This input event handling change is intended to address the following
design issues:
- Having `DOM::Position` is unnecessary complexity when `Selection`
exists because caret position could be described by the selection
object with a collapsed state. Before this change, we had to
synchronize those whenever one of them was modified, and there were
already bugs caused by that, i.e., caret position was not changed when
selection offset was modified from the JS side.
- Selection API exposes selection offset within `<textarea>` and
`<input>`, which is not supposed to happen. These objects should
manage their selection state by themselves and have selection offset
even when they are not displayed.
- `EventHandler` looks only at `DOM::Text` owned by `DOM::Position`
while doing text manipulations. It works fine for `<input>` and
`<textarea>`, but `contenteditable` needs to consider all text
descendant text nodes; i.e., if the cursor is moved outside of
`DOM::Text`, we need to look for an adjacent text node to move the
cursor there.
With this change, `EventHandler` no longer does direct manipulations on
caret position or text content, but instead delegates them to the active
`InputEventsTarget`, which could be either
`FormAssociatedTextControlElement` (for `<input>` and `<textarea>`) or
`EditingHostManager` (for `contenteditable`). The `Selection` object is
used to manage both selection and caret position for `contenteditable`,
and text control elements manage their own selection state that is not
exposed by Selection API.
This change improves text editing on Discord, as now we don't have to
refocus the `contenteditable` element after character input. The problem
was that selection manipulations from the JS side were not propagated
to `DOM::Position`.
I expect this change to make future correctness improvements for
`contenteditable` (and `designMode`) easier, as now it's decoupled from
`<input>` and `<textarea>` and separated from `EventHandler`, which is
quite a busy file.
There was no need to use FlyString for error messages, and it just
caused a bunch of churn since these strings typically only existed
during the lifetime of the error.
This is a method defined in the WebDriver spec, but requires access to a
bunch of private fields in these classes, so this is implemented in the
same manner as the reset algorithm.
Otherwise, it looks a bit awkward where the cursor position does not
update while the selection is elsewhere.
Note that this requires passing along the raw selection positions from
`set the selection range` to the elements. Otherwise, consider what will
happen if we set the selection start and end to the same value. By going
through the API accessor, we hit the case where the start and end are
the same value, and return the document cursor position. This would mean
the cursor position would not be updated.
The test changes here more closely match what Firefox produces now. It
is not a 100% match; the `select event fired` test case isn't right. The
problem is the event fires for the input element, but we most recently
focused the textarea element. Thus, when we retrieve the selection from
the input element, we return the document's cursor position, which is
actually in the textarea element. The fix will ultimately be to fully
implement the following:
https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#concept-textarea/input-cursor
That is, each input / textarea element should separately track its own
text cursor position.
For both types of elements, `.selectionStart`, `.selectionEnd`,
`.selectionDirection`, `.setSelectionRange()`, `.select()` and the
`select` event are now implemented.
Navigables are re-used for navigations within the same tab. Its current
ownership of the cursor position is a bit ad-hoc, so nothing in the spec
indicates when to reset the cursor, nor do we manually do so. So when a
cursor update happens on one page, that cursor is retained on the next
page.
Instead, let's have the document own the cursor. Each navigation results
in a new document, thus we don't need to worry about resetting cursors.
This also makes many of the callsites feel nicer. We were previously
often going from the node, to the document, to the navigable, to the
cursor. This patch removes the navigable hop.
Now that the implementation is in FormAssociatedElement, the
implementation in HTMLInputElement is effectively just a passthrough,
with some minor differences to handle small behavioural quirks between
the two (such as the difference in nullability of types).
When an element with an ID is added to or removed from the DOM, or if
an ID is added, removed, or changed, then we must reset the form owner
of all form-associated elements who have a form attribute.
We do this in 2 steps, using the DOM document as the messenger to handle
these changes:
1. All form-associated elements with a form attribute are stored on the
document. If the form attribute is removed, the element is removed
from that list as well.
2. When a DOM element with an ID undergoes any of the aforementioned
changes, it notifies the document of the change. The document then
forwards that change to the stored form-associated elements.
This should allow us to add a Element::attribute which returns an
Optional<String>. Eventually all callers should be ported to switch from
the DeprecatedString version, but in the meantime, this should allow us
to port some more IDL interfaces away from DeprecatedString.
These lambdas were marked mutable as they captured a Ptr wrapper
class by value, which then only returned const-qualified references
to the value they point from the previous const pointer operators.
Nothing is actually mutating in the lambdas state here, and now
that the Ptr operators don't add extra const qualifiers these
can be removed.
HTMLObjectElement will need to be both a FormAssociatedElement and a
BrowsingContextContainer. Currently, both of these classes inherit from
HTMLElement. This can work in C++, but is generally frowned upon, and
doesn't play particularly well with the rest of LibWeb.
Instead, we can essentially revert commit 3bb5c62 to remove HTMLElement
from FormAssociatedElement's hierarchy. This means that objects such as
HTMLObjectElement individually inherit from FormAssociatedElement and
HTMLElement now.
Some caveats are:
* FormAssociatedElement still needs to know when the HTMLElement is
inserted into and removed from the DOM. This hook is automatically
injected via a macro now, while still allowing classes like
HTMLInputElement to also know when the element is inserted.
* Casting from a DOM::Element to a FormAssociatedElement is now a
sideways cast, rather than directly following an inheritance chain.
This means static_cast cannot be used here; but we can safely use
dynamic_cast since the only 2 instances of this already use RTTI to
verify the cast.
This makes it available for all form associated elements and not just
select and input elements. It also makes it more spec compliant,
especially around the form attribute.
The main thing missing is re-associating form elements with a form
attribute when the form attribute changes or an element with an ID
is inserted/removed or has its ID changed.
The new event target implementation requires us to downcast an
EventTarget to a FormAssociatedElement to check if the current Element
EventTarget has a form owner to setup a with scope for the form owner.
This also makes all form associated elements inherit from
FormAssociatedElement where it was previously missing.
https://html.spec.whatwg.org/#form-associated-element
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 *
HTMLInputElement now inherits from FormAssociatedElement, which will
be a common base for the handful of elements that need to track their
owner form (and register with it for the form.elements collection.)
At the moment, the owner form is assigned during DOM insertion/removal
of an HTMLInputElement. I didn't implement any of the legacy behaviors
defined by the HTML parsing spec yet.
