|Summary:||[CSS Blending] Rendering defects when using background-blend-mode on a radial-gradient background image|
|Product:||WebKit||Reporter:||Ion Rosca <rosca>|
|Component:||Layout and Rendering||Assignee:||Nobody <webkit-unassigned>|
|Severity:||Normal||CC:||cabanier, dino, mihnea, simon.fraser, WebkitBugTracker|
|Version:||528+ (Nightly build)|
|Bug Depends on:|
Description Ion Rosca 2014-06-13 01:20:24 PDT
Rendering defects when using background-blend-mode on a radial-gradient background image. It looks like the initial backdrop for background blending is not initialized properly and blending is done on top of a layer with misc color information. Other possible consequence of this bug is that when using multiple radial-gradient background layers, only the top layer will be visible. http://codepen.io/adobe/full/8a939a42e4d0fd604790b676611a9006
Comment 3 Ion Rosca 2014-06-16 08:14:29 PDT
Created attachment 233159 [details] Screenshot blending on body
Comment 5 Ion Rosca 2014-06-16 09:20:06 PDT
I did a bit of investigation and it might be a CG issue. I'll describe the attached tests and what happens. "Test with body" * html: the body element has a background color (aqua), a radial-gradient image (a yellow oval) and background-blend-mode. * result: the yellow oval drawn over a background being random content from other tabs (see "Screenshot blending on body") "Test with divs" * html: div elements have background color (aqua), radial-gradient image (yellow circle) and background-blend-mode. * result: almost all divs (except those having normal and screen blend modes) contain a yellow circle on a white background. Debugging: * Everything up to CGContextDrawRadialGradient paints correctly (the aqua background color). * calling any CGContextFillRect function right before CGContextDrawRadialGradient will have no effect, because the latter replaces everything on the viewport. * calling CGContextFillRect with a red color right after CGContextDrawRadialGradient will draw the red rectangle, blending it correctly with the yellow gradient and other content in the viewport. Exceptions: * I could not reproduce "Test with body" on Safari 8, Mac OS 10.10, but "Test with divs" is still there. * Screen blend mode works everywhere. * Adding a css border on divs having background-blend-mode in the "Test with divs" file fixes the issue for this test case. * It works correctly in minibrowser.
Comment 6 Simon Fraser (smfr) 2014-06-16 11:11:53 PDT
Seems like a bug in Core Graphics accelerated drawing code.
Comment 7 Simon Fraser (smfr) 2014-06-16 11:13:57 PDT
Does this only happen with gradients, or other background images too?
Comment 8 Ion Rosca 2014-06-16 12:13:41 PDT
This happens only with *radial* gradients.
Comment 9 Ion Rosca 2014-09-18 06:23:24 PDT
I still can see this bug on Safari 8. I reported it at bugreport.apple.com as Problem #18379644.