As part of the ongoing effort to remove the `_proto: *Parent` field,
TaggedOpaque.fromJS is now offset based. Technically this should perform better
since we're no longer walking through pointers. But the real goal is that we
can now start removing _proto fields.
But, for fromJS to be offset-based, we had to make sure every prototype chain
was a contiguous allocation. The Factory did this, but not everything used the
factory. Now, everything does. This change alone, without the fromJS change,
made every WebAPI allocation more consistent.
Ultimately, our goal is to remove the `_proto: *Field`. That would save 24
bytes per Text node (or Element, ...). Large websites have 20K+ nodes, so we're
talking 300-500KB savings.
ef756b0c96 was the first phase of this. This is
the second, and it's targetting at CData for a simple reason: CData currently
has an optimization that makes removal of `_proto: *Field` difficult: it
directly embeds its empty types (most notably, Text). Zig's @offsetOf doesn't
work on tagged unions, so we'd have to jump through hoops to figure it out (it
is doable though). Also, CData has a "incorrect" flattened CDATASection
specifically so that Text doesn't inherit a _type union..so that's another
problem.
The solution is to move to bare unions, which allows us to use our Factory
to control the layout of the CData and thus have predictable offsets.
CData is now an inconsistent with the rest, but, at the very least, all Node
types will move in this direction.
This is groundwork for eventually removing the _proto: *X` field from some
types (in order to save 8 bytes per, e.g. Node). For now, all `_proto: *X`
fields are untouched, BUT, all compile-time chain walking now happens against
this new declaration.
Builds on top of the excellent https://github.com/lightpanda-io/browser/pull/3072
1 - HTMLAllCollection now composes NodeLive to get the performance benefit
2 - NodeLive now also optimizes for same-index access, e.g. x[i].a, x[i].b.
3 - NodeLive and RadioNodeList now don't lose their position when different
operations types are mixed (e.g. next() wit getAtIndex())
Karl Seguin