Bug 68899

Summary: [CG] Both ShadowBlur and CG Shadow are applied to the rect in GraphicsContext::fillRect()
Product: WebKit Reporter: Renata Hodovan <rhodovan.u-szeged>
Component: SVGAssignee: Nobody <webkit-unassigned>
Status: RESOLVED INVALID    
Severity: Normal CC: bfulgham, eric, krit, leviw, simon.fraser, thorton, zherczeg, zimmermann
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
Attachments:
Description Flags
with_contextShadow.png
none
without_contextShadow.png none

Renata Hodovan
Reported 2011-09-27 06:41:02 PDT
Original code: bool drawOwnShadow = !isAcceleratedContext() && hasBlurredShadow(m_state) && !m_state.shadowsIgnoreTransforms; // Don't use ShadowBlur for canvas yet. if (drawOwnShadow) { float shadowBlur = m_state.shadowsUseLegacyRadius ? radiusToLegacyRadius(m_state.shadowBlur) : m_state.shadowBlur; // Turn off CG shadows. CGContextSaveGState(context); CGContextSetShadowWithColor(context, CGSizeZero, 0, 0); ShadowBlur contextShadow(FloatSize(shadowBlur, shadowBlur), m_state.shadowOffset, m_state.shadowColor, m_state.shadowColorSpace); contextShadow.drawRectShadow(this, rect, RoundedRect::Radii()); } CGContextFillRect(context, rect); After some debugging it seems that the shadow applied twice both with ShadowBlur and CGShadow. We halved the rectangle to emphasize this effect: // Was CGContextFillRect(context, rect); FloatRect tmp2 = FloatRect(rect.x() + rect.width() / 4, rect.y() + rect.height() / 4, rect.width() / 2, rect.height() / 2); CGContextFillRect(context, tmp2); We attached two pics. In without_contextShadow.png the drawRectShadow was commented out while it was enabled on with_contextShadow.png. The strange thing was the shadow is still drawn when the drawRectShadow was commented out. Any idea?
Attachments
with_contextShadow.png (7.63 KB, image/png)
2011-09-27 06:41 PDT, Renata Hodovan 		no flags
Details
without_contextShadow.png (5.60 KB, image/png)
2011-09-27 06:42 PDT, Renata Hodovan 		no flags
Details
View All Add attachment proposed patch, testcase, etc.
Renata Hodovan
Comment 1 2011-09-27 06:41:48 PDT
Created attachment 108840 [details] with_contextShadow.png
Renata Hodovan
Comment 2 2011-09-27 06:42:32 PDT
Created attachment 108841 [details] without_contextShadow.png
Tim Horton
Comment 3 2011-09-27 15:33:25 PDT
I'm a bit confused. Where's the testcase; how can I reproduce this? Or is this in code you're currently working on? Anyway, how are you applying the shadow? -webkit-svg-shadow? If it's -webkit-svg-shadow, that gets applied via a transparency layer that gets created (in SVGRenderSupport::prepareToRenderSVGContent) whenever you first hit the -webkit-svg-shadow'd element, so each element has no need to draw its own shadow.
Renata Hodovan
Comment 4 2011-09-29 07:16:52 PDT
(In reply to comment #3) > I'm a bit confused. Where's the testcase; how can I reproduce this? Or is this in code you're currently working on? > Anyway, how are you applying the shadow? -webkit-svg-shadow? If it's -webkit-svg-shadow, that gets applied via a transparency layer that gets created (in SVGRenderSupport::prepareToRenderSVGContent) whenever you first hit the -webkit-svg-shadow'd element, so each element has no need to draw its own shadow. The test case was a reduced version of svg/css/group-with-shadow.svg. It uses -webkit-svg-shadow property. I faced this problem while I was working on a new renderer for SVGElements which painted with the shape's own painter without path's one. So if I tried to fill a rectangle with the platform dependent fillRect() it applied both of the shadows.
Simon Fraser (smfr)
Comment 5 2011-09-30 10:25:30 PDT
Why is SVG different from CSS here? CSS doesn't have this issue.
Renata Hodovan
Comment 6 2011-09-30 11:03:09 PDT
(In reply to comment #5) > Why is SVG different from CSS here? CSS doesn't have this issue. I don't know exactly the reason but it seems that doesn't matter if I turn out the shadow drawing it still will be painted. I guess it maybe related to context redirections...
Dirk Schulze
Comment 7 2014-05-12 06:42:09 PDT
rene, could you upload a test case please? Is this still the case?
Simon Fraser (smfr)
Comment 8 2015-12-04 21:24:48 PST
Still need a testcase.
Brent Fulgham
Comment 9 2022-07-15 14:58:40 PDT
It's difficult to confirm this bug without a test case. We don't believe there is an ongoing issue here. If you do feel there is a problem, please REOPEN this bug and include a test case illustrating the issue.
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