[comp.sys.mac.programmer] Garbage in the window/pane using bitmaps

dfranck@x102c.harris-atd.com (franck deniz 01591) (05/17/91)

Thanks to everyone who replied to my gopher/dawdle questions last time --
I used all of your suggestions!

Now I have a problem concerning bitmaps... I am now trying to 
"randomly" (using a chore/dawdle) print lines to a pane with a bitmap.
I have a Draw() and DoDawdle() ( a chore) method that I think should
take care of it, but I am getting a bunch of "noise" on the bottom
of my window. Plus, I only occasionally get my line.  Since I dont 
know if I am explaining this correctly, here is the code:

Draw()
{
  Rect NSpecGrid;
 
  SpecGrid = GetPicture(129);   /* instance variable holding resource */
  this->getAperture(&NSpecGrid); /* this is the pane object/screen */
  itsBitMap->BeginDrawing();
  DrawPicture(SpecGrid, &NSpecGrid);
  itsBitMap->EndDrawing();
  itsBitMap->CopyFrom(&NSpecGrid, &NSpecGrid, NULL);
}

DoDawdle(long *maxSleep);
{ 
  Rect NSpecGrid;

  *maxSleep = 12;
  Prepare();
  itsBitMap->CopyTo(&NSpecGrid,&NSpecGrid,NULL); /* added this in desperation*/
           /* ^^^ this also cleaned up a "noise" square in the upper left */  
  itsBitMap->BeginDrawing();
  DrawPicture(SpecGrid, &NSpecGrid);
  MoveTo(500,100);  /* this is the line */
  Line(0,50);
  itsBitMap->EndDrawing();
  Prepare();
  itsBitMap->CopyFrom(&NSpecGrid, &NSpecGrid, NULL);

}

Any suggestions as to why garbage appears as a result of this would be
GREATLY appreciated!

Deniz Franck