AdoptedStyleSheets.cpp still handled CSS-side fallout from adopted sheet
list mutations directly. Move sheet attachment and media-query setup to
a CSS invalidation helper, along with rule-cache invalidation.
The observable array callbacks continue to validate JS values and
same-document construction rules. The helper now owns the CSS work for
when a constructed stylesheet becomes visible to, or is removed from, a
Document or ShadowRoot.
CSSStyleSheet::evaluate_media_queries previously flagged "no recorded
result yet" as a match-state change, so every freshly-loaded sheet
fired MediaQueryChangedMatchState on the first pass through
Document::evaluate_media_rules. For sheets added through
adoptedStyleSheets that piled an extra full-document style invalidation
on top of the AdoptedStyleSheetsList one, recomputing every element a
second time for nothing.
Drop the !has_value() leg so the very first evaluation establishes the
baseline silently. The sheet's rules already entered the cascade through
StyleSheetListAddSheet, AdoptedStyleSheetsList, or invalidate_owners,
each of which performs its own targeted invalidation.
Two callers relied on the implicit "first eval forces a refresh"
behavior to handle freshly-mutated state:
- invalidate_owners resets m_did_match, then leans on the next eval to
repopulate it. With the new semantics it must also re-evaluate the
sheet eagerly so MediaList::matches() and inner @media state are
fresh before the next rule cache build reads them.
- The adoptedStyleSheets on_set callback didn't evaluate at all,
relying on Document::evaluate_media_rules to populate
MediaList::m_matches. That worked accidentally because the false
flip retriggered invalidate_rule_cache after the matches had been
populated. Mirror StyleSheetList::add_sheet by evaluating the sheet
at adopt time so the rule cache build sees the correct match state
even if it runs first (e.g. via a :has() invalidation pass).
Both Chromium and Gecko delay the document's load event for CSS image
resource requests (background-image, mask-image, etc). We now start
fetching CSS image resources as soon as their stylesheet is associated
with a document, rather than deferring until layout. This is done by
collecting ImageStyleValues during stylesheet parsing and initiating
their fetches when the stylesheet is added to the document.
Fixes#3448
Remove 11 heavy includes from Document.h that were only needed for
pointer/reference types (already forward-declared in Forward.h), and
extract the nested ViewportClient interface to a standalone header.
This reduces Document.h's recompilation cascade from ~1228 files to
~717 files (42% reduction). Headers like BrowsingContext.h that were
previously transitively included see even larger improvements (from
~1228 down to ~73 dependents).
Before this change, we've been maintaining various StyleComputer caches
at the document level.
This made sense for old-school documents without shadow trees, since
all the style information was document-wide anyway. However, documents
with many shadow trees ended up suffering since any time you mutated
a style sheet inside a shadow tree, *all* style caches for the entire
document would get invalidated.
This was particularly expensive on Reddit, which has tons of shadow
trees with their own style elements. Every time we'd create one of their
custom elements, we'd invalidate the document-level "rule cache" and
have to rebuild it, taking about ~60ms each time (ouch).
This commit introduces a new object called StyleScope.
Every Document and ShadowRoot has its own StyleScope. Rule caches etc
are moved from StyleComputer to StyleScope.
Rule cache invalidation now happens at StyleScope level. As an example,
rule cache rebuilds now take ~1ms on Reddit instead of ~60ms.
This is largely a mechanical change, moving things around, but there's
one key detail to be aware of: due to the :host selector, which works
across the shadow DOM boundary and reaches from inside a shadow tree out
into the light tree, there are various places where we have to check
both the shadow tree's StyleScope *and* the document-level StyleScope
in order to get all rules that may apply.
Invalidation for adopted style sheets was broken because we had an
assumption that "active" style sheet is always attached to
StyleSheetList which is not true for adopted style sheets. This change
addresses that by keeping track of all documents/shadow roots that own
a style sheet and notifying them about invalidation instead of going
through the StyleSheetList.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
