# Low Bandwidth X Extension

X Consortium Standard
Donna
Converse
Jim
Fulton
David
Lemke
Ralph
Mor
Keith
Packard
Ray
Tice
Dale
Tonogai
X Version 11, Release &fullrelvers;
Version 1.0
1996
X Consortium

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 the rights to use, copy, modify, merge, publish, distribute, sublicense, and sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Except as contained in this notice, the name of the X Consortium shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from the X Consortium.

X Window System is a trademark of The OpenGroup.

## Introduction

Low Bandwidth X (LBX) is a network-transparent protocol for running X Window System applications over transport channels whose bandwidth and latency are significantly worse than that used in local area networks. It combines a variety of caching and reencoding techniques to reduce the volume of data that must be sent over the wire. It can be used with existing clients by placing a proxy between the clients and server, so that the low bandwidth/high latency communication occurs between the proxy and server.

This extension was designed and implemented by Jim Fulton, David Lemke, Keith Packard, and Dale Tonogai, all of Network Computing Devices (NCD). Chris Kent Kantarjiev (Xerox PARC) participated in early design discussions. Ralph Mor (X Consortium) designed and implemented additional sections. Donna Converse (X Consortium) authored the protocol description and encoding from design notes and the implementation. Ray Tice (X Consortium) resolved the open issues in the design and specification. Bob Scheifler (X Consortium) helped out in many areas.

The extension name is "LBX".

## Description

The design center for LBX is to use a proxy as an intermediary between the client and server. The proxy reencodes and compresses requests, events, replies and errors, as well as the resulting data stream. Additionally, the proxy can cache information from the server to provide low-latency replies to clients. This reply generation by the proxy is known as short-circuiting. A proxy can handle multiple clients for a given server, but does not prevent clients from connecting directly to the server. The design allows the proxy to multiplex multiple clients into a single data stream to the server.

Much of LBX is implemented as an extension. The compression and reencoding changes can be isolated to the transport and dispatch portions of the server, while short-circuiting requires minor changes to the server’s colormap and property code.

LBX employs several different compression and short-circuiting methods. Use of these methods is negotiable, and in some cases, the algorithm used by a given method is negotiable as well. LBX also provides for negotiation of extensions to LBX.

### Data Flow

The LBX data stream goes through a number of layers:

1. Client requests

2. Read by LBX and potential byte-swapping

3. Request-specific compression

4. Potential byte swapping

5. Multiplexing of client request streams

6. Delta replacement

7. Stream compression

Transport

1. Stream decompression

2. Delta substitution

3. Demultiplexing of client request streams

4. Potential byte swapping

5. Reencoding

6. Request processing

The reverse process occurs with X server replies, events, and errors.

### Tags

Tags are used to support caching of large data items that are expected to be queried multiple times. Such things as the keyboard map and font metrics are often requested by multiple clients. Rather than send the data each time, the first time the data is sent it includes a tag. The proxy saves this data, so that subsequent requests can send only the tag to refer to that same data. The different types of tags are used for connection information, keyboard maps, modifier maps, fonts information and properties.

Tag usage is negotiated as a boolean in the LbxStartProxy message. The proxy controls how many tags are stored in the proxy. The server may wish to observe the proxy’s InvalidateTag behavior to limit how many tags are cached at any one time. Tagged data is not shared across types of tags, but the number space used for the tag ids is. The tag ids are generated by the server.

The X server keeps track of what tags are known to the proxy. The proxy can invalidate a tag if no tag bearing replies of that type are pending. The proxy sends an LbxInvalidateTag message to release the tagged data. The proxy must not invalidate connection tags unless instructed to do so by the server.

If the server wishes to discard tagged data, it must either have received an LbxInvalidateTag request from the proxy or send an LbxInvalidateTag event to the proxy for that tag.

#### Tag Substitution in Requests

Many substitution requests have a tag field, followed by fields marked optional. For these requests, if the optional fields are present, the data in them is stored in the indicated tag, unless the tag is 0. If the optional fields are absent, the tag field indicates the tag that contains the data for the "optional" fields.

#### Property Tags

Property data makes special use of tags. A common use of properties is for inter-client communication. If both clients use the proxy, it is wasteful to send the data to the server and then back, when the server may never need it. LbxChangeProperty request does the same work as the core ChangeProperty request, but it does not send the data. The reply to this request contains a tag id corresponding to the data. If the property information is used locally, the server responds to LbxGetProperty with the tag, and the property data need never be sent to the server. If the server does require the data, it can issue an LbxQueryTag message. The proxy can also send the data on at any time if it judges it appropriate (i.e., when the wire goes idle). Since the proxy owns the property data, it must not invalidate the tag before sending the data back to the server via an LbxTagData request.

### Short-circuiting

Short-circuiting is used to handle constant data. This includes atoms, color name/RGB mappings, and AllocColor calls. Atoms and color name/RGB mappings stay constant for the life of the server. AllocColor replies are constant for each colormap. Short-circuiting replaces round-trip requests with one-way requests, and can sometimes use one in place of many.

Atoms are used heavily for ICCCM communication. Once the proxy knows the string to atom mapping, it has no need to send subsequent requests for this atom to the server.

Colorname/RGB mappings are constant, so once the proxy sees the response from LookupColor , it need not forward any subsequent requests.

Clients often use the same color cells, so once a read-only color allocation has occurred, the proxy knows what RGB values should be returned to the client. The proxy doesn't need to forward any AllocColor requests it can resolve, but it must tell the server to modify the color cell's reference count. LbxIncrementPixel is used to support this.

For all three classes of short-circuiting, the proxy must still tell the server a request has occurred, so that the request sequence numbers stay in sync. This is done with LbxModifySequence .

Sequence numbers cause the major complication with short-circuiting. X guarantees that any replies, events or errors generated by a previous request will be sent before those of a later request. This means that any requests that can be handled by the proxy must have their reply sent after any previous events or errors.

If a proxy’s applications do not require strict adherence to the X protocol ordering of errors or events, a proxy might provide further optimization by avoiding the overhead of maintaining this ordering, however, the resulting protocol is not strictly X11 compliant.

### Graphics Re-encoding

The LBX proxy attempts to reencode PolyPoint, PolyLine, PolySegment, PolyRectangle, PolyArc, FillPoly, PolyFillRectangle, PolyFillArc, CopyArea, CopyPlane, PolyText8, PolyText16, ImageText8, and ImageText16 requests. If the request can be reencoded, it may be replaced by an equivalent LBX form of the request. The requests are reencoded by attempting to reduce 2-byte coordinate, length, width and angle fields to 1 byte. Where applicable, the coordinate mode is also converted to Previous to improve the compressibility of the resulting data. In image requests, the image data may also be compressed.

### Motion events

To prevent clogging the wire with MotionNotify events, the server and proxy work together to control the number of events on the wire. This is done with the LbxAllowMotion request. The request adds an amount to an allowed motion count in the server, which is kept on a per-proxy basis. Every motion notify event sent to the proxy decrements the allowed motion counter. If the allowed motion count is less than or equal to zero, motion events not required by the X protocol definition are not sent to the proxy. The allowed motion counter has a minimum value of -2^31.

### Event Squishing

In the core protocol, all events are padded as needed to be 32 bytes long. The LBX extension reduces traffic by removing padding at the end of events, and implying the event length from its type. This is known as squishing.

### Master Client

When the initial X connection between the proxy and the server is converted to LBX mode, the proxy itself becomes the master client. New client requests and some tag messages are sent in the context of the master client.

### Multiplexing of Clients

The LBX proxy multiplexes the data streams of all its clients into one stream, and then splits them apart again when they are received. The LbxSwitch message is used to tell each end which client is using the wire at the time.

The server should process delta requests in the order that they appear on the LBX connection. If the server does not maintain the interclient request order for requests sent by the proxy, it must still obey the semantics implied by the interclient request order so that the delta cache functions correctly.

The server can affect the multiplexing of clients by the proxy using the LbxListenToOne and LbxListenToAll messages. This is useful during grabs, since the master connection can not be blocked during grabs like other clients. The proxy is responsible for tracking server grabs issued by its clients so that the proxy can multiplex the client streams in an order executable by the server.

Replies must be ordered in the multiplexed data stream from the server to the proxy such that the reply carrying tagged data precedes replies that refer to that tagged data.

### Swapping

Swapping is handled as with any X extension, with one caveat. Since a proxy can be supporting clients with different byte orders, and they all share the same wire, the length fields of all messages between the server and proxy are expressed in the proxy byte order. This prevents any problems with length computation that may occur when clients are switched.

### Delta cache

LBX takes advantage of the fact that an X message may be very similar to one that has been previously sent. For example, a KeyPress event may differ from a previous KeyPress event in just a few bytes. By sending just the bytes that differ (or "deltas"), the number of bytes sent over the wire can be substantially reduced. Delta compaction is used on requests being sent by the proxy as well as on replies and events being sent by the server.

The server and the proxy each keep per-proxy request and response caches. The response cache contains events, errors and replies. All messages are saved in the appropriate delta cache if they are of an appropriate type and more than 8 bytes long but fit within the delta cache. The number of entries in the delta cache and the maximum saved message size are negotiated in the LbxStartProxy request.

The LBX requests that are never stored in the request delta cache are the LbxQueryVersion , LbxStartProxy , LbxSwitch , LbxNewClient , LbxAllowMotion , LbxDelta , LbxQueryExtension , LbxPutImage , LbxGetImage , LbxBeginLargeRequest , LbxLargeRequestData , LbxEndLargeRequest and LbxInternAtoms requests. The responses that are never stored in the response cache are LbxSwitchEvent and LbxDeltaResponse . The message carried by a delta message is also cached, if it meets the other requirements. Messages after the LbxStartProxy request are cached starting at index 0, and incrementing the index, modulo the number of entries, thereafter. The request and response caches are independently indexed.

If the current message is cachable and the same length as a message in the corresponding delta cache, a delta message may be substituted in place of the original message in the protocol stream.

### Stream Compression

Before being passed down to the transport layer messages can be passed through a general purpose data compressor. The choice of compression algorithm is negotiated with See LbxStartProxy. The proxy and server are not required to support any specific stream compressor. As an example, however, the X Consortium implementation of a ZLIB based compressor is described below.

