path: root/hw/dmx/doc/DMXSpec.txt

            Client-to-Server DMX Extension to the X Protocol

           $Date$, $Revision$

               Rickard E. (Rik) Faith (faith@redhat.com)
                    Kevin E. Martin (kem@redhat.com)

    Copyright 2002-2004 Red Hat Inc., Raleigh, North Carolina.

    Permission is hereby granted, free of charge, to any person
    obtaining a copy of this software and associated documentation files
    (the "Software"), to deal in the Software without restriction,
    including without limitation on the rights to use, copy, modify,
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1. Overview

    The client-to-server DMX extension to the X protocol (DMX) provides
    normal client applications with the ability to determine information
    about the characteristics of the Xdmx server and the back-end X
    servers that DMX is using.

    The name for this extension is "DMX".



2. Syntactic conventions

    This document uses the same syntactic conventions requests and data
    types as [X11R6.4].



3. Data types

    No new data types are defined by this extension.  All data types
    referenced in this document are defined in [X11R6.4].



4. Requests

    DMXQueryVersion
        ==>
        majorVersion: CARD32
        minorVersion: CARD32
        patchVersion: CARD32

        Errors: None

    The protocol this extension actually supports is indicated by
    majorVersion and minorVersion (patchVersion indicates the
    patchlevel and is for informational purposes only).

    Any incompatible changes to the protocol should be indicated by
    incrementing majorVersion.

    Small, upward-compatible changes should be indicated by incrementing
    minorVersion.

    Servers that support the protocol defined in this document will
    return a majorVersion of 2 and a minorVersion of 2.

    (Version 1.5 was the last version in the 1.x series; version 2.0 was
    a testing version that was poorly defined.)



    DMXSync
        ==>
        status: CARD32

        Errors: None

    This request was first supported in version 1.5 of this protocol.
    The status field in the reply was introduced in version 2.0 of this
    protocol.  Since the status field is ignored, no changes to the
    underlying protocol were required.

    This request flushes all pending protocol requests between the Xdmx
    server and each back-end X server.  It is used by clients that
    talk directly to back-end X servers to ensure that all pending Xdmx
    requests have reached all back-end servers and have been processed
    by those servers.

    The value of status is always 0.



    DMXForceWindowCreation
        window: CARD32
        ==>
        status: CARD32

        Errors: Window

    This request was first supported in version 1.2 of this protocol.
    This request was changed to have a reply in version 2.0 of this
    protocol.  The old version of this request was deprecated and will
    return BadImplementation.

    When using the lazy window creation optimization, windows are not
    created on the back-end X servers until they are required.  This
    request forces the immediate creation of the window requested.

    The value of status is always 0.




    DMXGetScreenCount
        ==>
        screenCount: CARD32

        Errors: None

    This request returns the number of screens that the Xdmx server
    controls.  Since a DMX screen usually fills all of the available
    area on a back-end server, there is usually a one-to-one
    correspondence between DMX screens and backend servers.  However, it
    is also possible for a DMX screen to cover only part of the
    available area on a back-end server, and for more than one DMX
    screen to occupy different parts of the visible area on the same
    back-end server.

    A DMX screen may be managed as a regular X screen in the Xdmx server
    or may be joined with other DMX screens using Xinerama.
    


    DMXGetScreenAttributes
        physicalScreen: CARD32
        ==>
        displayName: STRING8
        logicalScreen: CARD32
        screenWindowWidth: CARD16
        screenWindowHeight: CARD16
        screenWindowXoffset: INT16
        screenWindowYoffset: INT16
        rootWindowWidth: CARD16
        rootWindowHeight: CARD16
        rootWindowXoffset: INT16
        rootWindowYoffset: INT16
        rootWindowXorigin: INT16
        rootWindowYorigin: INT16

        Errors: Value

    This request is new in version 2.0 of this protocol.  The old
    DMXGetScreenInformation request is deprecated and will now return
    BadImplementation.

    This request returns attributes about a single DMX screen.

    The physicalScreen value is between 0 and screenCount-1, inclusive
    (values outside this range will result in a Value error).

    The displayname is the name used to open the display, either from
    the Xdmx command-line or from the configuration file.

    The logicalScreen value is the value of the screen that that Xdmx
    server exports to clients.  When Xinerama is in use, this value is
    typically 0 for all values of physicalScreen.  If Xinerama is in
    use, the rootWindowXOrigin and rootWindowYOrigin values specify
    where the physical screen is positioned in the global Xinerama
    coordinate system.  Otherwise, these values are set to 0.

