Revision 093b0b3d5d041c16ef342790acaf3e9c1b5e01e6 authored by Hayato Ito on 28 March 2018, 12:08:08 UTC, committed by Chromium WPT Sync on 28 March 2018, 12:08:08 UTC
For the purpose of rendering, Blink must calculate all pending slot assignments before UpdateStyle phase. Unless that, a recursive RecalcStyle() may not traverse a node which should be re-attached. e.g. Suppose the following tree, where #d1 is assigned to a slot. host ├──/shadow-root │ └── slot name=s1 └── div id=d1 slot=s1 Then, we change #d1's slot attribute to s2, like: > document.querySelector('#d1').setAttribute('slot', 's2'); host ├──/shadow-root │ └── slot name=s1 └── div id=d1 slot=s2 In this case, #d1 should be removed from a LayoutTree. In other words, Blink has to reattach #d1 somehow. However, if we don't recalc a slot assignment for the shadow tree before UpdateStyle, a recursive RecalcStyle never traverses the sub-tree because child-needs-style-recalc flag is not set for the node (and its ancestor nodes). A flag should be set as a result of slot assignment recalc. Thanks to the Incremental Shadow DOM, a slot assignemt recalc now becomes a local operatoin on each shadow tree, rather than one global operation for every shadow trees. We don't need to traverse a composed tree to recalc all. We can recalc a slot assignment for each shadow tree directly, without traversing a composed tree. For a shadow tree which is not connected, we don't need to recalc its slot assignment before UpdateStyle because such a shadow tree shouldn't have any effect on rendering. Lazy slot assignment recalc is enough for such a shadow tree. This CL doesn't introduce any optimization to minimize the number of to-be-reattached nodes. I'll optimize that as a next task. I'll use a sort of dynamic programming there, as I did at https://chromium-review.googlesource.com/c/chromium/src/+/535493 for non-Incremental Shadow DOM. Except for the performance, this CL should be the last part of Incremental Shadow DOM from the external behavior's perspective. Style and Layout should work correctly after this CL, even with Incremental Shadow DOM. BUG=776656 Change-Id: Id18e87ff59d92863c68c571e7db09253c08aa91f Reviewed-on: https://chromium-review.googlesource.com/964062 Reviewed-by: Takayoshi Kochi <kochi@chromium.org> Reviewed-by: Rune Lillesveen <futhark@chromium.org> Commit-Queue: Hayato Ito <hayato@chromium.org> Cr-Commit-Position: refs/heads/master@{#546458}
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