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This specifies a protocol between IM library and IM (Input Method) Server for internationalized text input, which is indepedent from any specific language, any specific input method and the transport layer used in communication between the IM library and the IM Server, and uses a client-server model. This protocol allows user to use his/her favorite method for all applications within the stand-along distrubuted environment.
Table of Contents
The internationalization in the X Window System Version 11, Release 5 (X11R5) provides a common API which application developers can use to create portable internationalized programs and to adapt them to the requirements of different native languages, local customs, and character string encodings (this is called "localization"). As one of its internationalization mechanisms X11R5 has defined a functional interface for internationalized text input, called XIM (X Input Method).
When a client-server model is used with an IM (Input Method) implementation, a protocol must be established between the client and the server. However, the protocol used to interface Input Method Servers (IM Servers) with the Input Method libraries (IM libraries) to which applications are linked was not addressed in X11R5. This led application developers to depend on vendor-specific input methods, decreased the user's choice of available input methods, and made it more difficult for developers to create portable applications. This paper describes the Input Method Protocol developed for X11R6 to resolve the above problems and to address the requirements of existing and future input methods.
The Input Method Protocol is independent from the transport layer used in communication between the IM library and the IM Server. Thus, the input method protocol can be built on any inter-process communication mechanism, such as TCP/IP or the X protocol.
In addition, the protocol provides for future extensions such as differing input model types.
Text input is much more simple for some languages than others. English, for instance, uses an alphabet of a manageable size, and input consists of pressing the corresponding key on a keyboard, perhaps in combination with a shift key for capital letters or special characters.
Some languages have larger alphabets, or modifiers such as accents, which require the addition of special key combinations in order to enter text. These input methods may require "dead-keys" or "compose-keys" which, when followed by different combinations of key strokes, generate different characters.
Text input for ideographic languages is much less simple. In these languages, characters represent actual objects rather than phonetic sounds used in pronouncing a word, and the number of characters in these languages may continue to grow. In Japanese, for instance, most text input methods involve entering characters in a phonetic alphabet, after which the input method searches a dictionary for possible ideographic equivalents (of which there may be many). The input method then presents the candidate characters for the user to choose from.
In Japanese, either Kana (phonetic symbols) or Roman letters are typed and then a region is selected for conversion to Kanji. Several Kanji characters may have the same phonetic representation. If that is the case with the string entered, a menu of characters is presented and the user must choose the appropriate one. If no choice is necessary or a preference has been established, the input method does the substitution directly.
These complicated input methods must present state information (Status Area), text entry and edit space (Preedit Area), and menu/choice presentations (Auxiliary Area). Much of the protocol between the IM library and the IM Server involves managing these IM areas. Because of the size and complexity of these input methods, and because of how widely they vary from one language or locale to another, they are usually implemented as separate processes which can serve many client processes on the same computer or network.
X11 internationalization support includes the following four types of input method:
- on-the-spot: | The client application is directed by the IM Server to display all pre-edit data at the site of text insertion. The client registers callbacks invoked by the input method during pre-editing. |
- off-the-spot: | The client application provides display windows for the pre-edit data to the input method which displays into them directly. |
- over-the-spot: | The input method displays pre-edit data in a window which it brings up directly over the text insertion position. |
- root-window: | The input method displays all pre-edit data in a separate area of the screen in a window specific to the input method. |
Client applications must choose from the available input methods supported by the IM Server and provide the display areas and callbacks required by the input method.
Within the X Window System environment, the following two typical architectural models can be used as an input method's implementation model.
- Client/Server model: | A separate process, the IM Server, processes input and handles preediting, converting, and committing. The IM library within the application, acting as client to the IM Server, simply receives the committed string from the IM Server. |
- Library model: | All input is handled by the IM library within the application. The event process is closed within the IM library and a separate IM Server process may not be required. |
Most languages which need complex preediting, such as Asian languages, are implemented using the Client/Server IM model. Other languages which need only dead key or compose key processing, such as European languages, are implemented using the Library model.
In this paper, we discuss mainly the Client/Server IM model and the protocol used in communication between the IM library (client) and the IM Server.
When the client connects or disconnects to the IM Server, an open or close operation occurs between the client and the IM Server.
The IM can be specified at the time of XOpenIM() by setting the locale of the client and a locale modifier. Since the IM remembers the locale at the time of creation XOpenIM() can be called multiple times (with the setting for the locale and the locale modifier changed) to support multiple languages.
In addition, the supported IM type can be obtained using XGetIMValues().
The client usually holds multiple input (text) fields. Xlib provides a value type called the "Input Context" (IC) to manage each individual input field. An IC can be created by specifying XIM using XCreateIC(), and it can be destroyed using XDestroyIC().
