The `RecordedNodeValue` struct contains a `GC::Ref` to a DOM node, which
might disappear as a result of a garbage collection. For example, during
the "outdent" command, we record nodes, split the parent of those nodes
potentially resulting in all kinds of DOM changes, and then try to
restore the nodes' values. This caused a crash in the
`editing/run/outdent.html` WPT subtests.
By returning a `ConservativeVector`, we make sure the `GC::Ref` gets
marked during sweeps and nodes do not suddenly disappear.
Noticed while working adjacent to these APIs that we take a Utf16String
and pass it around as a Utf16View, only to re-allocate the Utf16String
in many commands. Let's just pass the string itself around.
Both sides of the Editing internals now have to deal with some awkward
converting between UTF-8 and UTF-16, but the upside is that it
immediately exposed an issue with the `insertText` command: instead of
dealing with code units, it was iterating over code points causing the
selection to be updated only once instead of twice. This resulted in the
final selection potentially ending up in between a surrogate pair.
Fixes#5547 (pasting/typing surrogate pairs).
The algorithm referenced to in the Editing spec whenever they talk about
obtaining the "resolved" style or value is actually implemented in
ResolvedCSSStyleDeclaration, so use that instead of going directly to
the computed styles.
The DOM spec defines what it means for an element to be an "editing
host", and the Editing spec does the same for the "editable" concept.
Replace our `Node::is_editable()` implementation with these
spec-compliant algorithms.
An editing host is an element that has the properties to make its
contents effectively editable. Editable elements are descendants of an
editing host. Concepts like the inheritable contenteditable attribute
are propagated through the editable algorithm.
To facilitate the implementation of "delete" and all associated
algorithms, split off this piece of `Document` into a separate
directory.
This sets up the infrastructure for arbitrary commands to be supported.
