Re: Firefox field autocomplete drop-down menu annoying problem

> Does anyone know what _NET_FRAME_EXTENTS is supposed to mean?

It is used to notify the client about the width(s) of the
window decoration added by the window manager.

https://standards.freedesktop.org/wm-spec/wm-spec-latest.html

  A Client whose window has not yet been mapped can request
  of the Window Manager an estimate of the frame extents it
  will be given upon mapping. To retrieve such an estimate,
  the Client MUST send a _NET_REQUEST_FRAME_EXTENTS message
  to the root window. The Window Manager MUST respond by
  estimating the prospective frame extents and setting the
  window's _NET_FRAME_EXTENTS property accordingly. The Client
  MUST handle the resulting _NET_FRAME_EXTENTS PropertyNotify
  event. So that the Window Manager has a good basis for
  estimation, the Client MUST set any window properties it
  intends to set before sending this message. The Client MUST
  be able to cope with imperfect estimates.

  Rationale: A client cannot calculate the dimensions of
  its window's frame before the window is mapped, but some
  toolkits need this information. Asking the window manager
  for an estimate of the extents is a workable solution. The
  estimate may depend on the current theme, font sizes or
  other window properties. The client can track changes to
  the frame's dimensions by listening for _NET_FRAME_EXTENTS
  PropertyNotify events.