The IC can specify the type of IM which is supported by XIM for each input field, so each input field can handle a different type of IM.
Most importantly information such as the committed string sent from the IM Server to the client, is exchanged based on each IC.
Since each IC corresponds to an input field, the focused input field should be announced to the IM Server using XSetICFocus(). (XUnsetICFocus() can also be used to change the focus.)
Existing input methods support either the FrontEnd method, the BackEnd method, or both. This protocol specifically supports the BackEnd method as the default method, but also supports the FrontEnd method as an optional IM Server extension.
The difference between the FrontEnd and BackEnd methods is in how events are delivered to the IM Server. (Fig. 1)
In the BackEnd method, client window input events are always delivered to the IM library, which then passes them to the IM Server. Events are handled serially in the order delivered, and therefore there is no synchronization problem between the IM library and the IM Server.
Using this method, the IM library forwards all KeyPress and KeyRelease events to the IM Server (as required by the Event Flow Control model described in the section called “Event Flow Control”) and synchronizes with the IM Server (as described in the section called “Filtering Events”).
In the FrontEnd method, client window input events are delivered by the X server directly to both the IM Server and the IM library. Therefore this method provides much better interactive performance while preediting (particularly in cases such as when the IM Server is running locally on the user's workstation and the client application is running on another workstation over a relatively slow network).
However, the FrontEnd model may have synchronization problems between the key events handled in the IM Server and other events handled in the client, and these problems could possibly cause the loss or duplication of key events. For this reason, the BackEnd method is the core method supported, and the FrontEnd method is made available as an extension for performance purposes. (Refer to Appendix A, Common Extensions for more information.)
This protocol supports two event flow models for communication between the IM library and the IM Server (Static and Dynamic).
Static Event Flow requires that input events always be sent to the IM Server from the client.
Dynamic Event Flow, however, requires only that those input events which need to be processed (converted) be sent to the IM Server from the client.
For instance, in the case of inputing a combination of ASCII characters and Chinese characters, ASCII characters do not need to be processed in the IM Server, so their key events do not have to be sent to the IM Server. On the other hand, key events necessary for composing Chinese characters must be sent to the IM Server.
Thus, by adopting the Dynamic Event Flow, the number of requests among the
X Server, the client, and the IM Server is significantly reduced, and the
number of context switches is also reduced, resulting in improved performance.
The IM Server can send
XIM_REGISTER_TRIGGERKEYS
message in order to switch the event flow in the Dynamic Event Flow.
The protocol for this process is described in the section called “Event Flow Control”.
IM Servers are strongly encouraged to register their symbolic
names as the ATOM names into the IM Server directory property,
XIM_SERVERS,
on the root window of the screen_number 0.
This property can contain a list of ATOMs, and the each ATOM represents
each possible IM Server.
IM Server names are restricted to POSIX Portable Filename Character Set.
To discover if the IM Server is active, see if there is an owner for
the selection with that atom name. To learn the address of that IM Server,
convert the selection target
TRANSPORT,
which will return a string form of the transport address(es).
To learn the supported locales of that IM Server, convert the selection target
LOCALES,
which will return a set of names of the supported locales in the syntax
X/Open defines.
The basic semantics to determine the IM Server if there are
multiple ATOMs are found in
XIM_SERVERS
property, is first fit if the IM Server name is not given as
a X modifier's category
im.
The address information retrievable from the
TRANSPORT
target is a transport-specific name.
The preregistered formats for transport-specific names are listed in
Appendix B, Transport List.
Additional transport-specific names may be registered with X Consortium.
For environments that lack X connections, or for IM Servers which do not use the X Window System, the preconnection convention with IM Server may be given outside the X Window system (e.g. using a Name Service).
The protocol described below uses the bi-directional synchronous/asynchronous request/reply/error model and is specified using the same conventions outlined in Section 2 of the core X Window System protocol [1]:
This section describes the requests that may be exchanged between the client and the IM Server.
The basic request packet header format is as follows.
major-opcode: CARD8
minor-opcode: CARD8
length: CARD16
The MAJOR-OPCODE specifies which core request or extension package this
packet represents. If the MAJOR-OPCODE corresponds to a core request,
the MINOR-OPCODE contains 8 bits of request-specific data.
(If the MINOR-OPCODE is not used, it is 0.)
Otherwise, the MAJOR-OPCODE and the MINOR-OPCODE are specified by
XIM_QUERY_EXTENSION
message. (Refer to 4.7. Query the supported extension protocol list.)
The LENGTH field specifies the number of 4 bytes elements following the
header. If no additional data is followed by the header, the LENGTH field
will be 0.
