Magnification Composite Manager
Published: Jun 22, 2007The Magnification Composite Manager (MCM) is a magnifying tool for the Linux Gnome desktop. Visually-impaired users can use it to enlarge all or a portion of the screen. The user’s preferences are configured in the Gnome control panel for the magnifier, called Gnome Scope (gscope). The magnifier can increase the size of the desktop by a factor of two to 16.
MCM can operate in full-screen, line, lens or docked modes. Full-screen mode magnifies the whole display screen; line mode shows a magnified horizontal strip of the screen; lens mode shows a magnified square region and docked mode sets the magnified view at either the top, bottom, left or right of the screen or at one of the four corners.
The off-screen buffer of the desktop is managed by the magnifier by capturing images from multiple X windows (windows built with the X Window System, commonly called X11 or X) and composing them before returning back to the desktop. MCM uses the new Composite extension of the X Window System display server (Xserver) for handling the off-screen copy of the desktop windows.
The magnifier manages off-screen copies of all the windows on the desktop; it zooms and places them back on top of the desktop screen. If a screen reader is present, it can more accurately move the magnifier’s center of focus via the Assistive Technology Service Provider Interface (ATSPI). Otherwise, the magnifier’s focus follows the keyboard or mouse focus.
George Kraft IV is the technology author and he also leads the Linux Accessibility Project for IBM’s Software.
Source: IBM Alphawork
