The routine gSetImageClipMode() determines whether  output (to a bitmap metafile), is clipped to the drawing limits or to one pixel  less than this.
The default mode results in the metafile dimensions being NXPIX+1 by NYPIX +1, but includes all drawing  up to and icluding the specified drawing limits as set by gSetDrawingLimits(). The latter mode (GTRUE), will result in the metafile dimensions being NXPIX by NYPIX, but omit drawing at the extremity of the drawing limits.