The following data types are used in the core X IM Server protocol:
BITMASK16
CARD16
BITMASK32
CARD32
PADDING FORMAT
Where N is some expression, and Pad(N) is the number of bytes needed to round N up to a
Pad(N) = (4 - (N mod 4)) mod 4
LPCE
1 A character from the4 X Portable Character Set in Latin Portable
Character Encoding
STRING
2 n length of string in bytes
n LISTofLPCE string
p unused, p=Pad(2+n)
STR
1 n length of name in bytes
n STRING8 name
XIMATTR
2 CARD16 attribute ID (*1)
2 CARD16 type of the value (*2)
2 n length of im-attribute
n STRING8 im-attribute
p unused, p = Pad(2+n)
The im-attribute argument specifies XIM values such as XNQueryInputStyle.
XICATTR
2 CARD16 attribute ID (*1)
2 CARD16 type of the value (*2)
2 n length of ic-attribute
n STRING8 ic-attribute
p unused, p = Pad(2+n)
(*1) XIMATTR and XICATTR are used during the setup stage and XIMATTRIBUTE and
XICATTRIBUTE are used after each attribute ID has been recognized by
the IM Server and the IM library.
(*2) The value types are defined as follows:
| values | data | format | ||
|---|---|---|---|---|
| #0 | Separator of NestedList | -----(*3) | ||
| #1 | byte data | CARD8 | ||
| #2 | word data | CARD16 | ||
| #3 | long data | CARD32 | ||
| #4 | char data | STRING8 | ||
| #5 | Window | CARD32 | ||
| #10 | XIMStyles | 2 | n | number of XIMStyle list |
| 2 | unused | |||
| n | CARD32 | XIMStyle list | ||
| #11 | XRectangle | 2 | INT16 | X |
| 2 | INT16 | Y | ||
| 2 | CARD16 | width | ||
| 2 | CARD16 | height | ||
| #12 | XPoint | 2 | INT16 | X |
| 2 | INT16 | Y | ||
| #13 | XFontSet | 2 | n | length of Base font name |
| n | STRING8 | Base font name list | ||
| p | unused, p = Pad(2+n) | |||
| #15 | XIMHotKeyTriggers | 4 | n | number of XIMTRIGGERKEY list (*4) |
| n | XIMTRIGGERKEY | XIMHotkeyTrigger list | ||
| n | XIMHOTKEYSTATE | HotKey processing state | ||
| #17 | XIMStringConversion | XIMSTRCONVTEXT | ||
| #18 | XIMPreeditState | XIMPREEDITSTATE | ||
| #19 | XIMResetState | XIMRESETSTATE | ||
| #x7fff | NestedList | ----- |
(*3) The IC value for the separator of NestedList is defined as follows,
#define XNSeparatorofNestedList "separatorofNestedList"
, which is registered in X Consortium and cannot be used for any other purpose.
(*4) LISTofFOO
A Type name of the form LISTof FOO means a counted list of elements of type FOO.
The size of the length field may vary (it is not necessarily the same
size as a FOO), and in some cases, it may be implicit.
XIMTRIGGERKEY
4 CARD32 keysym
4 CARD32 modifier
4 CARD32 modifier mask
ENCODINGINFO
2 n length of encoding info
n STRING8 encoding info
p unused, p=Pad(2+n)
1 CARD8 extension major-opcode
1 CARD8 extension minor-opcode
2 n length of extension name
n STRING8 extension name
p unused, p = Pad(n)
XIMATTRIBUTE
2 CARD16 attribute ID
2 n value length
n value
p unused, p = Pad(n)
XICATTRIBUTE
2 CARD16 attribute ID
2 n value length
n value
p unused, p = Pad(n)
XIMSTRCONVTEXT
2 CARD16 XIMStringConversionFeedback
#x0000001 XIMStringConversionLeftEdge
#x0000002 XIMStringConversionRightEdge
#x0000004 XIMStringConversionTopEdge
#x0000008 XIMStringConversionBottomEdge
#x0000010 XIMStringConversionConvealed
#x0000020 XIMStringConversionWrapped
2 n byte length of the retrieved string
n STRING8 retrieved string
p unused, p = Pad(n)
2 m byte length of feedback array
2 unused
m LISTofXIMSTRCONVFEEDBACK feedback array(*1)
(*1) This field is reserved for future use.
