[webkit-changes] [WebKit/WebKit] f0109a: Put post-processed pixel buffer at correct location

[Matthew Finkel]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: f0109a1cfaae333c56ef9f5c93b3bc75b0fb9b3e
      https://github.com/WebKit/WebKit/commit/f0109a1cfaae333c56ef9f5c93b3bc75b0fb9b3e
  Author: Matthew Finkel <sysrqb at apple.com>
  Date:   2023-05-10 (Wed, 10 May 2023)

  Changed paths:
    M Source/WebCore/html/CanvasBase.cpp

  Log Message:
  -----------
  Put post-processed pixel buffer at correct location
https://bugs.webkit.org/show_bug.cgi?id=256563
rdar://109124810

Reviewed by Kimmo Kinnunen.

The call to ImageBuffer::putPixelBuffer may put the buffer at the wrong
location in the backend buffer if m_postProcessDirtyRect has a location at a
negative offset. This can happen, for example, if fillText draws outside the
bounds of the canvas. Therefore in this change we clip the dirty rect to
the bounds of the canvas, and we use the rect's location as the offset value.

* Source/WebCore/html/CanvasBase.cpp:
(WebCore::CanvasBase::postProcessDirtyCanvasBuffer const):

Canonical link: https://commits.webkit.org/263939@main