[webkit-changes] [WebKit/WebKit] 6d3572: UI-side Compositing: PDF scrollbars are not dragga...

[Richard Robinson]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 6d3572a224f0e70a963e9d00293e2c9562372ff8
      https://github.com/WebKit/WebKit/commit/6d3572a224f0e70a963e9d00293e2c9562372ff8
  Author: Richard Robinson <richard_robinson2 at apple.com>
  Date:   2023-03-23 (Thu, 23 Mar 2023)

  Changed paths:
    M Source/WebKit/WebProcess/Plugins/PDF/PDFPlugin.mm

  Log Message:
  -----------
  UI-side Compositing: PDF scrollbars are not draggable and don't grow when hovered
https://bugs.webkit.org/show_bug.cgi?id=254363
rdar://105908418

Reviewed by Tim Horton.

For some reason, when UI-side compositing is enabled, the scrollbar's layer's backing store
is larger than the layer itself when viewing a zoomed-in PDF. This causes the scrollbar's
appearance's y-value to be offset by some amount.

This PR works around this by clearing the contents of the layer so that CoreAnimation creates
a new backing store whenever the frame's change, which forces the new backing store to have the
correct size.

* Source/WebKit/WebProcess/Plugins/PDF/PDFPlugin.mm:
(WebKit::PDFPlugin::updateScrollbars):

Canonical link: https://commits.webkit.org/262043@main