XIMFEEDBACK
4 CARD32 XIMFeedback
#x000001 XIMReverse
#x000002 XIMUnderline
#x000004 XIMHighlight
#x000008 XIMPrimary
#x000010 XIMSecondary
#x000020 XIMTertiary
#x000040 XIMVisibleToForward
#x000080 XIMVisibleToBackward
#x000100 XIMVisibleCenter
XIMHOTKEYSTATE
4 CARD32 XIMHotKeyState
#x0000001 XIMHotKeyStateON
#x0000002 XIMHotKeyStateOFF
XIMPREEDITSTATE
4 CARD32 XIMPreeditState
#x0000001 XIMPreeditEnable
#x0000002 XIMPreeditDisable
XIMRESETSTATE
4 CARD32 XIMResetState
#x0000001 XIMInitialState
#x0000002 XIMPreserveState
Both the IM Server and the IM library return
XIM_ERROR
messages instead of the corresponding reply messages if any errors occur
during data processing.
At most one error is generated per request. If more than one error condition is encountered in processing a request, the choice of which error is returned is implementation-dependent.
XIM_ERROR (IM Server <--> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 BITMASK16 flag (*1)
#0000 Both Input-Method-ID and Input-Context-ID are invalid
#0001 Input-Method-ID is valid
#0002 Input-Context-ID is valid
2 CARD16 Error Code
#1 BadAlloc
#2 BadStyle
#3 BadClientWindow
#4 BadFocusWindow
#5 BadArea
#6 BadSpotLocation
#7 BadColormap
#8 BadAtom
#9 BadPixel
#10 BadPixmap
#11 BadName
#12 BadCursor
#13 BadProtocol
#14 BadForeground
#15 BadBackground
#16 LocaleNotSupported
#999 BadSomething (*2)
2 n byte length of error detail.
2 CARD16 type of error detail (*3)
n STRING8 error detail (*4)
p unused, p = Pad(n)
(*1) Before an IM is created, both Input-Method-ID and
Input-Context-ID are invalid.
Before an IC is created, only Input-Method-ID is valid.
After that, both of Input-Method-ID and Input-Context-ID are valid.
(*2) Unspecific error, for example "language engine died"
(*3) This field is reserved for future use.
(*4) Vendor defined detail error message
XIM_CONNECT
message requests to establish a connection over a mutually-understood virtual
stream.
XIM_CONNECT (IM library -> IM Server)
1 byte order
#x42 MSB first
#x6c LSB first
1 unused
2 CARD16 client-major-protocol-version (*1)
2 CARD16 client-minor-protocol-version (*1)
2 CARD16 number of client-auth-protocol-names
n LISTofSTRING client-auth-protocol-names
(*1) Specify the version of IM Protocol that the client supports.
A client must send
XIM_CONNECT
message as the first message on the connection.
The list specifies the names of authentication protocols the sending
IM Server is willing to perform.
(If the client need not authenticate, the list may be omited.)
XIM_AUTH_REQUIRED
message is used to send the authentication protocol name and protocol-specific
data.
XIM_AUTH_REQUIRED (IM library <--> IM Server)
1 CARD8 auth-protocol-index
3 unused
2 n length of authentication data
2 unused
n <varies> data
p unused, p = Pad(n)
The auth-protocol is specified by an index into the list of names
given in the
XIM_CONNECT
or
XIM_AUTH_SETUP
message. Any protocol-specific data that might be required is also sent.
The IM library sends
XIM_AUTH_REPLY
message as the reply to
XIM_AUTH_REQUIRED
message, if the IM Server is authenticated.
XIM_AUTH_REPLY (IM library -> IM Server)
2 n length of authentication data
2 unused
2 n length of authentication data
2 unused
n <varies> data
p unused, p = Pad(n)
The auth data is specific to the authentication protocol in use.
XIM_AUTH_NEXT
message requests to send more auth data.
XIM_AUTH_NEXT (IM library <--> IM Server)
2 n length of authentication data
2 unused
n <varies> data
p unused, p = Pad(n)
The auth data is specific to the authentication protocol in use.
The IM Server sends
XIM_AUTH_SETUP
message to authenticate the client.
XIM_AUTH_SETUP (IM Server -> IM library)
2 CARD16 number of client-auth-protocol-names
2 unused
n LISTofSTRING server-auth-protocol-names
The list specifies the names of authentication protocols the client is willing to perform.
XIM_AUTH_NG
message requests to give up the connection.
XIM_AUTH_NG (IM library <--> IM Server)
The IM Server sends
XIM_CONNECT_REPLY
message as the reply to
XIM_CONNECT
or
XIM_AUTH_REQUIRED
message.
XIM_CONNECT_REPLY (IM Server -> IM library)
2 CARD16 server-major-protocol-version (*1)
2 CARD16 server-minor-protocol-version (*1)
(*1) Specify the version of IM Protocol that the IM Server supports.
This document specifies major version one, minor version zero.
Here are the state diagrams for the client and the IM Server.
