[webkit-changes] [WebKit/WebKit] 45759e: Creating a transparency layer to draw a single ima...

[mattwoodrow]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 45759e33816f429a82e7b53b122abb0c579a45a8
      https://github.com/WebKit/WebKit/commit/45759e33816f429a82e7b53b122abb0c579a45a8
  Author: Matt Woodrow <mattwoodrow at apple.com>
  Date:   2023-04-17 (Mon, 17 Apr 2023)

  Changed paths:
    M Source/WebCore/rendering/RenderLayer.cpp
    M Source/WebCore/rendering/RenderLayer.h
    M Source/WebCore/rendering/RenderLayerBacking.cpp

  Log Message:
  -----------
  Creating a transparency layer to draw a single image with opacity can be slow.
https://bugs.webkit.org/show_bug.cgi?id=24438
<rdar://103334931>

Reviewed by Dean Jackson.

This detects the case where we want to create a transparency layer, but the only contents that
will be drawn is a single bitmap image. We can instead just set the alpha on the GraphicsContext
and save the transparency layer (as well as the save/restore pair and the clip).

This could be extended in the future to detect more cases where we will only do a single draw call
within the transparency layer.

* Source/WebCore/rendering/RenderLayer.cpp:
(WebCore::RenderLayer::beginTransparencyLayers):
(WebCore::RenderLayer::paintLayerContents):
(WebCore::RenderLayer::calculateClipRects const):
* Source/WebCore/rendering/RenderLayer.h:
(WebCore::RenderLayer::paintsWithTransparency const):
(WebCore::RenderLayer::canPaintTransparencyWithSetOpacity const):
(WebCore::RenderLayer::hasNonOpacityTransparency const):
* Source/WebCore/rendering/RenderLayerBacking.cpp:
(WebCore::RenderLayerBacking::isBitmapOnly const):

Canonical link: https://commits.webkit.org/263035@main