Bug 54507

Summary:	WebKit regression found in Cairo commit 51594d9
Product:	cairo	Reporter:	Sudarsana Nagineni <sudarsana.nagineni>
Component:	general	Assignee:	Carl Worth <cworth>
Status:	RESOLVED NOTOURBUG	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	blocker
Priority:	medium	CC:	dominik.rottsches
Version:	1.12.2
Hardware:	Other
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:
Attachments:	Test failure diff Test results with the failure Simplified test case cairo-trace of the test case

Description Sudarsana Nagineni 2012-09-04 19:28:42 UTC

Created attachment 66625 [details]
Test failure diff

Running latest WebKit GTK/EFL (r127473) against cairo git revision 51594d9 causes a regression when running the following webkit test to ensure correct behavior of canvas with fillRect using a gradient fillStyle and a shadow.

Test case: http://trac.webkit.org/export/127473/trunk/LayoutTests/fast/canvas/canvas-fillRect-gradient-shadow.html

I suspect that cairo matrix to pixman transform/offset conversion in _cairo_matrix_to_pixman_matrix_offset() causes this regression.

The test results with the failure can be seen in the attachments.

Comment 1 Sudarsana Nagineni 2012-09-04 19:34:44 UTC

Created attachment 66627 [details]
Test results with the failure

Comment 2 Chris Wilson 2012-09-04 19:36:02 UTC

Test case works under firefox... Is there any chance you can simplify it to the single failure to make extraction into C easier?

Comment 3 Sudarsana Nagineni 2012-09-04 20:16:44 UTC

Created attachment 66630 [details]
Simplified test case

Thanks for the quick look, Chris. I modified the test case to reproduce only the actual failure.

Comment 4 Chris Wilson 2012-09-24 08:11:10 UTC

The test case wasn't as simple as I was hoping for. :)

Can you run the test case locally whilst capturing the cairo calls:

  cairo-trace eflwebkit test.html

you might want to add some obvious fluff calls around the canvas to make the interesting section more clear.

Comment 5 Chris Wilson 2012-09-24 19:27:01 UTC

Created attachment 67642 [details]
cairo-trace of the test case

Having extracted the test case and saved the output to a file, the value of pixel (351, 751) is 0x00ff0000 (that is 100% red, 0% alpha). Yet the test case is reporting 0 red.

Can you enlighten me as to what magic 'ctx.getImageData(351, 751, 1, 1).data' performs?

Comment 6 Chris Wilson 2012-09-25 10:42:16 UTC

ShadowBlur::blurLayerImage() is broken for starters.

Comment 7 Sudarsana Nagineni 2012-09-26 09:45:30 UTC

Thanks, Chris. I will look into the shadowBlur and blur radius handling code in webkit.

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