State transitions for the client
init_status: | Use authorization function -> client_ask Not use authorization function -> client_no_check |
start: |
Send If client_ask -> client_wait1 If client_no_check, client-auth-protocol-names may be omited -> client_wait2 |
client_wait1: |
Receive Receive <other> -> client_NG |
client_check: |
If no more auth needed, send
If good auth data, send
If bad auth data, send |
client_wait2: |
Receive
Receive
Receive Receive <other> -> client_NG |
client_more: |
Send |
client_NG: |
Send |
State transitions for the IM Server
init_status: | Use authorization function -> server_ask Not use authorization function -> server_no_check |
start: |
Receive -> start2 Receive <other> -> server_NG |
start2: |
If client_ask, send
If client_no_check and
server_ask, send
If client_no_check and
server_no_check, send
|
server_wait1: |
Receive
Receive
Receive <other> -> server_NG |
server_more |
Send
|
server2 |
If server_ask, send
If server_no_check, send
|
server_wait2 |
Receive
Receive <other> -> server_NG |
server_check |
If no more auth data, send
If bad auth data, send
If good auth data, send
|
server_NG |
Send
|
XIM_DISCONNECT
message requests to shutdown the connection over a mutually-understood
virtual stream.
XIM_DISCONNECT (IM library -> IM Server)
XIM_DISCONNECT
is a synchronous request. The IM library should wait until it receives
either an
XIM_DISCONNECT_REPLY
packet or an XIM_ERROR packet.
XIM_DISCONNECT_REPLY (IM Server -> IM library)
XIM_OPEN
requests to establish a logical connection between the IM library and the IM
Server.
XIM_OPEN (IM library -> IM Server)
n STR locale name
p unused, p = Pad(n)
XIM_OPEN
is a synchronous request. The IM library should wait until receiving
either an XIM_OPEN_REPLY
packet or an XIM_ERROR packet.
XIM_OPEN_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 n byte length of IM attributes supported
n LISTofXIMATTR IM attributes supported
2 m byte length of IC attributes supported
2 CARD16 unused
m LISTofXICATTR IC attributes supported
XIM_OPEN_REPLY
message returns all supported IM and IC attributes in LISTofXIMATTR and
LISTofXICATTR. These IM and IC attribute IDs are used to reduce the amount
of data which must be transferred via the network. In addition, this
indicates to the IM library what kinds of IM/IC attributes can be used
in this session, and what types of data will be exchanged. This allows
the IM Server provider and application writer to support IM system
enhancements with new IM/IC attributes, without modifying Xlib.
The IC value for the separator of NestedList must be included in the
LISTofXICATTR.
XIM_CLOSE
message requests to shutdown the logical connection between the IM library
and the IM Server.
XIM_CLOSE (IM library -> IM Server)
2 CARD16 input-method-ID
2 unused
XIM_CLOSE
is a synchronous request. The IM library should wait until receiving
either an XIM_CLOSE_REPLY
packet or an XIM_ERROR packet.
XIM_CLOSE_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 unused
An IM Server must send
XIM_SET_EVENT_MASK
message to the IM library in order for events to be forwarded to the IM
Server, since the IM library initially doesn't forward any events to the
IM Server. In the protocol, the IM Server will specify masks of X events
to be forwarded and which need to be synchronized by the IM library.
XIM_SET_EVENT_MASK (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 EVENTMASK forward-event-mask (*1)
4 EVENTMASK synchronous-event-mask (*2)
(*1) Specify all the events to be forwarded to the IM Server by the IM library.
(*2) Specify the events to be forwarded with synchronous flag on by the IM library.
XIM_SET_EVENT_MASK
is an asynchronous request. The event masks are valid immediately after
they are set until changed by another
XIM_SET_EVENT_MASK
message. If input-context-ID is set to zero, the default value of the
input-method-ID will be changed to the event masks specified in the request.
That value will be used for the IC's which have no individual values.
Using the Dynamic Event Flow model, an IM Server sends
XIM_REGISTER_TRIGGERKEYS
message to the IM library before sending
XIM_OPEN_REPLY
message.
Or the IM library may suppose that the IM Server uses the Static Event Flow
model.
XIM_REGISTER_TRIGGERKEYS (IM Server -> IM library)
2 CARD16 input-method-ID
2 unused
4 n byte length of on-keys
n LISTofXIMTRIGGERKEY on-keys list
4 m byte length of off-keys
m LISTofXIMTRIGGERKEY off-keys list
XIM_REGISTER_TRIGGERKEYS
is an asynchronous request.
The IM Server notifys the IM library of on-keys and off-keys lists with
this message.
