Today, IBM released a full screen magnifier to IBM's emerging technology alphaWorks site called gScope. gScope is the first full screen magnifier solution on Linux to use of the new composite extension to X. Composite allows for redirecting of drawing commands to an off-screen buffer and then uses a compositing manager to decide how the windows will be arranged on the screen. While this facility can be used to create things like translucent windows it also may be used to allow for fast magnification.
Screen magnifiers on Windows have used drivers to redirect drawing calls into free memory on the card and then perform direct transfers to the screen using memory transfers on the card. This makes screen magnification fast. gScope uses composite to capture drawing calls redirected the desktop to create a managed off-screen buffer of it. gScope then works with the composite manage to copy the end result to the desktop in a magnification operation using the video hardware.
Before composite, magnification was peformed using system memory and the results provided were slower. The new magnifier will allow for magnification levels from 2 to 16. It can operate in full-sceen, line, lens, or docked window modes. In the spirit of open source this will come with source code and documentation. While this is an alpha release it is robust enough to allow distros to pick up the work. Strategically, the best place for this is in the Window manager as there can only be one composite manager running at a time. By providing an open source solution, KDE, Gnome and other UNIX desktop providers may get magnification for low vision users sooner rather than later. This fills a critical gap in an accessible Linux desktop offering.
IBM Emerging Technology Group places open source Linux screen magnifier on alphaWorks
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