[Bug 20354] New: [Shadow]: HOST_RULE should be less than 32.

https://www.w3.org/Bugs/Public/show_bug.cgi?id=20354

            Bug ID: 20354
           Summary: [Shadow]: HOST_RULE should be less than 32.
    Classification: Unclassified
           Product: WebAppsWG
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Component Model
          Assignee: dglazkov@chromium.org
          Reporter: tasak@google.com
        QA Contact: public-webapps-bugzilla@w3.org
            Blocks: 14978

>From the viewpoint of WebKit implementation, HOST_RULE type number should be <
32.
I mean, for example,

"partial interface CSSRule {
-    const unsigned short HOST_RULE = 1001;
+    const unsigned short HOST_RULE = 31;
};"

Because we can use only 5 bits for type number. In WebKit's StyleRuleBase
class:

class StyleRuleBase : public WTF::RefCountedBase {
...
    unsigned m_type : 5;
    signed m_sourceLine : 27;
}

I think, it would be not acceptable to make StyleRuleBase larger. Probably we
have to keep 32 bits (=5+27).
If we change m_sourceLine from 27 bits to 22 bits (1001 < 1024=2^10),
m_sourceLine's max is 4,194,303. I guess, 4,194,303 is a little small for real
world web.

Best regards,
Takashi Sakamoto

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Received on Wednesday, 12 December 2012 07:57:17 UTC