This comment at the end of LibWeb/HTML/Focus.cpp:
```
// What? It already doesn't have system focus, what possible
// platform-specific conventions are there?
```
Originally followed and referred to this FIXME on line 319:
```
// FIXME: Otherwise, apply any relevant platform-specific conventions
// for removing system focus from topDocument's
// browsing context, and run the focus update steps with old chain,
// an empty list, and null respectively.
```
During the course of #7233, it was accidentally moved and attached
to a different context, following this comment below on line 325:
```
// NOTE: The unfocusing steps do not always result in the focus
// changing, even when applied to the currently focused
// area of a top-level traversable. For example, if the currently
// focused area of a top-level traversable is a
// viewport, then it will usually keep its focus regardless until
// another focusable area is explicitly focused
// with the focusing steps.
```
Rather than move it to the correct place and become its git blame
villain in the process, I once more seek to remove it.
Model "viewport focus" with Document::focused_area == nullptr.
Focus.cpp:
When a blur occurs, remove the document entry from the old chain
before running the focusing steps. This ensures the document atop the
new chain is not discarded. Focus::run_focus_update_steps will then
set focused_area to nullptr, indicating viewport focus.
EventHandler.cpp:
Split hit testing in handle_mousedown. Use an exact hit test for
focus/blur decisions, and a subsequent cursor hit test for
selection/caret.
Update a couple of focus-related spec steps and their implementations.
The most relevant change is that we no longer allow focusing on elements
that return false for `->is_focusable()`, which necessitates fixing a
broken test that tried to `.focus()` on `<div>`s that were not
focusable. That test's output now more accurately reflects the expected
outcome as seen in other browsers.
And make it a DOM::Node, not DOM::Element. This makes everything flow
much better, such as spec texts that explicitly mention "focused area"
as the fact that we don't necessarily need to traverse a tree of
elements, since a Node can be focusable as well.
Eventually this will need to be a struct with a separate "focused area"
and "DOM anchor", but this change will make it easier to achieve that.
The focus chain always consists of newly created GC::Root objects, so
the condition always produced `false`. The fix is to use GC::Root's
overloaded operator== method, which compares the pointers of the stored
type.
This fixes Figma dropdowns and context menus instantly disappearing
upon opening them. This is because they become focused when they insert
them. Because of this bug, it would fire blur events all the way up to
and including the window. Figma listens for the blur event on the
window, and when received, it will instantly hide dropdowns and context
menus. The intention behind this seems to be hiding them when the user
clicks off the browser window, or switches tab.
I believe this is an error in the UI Events spec, and it should be
updated to match the HTML spec (which uses WindowProxy everywhere).
This fixes a bunch of issues already covered by existing WPT tests.
Spec bug: https://github.com/w3c/uievents/issues/388
Note that WebKit has been using WindowProxy instead of Window in
UI Events IDL since 2018:
816158b4aa
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