    The screenWindow values comprise a geometry specification (see
    X(7x)) for the location of the DMX screen on the back-end screen.
    The coordinant system of the back-end display is used.

    The first four rootWindow values comprise a geometry specification
    (see X(7x)) for the location of the root window on the screen
    window.  The coordinant system of the screen window is used.  In
    most cases, the root window will have the same geometry as the DMX
    screen window, and will occupy the same area of the back-end
    display.  (This would not be the case, for example, if automatic
    projector alignment is used.)



    DMXChangeScreensAttributes
        screenCount: CARD32
        maskCount: CARD32
        screens: LISTofCARD32
        valueMasks: LISTofCARD32
        valueList: LISTofVALUES
        ==>
        status: CARD32
        errorScreen: CARD32

        Errors: Length, Alloc

    This request was first supported in version 2.0 of this protocol.
    (A singular version of this request with the ability to change some
    RootWindow attributes was supported in version 1.3 of this protocol,
    has been deprecated, and will return BadImplementation.)

    This request changes the geometries and positions of the DMX screen
    and DMX root windows on the back-end X servers.
   
    The valueMask and valueList specify which attributes are to be
    changed.  The possible values are:

        Attribute               Type

        ScreenWindowWidth       CARD16
        ScreenWindowHeight      CARD16
        ScreenWindowXoffset     INT16
        ScreenWindowYoffset     INT16
        RootWindowWidth         CARD16
        RootWindowHeight        CARD16
        RootWindowXoffset       INT16
        RootWindowYoffset       INT16
        RootWindowXorigin       INT16
        RootWindowYorigin       INT16

    The attribute values have the same meaning as do the corresponding
    values for DMXGetScreenAttributes.

    Non-fatal errors will be returned in status (0 otherwise):
        DmxBadXinerama: Xinerama is not active
        DmxBadValue:    The resulting position is not allowed
                        (e.g., one corner is outside the bounding box)
    On error, errorScreen will contain the number of the screen that
    caused the first error.



    DMXAddScreen
        displayName: STRING8
        physicalScreen: CARD32
        valueMask: CARD32
        valueList: LISTofVALUES
        ==>
        status: CARD32
        physicalScreen: CARD32

        Errors: Length, Alloc, Value

    This request was first supported in version 2.2 of this protocol.

    This request re-attaches the back-end physicalScreen to the Xdmx
    server.  Only back-end screens that have been previously detached
    with DMXRemoveScreen may be added.  The name of the back-end display
    is given in displayName, and this will replace the name of the
    back-end screen that was detached.  Both the displayName and
    physicalScreen must be correct for this request to work.

    The valueMask and valueList specify the attributes to be used.  The
    possible values are:

        Attribute               Type

        ScreenWindowWidth       CARD16
        ScreenWindowHeight      CARD16
        ScreenWindowXoffset     INT16
        ScreenWindowYoffset     INT16
        RootWindowWidth         CARD16
        RootWindowHeight        CARD16
        RootWindowXoffset       INT16
        RootWindowYoffset       INT16
        RootWindowXorigin       INT16
        RootWindowYorigin       INT16

    The attribute values have the same meaning as do the corresponding
    values for DMXGetScreenAttributes.

    On success, status will be 0 and physicalScreen will contain the new
    screen number.  On failure, status will be non-zero.  The status
    will be 1 if any of the following occured:
        * the -addremovescreens command-line option was not specified on
          the Xdmx command line
        * the value of physicalScreen is out of range
        * physicalScreen has not been detached (with DMXRemoveScreen)
        * displayName cannot be opened
        * the visuals of displayname do not match the visuals that Xdmx
          is using
        * the screen data for displayName does not match the data for the
          previously removed display
    The status will be DmxBadValue if the attribute values are out of
    range.



    DMXRemoveScreen
        physicalScreen: CARD32
        ==>
        status: CARD32

        Errors: None

    This request was first supported in version 2.2 of this protocol.

    This request detaches the physicalScreen screen.

    On success, status will be 0.  On failure, the status will 1 if any
    of the following occur:
        * the -addremovescreens command-line option was not specified on
          the Xdmx command line
        * the value of physicalScreen is out of range
        * the back-end screen has already been detached.



    DMXGetWindowAttributes
        window: CARD32
        ==>
        screenCount: CARD32
        screens: LISTofCARD32
        windows: LISTofCARD32
        pos: LISTofRECTANGLE
        vis: LISTofRECTANGLE

        Errors: Window, Alloc

    This request computes the return values incorrectly for version 1.0
    of this protocol.  Version 1.1 of this protocol conforms to this
    description.  In version 2.0, the name of this request was changed
    from DMXGetWindowInformation.  However, since the request itself did
    not change, no changes to the underlying protocol were made.

