h6. [[FilterManager]] h6(. » [[FilterManager SWI Calls|SWI Calls]] h6((. » Filter_RegisterRectFilter h2. Filter_RegisterRectFilter h5. (SWI &42644) |_<^. Entry | | |<^. R0 |<^. Pointer to zero terminated filter name| |<^. R1 |<^. Address of [[Pre Rectangle Filter Code]]| |<^. R2 |<^. Value to be passed to R12 | |<^. R3 |<^. Task handle of task to which filter is applied, or 0 for all tasks | |_<^. Exit | |<. All registers preserved| h4. Use The purpose of this call is to add a new [[Wimp_GetRectangle]] filter to the list of pre-filters. This filter is called just before the drawing of a rectangle begins, before the window background has been filled, and before the VDU graphics window has been set up. h4. Notes The address pointed to by R1 will be called whenever the task who's handle is passed in R3 calls [[Wimp_GetRectangle]]. h4. See also * [[Filter_DeRegisterRectFilter]]