The XC-ZLIB compressor is presented with a simple byte stream - the X and LBX message boundaries are not apparent. The data is broken up into fixed sized blocks. Each block is compressed using zlib 1.0 (by Gailly & Adler), then a two byte header is prepended, and then the entire packet is transmitted. The header has the following information:

          out[0] = (length & 0xfff) >> 8 | ((compflag) ? 0x80 : 0);
          out[1] = length & 0xff;

### Authentication Protocols

The current version of LBX does not support multipass authentication protocols for clients of the proxy. These authentication protocols return an Authenticate message in response to a connection setup request, and require additional authentication data from the client after the LbxNewClient request, and before the reply to LbxNewClient . One example of such a protocol is XC-QUERY-SECURITY-1.

## C Library Interfaces

The C Library routines for LBX are in the Xext library. The prototypes are located in a file named "XLbx.h".

### Application Library Interfaces

In a proxy environment, applications do not need to call these routines to take advantage of LBX. Clients can, however, obtain information about the LBX extension to the server using this interface. Use of this routine may be altered when connected through a proxy, as described in See C Library Interfaces.

#### XLbxQueryVersion

To determine the version of LBX supported by the X server, call XLbxQueryVersion .

    Bool XLbxQueryVersion
          Display * display
          int * major_version_return
          int * minor_version_return

display

  Specifies the connection to the X server.

major_version_return

  Returns the extension major version number.

minor_version_return

  Returns the extension minor version number.

The XLbxQueryVersion function determines if the LBX extension is present. If the extension is not present, XLbxQueryVersion returns False ; otherwise, it returns True . If the extension is present, XLbxQueryVersion returns the major and minor version numbers of the extension as supported by the X server.

### Proxy Library Interfaces

The following interfaces are intended for use by the proxy.

#### XLbxQueryExtension

To determine the dynamically assigned codes for the extension, use the Xlib function XQueryExtension or the LBX function XLbxQueryExtension .

    Bool XLbxQueryExtension
          Display * display
          int * major_opcode_return
          int * first_event_return
          int * first_error_return

display

  Specifies the connection to the X server.

major_opcode_return

  Returns the major opcode.

first_event_return

  Returns the first event code.

first_error_return

  Returns the first error code.

The XLbxQueryExtension function determines if the LBX extension is present. If the extension is not present, XLbxQueryExtension returns False ; otherwise, it returns True . If the extension is present, XLbxQueryExtension returns the major opcode for the extension to major_opcode_return, the base event type code to first_event_return, and the base error code to first_error_return; otherwise, the return values are undefined.

#### XLbxGetEventBase

To determine the base event type code, use the Xlib function XQueryExtension or the LBX function XLbxGetEventBase.

    int XLbxGetEventBase
          Display * display

display

  Specifies the connection to the X server.

The XLbxGetEventBase function returns the base event type code if the extension is present; otherwise, it returns -1.

## Protocol

### Syntactic Conventions and Common Types

Please refer to the X Window System Protocol specification, as this document uses the syntactic conventions established there and references types defined there.

The following additional types are defined by this extension:

    DIFFITEM
    1      CARD8      offset
    1      CARD8      diff

    LBXANGLE: CARD8 or 2 BYTE
          where (in order of precedence):
          (0 <= in <= A(95)) && !(in % A(5))       out = 0x5a + (in /
    A(5))
          A(105) <= in <= A(360) && !(in % A(15))      out = 0x67 +
    (in / A(15))
          -A(100) <= in <= -A(5) && !(in % A(5))      out = 0xa6 +
    (in / A(5))
          -A(360) < in <= -A(105) && !(in % A(15))      out = 0x98 +
    (in / A(15))
          -A(360) < in <= A(360)      out[0] = in >> 8; out[1] = in

    LBXARC:
          [x, y: LBXINT16,
          width, height: LBXCARD16,
          angle1, angle2: LBXANGLE]

Within a list of arcs, after the first arc, x and y are relative to the corresponding fields of the prior arc.

    LBXCARD16: CARD8 or 2 BYTE
          where:
          0x0000 <= in < 0x00F0      CARD8
          0x00F0 <= in < 0x10F0      out[0] = 0xF0 | ((in - 0xF0) >>
    8)
                out[1] = in - 0xF0

    LBXGCANDDRAWENT
    [ gc-cache-index, drawable-cache-index: CARD4 ]

    LBXGCANDDRAWUPDATE
          drawable: DRAWABLE      /* present only if
    drawable-cache-index
     == 0 */
    gc: GC]      /* present only if gc-cache-index == 0 */

    LBXGCANDDRAWABLE
          cache-entries: LBXGCANDDRAWENT
          updates: LBXGCANDDRAWUPDATE

    LBXINT16: INT8 or 2 BYTE
          where:
          0xF790 <= in < 0xFF90      out[0] = 0x80 | (((in + 0x70) >>
    8) & 0x0F)
                out[1] = in + 0x70
          0xFF90 <= in < 0x0080      CARD8
          0x0080 <= in < 0x0880      out[0] = 0x80 | (((in - 0x80) >>
    8) & 0x0F)
                out[1] = in - 0x80

    LBXPINT16: CARD8 or 2 BYTE       /* for
    usually positive numbers */
          where:
          0xFE00 <= in < 0x0000      out[0] = 0xF0 | (((in + 0x1000)
    >> 8) & 0x0F)
                out[1] = in + 0x1000
          0x0000 <= in < 0x00F0       CARD8
          0x00F0 <= in < 0x0EF0      out[0] = 0xF0 | ((in - 0xF0) >>8)
                out[1] = in - 0xF0

    LBXPOINT: [x, y: LBXINT16]
          Within a list of points, after the first rectangle, x and y are
    relative to the corresponding fields of the prior point.

    LBXRECTANGLE:
          [x, y: LBXINT16,
          width, height: LBXCARD16]

Within a list of rectangles, after the first rectangle, x and y are relative to the corresponding fields of the prior rectangle.

MASK: CARD8

### Errors

As with the X11 protocol, when a request terminates with an error, the request has no side effects (that is, there is no partial execution).

There is one error, LbxClient . This error indicates that the client field of an LBX request was invalid, or that the proxy’s connection was in an invalid state for a start or stop proxy request.

### Requests

There is one request that is expected to be used only by the client: LbxQueryVersion

There is one request that is expected to be used by the client or the proxy: LbxQueryExtension .

The following requests are expected to be used only by the proxy, and are instigated by the proxy: LbxStartProxy , LbxStopProxy , LbxNewClient , LbxSwitch , LbxCloseClient , LbxModifySequence , LbxAllowMotion , LbxInvalidateTag , LbxTagData and LbxQueryTag .

All other requests are sent by the proxy to the LBX server and are instigated by reception of an X request from the client. They replace the X request.

#### Requests Initiated by the Proxy or by the Client

LbxQueryVersion
=>;
majorVersion: CARD16
minorVersion: CARD16

This request returns the major and minor version numbers of the LBX protocol.

The encoding of this request is on See LbxQueryVersion.

#### Requests Initiated or Substituted by the Proxy

LbxQueryExtension
nbytes : CARD32
name : STRING8
=>
num-requests: CARD8
present: BOOL
major-opcode: CARD8
first-event: CARD8
first-error: CARD8
reply-mask: LISTofMASK /* optional */
event-mask:LISTofMASK /* optional */
Errors: Alloc

This request is identical to the QueryExtension request, with an additional field, and two optional additional fields. When the client issues an QueryExtension request, the proxy will substitute an LbxQueryExtension request.

This request determines if the named extension is present. If so, the major opcode for the extension is returned, if it has one. Otherwise, zero is returned. Any minor opcode and the request formats are specific to the extension. If the extension involves additional event types, the base event type code is returned. Otherwise, zero is returned. The format of events is specific to the extension. If the extension involves additional error codes, the base error code is returned. Otherwise, zero is returned. The format of additional data in the errors is specific to the extension.

In addition, the number of requests defined by the named extension is returned. If the number of requests is nonzero, and if the information is available, reply-mask and event-mask will be included in the reply. The reply-mask represents a bit-wise one-to-one correspondence with the extension requests. The least significant bit corresponds to the first request, and the next bit corresponds to the next request, and so on. Each element in the list contains eight meaningful bits, except for the last element, which contains eight or fewer meaningful bits. Unused bits are not guaranteed to be zero. The bit corresponding to a request is set if the request could generate a reply, otherwise it is zero. In the same way, the event-mask represents a bit-wise one-to-one correspondence with the extension requests. A bit is set if the corresponding request could result in the generation of one or more extension or X11 events. If reply-mask is present in the reply, event-mask will also be present.

The encoding of this request is on See LbxQueryExtension.

#### Control Requests Initiated by the Proxy

LbxStartProxy
options : LISTofOPTION
=>
choices: LISTofCHOICE
Errors: LbxClient , Alloc
where:
OPTION [optcode: CARD8,
len: OPTLEN,
option: (See See StartProxy Options) ]
CHOICE [optcode: CARD8,
len: OPTLEN,
choice: (See See StartProxy Options) ]

##### StartProxy Options

optcode | option | choice | default
--- | --- | --- | ---
delta-proxy | DELTAOPT | DELTACHOICE | entries=16, maxlen=64
delta-server | DELTAOPT | DELTACHOICE | entries=16, maxlen=64
stream-comp | LISTofNAMEDOPT | INDEXEDCHOICE | No Compression
bitmap-comp | LISTofSTRING8 | LISTofINDEXEDOPT | No Compression
pixmap-comp | LISTofPIXMAPMETHOD | LISTofPIXMAPCHOICE | No Compression
use-squish | BOOL | BOOL | True
use-tags | BOOL | BOOL | True
colormap | LISTofSTRING8 | INDEXEDCHOICE | No Colormap Grabbing
extension | NAMEDOPT | INDEXEDCHOICE | Extension Disabled

DELTAOPT [minN, maxN, prefN: CARD8
minMaxMsgLen, maxMaxMsgLen, prefMaxMsgLen: CARD8]
DELTACHOICE [entries, maxlen: CARD8]
INDEXEDCHOICE [index: CARD8,
data: LISTofBYTE]
INDEXEDOPT [index, opcode: CARD8]
NAMEDOPT [name: STRING8,
detail: LISTofBYTE]
OPTLEN 1 or 3 CARD8
where:
(0 < in <= 0xFF): out = in
(0 <= in<= 0xFFFF): out[0] = 0; out[1] = in >> 8; out[2] = in& 0xFF;
PIXMAPMETHOD [name: STRING8,
format-mask: BITMASK,
depths: LISTofCARD8]
PIXMAPCHOICE [index, opcode: CARD8,
format-mask: BITMASK,
depths: LISTofCARD8]

This request negotiates LBX protocol options, and switches the proxy-server connection from X11 protocol to LBX protocol.

