Set the dialog to the centered alignment mode.
Let subject's node document be blocked by the modal dialog subject.
Let subject's node document be blocked by the modal dialog subject.
+ +This will cause the focused area of the + document to become inert (unless that currently focused area is a + shadow-including descendant of subject). In such cases, the focus + fixup rule will kick in and reset the focused area of the document to the + viewport for now. In a couple steps we will attempt to find a better candidate to + focus.
+If subject's node document's top layer does not
already contain subject, then HTMLDialogElement : HTMLElement {
If there isn't one of those either, then let control be subject.
Run the focusing steps for control.
Run the focusing steps for control.
+ +If control is not focusable, this will do nothing. For + modal dialogs, this means that any earlier + modifications to the focused area of the document will apply.
+Let topDocument be the active document of control's node document's browsing context's