    Given a window ID on the Xdmx server, this request returns data
    about how the window is represented on the back-end X servers.  For
    each back-end X server that displays a portion of the window, the
    following information is returned:
        1) the number of the physical screen containing that portion
           (which can be used with the DMXGetScreenAttributes request
           to obtain more information about the screen),
        2) the window ID on the back-end X server of the window
           containing that portion,
        3) the position and dimensions of the window on the back-end, in
           screen coordinates, and
        4) the visible area of the window on the back-end, in
           window-relative coordinates (all zeros for windows that are
           not visible).
    Note that DMX allows multiple back-end windows to overlap in their
    view of the DMX logical window.  Further, a logical window does not
    have to be completely covered by back-end windows -- there may be
    gaps.

    As an example, consider a 500x500 window that spans the top two
    1024x768 back-end displays (A and B) of a 2048x1536 DMX display
    composed of 4 1024x768 back-end displays arranged in a cube:
        A B
        C D

    In this case, the DMXGetWindowAttributes call would return the
    following information for the 500x500 window:

    display A: 500x500 window at 1024-250,0 (relative to back end)
               with 250x500 visible at 0,0 (relative to window origin)

    display B: 500x500 window at -250,0 (relative to back end)
               with 250x500 visible at 250,0 (relative to window origin)

    display C: 500x500 window at 1024-250,-768 with 0x0 visible at 0,0

    display D: 500x500 window at -250,-768 with 0x0 visible at 0,0

    Note that if the specified window has not yet been mapped when
    DMXGetWindowAttributes is called, then a subsequent XMapWindow call
    might be buffered in xlib while requests directly to the back-end X
    servers are processed.  This race condition can be solved by calling
    DMXSync before talking directly to the back-end X servers.



    DMXGetDesktopAttributes
        ==>
        width: INT16
        height: INT16
        shiftX: INT16
        shiftY: INT16

        Errors: None

    This request was first supported in version 2.0 of this protocol.

    This request returns the size of the bounding box of the whole
    screen in width and height.  The shiftX and shiftY values will
    always be 0.  The global bounding box is computed whether or not
    Xinerama is active, and may be larger than the Xinerama screen size
    because of information in the configuration file.



    DMXChangeDesktopAttributes
        valueMask: BITMASK
        valueList: LISTofVALUE
        ==>
        status: CARD32

        Errors: Length, Value

    This request was first supported in version 2.0 of this protocol.

    This request resizes the bounding box of the whole screen when using
    the Xinerama extension.  Otherwise, it has no effect on the screen
    layout.  The valueMask and valueList specify which attributes are to
    be changed.  The possible values are:

        Attriubute      Type

        Width           INT16
        Height          INT16
        ShiftX          INT16
        ShiftY          INT16

    Width and Height specify the new width and height for the bounding
    box.  ShiftX and ShiftY specify where the Xinerama origin will be
    placed with respect to the origin of the new bounding box.  This
    allows the left and upper edges of the bounding box to be changed
    without changing the visual position of the windows on the desktop.
    If Width or Height is not specified, the current values will be
    used.  If ShiftX or ShiftY is not specified, 0 will be used.

    All coordinants are in the global DMX coordinant system.  If
    Xinerama is not active, this request is not useful.

    Non-fatal errors will be returned in status (0 otherwise):
        DmxBadXinerama: Xinerama is not active
        DmxBadValue:    The size of the bounding box is too large



    DMXGetInputCount
        ==>
        inputCount: CARD32

    This request was first supported in version 1.1 of this protocol.

    This request returns the number of input devices connected to the
    Xdmx server.  This number is the same as that returned by
    XListInputDevices, but is available even when the XInput extension
    is not supported.



    DMXGetInputAttributes
        deviceId: CARD32
        ==>
        inputType: CARD32
        physicalScreen: CARD32
        physicalId: CARD32
        isCore: BOOL
        sendsCore: BOOL
        detached: BOOL
        name: STRING8

        Errors: Value

    This request was first supported in version 1.1 of this protocol.
    In version 2.0, the name of this request was changed from
    DMXGetInputInformation.  However, since the request itself did not
    change, no changes to the underlying protocol were made.  In version
    2.2, the name of detached was changed from reservation.  There was
    no change in underlying protocol.

    This request returns information about the specified input device
    that cannot be obtained from the XListInputDeivices call.  The
    deviceId is the same as that used by the XListInputDevices call, and
    must be in the range 0 to inputCount-1, inclusive (values outside
    this range will result in a Value error).