The proxy gives the preferred protocol options in the request. The server chooses from the given options and informs the proxy which to use. The options may be listed in any order, and the proxy may choose which options to negotiate. If an option is not successfully negotiated, the default is used.

The server delta cache and proxy delta caches can be configured for number of entries, and the length of entries. (See See Delta cache for details.) The delta caches are configured using the delta-server and delta-proxy options. To configure a cache, the proxy sends the minimum, maximum and preferred values for the number of cache entries, ( minN, maxN, prefN ), and the length of the cache entries, ( minMaxMsgLen, maxMaxMsgLen, prefMaxMsgLen ). The server’s reply fields, entries and maxlen , contains the values to use. These values must be within the ranges specified by the proxy. The server may also specify an entries value of 0 to disable delta caching. The cache entry lengths are specified in units of 4 bytes.

The stream compression algorithm is selected using the stream-comp option. (Stream compression is described in See Stream Compression.) Each algorithm has a name that follows the naming conventions in See Algorithm Naming. To negotiate using the stream-comp option, the proxy lists its available compressors. For each candidate algorithm, the proxy sends the name in the name field, and uses the detail field to send any additional data specific to each compression algorithm. The reply contains a 0-based index into the list of algorithms to indicate which algorithm to use, followed by data specific to that algorithm.

Bitmap compression is negotiated using the bitmap-comp option. The proxy sends a list of names of available algorithms, and the server reply lists the algorithms to use. For each bitmap algorithm in the reply, a 0-based index into the list of algorithms indicates the algorithm, and the opcode field gives the value for use in requests. The algorithm names follow the conventions in See Algorithm Naming.

Pixmap compression is negotiated using the pixmap-comp option. The proxy sends a list of available algorithms. For each algorithm, the list includes, the name, a bitmask of supported formats, and a list of depths that the format supports. The server reply lists the algorithms to use. For each pixmap algorithm in the reply, the reply contains a 0-based index into the list of proxy algorithms, the opcode to use in requests when referring to this algorithm, a mask of valid formats, and a list of valid depths. Algorithm names follow the conventions in See Algorithm Naming.

Squishing is negotiated using the use-squish option. If the proxy desires squishing, it sends a true value. The reply from the server indicates whether to do squishing, and will indicate squishing only if use-squish is set to true in the request.

Tag caching, described in See Tags, is negotiated using the use-tag option. If the proxy desires tag caching, it sends a true value. The reply from the server indicates whether to do tag caching, and will demand caching only if use-tag is set to true in the request.

The colormap option is used to negotiate what color matching algorithm will be used by the proxy when the proxy uses the LbxAllocColor request to allocate pixels in a grabbed colormap. To negotiate using the colormap option, the proxy lists the names of available colormap algorithms. The choice in the reply contains a 0-based index into the list of algorithms to indicate which algorithm to use, followed by data specific to that algorithm. If no colormap algorithm is successfully negotiated, then the LbxAllocColor , LbxGrabCmap , and LbxReleaseCmap requests will not be used.

The extension option is used to control extensions to LBX. These extensions may, for example, enable other types of compression. To negotiate an extension, the name of the extension is sent, followed by any data specific to that extension. The extension name follows the conventions in See Algorithm Naming. The extension option may occur multiple times in the start proxy message, since multiple extensions can be negotiated. The reply to an extension option contains the zero-based index of the extension option, as counted in the LbxStartProxy message. This index is followed by extension-specific information. The server does not respond to extensions it does not recognize.

An LbxClient error is returned when a client which is already communicating through an LBX proxy to the X server sends a LbxStartProxy request.

The encoding for this request is on See LbxStartProxy.

LbxStopProxy
Errors: LbxClient

This request terminates the connection between the proxy and X server, and terminates any clients connected through the proxy.

The encoding for this request is on See LbxStopProxy.

An LbxClient error is returned if the requesting client is not an LBX proxy.

LbxNewClient
byte-order : CARD8
client-id : CARD32
protocol-major-version : CARD16
protocol-minor-version: CARD16
authorization-protocol-name : STRING8
authorization-protocol-data : STRING8
=>
Core X reply (if connection is rejected)
OR
success: BOOL
change-type: {NoDeltas, NormalClientDeltas, AppGroupDeltas}
protocol-major-version: CARD16
protocol-minor-version: CARD16
tag-id: CARD32
length: CARD16
connection-data: CONINFO or CONDIF or CONDIFROOT
where:
CONINFO: (the "additional data" portion of the core connection reply for successes)
CONDIF: [resource-id-base: CARD32,
root-input-masks: LISTofSETofEVENT]
CONDIFROOT: [resource-id-base: CARD32,
root: WINDOW
root-visual: VISUALID
default-colormap: COLORMAP
white-pixel, black-pixel: CARD32
root-input-masks: LISTofSETofEVENT]

Errors: LbxClient, Alloc

This request, which is sent by the proxy over the control connection, creates a new virtual connection to the server.

Much of the information in the LbxNewClient request and reply is identical to the connection setup and reply information in the core X protocol.

For the LbxNewClient request, the field unique to LBX is client-id. For the LbxNewClient reply, tag-id and change-type are fields unique to LBX, and the contents of connection-data may be different in LBX from the core X protocol (see below).

The proxy assigns each virtual connection a unique identifier using the client-id field in the LbxNewClient request. This client-id is used in the LBX protocol to specify the current client (see the LbxSwitch request and the LbxSwitchEvent ). client-id 0 is reserved for the proxy control connection. An LbxClient error will result if the LbxNewClient request contains a client-id of 0 or an already in use client-id.

If the server rejects this new virtual connection, the server sends a core X connection failure reply to the proxy. The current version of LBX does not support the return of an Authenticate reply.

If the change-type field is set to NoDeltas , then connection-data is sent using the CONINFO structure, which is identical to the additional data of the core connection reply. If the tag-id is non-zero, then the connection-data is stored by the proxy using this tag value. Tagged connection data must be stored by the proxy, and can not be invalidated by the proxy until an LbxInvalidateTag event is received for that tag.

When the change-type field is not set to NoDeltas , then connection data is sent as changes against connection information previously sent to the proxy. The tag-id field, if non-zero, has the tag of the previously sent data to apply the changes to. A zero tag-id indicates that the changes are with respect to the connection information sent when the proxy connected to the server.

If the change-type field is set to NormalClientDeltas , then connection-data is sent using the CONDIF structure. The values in the CONDIF structure are substituted for the identically named fields of the connection information for the new connection.

If the change-type field is set to AppGroupDeltas , then connection-data is sent using the CONDIFROOT structure. The root , root-visual , and default-colormap fields, when nonzero, are substituted for the corresponding fields in the reference connection information. The white-pixel and black-pixel fields are substituted only when the default-colormap field of the reply is non-zero. When default-colormap field of the reply is zero, so are white-pixel and black-pixel . The first entry in the root-input-masks field is the current-input-mask for the default root window. The remaining entries in root-input-masks are input masks for non-video screens, as defined by the X Print Extension. The number of non-video screens is one less than the number of entries in root-input-masks . These screens are at the end of screen list in the reference connection information.

The encoding for this request is on See The description of this request is on page 13..

LbxCloseClient
client : CARD32
Errors: LbxClient

This requests the server to close down the connection represented by the specified proxy’s client identifier. If the specified client wasn’t previously registered with the server by a LbxNewClient request, the server will send the LbxClient error.

The encoding for this request is on See The description of this request is on page 12..

LbxSwitch
client : CARD32
Errors: LbxClient

This request causes the X server to treat subsequent requests as being from a connection to the X server represented by the specified client identifier.

If the client making the request is not the proxy, or if the client identifier sent in the request was not previously sent in a LbxNewClient request, an LbxClient error is returned.

The encoding for this request is on See LbxSwitch.

LbxSync
=>

The sync request causes the server to send a reply when all requests before the sync request have been processed.

The encoding for this client is on See LbxSync.

LbxModifySequence
adjust : CARD32
Errors: None

This request advances the sequence number of the virtual client connection by the specified amount. The proxy sends the LbxModifySequence request to the server when it replies to a client request without forwarding the client request on to the X server.

The encoding for this client is on See The description of this request is on page 13..

LbxAllowMotion
num : CARD32
Errors: None

This request controls the delivery of optional motion notify events, as described in See Motion events. The num field specifies an increase in the allowed number of motion notify events sent.

The encoding for this request is on See The description of this request is on page 14..

LbxInvalidateTag
tag : CARD32

The LBX proxy sends this notification to the X server when it refuses to store tagged data, or when it releases tagged data which was previously stored and which was not invalidated by a notification from the X server.

The encoding for this request is on See LbxInvalidateTag.

LbxTagData
tag : CARD32
real-length : CARD32
data : LISTofBYTE

This request specifies the data associated with a previously assigned tag. It is sent in two circumstances: in response to receiving a SendTagDataEvent , and spontaneously, when the proxy must rely on the server to store data which was not previously received from the server. The data is carried in the byte order and structure as would have originally been sent in the core protocol request.

The encoding for this request is on See LbxTagData.

LbxGrabCmap
cmap : Colormap
=>
smart-grab : BOOL
large-pixel: BOOL /* optional */
auto-release: BOOL /* optional */
three-channels : BOOL /* optional */
bits-per-rgb: CARD4 /* optional */
cells : LISTofCHAN /* optional */
where:
CHAN: LISTofLBXPIXEL
LBXPIXEL: PIXELPRIVATE or PIXELPRIVATERANGE or
PIXELALLOC or PIXELALLOCRANGE
PIXEL: CARD8 or CARD16
PIXELPRIVATE: [ pixel: PIXEL ]
PIXELPRIVATERANGE: [ first-pixel, last-pixel: PIXEL]
PIXELALLOC: [ pixel: PIXEL,
color: COLORSINGLE or COLORTRIPLE]
PIXELALLOCRANGE: [ first-pixel, last-pixel: PIXEL,
colors: LISTofCOLORSINGLE or LISTofCOLORTRIPLE]
COLORSINGLE: [ value: CARD8 or CARD16 ]
COLORTRIPLE: [ r, g, b: COLORSINGLE]
Errors: Colormap

This request asks the server for control of allocating new colormap cells in the specified colormap. The server grants control by replying to this request. If no changes have occurred since the last time this proxy grabbed this colormap, then the smart-grab field of the reply is set to true, and the optional fields are not sent. Otherwise, the current contents of the colormap are placed in the reply, as described later in this section.

Once the proxy has received the reply, it can use the LbxAllocColor request to allocate new colormap cells without the performance penalty of round trips. The proxy is still permitted to use the normal colormap and LbxIncrementPixel requests while the colormap is grabbed. The grab is valid across all virtual connections of the proxy.