The IM library notifys the IM Server with
XIM_TRIGGER_NOTIFY
message that a key event matching either on-keys or off-keys has been occurred.
XIM_TRIGGER_NOTIFY (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 CARD32 flag
#0 on-keys list
#1 off-keys list
4 CARD32 index of keys list
4 EVENTMASK client-select-event-mask (*1)
(*1) Specify the events currently selected by the IM library with XSelectInput.
XIM_TRIGGER_NOTIFY
is a synchronous request. The IM library should wait until receiving
either an XIM_TRIGGER_NOTIFY_REPLY
packet or an XIM_ERROR packet.
XIM_TRIGGER_NOTIFY_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_ENCODING_NEGOTIATION
message requests to decide which encoding to be sent across the wire.
When the negotiation fails, the fallback default encoding is Portable
Character Encoding.
XIM_ENCODING_NEGOTIATION (IM library -> IM Server).sp 6p
2 CARD16 input-method-ID
2 n byte length of encodings listed by name
n LISTofSTR list of encodings supported in the IM library.
p unused, p = Pad(n)
2 m byte length of encodings listed by detailed data
2 unused
m LISTofENCODINGINFO list of encordings supported in the IM library
The IM Server must choose one encoding from the list sent by the IM library.
If index of the encording determined is -1 to indicate that the negotiation
is failed, the fallback default encoding is used.
The message must be issued after sending
XIM_OPEN message via XOpenIM().
The name of encoding may be registered with X Consortium.
XIM_ENCODING_NEGOTIATION
is a synchronous request. The IM library should wait until receiving
either an XIM_ENCODING_NEGOTIATION_REPLY
packet or an XIM_ERROR packet.
XIM_ENCODING_NEGOTIATION_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 category of the encoding determined.
#0 name
#1 detailed data
2 INT16 index of the encoding determinated.
2 unused
XIM_QUERY_EXTENSION
message requests to query the IM extensions supported by the IM Server to
which the client is being connected.
XIM_QUERY_EXTENSION (IM library -> IM Server)
2 CARD16 input-method-ID
2 n byte length of extensions supported by the IM library
n LISTofSTR extensions supported by the IM library
p unused, p = Pad(n)
An example of a supported extension is FrontEnd.
The message must be issued after sending
XIM_OPEN message via XOpenIM().
If n is 0, the IM library queries the IM Server for all extensions.
If n is not 0, the IM library queries whether the IM Server supports the contents specified in the list.
If a client uses an extension request without previously having issued a
XIM_QUERY_EXTENSION
message for that extension, the IM Server responds with a
BadProtocol
error. If the IM Server encounters a request with an unknown MAJOR-OPCODE
or MINOR-OPCODE, it responds with a
BadProtocol error.
XIM_QUERY_EXTENSION
is a synchronous request. The IM library should wait until receiving
either an XIM_QUERY_EXTENSION_REPLY
packet or an XIM_ERROR packet.
XIM_QUERY_EXTENSION_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 n byte length of extensions supported by both the IM library and the IM Server
n LISTofEXT list of extensions supported by both the IM library and the IM Server
XIM_QUERY_EXTENSION_REPLY
message returns the list of extensions supported by both the IM library and
the IM Server. If the list passed in
XIM_QUERY_EXTENSION
message is NULL, the IM Server returns the full list of extensions supported
by the IM Server. If the list is not NULL, the IM Server returns the
extensions in the list that are supported by the IM Server.
A zero-length string is not a valid extension name. The IM library should disregard any zero-length strings that are returned in the extension list. The IM library does not use the requests which are not supported by the IM Server.
XIM_SET_IM_VALUES
requests to set attributes to the IM.
XIM_SET_IM_VALUES (IM library -> IM Server)
2 CARD16 input-method-ID
2 n byte length of im-attribute
n LISTofXIMATTRIBUTE im-attributes
The im-attributes in
XIM_SET_IM_VALUES
message are specified as a LISTofXIMATTRIBUTE, specifying the attributes
to be set. Attributes other than the ones returned by
XIM_OPEN_REPLY
message should not be specified.
XIM_SET_IM_VALUES
is a synchronous request. The IM library should wait until receiving
either an
XIM_SET_IM_VALUES_REPLY
packet or an
XIM_ERROR
packet, because it must receive the error attribute if
XIM_ERROR message is returned.
XIM_SET_IM_VALUES_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 unused
XIM_SET_IM_VALUES_REPLY
message returns the input-method-ID to distinguish replies from multiple IMs.
XIM_GET_IM_VALUES
requests to query IM values supported by the IM Server currently being
connected.
