void addBlock(RenderableBlock block) {
// make sure block isn't a null instance
if (block == null || Block.NULL.equals(block.getBlockID())) return;
addToBlockLayer(block);
block.setHighlightParent(this);
block.addComponentListener(this);
}
void removeBlock(RenderableBlock block) {
// make sure block isn't a null instance
if (block == null || Block.NULL.equals(block.getBlockID())) return;
// remove from canvas graphically
this.remove(block);
block.setHighlightParent(this);
block.removeComponentListener(this);
}