The LbxGrabCmap request is limited to colormaps for the visual types negotiated as part of the colormap algorithm negotiation in the start proxy request at connection setup.

The server and other proxies may not allocate new colormap cells in the colormap while the colormap is grabbed by this proxy. If the server or another proxy needs to allocate new colormap cells, the server sends a Lbx ReleaseCmap event to the proxy holding the grab, which then issues an LbxReleaseCmap request.

The server and other proxies may free colormap cells in a colormap grabbed by a proxy. The server will send an LbxFreeCells event to the proxy that currently has the colormap grabbed when the cell reference count reaches 0.

If the colormap is a of a static visual type, such as StaticGray , StaticColor , GrayScale , or TrueColor , then the proxy’s grab is immediately released by the server, and the proxy must use LbxIncrementPixel requests in place of LbxAllocColor requests for this colormap.

If the cmap field does not refer to a valid colormap or the colormap is already grabbed by this proxy then a Colormap error is generated.

The reply describes the contents of the colormap via several arguments and a descriptive list containing one or three channels, with each channel describing allocations in the colormap.

The large-pixel argument, if True, specifies that PIXEL indices will be listed as CARD16 quantities instead of CARD8. The auto-release field, if True, indicates that this colormap is of a static visual type and the proxy’s grab is immediately released by the server.

If three-channels is False, a single channel is enclosed and color values are described using COLORTRIPLE, which has fields for red, green and blue. A single channel is used when the visual type is not DirectColor or TrueColor .

If three-channels is True, separate red, green and blue channel lists are enclosed, for describing a DirectColor or TrueColor colormap. Color values for entries in each channel are sent using COLORSINGLE and the corresponding PIXEL value refers to the RGB subfield of the current channel, as defined by the corresponding red-mask, green-mask and blue-mask of the visual.

The bits-per-rgb value is one less than the bits-per-rgb-value field of the visual that the colormap belongs to. If the value is 7 or less, then COLORSINGLE values in the descriptive list are sent using CARD8 fields. Otherwise these values are sent using CARD16 fields.

The list describing current colormap allocations contains entries of the following types:

An LBXPIXELPRIVATE entry indicates that the pixel in the pixel field is unavailable for allocation.

An LBXPIXELPRIVATERANGE entry indicates that a contiguous range of pixels are unavailable for allocation. The range is first-pixel to last-pixel , and includes last-pixel .

An LBXPIXELALLOC entry indicates that the pixel in the pixel field is allocated as a read-only pixel. The color field carries the color information of the pixel.

An LBXPIXELALLOCRANGE entry indicates that a contiguous range of pixels are allocated as read-only. The range starts first-pixel to last-pixel , and includes last-pixel . These fields are followed by a list of COLORSINGLE or COLORTRIPLE, depending on the value of three-channels .

A NEXTCHANNEL entry indicates that the next channel of the colormap will be described.

A LISTEND entry indicates the end of the colormap description.

All pixels not described in the reply are unallocated.

The encoding for this request is on See LbxGrabCmap.

LbxReleaseCmap
cmap : Colormap

This request releases the specified grabbed colormap. If the cmap field does not refer to a colormap, a BadColormap error is produced.

The proxy must remember the state of the colormap when the LbxReleaseCmap request is issued if this proxy may at some future time issue another LbxGrabCmap request on this colormap before the state of the colormap changes.

The encoding for this request is on See LbxReleaseCmap.

LbxInternAtoms
count : CARD16
names: LISTofSTRING8
=>
atoms : LISTofATOM
Errors: Alloc

This request allows the proxy to intern a group of atoms in a single round trip. The server will create any atoms that do not exist.

The encoding for this request is on See LbxInternAtoms.

#### Substitution Requests

LbxAllocColor
cmap : Colormap
pixel : CARD32
red , green , blue : CARD16

This request is sent by a proxy that has given colormap grabbed to allocate a new read-only cell in the colormap. The proxy may substitute this request for the core AllocColor and AllocNamedColor requests.

The pixel field identifies the colormap cell to allocate. The red , green , and blue fields are the hardware specific color values of the corresponding fields of the core AllocColor request. The mapping to hardware specific colormap values by the proxy is performed using the color algorithm negotiated by LbxStartProxy .

For colormaps of static visual types, the LbxIncrementPixel request is used instead of LBX AllocColor .

If the cmap field does not identify a grabbed colormap then a BadAccess error is produced. If the pixel field refers to a read-write entry, or the pixel field refers to a pixel outside of the range of this colormap, a BadAlloc error is produced.

The encoding for this request is on See LbxAllocColor.

LbxIncrementPixel
cmap : COLORMAP
pixel : CARD32
Errors: None

This request replaces the AllocColor request for read-only pixels currently allocated for the current client. If the visual type of the colormap is of a static type, this request may be used on currently unallocated pixels. The colormap is not required to be grabbed to use this request.

The encoding for this request is on See The description of this request is on page 14..

LbxDelta
count : CARD8
cache-index : CARD8
diffs : LISTofDIFFITEM

This request contains a minimal amount of information relative to a similar prior request. The information is in the form of a difference comparison to a prior request. The prior request is specified by an index to a cache, independently maintained by both the proxy and the server.

The encoding for this request is on See The description of this request is on page 18..

LbxGetModifierMapping
=>
keyspermod : CARD8
tag : CARD32
keycodes : LISTofKEYCODE /* optional */

This request is identical to the core GetModifierMapping request, with the addition of a tag being returned in the reply. See See Tag Substitution in Requests for a description of the tag field and optional fields.

The encoding for this request is on See LbxGetModifierMapping.

LbxGetKeyboardMapping
firstKeyCode : KEYCODE
count : CARD8
=>
keysperkeycode : CARD8
tag : CARD32
keysyms : LISTofKEYSYM /* optional */
Errors: Value

This request is identical to the X GetKeyboardMapping protocol request, with the addition that a tag is returned in the reply. See See Tag Substitution in Requests for a description of the tag field and optional fields.

The encoding for this request is on See LbxGetKeyboardMapping.

LbxGetWinAttrAndGeom
window : WINDOW
=>
visual: VISUALID
class: {InputOutput, InputOnly}
bit-gravity: BITGRAVITY
win-gravity: WINGRAVITY
backing-store: {NotUseful, WhenMapped, Always}
backing-planes: CARD32
backing-pixel: CARD32
save-under: BOOL
colormap: COLORMAP or None
map-is-installed: BOOL
map-state: {Unmapped, Unviewable, Viewable}
all-event-masks, your-event-mask: SETofEVENT
do-not-propagate-mask: SETofDEVICEEVENT
override-redirect: BOOL
root: WINDOW
depth: CARD8
x, y: INT16
width, height, border-width: CARD16
Errors: Window

GetWindowAttributes and GetGeometry are frequently used together in the X protocol. LbxGetWinAttrAndGeom allows the proxy to request the same information in one round trip.

The encoding for this request is on See LbxGetWinAttrAndGeom.

LbxQueryFont
font : FONTABLE
=>
compression: BOOL
tag: CARD32
font-info: FONTINFO /* optional */
char-infos: LISTofCHARINFO or LISTofLBXCHARINFO /* optional */
where:
LBXCHARINFO: [left-side-bearing: INT6
right-side-bearing: INT7
character-width: INT6
ascent: INT6
descent: INT7]
Errors: Font,Alloc

This request is used to replace the core QueryFont request and has identical semantics.

See See Tag Substitution in Requests for a description of the tag field and optional fields.

The compression field is True if the char-infos field is represented using LBXCHARINFO.

The per-character information will be encoded in an LBXCHARINFO when, for every character, the character-width, left-side-bearing, and ascent can each be represented in not more than 6 bits, and the right-side-bearing and descent can each be represented in not more than 7 bits, and the attributes field is identical the attributes field of the max_bounds of the font_info field of the font.

The encoding for this request is on See LbxQueryFont.

LbxChangeProperty
window : WINDOW
property : ATOM
type : ATOM
format : {0,8,16,32}
mode : {Replace, Prepend, Append}
nUnits : CARD32
=>
tag: CARD32

This request is sent to the server when the client sends an X ChangeProperty request through the proxy. The size of the data is sent with this request, but not the property data itself. The server reply contains a tag identifier for the data, which is stored in the proxy. The proxy must not discard this data before it is sent to the server, or invalidated by the server. This means that before issuing an LbxStopProxy request, or exiting, the proxy must send Lbx TagData requests for these items. If the server loses the connection before the information is sent back, the server should revert the property value to its last known value, if possible.

If the mode field is Prepend or Append , the tag refers only to the prepended or appended data.

If the tag in the reply is zero, then the change was ignored by the server, as defined in the security extension. The proxy should dump the associated data, since the server will never ask for it.

The encoding for this request is on See LbxChangeProperty.

LbxGetProperty
window : WINDOW
property : ATOM
type : ATOM or AnyPropertyType
long-offset : CARD32
long-length : CARD32
delete : CARD8
=>
type: ATOM or None
format: {0, 8, 16, 32}
bytes-after: CARD32
nItems: CARD32
tag: CARD32
value: LISTofINT8 or LISTofINT16 or LISTofINT32

This request may be used by the proxy as a substitution for a core GetProperty request. It allows tags to be used for property data that is unlikely to change often in value, but is likely to be fetched by multiple clients.

The LbxGetProperty request has the same arguments as the core GetProperty request. The reply for LbxGetProperty has all of the fields from the core GetProperty reply, but has the additional fields of nItems and tag .

In order to utilize tags in LbxGetProperty for a specific property, the server must first send the complete property data to the proxy and associate this data with a tag. More precisely, the server sends an LbxGetProperty reply with a new tag , nItems set to the number of items in the property, the size of the property data in the reply length field, and the complete property data in value. The proxy stores the property data in its tag cache and associates it with the specified tag.

In response to future LbxGetProperty requests for the same property, if the server thinks that the proxy has the actual property data in its tag cache, it may choose to send an LbxGetProperty reply without the actual property data. In this case, the reply would include a non-zero tag , a zero reply length, and no data for value.

If the server chooses not to generate a tagged reply to LbxGetProperty , or for some reason is unable to do so, it would send a reply with a tag of zero, the size of the property data in the reply length field, and the complete property data in value.

The encoding for this request is on See LbxGetProperty.

LbxPolyPoint
gc-and-drawable: LBXGCANDDRAWABLE
points : LISTofLBXPOINT
Errors: Alloc and those given for the corresponding X request.

