A Screen Magnifier Using “High Level” Implementation Techniques

This paper presents the architecture of, and the techniques used to build, a screen magnifier for visually impaired people that uses the "high-level" features of the Microsoft Windows operating system. The magnifier uses information from the Desktop Window as its source and overlays this with a topmost, transparent, layered window that contains the magnified image. Issues concerning cursor enlargement, tooltip suppression, and focus tracking are discussed. A stable magnifier results that does not need to use the "dirty" low-level techniques that are typically used to build screen magnifiers. The only known problem of the magnifier is that it fails to suppress the original, unmagnified cursor of the few applications that use custom cursors