    The value of inputType will always be valid, and will be one of the
    following values:
        0 for local (and dummy) devices,
        1 for console devices, and
        2 for back-end devices.

    For local devices, all other fields returned, except isCore and
    sendsCore, are invalid.

    For console devices, the physicalScreen and physicalID will be
    invalid, and the name will return the name of the X server on which
    the console window is displayed.

    For back-end devices, the physicalScreen will identify the back-end
    display and can be used as an argument to DMXGetScreenAttributes to
    obtain more information; the physicalId will be the XInput device id
    on the back-end X server; and the name will be invalid (since it
    does not provide any additional information that cannot be obtained
    with DMXGetScreenAttributes).

    If isCore is True, then this device is active as a true core input
    device and will send core events.  If sendsCore is True, then this
    device is an XInput extension device, but sends core events instead
    of extension events.  Note that this behavior is different from that
    of XFree86 or Xorg, where XInput extension devices may send both
    extension events and core events.

    If detached is True, then this device has been detached and is no
    longer producing input events.  The device may be reattached using
    DMXAddInput.

    

    DMXAddInput
        displayName: STRING8
        valueMask: CARD32
        valueList: LISTofVALUES
        ==>
        status: CARD32
        physicalId: CARD32

        Errors: Value, Access

    This request was first supported in version 2.2 of this protocol.

    The valueMask and valueList specify the attributes to be used.  The
    possible values are:

        Attribute               Type

        InputType               CARD32
        InputPhysicalScreen     CARD32
        InputSendsCore          BOOL

    This request attaches an input device to the Xdmx server.  The value
    of inputType will be one:
        1 for console devices, and
        2 for back-end devices.
    Other values of InputType will return a BadValue error.  Local
    devices (inputType=0 in DMXGetInputAttributes) cannot be attached or
    removed.  For console devices, displayName will store the name of
    the display to be used.

    For back-end devices, InputPhysicalScreen will specify the screen
    number.  BadValue will be returned if the screen number is out of
    range.  BadAccess will be returned if the input has already been
    attached or if the backend screen is currently detached.

    If InputSendsCore is True, the new device will be added as a true
    core device.

    If a device was removed with DMXRemoveInput an attempt will be made
    to reconnect the previous devices (InputSendsCore is ignored in this
    case).



    DMXRemoveInput
        physicalId: CARD32
        ==>
        status: CARD32

        Errors: Value, Access

    This request was first supported in version 2.2 of this protocol.

    This request detaches the input device with physicalId, and all
    associated inputs (e.g., if the physicalId is a backend mouse, and a
    keyboard is also attached to the backend, then both devices will be
    detached).  If the physicalId is outside the valid range (0 to one
    less than the value returned by DMXInputCount), BadValue is
    returned.  If the physicalId has already been detached, BadAccess is
    returned.  The status is always 0.



5. Events

    No new events are defined by this extension.



6. Errors

    No new events are defined by this extension.



7. Encoding

    Deprecated DMX opcodes:
        DMXGetScreenInformation           2
        DMXForceWindowCreation            6
        DMXReconfigureScreen              7

    Valid DMX opcodes:
        DMXQueryVersion                   0
        DMXSync                           8
        DMXForceWindowCreation            9

        DMXGetScreenCount                 1
        DMXGetScreenAttributes           10
        DMXChangeScreensAttributes       11
        DMXAddScreen                     12
        DMXRemoveScreen                  13

        DMXGetWindowAttributes            3

        DMXGetDesktopAttributes          14
        DMXChangeDesktopAttributes       15

        DMXGetInputCount                  4
        DMXGetInputAttributes             5
        DMXAddInput                      16
        DMXRemoveInput                   17

    DMXQueryVersion
        1           CARD8           opcode (X assigned)
        1           0               DMX opcode (X_DMXQueryVersion)
        2           1               request length
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          majorVersion
        4           CARD32          minorVersion
        4           CARD32          patchVersion
        12                          unused

    DMXSync
        1           CARD8           opcode (X assigned)
        1           8               DMX opcode (X_DMXSync)
        2           1               request length
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          status
        20                          unused

    DMXForceWindowCreation
        1           CARD8           opcode (X assigned)
        1           9               DMX opcode (X_DMXForceWindowCreation)
        2           2               request length
        4           CARD32          window
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          status
        20                          unused


    DMXGetScreenCount
        1           CARD8           opcode (X assigned)
        1           1               DMX opcode (X_DMXGetScreenCount)
        2           1               request length
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          screenCount
        20                          unused

