If `load_document()` is called with a response that has a mime type we
can't use to build a document, we should return nullptr as the spec
says, instead of crashing. Also we should not crash if error happened
during parsing.
This fixes issue reproducing with following steps:
1. Node::insert_before() adopts a node into another document.
2. Node::insert_before() runs insertion steps for adopted node (adopted
node style is not invalidated yet).
3. Insertion steps execute spin_until() on event loop.
4. The next task on event loop does Document::update_style() which
requires layout tree rebuild.
5. Layout tree rebuild fails because there is a node with invalidated
style.
These are required for porting over Document from DeprecatedString to
String. We unfortunately can't port this completely over yet as
ParentNode is included by the Element IDL interface, which has not yet
been ported over from DeprecatedString.
Most events on a slottable are composed, meaning they propagate from the
slottable and through its shadow tree before bubbling up to the parent
of the slottable.
This implements looking up a slottable's assigned slot, and a slot's
list of assigned slottables. For the latter, only unflattened lookups
are implemented so far.
This implements automatic slottable assignment by way of hooking into
the element attribute change steps. When the `name` attribute of a slot
or the `slot` attribute of a slottable changes, assignment is performed.
This implements manual slottable assignment by way of HTMLSlotElement's
`assign` API. This includes all of the slottable-related AOs needed to
perform the assignment.
A slottable is either a DOM element or a DOM text node. They may be
assigned to slots (HTMLSlotElement) either automatically or manually.
Automatic assignment occurs by matching a slot's `name` attribute to
a slottable's `slot` attribute. Manual assignment occurs by using the
slot's (not yet implemented) `assign` API.
This commit does not perform the above assignments. It just sets up the
slottable concept via IDL and hooks the slottable mixin into the element
and text nodes.
This is similar to the run activation behavior in that elements may
define these steps themselves. HTMLSlotElement is one such element. The
existing (ad-hoc) Element::attribute_changed() method is not sufficient
there as the steps require knowledge of the attribute's old value and
its namespace, which this extension provides.
Unlike the run activation behavior, we store these steps in a list. An
element may end up defining multiple attribute change steps. For example
all DOM elements must define steps to handle the "slot" attribute, and
HTMLSlotElement must define steps to handle the "name" attribute.
This is a `<display-inside>` keyword added by the MathML spec, and has
the rough meaning of "display in the default way". It enables the
standard layout rules for each MathML element (and is ignored for
anything that isn't a MathML element).
I believe we'll need an actual MathML formatting context to do the
layout correctly, but we can at least support a couple of elements that
behave the same as HTML ones.
These functions are required in the porting of the DocumentFragment
interface from DeprecatedString to String. Unfortunately since
ParentNode is used by Document, we can't fully remove the deprecated
versions of these functions yet.