This request replaces the PolyPoint request. Not all PolyPoint requests can be represented as LbxPolyPoint requests.

The proxy will convert the representation of the points to be relative to the previous point, as described by previous coordinate mode in the X protocol.

The encoding for this request is on See LbxPolyPoint.

LbxPolyLine
gc-and-drawable: LBXGCANDDRAWABLE
points : LISTofLBXPOINT
Errors: Alloc and those given for the corresponding X request.

This request replaces the PolyLine request. Not all PolyLine requests can be represented as LbxPolyline requests.

The proxy will convert the representation of the points to be relative to the previous point, as described by previous coordinate mode in the X protocol.

The encoding for this request is on See The description of this request is on page 21..

LbxPolySegment
gc-and-drawable: LBXGCANDDRAWABLE
segments : LISTofLBXSEGMENT
where:
LBXSEGEMENT; [x1, y1, x2, y2: LBXINT16]
Errors: Alloc and those given for the corresponding X request.

This request replaces the PolySegment request. Not all PolySegment requests can be represented as LbxPolySegment requests.

For segments other than the first segment of the request, [x1, y1] is relative to [x1, y1] of the previous segment. For all segments, [x2, y2] is relative to that segment’s [x1, y1].

The encoding for this request is on See LbxPolySegment.

LbxPolyRectangle
gc-and-drawable: LBXGCANDDRAWABLE
rectangles : LISTofLBXRECTANGLE
Errors: Alloc and those given for the corresponding X request.

This request replaces the PolyRectangle request. Not all PolyRectangle requests can be represented as LbxPolyRectangle requests.

The encoding for this request is on See The description of this request is on page 22..

LbxPolyArc
gc-and-drawable: LBXGCANDDRAWABLE
arcs : LISTofLBXARC
Errors: Alloc and those given for the corresponding X request.

This request replaces the PolyArc request. Not all PolyArc requests can be represented as LbxPolyArc requests.

The encoding for this request is on See LbxPolyArc.

LbxPolyFillRectangle
gc-and-drawable: LBXGCANDDRAWABLE
rectangles : LISTofLBXRECTANGLE
Errors: Alloc and those given for the corresponding X request.

This request replaces the PolyFillRectangle request. Not all PolyFillRectangle requests can be represented as LbxPolyFillRectangle requests.

The encoding for this request is on See LbxPolyFillRectangle.

LbxPolyFillArc
gc-and-drawable: LBXGCANDDRAWABLE
arcs : LISTofLBXARC
Errors: Alloc and those given for the corresponding X request.

This request replaces the PolyFillArc request. Not all PolyFillArc requests can be represented as LbxPolyFillArc requests.

The encoding for this request is on See The description of this request is on page 22..

LbxFillPoly
gc-and-drawable: LBXGCANDDRAWABLE
shape : BYTE
points : LISTofLBXPOINT
Errors: Alloc and those given for the corresponding X request.

This request replaces the FillPoly request. Not all FillPoly requests can be represented as LbxFillPoly requests.

The proxy will convert the representation of the points to be relative to the previous point, as described by previous coordinate mode in the X protocol.

The encoding for this request is on See LbxFillPoly.

LbxCopyArea
srcCache : CARD8 /* source drawable */
gc-and-drawable: LBXGCANDDRAWABLE
src-Drawable : CARD32
src-x : LBXPINT16
src-y : LBXPINT16
width : LBXCARD16
height : LBXCARD16
dst-x : LBXPINT16
dst-y : LBXPINT16
Errors: Those given for the corresponding X request.

This request replaces the CopyArea request for requests within its encoding range.

The encoding for this request is on See LbxCopyArea.

LbxCopyPlane
bit-plane : CARD32
src-cache : CARD8 /* cache reference for source drawable */
gc-and-drawable: LBXGCANDDRAWABLE
src-drawable : CARD32
src-x : LBXPINT16
src-y : LBXPINT16
width : LBXCARD16
height : LBXCARD16
dst-x : LBXPINT16
dst-y : LBXPINT16
Errors: Those given for the corresponding X request.

This request replaces the CopyPlane request for requests within its coding range.

The encoding for this request is on See LbxCopyPlane.

LbxPolyText8
gc-and-drawable: LBXGCANDDRAWABLE
x : LBXPINT16
y : LBXPINT16
items : LISTofTEXTITEM8
Errors: Alloc , and those given for the corresponding X request.

This request replaces the PolyText8 request for requests within its encoding range.

The encoding for this request is on See The description of this request is on page 23..

LbxPolyText16
gc-and-drawable: LBXGCANDDRAWABLE
x: LBXPINT16
y : LBXPINT16
items : LISTofTEXTITEM16
Errors: Alloc , and those given for the corresponding X request.

This request replaces the PolyText16 request for requests within its encoding range.

The encoding for this request is on See The description of this request is on page 24..

LbxImageText8
gc-and-drawable: LBXGCANDDRAWABLE
nChars : CARD8
x : LBXPINT16
y : LBXPINT16
string : STRING8
Errors: Alloc , and those given for the corresponding X request.

This request replaces the ImageText8 request for requests within its encoding range.

The encoding for this request is on See The description of this request is on page 24..

LbxImageText16
nChars : CARD8
gc-and-drawable: LBXGCANDDRAWABLE
x: LBXPINT16
y : LBXPINT16
string : STRING16
Errors: Alloc , and those given for the corresponding X request.

This request replaces the ImageText16 request for requests within its encoding range.

The encoding for this request is on See The description of this request is on page 24..

LbxPutImage
compression-method : CARD8
format : { Bitmap , XYPixmap , ZPixmap } /* packed */
gc-and-drawable: LBXGCANDDRAWABLE
width , height : LBXCARD16
dst-x , dst-y : LBXPINT16
depth : CARD8 /* packed */
left-pad : CARD8 /* packed */
pad-bytes : CARD8 /* packed */
data :LISTofBYTE
Errors: Alloc , Value

When the request can be usefully compressed, this request replaces the PutImage request. The compression-method parameter contains the opcode of a compression method returned in the LbxStartProxy reply. The pad-bytes parameter gives the number of unused pad bytes that follow the compressed image data. All other parameters are as in the X request. If the specified compression method is not recognized, the server returns a Value error.

The encoding for this request is on See LbxPutImage.

LbxGetImage
drawable : DRAWABLE
x , y : INT16
width , height : CARD16
plane-mask : CARD32
format : {XYPixmap, ZPixmap}
=>
depth: CARD8
x-length: CARD32
visual: VISUALID or None
compression-method: CARD8
data: LISTofBYTE
Errors: Alloc,Match,Value

This request can replace the GetImage request. The same semantics apply, with the following exceptions.

The compression-method field contains the opcode of the compression method used in the reply. The compression opcodes are supplied in the LbxStartProxy reply. The x-length field contains the length of the uncompressed version of the reply in 4 byte units.

A Value error is returned if the format is not recognized by the X server. A Match error is returned under the same circumstances as described by the GetImage request.

The encoding for this request is on See LbxGetImage.

LbxBeginLargeRequest
large-request-length : CARD32
Errors: Alloc

This request, along with the Lbx LargeRequestData and Lbx EndLargeRequest requests, is used to transport a large request in pieces. The smaller size of the resulting requests allows smoother multiplexing of clients on a single low bandwidth connection to the server. The resulting finer-grained multiplexing improves responsiveness for the other clients.

After a LbxBeginLargeRequest request is sent, multiple LbxLargeRequestData requests are sent to transport all of the data in the large request, and finally an LbxEndLargeRequest request is sent. The large-request-length field expresses the total length of the transported large request, expressed as the number of bytes in the transported request divided by four.

The encoding for this request is on See The description of this request is on page 25..

LbxLargeRequestData
data : LISTofBYTE
Errors: Alloc

This request is used to carry the segments of a larger request, as described in the definition of LbxBeginLargeRequest . The data must be carried in order, starting with the request header, and each segment must be multiples of 4 bytes long. If the LbxLargeRequestData is not preceded by a corresponding LbxBeginLargeRequest , a BadAlloc error is generated.

The encoding for this request is on See The description of this request is on page 26..

LbxEndLargeRequest
Errors: Length, Alloc

As described in the definition of LbxBeginLargeRequest , LbxEndLargeRequest is used to signal the end of a series of LargeRequestData requests. If the total length of the data transported by the LbxLargeRequestData requests does not match the large-request-length field of the preceding LbxBeginLargeRequest request, then a Length error occurs. If the LbxEndLargeRequest is not preceded by a corresponding LbxBeginLargeRequest , a BadAlloc error is generated. The request is executed in order for that client as if it were the request after the request preceding LbxEndLargeRequest .

The encoding for this request is on See LbxEndLargeRequest.

### Events

LbxSwitchEvent
client : CARD32

Notify the proxy that the subsequent replies, events, and errors are relative to the specified client.

The encoding for this event is on See LbxSwitchEvent.

LbxCloseEvent
client : CARD32

Notify the proxy that the specified client's connection to the server is closed.

The encoding for this event is on See The description of this event is on page 27..

LbxInvalidateTagEvent
tag : CARD32
tag-type : {Modmap, Keymap, Property, Font, ConnInfo}

This message informs the proxy that the tag and the server data referenced by the tag are obsolete, and should be discarded. The tag type may be one of the following values: LbxTagTypeModmap , LbxTagTypeKeymap , LbxTagTypeProperty , LbxTagTypeFont , LbxTagTypeConnInfo .

The encoding for this event is on See LbxInvalidateTagEvent.

LbxSendTagDataEvent
tag : CARD32
tag-type : {Property}

The server sends this event to the proxy to request a copy of tagged data which is being stored by the proxy. The request contains a tag which was previously assigned to the data by the server. The proxy should respond to SendTagData by sending a TagData request to the server. The tag type may be one of the following values: LbxTagTypeProperty .

The encoding for this event is on See LbxSendTagDataEvent.

LbxListenToOne
client : CARD32 or 0xffffffff

When the server is grabbed, ListenToOne is sent to the proxy. As an X client, the proxy itself is unaffected by grabs, in order that it may respond to requests for data from the X server.

When the client grabbing the server is managed through the proxy, the proxy will permit messages from itself and the grabbing client to be sent immediately to the server, and may buffer requests from other clients of the proxy. The client is identified in the event.

When the client grabbing the server is not managed through the proxy, the client field in the event will be 0xffffffff . The proxy will communicate with the server, and it may buffer requests from other clients. The proxy will continue to handle new connections while the server is grabbed.