XIM_GET_IM_VALUES (IM library -> IM Server)
2 CARD16 input-method-ID
2 n byte length of im-attribute-id
n LISTofCARD16 im-attribute-id
p unused, p=Pad(n)
XIM_GET_IM_VALUES
is a synchronous request. The IM library should wait until it receives
either an
XIM_GET_IM_VALUES_REPLY
packet or an XIM_ERROR packet.
XIM_GET_IM_VALUES_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 n byte length of im-attributes returned
n LISTofXIMATTRIBUTE im-attributes returned
The IM Server returns IM values with
XIM_GET_IM_VALUES_REPLY
message. The order of the returned im-attribute values corresponds directly
to that of the list passed with the
XIM_GET_IM_VALUES message.
XIM_CREATE_IC message requests to create an IC.
XIM_CREATE_IC (IM library -> IM Server)
2 CARD16 input-method-ID
2 n byte length of ic-attributes
n LISTofXICATTRIBUTE ic-attributes
The input-context-id is specified by the IM Server to identify the client
(IC). (It is not specified by the client in
XIM_CREATE_IC
message.), and it should not be set to zero.
XIM_CREATE_IC
is a synchronous request which returns the input-context-ID.
The IM library should wait until it receives either an
XIM_CREATE_IC_REPLY
packet or an
XIM_ERROR
packet.
XIM_CREATE_IC_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_DESTROY_IC
message requests to destroy the IC.
XIM_DESTROY_IC (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_DESTROY_IC
is a synchronous request. The IM library should not free its resources
until it receives an
XIM_DESTROY_IC_REPLY
message because XIM_DESTROY_IC
message may result in Callback packets such as
XIM_PREEDIT_DRAW
and XIM_PREEDIT_DONE.
XIM_DESTROY_IC_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_SET_IC_VALUES
messages requests to set attributes to the IC.
XIM_SET_IC_VALUES (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 n byte length of ic-attributes
2 unused
n LISTofXICATTRIBUTE ic-attributes
The ic-attributes in
XIM_SET_IC_VALUES
message are specified as a LISTofXICATTRIBUTE, specifying the attributes
to be set. Attributes other than the ones returned by
XIM_OPEN_REPLY message should not be specified.
XIM_SET_IC_VALUES
is a synchronous request. The IM library should wait until receiving
either an XIM_SET_IC_VALUES_REPLY
packet or an XIM_ERROR
packet, because it must receive the error attribute if
XIM_ERROR message is returned.
XIM_SET_IC_VALUES_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_GET_IC_VALUES
message requests to query IC values supported by the IM Server currently
being connected.
XIM_GET_IC_VALUES (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 n byte length of ic-attribute-id
n LISTofCARD16 ic-attribute-id
p unused, p=Pad(2+n)
In LISTofCARD16, the appearance of the ic-attribute-id for the separator of NestedList shows the end of the heading nested list.
XIM_GET_IC_VALUES
is a synchronous request and returns each attribute with its values to
show the correspondence. The IM library should wait until receiving
either an XIM_GET_IC_VALUES_REPLY
packet or an XIM_ERROR packet.
XIM_GET_IC_VALUES_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 n byte length of ic-attribute
2 unused
n LISTofXICATTRIBUTE ic-attribute
XIM_SET_IC_FOCUS
message requests to set the focus to the IC.
XIM_SET_IC_FOCUS (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_SET_IC_FOCUS is an asynchronous request.
XIM_UNSET_IC_FOCUS
message requests to unset the focus to the focused IC.
XIM_UNSET_IC_FOCUS (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_UNSET_IC_FOCUS
is an asynchronous request.
Event filtering is mainly provided for BackEnd method to allow input method to capture X events transparently to clients.
X Events are forwarded by
XIM_FORWARD_EVENT message.
This message can be operated both synchronously and asynchronously.
If the requester sets the synchronous flag, the receiver must send
XIM_SYNC_REPLY
message back to the requester when all the data processing is done.
Protocol flow of BackEnd model
With BackEnd method, the protocol flow can be classified into two
methods in terms of synchronization, depending on the synchronous-eventmask
of XIM_SET_EVENT_MASK
message. One can be called on-demand-synchronous method and another
can be called as full-synchronous method.
In on-demand-synchronous method, the IM library always receives
XIM_FORWARD_EVENT
or
XIM_COMMIT
message as a synchronous request. Also, the IM Server needs to synchronously
process the correspondent reply from the IM library and the following
XIM_FORWARD_EVENT
message sent from the IM library when any of the event causes the IM Server
to send
XIM_FORWARD_EVENT
or
XIM_COMMIT
message to the IM library, so that the input service is consistent. If the
IM library gets the control back from the application after receiving the
synchronous request, the IM library replies for the synchronous request before
processing any of the events. In this time, the IM Server blocks
XIM_FORWARD_EVENT
message which is sent by the IM library, and handles it after receiving the
reply. However, the IM Server handles the other protocols at any time.
