       The program tksipp is a Tk wish shell containing Tcl-SIPP,
       the photo widget and additional commands to render to  the
       photo widget and save its contents in files.  This section
       describes the commands available for rendering images in a
       Tk application.

       During  the  rendering  of a scene, events will be handled
       via the Tk update mechanism.  The  update  period  may  be
       specified  as  an option to any of the rendering commands.
       The unit of the update period is approximately the  amount
       of  time  taken  to  render one pixel in an average scene.
       The updates themselves occur at points  in  the  rendering
       other  than the direct rendering of the picture, this time
       unit is just a guideline.   Specifying  a  smaller  period
       makes  an application more responsive, specifying a larger
       period speeds the rendering.

       SIPP commands may not be used by events that  occur  while
       rendering, they will return an error if this is attempted.
       The SippInfo command may be used to determine if rendering
       is  in  progress.   An application should normally disable
       any widgets that might invoke a  command  that  result  in
       SIPP commands being executed while a during rendering.  It
       is possible to abort a rendering in progress with the Sip-
       pAbortRender command.

       See  the  photo  widget  manual page for details in how to
       create and manage a photo widget instance.  The photo wid-
       get may have images displayed on it with the SippRender or
       the SippCopy commands.  The widget's blank color is set to
       the background color at the start of the output.