The server will send ListenToAll to the proxy when the server is ungrabbed. There is no time-out for this interval in the protocol.

The encoding for this event is on See The description of this event is on page 27..

LbxListenToAll

Notify the proxy that the server has been ungrabbed, and that the proxy may now send all buffered client requests on to the server.

The encoding for this event is on See The description of this event is on page 27..

LbxQuickMotionDeltaEvent
deltaTime : CARD8
deltaX : INT8
deltaY : INT8

This event is used as a replacement for the MotionNotify event when possible. The fields are used as deltas to the most recent MotionNotify event encoded as a MotionNotify event, LbxQuickMotionDeltaEvent , or LbxMotionDeltaEvent . Not every MotionNotify event can be encoded as a LbxQuickMotionDeltaEvent .

The encoding for this event is on See LbxQuickMotionDeltaEvent.

LbxMotionDeltaEvent
deltaX : INT8
deltaY : INT8
deltaTime : CARD16
deltaSequence : CARD16

This event is used as a replacement for the MotionNotify event when possible. The fields are used as deltas to the most recent MotionNotify event encoded as a MotionNotify event, LbxQuickMotionDeltaEvent , or LbxMotionDeltaEvent . Not every MotionNotify event can be encoded as a LbxMotionDeltaEvent .

The encoding for this event is on See LbxMotionDeltaEvent.

LbxReleaseCmapEvent
colormap : Colormap

This event notifies the proxy that it must release the grab on this colormap via the ReleaseCmap request. See LbxReleaseCmap

The encoding for this event is on See LbxReleaseCmapEvent.

LbxFreeCellsEvent
colormap : Colormap
pixelStart, pixelEnd : CARD32

The LbxFreeCells event is sent to a proxy that has a colormap grabbed to notify the proxy that the reference count of the described cells were decremented to zero by the server or another proxy. The reference count includes those by this proxy. The proxy must update its copy of the colormap state accordingly if the colormap is still grabbed, or if the proxy may in the future grab the colormap using smart-grab mode. See LbxGrabCmap

The pixelStart and pixelEnd fields of the event denote a continuous range of cells that were freed.

The encoding for this event is on See LbxFreeCellsEvent.

### Responses

Responses are messages from the server to the proxy that not, strictly speaking, events, replies or errors.

LbxDeltaResponse
count : CARD8
cache-index : CARD8
diffs : LISTofDIFFITEM

This response carries an event, reply, or error that has been encoded relative to a message in the response delta cache. The cache-index field is the index into the cache. Each entry in diffs provides a byte offset and replacement value to use in reconstructing the response.

The encoding for this event is on See LbxDeltaResponse.

## Algorithm Naming

To avoid potential clashes between different but similar algorithms for stream, bitmap, and pixmap compression, the following naming scheme will be adhered to:

Each algorithm has a unique name, which is a STRING8, of the following form:

<organization>-<some-descriptive-name>

The organization field above is the organization name as registered in section 1 of the X Registry (the registry is provided as a free service by the X Consortium.) This prevents conflicts among different vendor’s extensions.

As an example, the X Consortium defines a zlib-based stream compression algorithm called XC-ZLIB.

## Encoding

The syntax and types used in the encoding are taken from the X protocol encoding. Where LBX defines new types, they are defined earlier in this document.

As in the X protocol, in various cases, the number of bytes occupied by a component will be specified by a lowercase single-letter variable name instead of a specific numeric value, and often some other component will have its value specified as a simple numeric expression involving these variables. Components specified with such expressions are always interpreted as unsigned integers. The scope of such variables is always just the enclosing request, reply, error, event, or compound type structure.

For unused bytes, the encode-form is:

    N            unused

If the number of unused bytes is variable, the encode-form typically is:

    p            unused, p=pad(E)

where E is some expression, and pad(E) is the number of bytes needed to round E up to a multiple of four.

pad(E) = (4 - (E mod 4)) mod 4

In many of the encodings, the length depends on many variable length fields. The variable L is used to indicate the number of padded 4 byte units needed to carry the request. Similarly, the variable Lpad indicates the number of bytes needed to pad the request to a 4 byte boundary.

    For counted lists there is a common encoding of NLISTofFOO:

    NLISTofFOO
    1      m      num items
    m      LISTofFOO      items

For cached GC and Drawables:

    LBXGCANDDRAWUPDATE
    4 or 0      DRAWBLE      optional drawable
    4 or 0      GC           optional GC

    LBXGCANDDRAWABLE
    8      LBXGCANDDRAWENT      cache-entries
    8                           unused
    m      LBXGCANDDRAWUPDATE   optional GC and Drawable

### Errors

    LbxClient
    1      0          Error
    1      CARD8      error-base + 0
    2      CARD16     sequence number
    4                 unused
    2      CARD16     lbx opcode
    1      CARD8      major opcode
    21                unused

### Requests

    LbxQueryVersion
    1      CARD8      opcode
    1      0          lbx opcode
    2      1          request length
    =>
    1      1          Reply
    1                 unused
    2      CARD16     sequence number
    4      0          reply length
    2      CARD16     major version
    2      CARD16     minor version
    20                unused

The description of this request is on See LbxQueryVersion.

    LbxStartProxy
    1      CARD8                      opcode
    1      1                          lbx opcode
    2      L                          request length
    n      NLISTofOPTION-REQUEST      options
    p                                 unused, p=pad(n)

    OPTION-REQUEST
    1      OPTCODE                    option-code
    m      OPTLEN                     option-request-byte-length, (b=m+a+1)
    a      DELTAOPT or                option
           NLISTofNAMEDOPT or
           NLISTofSTR or
           NLISTofPIXMAPMETHOD or
           BOOL

The encoding of the option field depends on the option-code. See See StartProxy Options.

    1      OPTCODE                               option-code
    0      LbxOptionDeltaProxy
    1      LbxOptionDeltaServer
    2      LbxOptionStreamCompression
    3      LbxOptionBitmapCompression
    4      LbxOptionPixmapCompression
    5      LbxOptionMessageCompression              /* also known as squishing */
    6      LbxOptionUseTags
    7      LbxOptionColormapAllocation
    255    LbxOptionExtension

OPTLEN has two possible encodings, depending on the size of the value carried:

    OPTLEN
    1      CARD8              b (0 < b <= 255)

    OPTLEN
    1      0                  long length header
    1      c                  length0, c = b >> 8
    1      d                  length1, d= b & #xff

    DELTAOPT
    1      CARD8      min-cache-size
    1      CARD8      max-cache-size
    1      CARD8      preferred-cache-size
    1      CARD8      min-message-length
    1      CARD8      max-message-length (in 4-byte units)
    1      CARD8      preferred-message-length

    NAMEDOPT
    f      STR             type-name
    1      g+1             option-data-length
    g      LISTofBYTE      option-data (option specific)

    PIXMAPMETHOD
    h      STR              name
    1      BITMASK          format mask
    1      j                depth count
    j      LISTofCARD8      depths

    =>
    =>

    1      1                 Reply
    1      CARD8             count

    0xff      options in request cannot be decoded
    2      CARD16            sequence number
    4      (a+p-32)/4        reply length
    a      LISTofCHOICE      options-reply
    p            unused, if (n<24) p=24-n else p=pad(n)

    CHOICE
    1      CARD8                request-option-index
    b      OPTLEN               reply-option-byte-length
    c      DELTACHOICE or       choice
          INDEXEDCHOICE or
          NLISTofINDEXEDOPT or
          NLISTofPIXMAPCHOICE or
          BOOL or
          INDEXEDCHOICE

The encoding of the choice field depends on the option-code. See See StartProxy Options.

    DELTACHOICE
    1      CARD8      preferred cache size
    1      CARD8      preferred message length in 4-byte units

    INDEXEDCHOICE
    1      CARD8           index
    d      LISTofBYTE      data

    PIXMAPCHOICE
    1      CARD8           index
    1      CARD8           opcode
    1      BITMASK         format mask
    e      NLISTofCARD8    depths

The description of this request is on See LbxStartProxy.

    LbxStopProxy
    1      CARD8      opcode
    1      2          lbx opcode
    2      1          request length

The description of this request is on See LbxStopProxy.

    LbxSwitch
    1      CARD8      opcode
    1      3          lbx opcode
    2      2          request length
    4      CARD32     client

The description of this request is on See LbxSwitch.

    LbxNewClient
    1      CARD8      opcode
    1      4          lbx opcode
    2      L          request length
    4      CARD32     client
    The remaining bytes of the request are the core connection setup.
    =>
    If the connection is rejected, a core connection reply is sent. Otherwise the
    reply has the form:
    1      BOOL      success
    1                change type
          0          no-deltas
          1          normal-client-deltas
          2          app-group-deltas
    2      CARD16    major version
    2      CARD16    minor version
    2      1 + a     length
    4      CARD32    tag id

The remaining bytes depend on the value of change-type and length.

For no-deltas, the remaining bytes are the "additional data" bytes of the core reply. (a = length of core reply, in 4 byte quantities).

For normal-client-deltas, the additional bytes have the form, with a length (a = 1 +b):

    4      CARD32                 resource id base
    4b      LISTofSETofEVENT      root input masks

For app-group-deltas, the additional bytes have the following form, with a length of (a = 1 + 4c):

    4      CARD32                resource id base
    4      WINDOW                root id base
    4      VISUALID              visual
    4      COLORMAP              colormap
    4      CARD32                white pixel
    4      CARD32                black pixel
    4c     LISTofSETofEVENT      root input masks

The description of this request is on See LbxNewClient.

    LbxCloseClient
    1      CARD8      opcode
    1      5          lbx opcode
    2      2          request length
    4      CARD32     client

The description of this request is on See LbxCloseClient.

    LbxModifySequence
    1      CARD8      opcode
    1      6          lbx opcode
    2      2          request length
    4      CARD32     offset to sequence number

The description of this request is on See LbxModifySequence.

    LbxAllowMotion
    1      CARD8      opcode
    1      7          lbx opcode
    2      2          request length
    4      CARD32     number of MotionNotify events

The description of this request is on See LbxAllowMotion.

    LbxIncrementPixel
    1      CARD8      opcode
    1      8          lbx opcode
    2      3          request length
    4      COLORMAP   colormap
    4      CARD32      pixel

The description of this request is on See LbxIncrementPixel.

    LbxDelta
    1      CARD8              opcode
    1      9                  lbx opcode
    2      1+(2n +p+2)/4      request length
    1      n                  count of diffs
    1      CARD8              cache index
    2n      LISTofDIFFITEM    offsets and differences
    p                         unused, p=pad(2n + 2)

The description of this request is on See LbxDelta.

