188060 2018-07-26 08:59:52 -0700 SVG text on a path with a gradient fill is very slow to render 2018-07-28 15:15:45 -0700 1 1 1 Unclassified WebKit SVG WebKit Nightly Build Unspecified Unspecified NEW InRadar P2 Normal --- 1 simon.fraser webkit-unassigned dino sabouhallawa simon.fraser webkit-bug-importer zimmermann oldest_to_newest 1445432 0 345849 simon.fraser 2018-07-26 08:59:52 -0700 Created attachment 345849 Testcase (hangs!) The attached file causes a webcontent hang. Lots of CPU time under: 2035 WebCore::RenderLineBoxList::paint(WebCore::RenderBoxModelObject*, WebCore::PaintInfo&, WebCore::LayoutPoint const&) const (in WebCore) + 870 [0x108234cf6] 2035 WebCore::SVGRootInlineBox::paint(WebCore::PaintInfo&, WebCore::LayoutPoint const&, WebCore::LayoutUnit, WebCore::LayoutUnit) (in WebCore) + 276 [0x1083a8bf4] 1990 WebCore::SVGInlineFlowBox::paint(WebCore::PaintInfo&, WebCore::LayoutPoint const&, WebCore::LayoutUnit, WebCore::LayoutUnit) (in WebCore) + 100 [0x1095f29a4] ! 1989 WebCore::SVGInlineTextBox::paint(WebCore::PaintInfo&, WebCore::LayoutPoint const&, WebCore::LayoutUnit, WebCore::LayoutUnit) (in WebCore) + 865 [0x1083a9021] ! : 1989 WebCore::SVGInlineTextBox::paintText(WebCore::GraphicsContext&, WebCore::RenderStyle const&, WebCore::RenderStyle const&, WebCore::SVGTextFragment const&, bool, bool) (in WebCore) + 469 [0x1095f7295] ! : 1947 WebCore::SVGInlineTextBox::paintTextWithShadows(WebCore::GraphicsContext&, WebCore::RenderStyle const&, WebCore::TextRun&, WebCore::SVGTextFragment const&, unsigned int, unsigned int) (in WebCore) + 481 [0x1095f78b1] ! : | 1931 WebCore::RenderSVGResourceGradient::postApplyResource(WebCore::RenderElement&, WebCore::GraphicsContext*&, WTF::OptionSet<WebCore::RenderSVGResourceMode>, WebCore::Path const*, WebCore::RenderSVGShape const*) (in WebCore) + 685 [0x1095e451d] ! : | + 1931 WebCore::ImageBufferData::~ImageBufferData() (in WebCore) + 99 [0x1093b06e3] ! : | + 1931 WebCore::GraphicsContext::~GraphicsContext() (in WebCore) + 18 [0x109367042] ! : | + 1931 WebCore::GraphicsContext::platformDestroy() (in WebCore) + 34 [0x1081dbee2] and huge memory use (> 1GB). 1445436 1 webkit-bug-importer 2018-07-26 09:05:14 -0700 <rdar://problem/42625890> 1445464 2 sabouhallawa 2018-07-26 10:31:59 -0700 I did not see a hang when I opened the attached test case in either WK1 or WK2, WebKit is just extremely slow. After few seconds, I could see the path text filed with gradient as expected and I could even select the text and interact with the Mini-Browser UI but with a large delay. I did not see a huge memory allocation when opening this file. All I saw was allocation of 35MB. When opening the attached test case in Chrome, the text shows a lot faster and the selection is drawn instantaneously. 1446019 3 simon.fraser 2018-07-28 15:13:04 -0700 For text on a path, we split the text into text fragments, each of which is one glyph. For each fragment (including whitespace?) we run through RenderStyle::paintTypesForPaintOrder(), each of which hits RenderSVGResourceGradient::postApplyResource() which does the gradient fill, and each gradient fill involves rendering to an image buffer and clipping. That's a lot of work! 1446020 4 simon.fraser 2018-07-28 15:14:52 -0700 Optimization thoughts: * paint all the text for one path in one go, doing the gradient fill and clip once. * avoid doing work for whitespace-only text fragments * cache the gradient rendering * optimize away 'paintOrder' paths that will paint nothing 345849 2018-07-26 08:59:52 -0700 2018-07-26 08:59:52 -0700 Testcase (hangs!) 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