$WW,1$$LK,"gr.text_base",A="MN:CGrGlobals"$ must be updated 30fps in your Fs->draw_it() callback. You probably want $LK,"GrPrint",A="MN:GrPrint"$() or just $LK,"Print",A="MN:Print"$(). The $LK,"DolDoc",A="FI:::/Doc/DolDocOverview.DD"$ code takes care of plotting text to $LK,"gr.text_base",A="MN:CGrGlobals"$.
$LK,"GrUpdateTaskWin",A="MN:GrUpdateTaskWin"$() calls $LK,"DocUpdateTaskDocs",A="MN:DocUpdateTaskDocs"$() which calls $LK,"DocRecalc",A="MN:DocRecalc"$() where the document text is plotted into $LK,"gr.text_base",A="MN:CGrGlobals"$. Then, $LK,"GrUpdateTextBG",A="MN:GrUpdateTextBG"$() and $LK,"GrUpdateTextFG",A="MN:GrUpdateTextFG"$() render the $LK,"gr.text_base",A="MN:CGrGlobals"$ onto $LK,"gr.dc2",A="MN:CGrGlobals"$, a raw graphic bitmap.