    LbxGetModifierMapping
    1      CARD8      opcode
    1      10         lbx opcode
    2      1          request length
    =>
    1      1          Reply
    1      n          keycodes-per-modifier
    2      CARD16     sequence number
    4      2n         reply length
    4      CARD32     tag
    20                unused
    8n     LISTofKEYCODE      keycodes

The description of this request is on See LbxGetModifierMapping.

    LbxInvalidateTag
    1      CARD8      opcode
    1      12         lbx opcode
    2      2          request length
    4      CARD32     tag

The description of this request is on See LbxInvalidateTag.

    LbxPolyPoint
    1      CARD8      opcode
    1      13      lbx opcode
    2      1+(m+n+p)/4      request length
    m      LBXGCANDDRAWABLE      cache entries
    n      LISTofLBXPOINT      points (n is data-dependent)
    p      0      unused, p=Lpad

The description of this request is on See LbxPolyPoint.

    LbxPolyLine
    1      CARD8      opcode
    1      14      lbx opcode
    2      1+(m+n+p)/4      request length
    m      LBXGCANDDRAWABLE      cache entries
    n      LISTofLBXPOINT      points (n is data-dependent)
    p      0      unused, p=Lpad

The description of this request is on See LbxPolyLine.

    LbxPolySegment
    1      CARD8      opcode
    1      15      lbx opcode
    2      1+(m+n+p)/4      request length
    m      LBXGCANDDRAWABLE      cache entries
    n      LISTofLBXSEGMENT      segments (n is data-dependent)
    p      0      unused, p=Lpad

The description of this request is on See LbxPolySegment.

    LbxPolyRectangle
    1      CARD8      opcode
    1      16      lbx opcode
    2      1+(m+n+p)/4      request length
    m      LBXGCANDDRAWABLE      cache entries
    n      LISTofLBXRECTANGLE      rectangles (n is data-dependent)
    p      0      unused, p=pad(m+n)

The description of this request is on See LbxPolyRectangle.

    LbxPolyArc
    1      CARD8      opcode
    1      17      lbx opcode
    2      1+(m+n+p)/4      request length
    m      LBXGCANDDRAWABLE      cache entries
    n      LISTofLBXARCS      arcs (n is data-dependent)
    p      0      unused, p=Lpad

The description of this request is on See LbxPolyArc.

    LbxFillPoly
    1      CARD8      opcode
    1      18      lbx opcode
    2      1+(3+m+n+p)/4      request length
    1      LBXGCANDDRAWENT      cache entries
    1            shape
    0      Complex
    1      Nonconvex
    2      Convex
    1      p      pad byte count
    m      LBXGCANDDRAWUPDATE      optional gc and drawable
    n      LISTofLBXPOINT      points (n is data-dependent)
    p      0      unused, p=Lpad

The description of this request is on See LbxFillPoly.

    LbxPolyFillRectangle
    1      CARD8      opcode
    1      19      lbx opcode
    2      1+(m+n+p)/4      request length
    m      LBXGCANDDRAWABLE      cache entries
    n      LISTofLBXRECTANGLE      rectangles (n is data-dependent)
    p      0      unused, p=Lpad

The description of this request is on See LbxPolyFillRectangle.

    LbxPolyFillArc
    1      CARD8      opcode
    1      20      lbx opcode
    2      1+(m+n+p)/4      request length
    m      LBXGCANDDRAWABLE      cache entries
    n      LISTofLBXARC      arcs (n is data-dependent)
    p      0      unused, p=Lpad

The description of this request is on See LbxPolyFillArc.

    LbxGetKeyboardMapping
    1      CARD8      opcode
    1      21      lbx opcode
    2      2      request length
    1      KEYCODE      first keycode
    1      m      count
    2            unused
    =>
    1      1      Reply
    1      n      keysyms-per-keycode
    2      CARD16      sequence number
    4      nm      reply length (m = count field from the request)
    4      CARD32      tag
    20            unused
    4nm      LISTofKEYSYM      keysyms

The description of this request is on See LbxGetKeyboardMapping.

    LbxQueryFont
    1      CARD8      opcode
    1      22      lbx opcode
    2      2      request length
    4      FONTABLE      font
    =>
    1      1      Reply
    1      BOOL      compression
    2      CARD16      sequence number
    4      L      reply length
    4      CARD32      tag
    20            unused
    All of the following is conditional:
    12      CHARINFO      min-bounds
    4            unused
    12      CHARINFO      max-bounds
    4            unused
    2      CARD16      min-char-or-byte2
    2      CARD16      max-char-or-byte2
    2      CARD16      default-char
    2      n      number of FONTPROPs in properties
    1            draw-direction
    0      LeftToRight
    1      RightToLeft
    1      CARD8      min-byte1
    1      CARD8      max-byte1
    1      BOOL      all-chars-exist
    2      INT16      font-ascent
    2      INT16      font-descent
    4      m      number of elements in char-infos
    8n      LISTofFONTPROP      properties
    and either
    12m      LISTofCHARINFO      char-infos
    or
    m      LISTofLBXCHARINFO      char-infos

The description of this request is on See LbxQueryFont.

    LbxChangeProperty
    1      CARD8      opcode
    1      23      lbx opcode
    2      6      request length
    4      WINDOW      window
    4      ATOM      property
    4      ATOM      type
    1      CARD8      format
    1            mode
    0      Replace
    1      Preprend
    2      Append
    2            unused
    4      CARD32      length of data in format units
                (= n for format = 8)
                (= n/2 for format = 16)
                (= n/4 for format = 32)
    =>
    1      1      Reply
    1            unused
    2      CARD16      sequence number
    4      0      reply length
    4      CARD32      tag
    20            unused

The description of this request is on See LbxChangeProperty.

    LbxGetProperty
    1      CARD8      opcode
    1      24      lbx opcode
    2      7      request length
    4      WINDOW      window
    4      ATOM      property
    4      ATOM      type
    0      AnyPropertyType
    1      CARD8      delete
    3            unused
    4      CARD32      long-offset
    4      CARD32      long-length
    =>
    1      1      Reply
    1      CARD8      format
    2      CARD16      sequence number
    4      CARD32      reply length
    4      ATOM      type
    0      None
    4      CARD32      bytes-after
    4      CARD32      length of value in format units
                (= 0 for format = 0)
                (= n for format = 8)
                (= n/2 for format = 16)
                (= n/4 for format = 32)
    4      CARD32      tag
    8            unused

The description of this request is on See LbxGetProperty.

    LbxTagData
    1      CARD8      opcode
    1      25      lbx opcode
    2      3+(n+p)/4      request length
    4      CARD32      tag
    4      CARD32      length of data in bytes
    n      LISTofBYTE      data
    p            unused, p=pad(n)

The description of this request is on See LbxTagData.

    LbxCopyArea
    1      CARD8      opcode
    1      26      lbx opcode
    2      L      request length
    1      CARD8      source drawable cache entry
    1      LBXGCANDDRAWENT      cache entries
    4 or 0      DRAWABLE      optional source drawable
    b      LBXGCANDDRAWUPDATE      optional gc and dest drawable
    c      LBXPINT16      src-x
    d      LBXPINT16      src-y
    e      LBXPINT16      dst-x
    f      LBXPINT16      dst-y
    g      LBXCARD16      width
    h      LBXCARD16      height
    p            unused, p=Lpad

The description of this request is on See LbxCopyArea.

    LbxCopyPlane
    1      CARD8      opcode
    1      27      lbx opcode
    2      L      request length
    4      CARD32      bit plane
    1      CARD8      source drawable cache entry
    1      LBXGCANDDRAWENT      cache entries
    4 or 0      DRAWABLE      optional source drawable
    b      LBXGCANDDRAWUPDATE      optional gc and dest drawable
    c      LBXPINT16      src-x
    d      LBXPINT16      src-y
    e      LBXPINT16      dst-x
    f      LBXPINT16      dst-y
    g      LBXCARD16      width
    h      LBXCARD16      height
    p            unused, p=Lpad

The description of this request is on See LbxCopyPlane.

    LbxPolyText8
    1      CARD8      opcode
    1      28      lbx opcode
    2      L      request length
    1      LBXGCANDDRAWENT      cache entries
    a      LBXGCANDDRAWUPDATE      optional gc and drawable
    b      LBXPINT16      x
    c      LBXPINT16      y
    n      LISTofTEXTITEM8      items
    p            unused, p=Lpad

The description of this request is on See LbxPolyText8.

    LbxPolyText16
    1      CARD8      opcode
    1      29      lbx opcode
    2      L      request length
    1      LBXGCANDDRAWENT      cache entries
    a      LBXGCANDDRAWUPDATE      optional gc and drawable
    b      LBXPINT16      x
    c      LBXPINT16      y
    2n      LISTofTEXTITEM16      items
    p            unused, p=Lpad

The description of this request is on See LbxPolyText16.

    LbxImageText8
    1      CARD8      opcode
    1      30      lbx opcode
    2      L      request length
    1      LBXGCANDDRAWENT      cache entries
    a      LBXGCANDDRAWUPDATE      optional gc and drawable
    b      LBXPINT16      x
    c      LBXPINT16      y
    n      STRING8      string
    p            unused, p=Lpad

The description of this request is on See LbxImageText8.

    LbxImageText16
    1      CARD8      opcode
    1      31      lbx opcode
    2      L      request length
    1      LBXGCANDDRAWENT      cache entries
    a      LBXGCANDDRAWUPDATE      optional gc and drawable
    b      LBXPINT16      x
    c      LBXPINT16      y
    2n      STRING16      string
    p            unused, p=Lpad

The description of this request is on See LbxImageText16.

    LbxQueryExtension
    1      CARD8      opcode
    1      32      lbx opcode
    2      2+(n+p)/4      request length
    4      n      length of extension name
    n      STRING8      extension name
    p            unused, p=pad(n)
    =>
    1      1      Reply
    1      n      number of requests in the extension
    2      CARD16      sequence number
    4      0 or 2*(m + p)      reply length, m = (n+7)/8
    1      BOOL      present
    1      CARD8      major opcode
    1      CARD8      first event
    1      CARD8      first error
    20            unused
    m      LISTofMASK      optional reply-mask
    p            unused, p=pad(m)
    m      LISTofMASK      optional event-mask
    p            unused, p=pad(m)

The description of this request is on See LbxQueryExtension.

