Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 183405b4b633edb81bd6a4e82805bb828ed4a582
https://github.com/WebKit/WebKit/commit/183405b4b633edb81bd6a4e82805bb828ed4a582
Author: Ahmad Saleem <[email protected]>
Date: 2026-10-13 (Tue, 13 Oct 2026)
Changed paths:
M Source/WTF/wtf/StdLibExtras.h
M Tools/TestWebKitAPI/Tests/WTF/StdLibExtrasTests.cpp
Log Message:
-----------
Style tuple-like blending helpers copy every field on each blend/equality
check
https://bugs.webkit.org/show_bug.cgi?id=325388
rdar://188497454
Reviewed by Sam Weinig.
The *OnTupleLike helpers in StyleValueTypes.h (equalsForBlending, canBlend,
requiresInterpolationForAccumulativeIteration, and blend) feed their operands
through WTF::tuple_zip() and fold over the result. tuple_zip built its
transposed tuple out of std::tuple_element_t, which for the common tuple-like
aggregates (SpaceSeparatedTuple, pairs, points, sizes, arrays) is a value type.
As a result every field of both operands was copied into that intermediate
tuple on each call, even for the equality/canBlend paths that build no output.
These run per-frame on animation hot paths.
Make tuple_zip zip references instead. zip_tuple_at_index now uses
std::forward_as_tuple(get<I>(...)...), which preserves the reference and
const-ness of each source element, so the returned tuple binds references
rather than copying the fields. The outer tuple is spelled out explicitly (not
via CTAD), so single-field tuple-likes still produce a one-element outer tuple.
get<I> stays unqualified so user-defined tuple-likes are found via ADL. The
StyleValueTypes.h helpers are unchanged and keep using tuple_zip + WTF::apply.
Behavior is
unchanged; the sources already outlive the zipped result at every call site.
Add API tests covering the subtle parts: transposition, reference binding and
aliasing, const preservation, single-element and single-operand inputs, mixed
std::pair/std::array operands, user-defined tuple-likes, and use with
WTF::apply.
* Source/WTF/wtf/StdLibExtras.h:
(WTF::detail::zip_tuple_at_index):
(WTF::detail::tuple_zip_impl):
* Tools/TestWebKitAPI/Tests/WTF/StdLibExtrasTests.cpp:
(TestWebKitAPI::TEST(WTF_StdLibExtras, TupleZipTransposes)):
(TestWebKitAPI::TEST(WTF_StdLibExtras, TupleZipBindsReferencesToLvalues)):
(TestWebKitAPI::TEST(WTF_StdLibExtras, TupleZipPreservesConst)):
(TestWebKitAPI::TEST(WTF_StdLibExtras, TupleZipSingleElement)):
(TestWebKitAPI::TEST(WTF_StdLibExtras, TupleZipSingleOperand)):
(TestWebKitAPI::TEST(WTF_StdLibExtras, TupleZipMixedTupleLikes)):
(TestWebKitAPI::TEST(WTF_StdLibExtras, TupleZipUserDefinedTupleLike)):
(TestWebKitAPI::TEST(WTF_StdLibExtras, TupleZipWithApply)):
Canonical link: https://commits.webkit.org/323690@main
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