [email protected] Roll Packages from 740f093 to bd3cbc1 (7 revisions) (flutter/flutter#191886) 2026-08-27 [email protected] Disable more Windows tests that have been causing CI flakes (flutter/flutter#191822) 2026-08-27 [email protected] Roll Skia from d32721369bd8 to 82e972ea84b1 (2 revisions) (flutter/flutter#191880) 2026-08-27 [email protected] Roll Skia from 3640b8edd16c to d32721369bd8 (10 revisions) (flutter/flutter#191858) 2026-08-27 [email protected] Revert: [AGP 9] Update remaining tests to AGP 9 (flutter/flutter#191863) 2026-08-27 [email protected] Roll Fuchsia Test Scripts from 0iCv10IlKfiilEBOU... to 6SXRz6wsA2Zm_rAqP... (flutter/flutter#191852) 2026-08-27 [email protected] Roll pub packages (flutter/flutter#191851) 2026-08-27 [email protected] Refactor FormField build wrappers (flutter/flutter#185795) 2026-08-27 [email protected] Make ScrollPhysics reactive by introducing shouldUpdate (flutter/flutter#189664) 2026-08-27 [email protected] macOS: Fix crash on out-of-bounds text input ranges (flutter/flutter#191780) 2026-08-27 [email protected] Add HCPP feature flag, and turn it on by default in beta/master (flutter/flutter#190623) 2026-08-27 [email protected] [tool] Migrate CleanCommand to modular dependency injection (flutter/flutter#190742) 2026-08-26 [email protected] Update triage docs for ecosystem and codelab changes (flutter/flutter#191809) 2026-08-26 [email protected] [AGP 9] Update remaining tests to AGP 9 (flutter/flutter#191824) 2026-08-26 [email protected] [UIScene] Migrate dev/benchmarks/complex_layout to UIScene lifecycle (flutter/flutter#191619) 2026-08-26 [email protected] Add SliverAppBar showOnScreen semantics test coverage (flutter/flutter#190410) 2026-08-26 [email protected] Add prompt_suggestion icon to list of RTL mirroring icons. (flutter/flutter#191741) 2026-08-26 [email protected] Remove bringup for batch 3 (flutter/flutter#191750) 2026-08-26 [email protected] Roll Skia from b5465d7b0b77 to 3640b8edd16c (6 revisions) (flutter/flutter#191835) 2026-08-26 [email protected] Uiscene migrate custom channels views (flutter/flutter#191817) 2026-08-26 [email protected] Support --[no-]adb-log-filtering CLI option (flutter/flutter#187252) 2026-08-26 [email protected] Roll Dart SDK from cb8a4e1a0fbb to cb4c39d067f3 (2 revisions) (flutter/flutter#191825) 2026-08-26 [email protected] Fix `Navigator.pushNamed<T>()` type checking (flutter/flutter#188148) 2026-08-26 [email protected] Handle the case where a window doesn't have a title set (flutter/flutter#191767) 2026-08-26 [email protected] [Android] Remove old `InputType` constructor from embedding (flutter/flutter#191244) 2026-08-26 [email protected] Roll Skia from 244a6a0f8f92 to b5465d7b0b77 (19 revisions) (flutter/flutter#191810) 2026-08-26 [email protected] Tolerate floating-point rounding in paintImage centerSlice assertion (flutter/flutter#185789) 2026-08-26 [email protected] Fixes translated bounded blurs (flutter/flutter#191615) 2026-08-26 [email protected] Roll Fuchsia Linux SDK from MstTWE1RDOT-RnrtH... to qjOQi-zAgu_tADorh... (flutter/flutter#191769) 2026-08-26 [email protected] Lerp HSVColor and HSLColor hue along the shortest arc (flutter/flutter#191186) 2026-08-26 [email protected] Fix enum instances comparison to use `equality ==` since dart has the correct behavior now (flutter/flutter#191537) 2026-08-26 [email protected] Switches windows to opengles 3 (flutter/flutter#191516) 2026-08-26 [email protected] Roll Dart SDK from 7739e8602bc1 to cb8a4e1a0fbb (1 revision) (flutter/flutter#191784) 2026-08-26 [email protected] iOS,macOS: Check viewType before creating a platform view (flutter/flutter#191777) 2026-08-26 [email protected] Revert: [tool_tests] Remove bringup from Windows tool_tests_commands_2_2 (flutter/flutter#191793) 2026-08-26 [email protected] refactor(flutter_tools): clean up dead unreferenced declarations (flutter/flutter#191163) 2026-08-26 [email protected] Roll Fuchsia GN SDK from a87CbQSWEjkPUK1ZY... to ZsxUUK2SfA-TrNvb8... (flutter/flutter#191763) 2026-08-26 [email protected] [tool_tests] Remove bringup from Windows tool_tests_commands_2_2 (flutter/flutter#191732) 2026-08-25 [email protected] Remove legacy gen_defaults analyze checks (flutter/flutter#191629) 2026-08-25 [email protected] Refactors `try` to avoid `unawaited_return_in_try_block` case (flutter/flutter#191129) 2026-08-25 [email protected] Roll Dart SDK from 8996935d3d0a to 7739e8602bc1 (1 revision) (flutter/flutter#191754) ...

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glitchfl force-pushed the lerp-hue-shortest-arc branch from c7fa1fd to 1571b5a Compare August 21, 2026 18:47

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glitchfl added 2 commits August 25, 2026 15:50

Lerp HSVColor and HSLColor hue along the shortest arc

1a92c17

fixed HSVColor and HSLColor hue lerp when reversed taking the opposit…

e070b75

…e arc

Renzo-Olivares force-pushed the lerp-hue-shortest-arc branch from 85a8088 to e070b75 Compare August 25, 2026 22:50

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Roll Flutter from 15d8908addf6 to e8dca90ec9e0 (58 revisions) flutter/packages#12660

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Lerp HSVColor and HSLColor hue along the shortest arc - #191186

Lerp HSVColor and HSLColor hue along the shortest arc#191186
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