    LbxPutImage
    1      CARD8      opcode
    1      33      lbx opcode
    2      L      request length
    1      CARD8      compression method
    1      LBXGCANDDRAWENT      cache entries
    a      PIPACKED            bit-packed
    b      LBXGCANDDRAWUPDATE      optional gc and drawable
    c      LBXCARD16      width
    d      LBXCARD16      height
    e      LBXPINT16      x
    f      LBXPINT16      y
    n      LISTofBYTE      compressed image data
    p            unused, p=Lpad

If there is no left padding and the depth is less than or equal to nine, PIPPACKED is encoded as follows:

    PIPACKED
    1      #x80 | (format << 5) | ((depth -1) << 2)

Otherwise PIPACKED is defined as:

    PIPACKED
    1      (depth -1) << 2)
    1      (format << 5) | left-pad

The description of this request is on See LbxPutImage.

    LbxGetImage
    1      CARD8      opcode
    1      34      lbx opcode
    2      6      request length
    4      DRAWABLE      drawable
    2      INT16      x
    2      INT16      y
    2      CARD16      width
    2      CARD16      height
    4      CARD32      plane mask
    1      CARD8      format
    3            unused
    =>
    1      1      Reply
    1      CARD8      depth
    2      CARD16      sequence number
    4      (n+p)/4      reply length
    4      (m+p)/4      X reply length; if uncompressed, m=n
    4      VISUALID      visual
    0      None
    1            compression method
    15            unused
    n      LISTofBYTE      data
    p            unused, p=pad(n)

The description of this request is on See LbxGetImage.

    LbxBeginLargeRequest
    1      CARD8      opcode
    1      35      lbx opcode
    2      2      request length
    4      CARD32      large request length

The description of this request is on See LbxBeginLargeRequest.

    LbxLargeRequestData
    1      CARD8      opcode
    1      36      lbx opcode
    2      1+n      request length
    4n      LISTofBYTE      data

The description of this request is on See LbxLargeRequestData.

    LbxEndLargeRequest
    1      CARD8      opcode
    1      37      lbx opcode
    2      1      request length

The description of this request is on See LbxEndLargeRequest.

    LbxInternAtoms
    1      CARD8      opcode
    1      38      lbx opcode
    2      1+(2+m+n+p)/4      request length
    2      m      num-atoms
    n      LISTofLONGSTR      names
    p            pad p=Lpad
    =>
    1      1      Reply
    1            unused
    2      CARD16      sequence number
    4      a      reply length, a = MAX(m - 6, 0)
    4*m      LISTofATOM      atoms
    p            pad p = MAX(0, 4*(6 - m))

    LONGSTR
    2      c      string length
    c      STRING8      string

The description of this request is on See LbxInternAtoms.

    LbxGetWinAttrAndGeom
    1      CARD8      opcode
    1      39      lbx opcode
    2      2      request length
    4      CARD32      window id
    =>
    1      1      Reply
    1            backing store
    0      NotUseful
    1      WhenMapped
    2      Always
    2      CARD16      sequence number
    4      7      reply length
    4      VISUALID      visual id
    2            class
    1      InputOutput
    2      InputOnly
    1      BITGRAVITY      bit gravity
    1      WINGRAVITY      window gravity
    4      CARD32      backing bit planes
    4      CARD32      backing pixel
    1      BOOL      save under
    1      BOOL      map installed
    1            map state
    0      Unmapped
    1      Unviewable
    2      Viewable
    1      BOOL      override
    4      COLORMAP      colormap
    4      SETofEVENT      all events mask
    4      SETofEVENT      your event mask
    2      SETofDEVICEEVENT      do not propagate mask
    2            unused
    4      WINDOW      root
    2      INT16      x
    2      INT16      y
    2      CARD16      width
    2      CARD16      height
    2      CARD16      border width
    1      CARD8      depth
    1            unused

The description of this request is on See LbxGetWinAttrAndGeom.

    LbxGrabCmap
    1      CARD8      opcode
    1      40      lbx opcode
    2      2      request length
    4      COLORMAP      colormap
    =>

If smart-grab is true, the reply is as follows:

    1      1      Reply
    1      #x80      flags
    2      CARD16      sequence number
    4      0      reply length
    24            unused

    If smart-grab is false, the reply is as follows:

    1      1      Reply
    1            flags (set of)
           #x40      auto-release
           #x20      three-channels
           #x10      two-byte-pixels
    lower four bits specifies bits-per-pixel
    2      CARD16      sequence number
    4      L      reply length
    m      CHAN or CHANNELS      cells (CHAN if !three-channels)
    p      0      pad(m)

    CHANNELS
    a      CHAN      red
    1      5            next channel
    b      CHAN      green
    1      5      next channel
    c      CHAN      blue
    1      0      list end

    CHAN
    d      LISTofLBXPIXEL

    LBXPIXEL
    e      PIXELPRIVATE or
          PIXELPRIVATERANGE or
          PIXELALLOC or
          PIXELALLOCRANGE

    PIXELPRIVATE
    1      1      pixel-private
    f      PIXEL      pixel

    PIXEL
    f      CARD8 or CARD16      (CARD8 if !two-byte-pixels)

    PIXELPRIVATERANGE
    1      2      pixel-private-range
    f      PIXEL      fist-pixel
    f      PIXEL      last-pixel

    PIXELALLOC
    1      3      pixel-private
    f      PIXEL      pixel
    g      COLORSINGLE or COLORTRIPLE      color       (COLORSINGLE if
    three-channels)

    COLORSINGLE
    h      CARD8 or CARD16      value (CARD8       if bits-per-rgb =< 7)

    COLORTRIPLE
    h      COLORSINGLE      red
    h      COLORSINGLE      green
    h      COLORSINGLE      blue

    PIXELALLOCRANGE
    1      4      pixel-private
    f      PIXEL      first-pixel
    f      PIXEL      last-pixel
    j      LISTofCOLORSINGLE or       color       (COLORSINGLE if three-channels)
          LISTofCOLORTRIPLE

The description of this request is on See LbxGrabCmap.

    LbxReleaseCmap
    1      CARD8      opcode
    1      41      lbx opcode
    2      2      request length
    4      COLORMAP      cmap

The description of this request is on See LbxReleaseCmap.

    LbxAllocColor
    1      CARD8      opcode
    1      42      lbx opcode
    2      5      request length
    4      COLORMAP      colormap
    4      CARD32      pixel
    2      CARD16      red
    2      CARD16      green
    2      CARD16            blue
    2            unused

The description of this request is on See LbxAllocColor.

    LbxSync
    1      CARD8      opcode
    1      43      lbx opcode
    2      1      request length
    =>
    1      1      Reply
    1      n      unused
    2      CARD16      sequence number
    4      0      reply length
    24            unused

The description of this request is on See LbxSync.

### Events

    LbxSwitchEvent
    1      base + 0      code
    1      0      lbx type
    2      CARD16      sequence number
    4      CARD32      client
    24            unused

The description of this event is on See LbxSwitchEvent.

    LbxCloseEvent
    1      base + 0      code
    1      1      lbx type
    2      CARD16      sequence number
    4      CARD32      client
    24            unused

The description of this event is on See LbxCloseEvent.

    LbxInvalidateTagEvent
    1      base + 0      code
    1      3      lbx type
    2      CARD16      sequence number
    4      CARD32      tag
    4            tag-type
    1      LbxTagTypeModmap
    2      LbxTagTypeKeymap
    3      LbxTagTypeProperty
    4      LbxTagTypeFont
    5      LbxTagTypeConnInfo
    20            unused

The description of this event is on See LbxInvalidateTagEvent.

    LbxSendTagDataEvent
    1      base + 0      code
    1      4      lbx type
    2      CARD16      sequence number
    4      CARD32      tag
    4            tag-type
    3      LbxTagTypeProperty
    20            unused

The description of this event is on See LbxSendTagDataEvent.

    LbxListenToOne
    1      base + 0      code
    1      5      lbx type
    2      CARD16      sequence number
    4      CARD32      client
    #xFFFFFFFF
    a client not managed by the proxy
    24            unused

The description of this event is on See LbxListenToOne.

    LbxListenToAll
    1      base + 0      code
    1      6      lbx type
    2      CARD16      sequence number
    28            unused

The description of this event is on See LbxListenToAll.

    LbxQuickMotionDeltaEvent
    1      base + 1      code
    1      CARD8      delta-time
    1      INT8      delta-x
    1      INT8      delta-y

This event is not padded to 32 bytes.

The description of this event is on See LbxQuickMotionDeltaEvent.

    LbxMotionDeltaEvent
    1      base + 0      code
    1      7                  lbx type
    1      INT8      delta-x
    1      INT8      delta-y
    2      CARD16      delta-time
    2      CARD16      delta-sequence

This event is not padded to 32 bytes.

The description of this event is on See LbxMotionDeltaEvent.

    LbxReleaseCmapEvent
    1      base + 0      code
    1      8                  lbx type
    2      CARD16      sequence number
    4      COLORMAP      colormap
    24            unused

The description of this event is on See LbxReleaseCmapEvent.

    LbxFreeCellsEvent
    1      base + 0      code
    1      9                  lbx type
    2      CARD16      sequence number
    4      COLORMAP      colormap
    4      PIXEL      pixel start
    4      PIXEL      pixel end
    16            unused

The description of this event is on See LbxFreeCellsEvent.

### Re-encoding of X Events

The X protocol requires all X events to be 32 bytes. The LBX server reduces the number of bytes sent between the server and the proxy for some X events by not appending unused pad bytes to the event data. The offsets of X event data are unchanged. The proxy will pad the events to 32 bytes before passing them on to the client.

LBX reencodes X event representations into the following sizes, if squishing is enabled:

    KeyOrButton            32
    EnterOrLeave           32
    Keymap                 32
    Expose                 20
    GraphicsExposure       24
    NoExposure             12
    VisibilityNotify       12
    CreateNotify           24
    DestroyNotify          12
    UnmapNotify            16
    MapNotify              16
    MapRequest             12
    Reparent               24
    ConfigureNotify        28
    ConfigureRequest       28
    GravityNotify          16
    ResizeRequest          12
    Circulate              20
    Property      Notify   20
    SelectionClear         20
    SelectionRequest       28
    SelectionNotify        24
    Colormap      Notify   16
    MappingNotify          8
    ClientMessage          32
    Unknown                32

### Responses

    LbxDeltaResponse
    1      event_base + 0      event code
    1      2      lbx type
    2      1+(2+2n+p)/4      request length
    1      n      count of diffs
    1      CARD8      cache index
    2n      LISTofDIFFITEM      offsets and differences
    p            unused, p=pad(2n)

The description of this response is on See LbxDeltaResponse.