The basics

• I validated my changes

The details

Resolves

• Fixes Dropdown keyboard nav position moves unexpectedly when scrolling into view #8745
• Fixes Moving mouse out of dropdown or context menu loses focus interfering with keyboard nav #8746

Proposed Changes

This PR updates the menu to check if the pointer has actually moved before selecting the hovered menu item in response to an alleged pointer move event. Previously, it was listening for pointerover events, and selecting the hovered menu item. In the case where the user has their pointer over the menu, and is scrolling through the list of menu items via the up/down arrows, the menu items will scroll into view when the selection reaches the beginning/end of the visible set of menu items. This movement of elements under the pointer causes a pointerover event to fire, even though the pointer has been stationary, which had the effect of jumping the selection backwards to whatever menu item was under the pointer.

Although pointerover events have movementX/movementY properties, these are unpopulated (at least in Chrome), so I changed the code to listen for pointermove instead, which does populate them. This allows checking whether the event was triggered due to movement, and disregarding it if not.

Experimentally, this gives the desired behavior in Chrome/Safari/Firefox: moving the pointer highlights the corresponding menu items, but keyboard navigation takes precedence for navigating through menu items, until such time as the pointer is actually moved.

I also updated the field names to reference "pointer" instead of "mouse" since they were all private.

Additionally, this PR fixes an issue that caused menus to lose focus when the pointer exited their bounds.