    DMXGetScreenAttributes
        1           CARD8           opcode (X assigned)
        1           10               DMX opcode (X_DMXGetScreenAttributes)
        2           2               request length
        4           CARD32          physicalScreen
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           1+(n+p)/4       reply length
        4           n               displayNameLength
        4           CARD32          logicalScreen
        2           CARD16          screenWindowWidth
        2           CARD16          screenWindowHeight
        2           INT16           screenWindowXoffset
        2           INT16           screenWindowYoffset
        2           CARD16          rootWindowWidth
        2           CARD16          rootWindowHeight
        2           INT16           rootWindowXoffset
        2           INT16           rootWindowYoffset
        2           INT16           rootWindowXorigin
        2           INT16           rootWindowYorigin
        n                           displayName
        p                           pad(n)

    DMXChangeScreensAttributes
        1           CARD8           opcode (X assigned)
        1           11              DMX opcode (X_DMXChangeScreenAttributes)
        2           3+s+m+n         request length
        4           s               screenCount
        4           m               maskCount
        4s          LISTofCARD32    screens
        4m          LISTofCARD32    valueMasks
        4n          LISTofVALUES    valueList
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          status
        4           CARD32          errorScreen
        16                          unused


    DMXAddScreen
        1           CARD8           opcode (X assigned)
        1           12              DMX opcode (X_DMXAddScreen)
        2           3+m+(n+p)/4     request length
        4           n               displayNameLength
        4           CARD32          physicalScreen
        4           CARD32          valueMask
        4m          LISTofVALUES    valueList
        n                           displayName
        p                           pad(n)
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          status
        4           CARD32          physicalScreen
        16                          unused

    DMXRemoveScreen
        1           CARD8           opcode (X assigned)
        1           13              DMX opcode (X_DMXRemoveScreen)
        2           2               request length
        4           CARD32          physicalScreen
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          status
        20                          unused

    DMXGetWindowAttributes
        1           CARD8           opcode (X assigned)
        1           3               DMX opcode (X_DMXGetWindowAttributes)
        2           2               request length
        4           CARD32          window
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           n*6             reply length
        4           n               screenCount
        20                          unused
        n*4         LISTofCARD32    screens
        n*4         LISTofCARD32    windows
        n*8         LISTofRECTANGLE pos
        n*8         LISTofRECTANGLE vis

    DMXGetDesktopAttributes
        1           CARD8           opcode (X assigned)
        1           14              DMX opcode (X_DMXGetDesktopAttributes)
        2           1               request length
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        2           INT16           width
        2           INT16           height
        2           INT16           shiftX
        2           INT16           shiftY
        16                          unused

    DMXChangeDesktopAttributes
        1           CARD8           opcode (X assigned)
        1           15              DMX opcode (X_DMXChangeDesktopAttributes)
        2           2+n             request length
        4           BITMASK         valueMask
        4n          LISTofVALUES    valueList
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          status
        20                          unused

    DMXGetInputCount
        1           CARD8           opcode (X assigned)
        1           4               DMX opcode (X_DMXGetInputCount)
        2           1               request length
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          inputCount
        20                          unused

    DMXGetInputAttributes
        1           CARD8           opcode (X assigned)
        1           5               DMX opcode (X_DMXGetInputAttributes)
        2           2               request length
        4           CARD32          deviceId
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           (n+p)/4         reply length
        4           CARD32          inputType
        4           CARD32          physicalScreen
        4           CARD32          physicalId
        4           n               nameLength
        1           BOOL            isCore
        1           BOOL            sendsCore
        1           BOOL            detached
        5                           unused
        n                           name
        p                           pad(n)

    DMXAddInput
        1           CARD8           opcode (X assigned)
        1           16              DMX opcode (X_DMXAddInput)
        2           3+m+(n+p)/4     request length
        4           n               displayNameLength
        4           CARD32          valueMask
        4m          LISTofVALUES    valueList
        n                           displayName
        p                           pad(n)
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          status
        4           CARD32          physicalId
        16                          unused

    DMXRemoveInput
        1           CARD8           opcode (X assigned)
        1           17              DMX opcode (X_DMXRemoveInput)
        2           3               request length
        4           CARD32          physicalId
    ==>
        1           1               Reply
        1                           unused
        2           CARD16          sequence number
        4           0               reply length
        4           CARD32          status
        20                          unused


8. Changes to existing requests/replies/events

    No changes to existing requests, replies, or events are necessitated
    by this extension.



9. Acknowledgments



10. References

    [X11R6.4] Robert W. Sheifler.  X Window System Protocol, X Consortium
              Standard, X Version 11, Release 6.4.  Available from
              xc/doc/specs/XProtocol and xc/doc/hardcopy/XProtocol.