Ah, that is the ZBar library at work! ZBar is amazing -- the barcode in the image can be right side up, upside down, diagonal, only fill half the frame, be half covered in shadow... ZBar will still find it and pick it up. It can also recognize and collect multiple barcodes in a single frame.

Heck, the autofocus that mbarcode does (and most other barcode apps do as well) just slows things down; I keep the camera at a fixed focus and just place it over the barcode at about the right distance...