2.2. Screen Readers Interpret the Graphical User INterface as Text

Screen readers are programs that make the user interface accessible For the visually impaired user. A screen reader is a program converting the graphical user interface and its events into synthetic speech and braille (Microsoft 1999, Types of Accessibility Aids). Speech and braille, both of which can be reduced to text, replace the display and the keyboard is used to substitute the mouse.

At the technical level, a screen reader examines the applications running under Windows together with their events. A screen reader must have access to all of the user interface controls including their types and states in the applications being currently executed. The screen reader builds a so called off-screen model out of these controls and interpretes elements of this model to the user. It is also vital to react to changes in keyboard focus when the user moves between the different controls. Surprisingly, the built-in accessibility functions in the Win32 API don't deal with implementing a screen reader at all. In stead they provide access to accessibility related services built into Windows (such as high contrast).

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