[webkit-changes] [WebKit/WebKit] f5aa57: [Cocoa] Add a heuristic to detect and sample color...

[Wenson Hsieh]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: f5aa57b6b88aa2ffca5cd1457a45c56723031bcd
      https://github.com/WebKit/WebKit/commit/f5aa57b6b88aa2ffca5cd1457a45c56723031bcd
  Author: Wenson Hsieh <wenson_hsieh at apple.com>
  Date:   2025-02-14 (Fri, 14 Feb 2025)

  Changed paths:
    M Source/WebCore/Headers.cmake
    M Source/WebCore/WebCore.xcodeproj/project.pbxproj
    M Source/WebCore/page/LocalFrameView.cpp
    M Source/WebCore/page/LocalFrameView.h
    M Source/WebCore/page/PageColorSampler.cpp
    M Source/WebCore/page/PageColorSampler.h
    A Source/WebCore/platform/FixedContainerEdges.h

  Log Message:
  -----------
  [Cocoa] Add a heuristic to detect and sample colors in fixed-position elements at the edges of the viewport
https://bugs.webkit.org/show_bug.cgi?id=287690
rdar://144839983

Reviewed by Abrar Rahman Protyasha.

Work towards rdar://144839983; see below for more details.

* Source/WebCore/Headers.cmake:
* Source/WebCore/WebCore.xcodeproj/project.pbxproj:
* Source/WebCore/page/LocalFrameView.cpp:
(WebCore::LocalFrameView::fixedContainerEdges const):

Add a helper method that returns the set of `FixedContainerEdges` (see the new header below), by
first hit-testing around all 4 edges of the layout viewport in search of elements with fixed-
position ancestors in the render tree; for each edge with a fixed ancestor, we then use the new
page color sampling helper below to extract the predominant color.

* Source/WebCore/page/LocalFrameView.h:
* Source/WebCore/page/PageColorSampler.cpp:
(WebCore::PageColorSampler::predominantColor):

Add a helper method that samples the predominant color in the given rect (in absolute coordinates)
by taking a snapshot, building a histogram of color frequencies, and checking whether the number of
similar colors represents a majority of all sampled colors.

* Source/WebCore/page/PageColorSampler.h:
* Source/WebCore/platform/FixedContainerEdges.h: Added.

Add a helper class, `FixedContainerEdges`, that represents two pieces of information about each of
the 4 edges of the layout viewport (top, left, bottom, right):

-   Whether there's a fixed-position container near that edge.
-   A sampled predominant color, or the invalid color if none is detected (e.g. due to too many
    different colors).

Canonical link: https://commits.webkit.org/290411@main



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