BEAM SCREEN READER API
Overview of BEAM Screen Reader API
The purpose of the BEAM Screen Reader API (BSRAPI) is to provide a screen
reader with information regarding the graphical user interface (GUI) of
The main features for the BEAM Screen Reader API (BSRAPI) include:
Application GUI independent: The BSRAPI has been made independent on the
particular GUI in use. This will allow functionality with the current GUI
tool kits such as Motif, Xt, KDE, Gnome and TK with an appropriate GUI
tool kit interface module.
Can use information from the tool kit in use or directly from the application.
This enables easy retrofit to existing applications with simple GUI tool
kit library changes. For critical applications, the application can take
over or modify the tool kit interface for a more sophisticated interface.
Can be used with applications not using a GUI such as ASCII terminal based
Independent of the X-Windows system and platform independent.
The BSRAPI system consists a client application shared library, GUI tool
kit interface libraries and a screen reader server module.
When an application is invoked, the GUI tool kit or application initialises
the BSRAPI. This attempts to connect to a screen reader on the host which
is providing the GUI. Once connected the screen reader can ask the application
for information on the GUI using the BSRAPI. It can also ask for events
to be sent on certain conditions, such as a change in keyboard focus.
The GUI is described as a set of generic objects. These can be accessed
either in hierarchical form to match the typical GUI object layout or in
viewable 2D forms. The object types provided include:
||Top level application window
||Displays a label on the screen
||A single line text entry box
||A multiple line text entry box
||A push button
||A toggle button
||A list of items
||A container holding other objects
||A table object
Each object has an application unique id and has a number of attributes.
The Object ID 0 is a special case defining the whole application. Within
this object will be the applications main top level windows. The following
functionality is provided:
|List GetObjects(ID id)
||Gets a list of the objects contained within the given object id.
|List GetObjectLine(ID id)
||Gets a list of the objects on the given line
|Text GetTextLine(ID id, int line)
||Gets a line of text from the objects data
|ObjInfo GetInfo(ID id)
||Gets generic info on the object. Includes: type, label, position, size
|String GetParam(ID id, String paramName)
||Gets the value of a named parameter from the object
|Event EnableEvents(EventMask mask)
||Enable the given events to be generated
An objects state, as returned by GetInfo() includes the following attributes:
||The object type
||A label for the object
||Some textual information about the object
||The X,Y position in pixels of the object relative to the applications
top level window
||The width and height of the object in pixels
||Object is mapped onto the display
||This is a major display object (not a frame etc.) normally a bottom
of tree object
||The contents can be changed by the user, ie not a fixed display
||When the application changes the object to which keyboard entry is
directed, this event is generated.
||When a text cursor is moved, or redrawn this event is generated
||When a window is displayed onto the screen, this event is generated
||When a window is withdrawn from the screen, this event is generated.
||When the text displayed is changed, this event is generated.
||When an objects children list has changed, this event is generated.