[webkit-changes] [WebKit/WebKit] 1aa517: Hit testing on element with 180deg flip inside pre...

[mattwoodrow]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 1aa517d47471fdc37ac5b6e2f3809de704ea8ac5
      https://github.com/WebKit/WebKit/commit/1aa517d47471fdc37ac5b6e2f3809de704ea8ac5
  Author: Matt Woodrow <mattwoodrow at apple.com>
  Date:   2023-07-23 (Sun, 23 Jul 2023)

  Changed paths:
    M LayoutTests/compositing/backing/backface-visibility-flip-expected.txt
    M LayoutTests/compositing/layer-creation/overlap-transformed-preserved-3d-expected.txt
    M LayoutTests/fast/text/combining-character-sequence-vertical.html
    M LayoutTests/fast/text/vertical-quotation-marks.html
    M LayoutTests/platform/ios-wk2/compositing/tiling/backface-preserve-3d-tiled-expected.txt
    M LayoutTests/platform/ios-wk2/compositing/visible-rect/flipped-preserve-3d-expected.txt
    M LayoutTests/platform/mac/compositing/tiling/backface-preserve-3d-tiled-expected.txt
    M LayoutTests/platform/mac/compositing/visible-rect/flipped-preserve-3d-expected.txt
    A LayoutTests/transforms/3d/hit-testing/hit-preserves-3d-3-expected.txt
    A LayoutTests/transforms/3d/hit-testing/hit-preserves-3d-3.html
    M Source/WebCore/platform/graphics/transforms/TransformationMatrix.cpp

  Log Message:
  -----------
  Hit testing on element with 180deg flip inside preserve-3d not finding correct element.
https://bugs.webkit.org/show_bug.cgi?id=258565
<rdar://111393557>

Reviewed by Simon Fraser.

Floating point precision (using double) meant that sin(180deg) wasn't returning exactly 0.

When combining multiple transforms together using preserve-3d, this meant that layers that are intended to be coplanar
ended up at slightly different depths.

This adds rounding for tiny values to make them exactly zero, so that the layers end up coplanar again, and we hit
test in DOM order for those.

* LayoutTests/transforms/3d/hit-testing/hit-preserves-3d-3-expected.txt: Added.
* LayoutTests/transforms/3d/hit-testing/hit-preserves-3d-3.html: Added.
* Source/WebCore/platform/graphics/transforms/TransformationMatrix.cpp:
(WebCore::roundEpsilonToZero):
(WebCore::TransformationMatrix::rotate3d):
(WebCore::TransformationMatrix::rotate):

Canonical link: https://commits.webkit.org/266237@main