Bug 55734

Summary: REGRESSION (r72141): Acid3 rendering is not pixel perfect.
Product: WebKit Reporter: Andy Estes <aestes>
Component: Layout and RenderingAssignee: Nobody <webkit-unassigned>
Status: RESOLVED FIXED    
Severity: Normal CC: aestes, hyatt, mitz
Priority: P2 Keywords: HasReduction, InRadar, Regression
Version: 528+ (Nightly build)   
Hardware: PC   
OS: OS X 10.5   
URL: http://acid3.acidtests.org/
Attachments:
Description Flags
WebKit rendering of Acid3
none
Reference rendering
none
WebKit rendering of Acid3
none
Reference rendering
none
Reduction
none
Patch mitz: review+

Andy Estes
Reported 2011-03-03 17:38:21 PST
Created attachment 84665 [details] WebKit rendering of Acid3 Our Acid3 rendering no longer matches the reference image pixel-for-pixel after <http://trac.webkit.org/changeset/72141>. It appears that the "100/100" text is a pixel higher in our rendering than it is in the reference image. See the attached screenshots.
Attachments
WebKit rendering of Acid3 (deleted)
2011-03-03 17:38 PST, Andy Estes 		no flags
Details
Reference rendering (deleted)
2011-03-03 17:38 PST, Andy Estes 		no flags
Details
WebKit rendering of Acid3 (43.29 KB, image/png)
2011-03-03 18:06 PST, Andy Estes 		no flags
Details
Reference rendering (43.15 KB, image/png)
2011-03-03 18:07 PST, Andy Estes 		no flags
Details
Reduction (650 bytes, text/html)
2011-04-11 14:15 PDT, Andy Estes 		no flags
Details
Patch (20.53 KB, patch)
2011-04-14 03:33 PDT, Andy Estes 		mitz: review+
DetailsFormatted DiffDiff
Show Obsolete (2) View All Add attachment proposed patch, testcase, etc.
Andy Estes
Comment 1 2011-03-03 17:38:39 PST
Created attachment 84666 [details] Reference rendering
Andy Estes
Comment 2 2011-03-03 17:40:02 PST
<rdar://problem/9084992>
William Siegrist
Comment 3 2011-03-03 18:02:03 PST
The content of attachment 84665 [details] has been deleted by William Siegrist <wsiegrist@apple.com> who provided the following reason: Deleted per request from Andy Estes The token used to delete this attachment was generated at 2011-03-03 18:01:27 PST.
William Siegrist
Comment 4 2011-03-03 18:02:16 PST
The content of attachment 84666 [details] has been deleted by William Siegrist <wsiegrist@apple.com> who provided the following reason: Deleted per request from Andy Estes The token used to delete this attachment was generated at 2011-03-03 18:02:12 PST.
Andy Estes
Comment 5 2011-03-03 18:06:48 PST
Created attachment 84670 [details] WebKit rendering of Acid3
Andy Estes
Comment 6 2011-03-03 18:07:32 PST
Created attachment 84671 [details] Reference rendering
Andy Estes
Comment 7 2011-04-11 14:15:12 PDT
Created attachment 89085 [details] Reduction
Andy Estes
Comment 8 2011-04-11 20:54:15 PDT
I took a look at it for an hour or so. It seems like this is specific to the combination of having 0 font-size and 0 line-spacing, and due to this I think we compute a bogus descent when looking at the root linebox (1px ascent, -1px descent). It doesn't seem right that a 0px font with 0 leading should have an ascent.
Andy Estes
Comment 9 2011-04-14 03:33:41 PDT
Created attachment 89552 [details] Patch
mitz
Comment 10 2011-04-14 11:03:06 PDT
Comment on attachment 89552 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=89552&action=review > Source/WebCore/css/CSSStyleSelector.cpp:6808 > + if (fabsf(specifiedSize - 0.0f) < std::numeric_limits<float>::epsilon()) Looks good, but why is it necessary to subtract 0?
Andy Estes
Comment 11 2011-04-14 12:00:30 PDT
(In reply to comment #10) > (From update of attachment 89552 [details]) > View in context: https://bugs.webkit.org/attachment.cgi?id=89552&action=review > > > Source/WebCore/css/CSSStyleSelector.cpp:6808 > > + if (fabsf(specifiedSize - 0.0f) < std::numeric_limits<float>::epsilon()) > > Looks good, but why is it necessary to subtract 0? Ah, it isn't! Good call. I can take that out before landing.
Andy Estes
Comment 12 2011-04-14 13:34:39 PDT
Committed r83889: <http://trac.webkit.org/changeset/83889>
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