Abstract: Described is a filtering mechanism/process that selectively controls whether graphics primitives are provided to a given driver. For example, graphics primitives of an accessibility (e.g., magnification) program may be excluded from being obtained by mirror drivers associated with the accessibility programs, so that the mirror drivers receive only the primitives of unmagnified windows. A registration mechanism allows a program to identify its window as being associated with a class of drivers for filtering, and the drivers may identify themselves as being of the class. By maintaining data that associates windows with a class of drivers, when graphics primitives associated with a registered window are received, a filtering operation be activated to determine which graphics primitives are provided to which driver or drivers. Filtering may be by exclusion to prevent certain primitives from being obtained by excluded drivers, or by inclusion whereby only included drivers receive certain primitives.

Abstract: Described is an engine and API that couples an application program to an effects program such as a magnification program. For example, source content may be magnified for viewing in an output region. Magnification may be accomplished by identifying a magnification window to the magnification engine, a source region to magnify, a magnification transform, and possibly filtering criteria, such as any windows to include or exclude from magnification. A request to display a region of displayed graphics as modified by a transform may be received, and when graphics commands corresponding to that region are received, the graphics commands are processed to show a transformed representation of the region. The engine and API may work with immediate mode graphics primitives (e.g., GDI commands) and retained mode graphics primitives (e.g., primitives corresponding to a rendering tree; a composition engine composes the output, including any magnified output.

Abstract: Described is a context map that assists users in determining a current location within a source region of a display monitor that is being magnified. The context map comprises a visible image representing a location of the unmagnified region that is being magnified. The visible image may be an indicator such as a pointer, or a reduced-size representation of the desktop with an indicator therein. The visible image may be made to selectively appear, such as by user command. The magnified content may be displayed on one monitor, and the context map on another. The context map alternatively may be on the same monitor, possibly superimposed over some part of the magnified content. The magnification window may move with a pointing device, and the context map may be docked, or displayed over at least part of the floating window such that the context map also moves with it.