Abstract: A data processing system which defines a plurality of logical workspaces for performing tasks in response to operations performed by a system user and provides communication between two or more of the workspaces. When a user in a first workspace selects a screen object (`door`) corresponding to a second workspace, visual, audio and data communication are initiated between the first user and the second workspace according to predefined access privileges associated with the first user.Access privileges are typically predefined by the owner of the workspace.

Abstract: In a data processing system which defines and processes objects and defines a plurality of virtual screens of display data with which views of objects can be associated, the system defines distinct anterior and posterior display layers for display, with the anterior layer having a background such that the content of the posterior display layer can be viewed therethrough and with one of the layers being assignable for the display of a selected virtual screen and the other display layer being dedicated for the display of an additional screen. The system also provides for the transfer of objects between the anterior and posterior display layers such that the dedicated layer can be used for transporting objects between virtual screens.

Abstract: In an interactive graphics display system in which pels in a frame buffer are mapped to the display screen of a raster display device, a method of automatically highlighting and de-highlighting graphic segments as a cursor is moved across the display screen comprises sampling a locator device at successive points in time to generate a screen cursor at corresponding positions on the screen, examining pels in the frame buffer along a line which extends from the pel corresponding to the previous cursor position to the pel corresponding to the current cursor position to determine whether a pel is "on" along the line, automatically performing a correlate operation in respect of the "on" pel (if any) to identify the graphic segment associated with that pel, and highlighting the segment so identified, any highlighted segment being de-highlighted prior to highlighting a different segment.

Abstract: An interactive raster-scanned display device has a microprocessor (1) and random access memory (3) which operate to issue instructions to a drawing engine (7) to cause it to load and erase image pel representation in an image buffer (9) in order to control display of images on, or removal of images from a display screen (8) in a conventional manner. A cursor control device (10) enables a user to interact by means of a cursor symbol with images on the screen. In order to reduce the demands imposed on the drawing engine during transformation of images over the screen, the system is configured so that transformation operations are performed using alternative images substituted for the full images. Each alternative image contains considerably less detail to be drawn and erased than the full image it replaces and therefore the operation is more likely to be performed at the rate desired by the user.

Abstract: A stylus for interactive use with a graphics input tablet provides a user with a tactile response whenever the stylus tip (5) passes through the in-presence boundary of the tablet. The boundary defines the limit of the distance of the stylus above the tablet surface beyond which stylus position signals are regarded as unreliable. The tactile response is produced by a movable mass (2) within the body (1) of the stylus which is propelled by an internal mechanism (9, 10) into a lower end stop (11) as the tip passes through the in-presence boundary towards the tablet, and into an upper end stop (3) as the stylus passes through the boundary away from the tablet. The tactile response experience by a user in each case is different. In an alternative arrangement, the stylus tip (5) is attached to the moving mass (2) and arranged normally to be held retracted within the stylus body (1) but to automatically protrude from the body as the end of the stylus passes through the in-presence boundary.

Abstract: A raster-scanned CRT device includes auxiliary vertical deflection means operable during each scan line of the raster to deflect the electron beam selectively between adjacent pairs of uniformly spaced image lines on the screen. Control logic operates in response to video information representing an image to be displayed to write image pels on the screen during two successive field scans of the raster. The auxilliary deflection means is controlled so that the entire image is formed on the image lines, and the field scan in which the pels are allocated for display is selected on-the-fly for successive portions of the input video in such a way that pel imbalance between the two fields constituting the final image is minimized.

Abstract: In a cell-organized graphic display apparatus a set of canonical or standard cells is stored in a character generator. A data processor loads character codes into a character buffer and attribute bits into an attribute buffer. Lines to be displayed are computed on a cell-by-cell basis by the processor using pairs of canonical cells and the computed character codes are stored in the character buffer and attribute bits representing displacements of the required canonical cells are loaded into the attribute buffer. During accessing of the character generator, an adder shifts the bit patterns in accordance with the attribute bits. Optionally a second character buffer, a second character generator and a logic mixer are used to allow logical combining of cell images in accordance with attribute bits.

Abstract: A raster display apparatus capable of displaying graphic pictures includes a processor 13 for loading character codes (pointers) in a character buffer 12. The pointers address a character/cell generator 22 to derive the bit patterns necessary to refresh the display 1 under control of refresh logic 19. As the picture becomes increasingly complex, requiring more and more different character cells, the character/cell generator 22 fills. Space is created by combining two or more adjacent cells into a single low-resolution-displayed cell: an op code associated with each character code (pointer) determines whether the cell is to be displayed at full or reduced resolution and causes the refresh logic to clock bit patterns associated with low resolution cells at a slower rate. Optionally, the processor 13 changes low resolution parts of the picture to high resolution when an operator interacts with the low resolution part using a light pen 30.