The Patent Office and the courts have had a difficult time with computer software. The Patent Office refused until recently to hire Computer Science graduates as examiners, and in any case does not offer competitive salaries for the field. Their task is made more difficult because many commonly-used software techniques do not appear in the scientific literature of computer science.
Computer scientists know many techniques that can be generalized to widely varying circumstances.
But the Patent Office seems to believe that each separate use of a technique is a candidate for a new patent. Scrolling and subwindows are well-known techniques, but combining them is now apparently illegal. The granting of a patent by the Patent Office carries a presumption in law that the patent is valid. Patents for well-known techniques that were in use many years before the patent application have been upheld by federal courts. It can be hard to prove a technique was well known at the time in question.