28522 2015-04-21 07:27:54 +0000 [Shadow] Cascading for trees of no-inner/outer and no-younger/older relationship 2015-04-28 04:42:25 +0000 1 1 1 Unclassified WebAppsWG HISTORICAL - Component Model unspecified All All RESOLVED WONTFIX P2 normal --- 28552 1 kojiishi dglazkov annevk jackalmage mike public-webapps rune tasak public-webapps-bugzilla oldest_to_newest 119710 0 kojiishi 2015-04-21 07:27:54 +0000 This issue should land on CSS Scoping spec, but I think it's better to discuss here and have some level of common understanding before we go www-style, because complex tree of trees is too much for most members at www-style. If this doesn't look right, please close and I'll go www-style. The Shadow Cascading of CSS Scoping spec[1] defines: * Outer wins if inner/outer * Younger wins if younger/older But Takashi and I are finding a few cases where trees have more complex relationships. We should define how cascading occurs in such cases, which wins, or prohibit. Case 1: Re-distributions By using multiple and nesting together, re-distribution can cause such relationship. Example: http://jsbin.com/wabigi div div SR-OLDER div content SR-NEST-OF-OLDER style ::content * {color:red} content SR-YOUNGER style ::content * {color:green} shadow Case 2: :host and shadow-piercing descendant combinator The combination of :host and shadow-piercing descendant combinator can select descendants of younger/older trees. [1] http://dev.w3.org/csswg/css-scoping/#cascading 119714 1 kojiishi 2015-04-21 07:57:37 +0000 My current opinion is: Case 1: The final destination wins for re-distributions. Case 2: Prohibit this combination. I think the use cases for the shadow-piercing descendant combinator is mostly "html >>>" or "* >>>", IIUC. 119725 2 kojiishi 2015-04-21 13:32:24 +0000 Takashi found another combination that causes cascading from non-parent/younger/older relationship: Case 3: ::content /deep/ 119870 3 kojiishi 2015-04-24 04:11:22 +0000 A previous discussion at www-style here: https://lists.w3.org/Archives/Public/www-style/2015Feb/0026.html 119967 4 kojiishi 2015-04-28 04:42:25 +0000 This is no longer an issue because multiple shadow roots and piercing combinators were both removed.