# Stable (filter)

The Stable filter is used to mask out changes to its child's preferred size.

Shape
  The max and min are its child's max and min size. The preferred size is the projection of its own size into the child's size range. Its own size is its current size if this is non-empty, or its last non-empty size otherwise.
Notes
  A Stable is part of a ZChassis. In this way, whenever the user changes the size of a subwindow, that size will take precedence over any new size preferences given by the ZChassis's child. A Stable is also inserted automatically by Trestle whenever a window is installed.