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draw — Inferno 1.1ed

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draw

draw - graphics device

Synopsis

bind '#d' /dev
/dev/drawnew
/dev/drawn/ctl
/dev/drawn/data
/dev/drawn/refresh

Description

The draw device serves a two-level file system providing an interface to the graphics facilities of the system; the Limbo Draw module (see Limbo Draw Modules ) accesses the device to implement its functions.

Each client of the device connects by opening /dev/drawnew and reading back seven decimal numbers in the standard 12-character format. The seven values are:

  • The connection number, n.

  • The image id of the display image (always zero).

  • The ldepth of the display image.

  • Four values (min.x, min.y, max.x, and max.y) that define the display image.

  • The client can then open the directory /dev/drawn/ (where n is the connection number) to access the ctl, data, and refresh files associated with the connection.
    ctl

    The ctl file accepts no messages; its only purpose is to return the initialization information.

    data

    The data file accepts messages corresponding to procedures in the Draw module:

    Allocate a window or image

    Draw on the image.

    Paint text

    etc.

    Some such messages generate data to be returned to the client. The client can recover it by reading the data file. The format of the messages to and from the data file will be supplied later.

    refresh (read-only)

    As windows owned by the client are uncovered, if they cannot be refreshed by the server (e.g., they have refresh functions associated with them), the client is notified by a message refresh file. reporting what needs to be repainted by the client. The message has five decimal integers formatted as in the ctl message:

    The image id of the window.

    Four decimal values (min.x, min.y, max.x, and max.y) that define the display image in need of refreshment.

    See Also

    Limbo Draw Modules



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