There's a subtle difference here. A "block box" in the spec is a
block-level box, while a "block container" is a box whose children are
either all inline-level boxes in an IFC, or all block-level boxes
participating in a BFC.
Notably, an "inline-block" box is a "block container" but not a "block
box" since it is itself inline-level.
Our "frame" concept very closely matches what the web specs call a
"browsing context", so let's rename it to that. :^)
The "main frame" becomes the "top-level browsing context",
and "sub-frames" are now "nested browsing contexts".
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
This is because it includes the initial node that the function was
called on, which makes it "inclusive" as according to the spec.
This is important as there are non-inclusive variants, particularly
used in the node mutation algorithms.
This also adds an API to Label to determine if the Label itself or its
child TextNode is hovered. This allows ButtonBox to render in a hovered
state when the label is hovered.
A label's format is: <label>Label text</label>
So, a TextNode is created as a child of the Label node, and EventHandler
will send events to the TextNode. This changes TextNode to accept mouse
events if its parent is a Label, and to forward those events upward.
The HTML <label> element is special in that it may be associated with
some other <input> element. When the label element is clicked, the input
element should be activated.
To achieve this, a LableableNode base class is introduced to provide an
interface for "labelable" elements to handle mouse events on their
associated labels. This not only allows clicking the label to activate
the input, but dragging the mouse from the label to the input (and vice-
versa) while the mouse is clicked will also active the label.
As of this commit, this infrastructure is not hooked up to any elements.
