h6. [[Programmer's Reference Manuals]] h6(. » [[List of modules]] h6((. » FilterManager The Filter Manager provides applications with the facility to register pre and post-filters against [[WIMP task|WIMP tasks]]. Filters are useful when a task needs to intercept events that may or may not be under the control of the task. Filters do not need to be applied to a specific task as they can be assigned to respond to all tasks. Each filter is a routine that must have well defined entry and exit conditions. h4. Pre-Filters Pre-filters are called when a task calls the Wimp (e.g. via [[Wimp_Poll]]). They are called before control passes to the Wimp, allowing the filter to adjust the parameters of the call or override it completely. h4. Post-Filters Post-filters are called when the Wimp passes control of execution back to a task. This allows the filter to monitor or adjust the result of a call that the task had made, or perform additional processing such as rendering an image over the top of a window. h4. Details * [[FilterManager Service Calls|Service Calls]] * [[FilterManager SWI Calls|SWI Calls]] * [[FilterManager *Commands|*Commands]]