Bug 306936 – REGRESSION (283678@main): WebKit::RemoteImageBufferSet contains duplicate m_previouslyPaintedRect member variable from base class

• Status: RESOLVED
• Resolution: FIXED
• Component: WebKit Process Model

[David Kilzer (:ddkilzer)]

The `m_previouslyPaintedRect` member variable is declared in both `WebKit::ImageBufferSet` (base class) and `WebKit::RemoteImageBufferSet` (subclass), causing the subclass member to shadow the base class member.

Files affected:
- `Source/WebKit/Shared/graphics/ImageBufferSet.h`
- `Source/WebKit/GPUProcess/graphics/RemoteImageBufferSet.h`

Both declare: `std::optional<WebCore::IntRect> m_previouslyPaintedRect;`

This can lead to subtle bugs where code in the base class writes to its member while the subclass reads its own shadowed member (or vice versa).

Regressed in:
    Share code for buffer swapping and copy-forward between RemoteLayerWithInProcessRendering and RemoteImageBufferSet.
    <https://bugs.webkit.org/show_bug.cgi?id=266201>
    <rdar://119474592>
    <https://github.com/WebKit/WebKit/commit/27846c09e4fee72c441c3d78c0c93ed53bae2b2e>

[Radar WebKit Bug Importer]

<rdar://problem/169600253>

[Radar WebKit Bug Importer]

<rdar://problem/169600258>

[David Kilzer (:ddkilzer)]

Pull request: https://github.com/WebKit/WebKit/pull/57848

[EWS]

Committed 306794@main (d96a37b422a9): <https://commits.webkit.org/306794@main>

Reviewed commits have been landed. Closing PR #57848 and removing active labels.