code: public void propagateDirtyRegions (ActiveRepaintManager repmgr, JRootPane root)
      {
          if (_metamgr.needsPaint()) {
              // tell the repaint manager about our raw (unmerged) dirty regions so that it can dirty
              // only components that are actually impacted
              List<Rectangle> dlist = _metamgr.getRegionManager().peekDirtyRegions();
              for (int ii = 0, ll = dlist.size(); ii < ll; ii++) {
                  Rectangle dirty = dlist.get(ii);
                  repmgr.addDirtyRegion(root, dirty.x - root.getX(), dirty.y - root.getY(),
                                        dirty.width, dirty.height);
              }
          }
      }
docs: Called by the {@link FrameManager} to propagate our dirty regions to the active repaint
  manager so that it can repaint the underlying components just prior to our painting our
  media. This will be followed by a call to {@link #paint} after the components have been
  repainted.