[Webkit-unassigned] [Bug 91058] New: Modifying an attribute for which there is a selector in html.css does not cause a style recalc

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=91058

           Summary: Modifying an attribute for which there is a selector
                    in html.css does not cause a style recalc
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: CSS
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: falken at chromium.org
                CC: ojan at chromium.org
            Blocks: 90931


Modifying an attribute for which there is a selector in html.css does not initially cause a style recalc. But once a recalc is forced (e.g., by zooming in/out or opening debug console), modifying the attribute thereafter will cause the style recalc to happen.

In practice, the bug does not occur in Safari, but it does occur when the layout tests are run. The bug occurs on Chromium in the browser itself and layout tests.

I believe the problem is the Document's StyleResolver does not yet have m_features.attrsInRules populated, so the code in Element::attributeChanged doesn't cause a style recalc. Once the recalc is forced (as mentioned above), the attributeChanged will trigger the recalc.

I discovered this in the patch for bug 90931 (https://bug-90931-attachments.webkit.org/attachment.cgi?id=151653). I tried to come up with a simpler test case, but it seems the relevant attributes in html.css already have special code to trigger a recalc. For example, iframe seamless has code in HTMLIFrameElement::parseAttribute:

  // If we're adding or removing the seamless attribute, we need to force the content document to recalculate its StyleResolver.
  if (contentDocument())
      contentDocument()->styleResolverChanged(DeferRecalcStyle);

I'll see if I can create a simpler test case apart from bug 90931 later.

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