In full-synchronous method, the IM library always sends
XIM_FORWARD_EVENT
message to the IM Server as a synchronous request. Therefore, the reply to it
from the IM Server will be put between the
XIM_FORWARD_EVENT message and its
XIM_SYNC_REPLY message. In case of sending
XIM_FORWARD_EVENT or
XIM_COMMIT
message, the IM Server should set the synchronous flag off. Because the
synchronization can be done by the following
XIM_SYNC_REPLY message.
Following chart shows one of the simplest protocol flow which only deals with keyevents for preediting operation.
Following chart shows one of the complex protocol flow, which deals with multiple focus windows and button press event as well as keyevent, and the focus is moved by the application triggered by both of keyevent and button press event.
XIM_FORWARD_EVENT (IM library <--> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 BITMASK16 flag
#0001 synchronous
#0002 request filtering (*1)
#0004 request lookupstring (*2)
2 CARD16 serial number
XEVENT X event
(*1) Indicate the receiver should filter events and possible preedit may be invoked.
(*2) Indicate the receiver should only do lookup string. The IM Server is expected
to just do a conversion of the key event to the best candidate. This bit may
affect the state of the preedit state (e.g. compose of dead key sequences).
XEVENT format is same as the X Protocol event format(xEvent). As the value of xEvent's sequenceNumber is the bottom of 16 bit of XEvent's xany.serial, the top of 16 bit is sent by serial number(INT16).
XIM_FORWARD_EVENT
message is used for forwarding the events from the IM library to the IM Server
in order for IM to be able to filter the event. On the other hand, this
message is also used for forwarding the events from the IM Server to the IM
library if the event forwarded from the IM library is not filtered.
The IM Server, which receives
XIM_FORWARD_EVENT
message without synchronous bit, should set synchronous bit.
If both "request event filtering" and "request lookupstring" flag are
set, then both filtering and lookup should be done for the same event.
XIM_SYNC
message requests to synchronize the IM library and the IM Server.
XIM_SYNC (IM library <--> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
This synchronization can be started either on the IM library side or on the
IM Server side. The side which receives
XIM_SYNC
message should process all XIM requests before replying. The input-context-ID
is necessary to distinguish the IC with which the IM library and the IM
Server are synchronized.
XIM_SYNC_REPLY (IM Server <--> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
The side which receives
XIM_FORWARD_EVENT,
XIM_COMMIT
or any other message with synchronous bit, should process all XIM request
before replying, and send
XIM_SYNC_REPLY
message as the reply to the previous message.
When the IM Server commits a string, the IM Server sends either the committed
string or list of KeySym, or both, by
XIM_COMMIT
message.
XIM_COMMIT (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 BITMASK16 flag
#0001 synchronous
#0002 XLookupChars
#0004 XLookupKeySym
#0006 XLookupBoth = XLookupChars | XLookupKeySym
If flag is XLookupKeySym, the arguments continue as follows:
2 unused
4 KEYSYM KeySym
If flag is XLookupChars, the arguments continue as follows
2 m byte length of committed string
m LISTofBYTE committed string
p unused, p = Pad(m)
If flag is XLookupBoth, the arguments continue as follows
2 unused
4 KEYSYM KeySym
2 n byte length of committed string
n LISTofBYTE committed string
p unused, p = Pad(2+n)
The IM Server which receives
XIM_COMMIT
message without synchronous bit should set synchronous bit.
XIM_RESET_IC
message requests to reset the status of IC in the IM Server.
XIM_RESET_IC (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_RESET_IC
is a synchronous request. The IM library should wait until receiving either an
XIM_RESET_IC_REPLY packet or an
XIM_ERROR packet.
XIM_RESET_IC_REPLY (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 n byte length of preedit string
n LISTofBYTE preedit string
p unused, p = Pad(2+n)
XIM_RESET_IC_REPLY
message returns the input-context-ID to distinguish replies from multiple ICs.
If XIMStyle has XIMPreeditArea or XIMStatusArea set, XIMGeometryCallback may be used, and if XIMPreeditCallback and/or XIMStatusCallback are set, corresponding callbacks may be used.
Any callback request may be sent from an IM Server to an IM client asynchronously in response to any request previously sent by the IM client to the IM Server.
When an IM Server needs to send a callback request synchronously with the request previously sent by an IM client, the IM Server sends it before replying to the previous request.
The IM Server sends
XIM_GEOMETRY
message to start geometry negotiation, if XIMStyle has XIMPreeditArea or
XIMStatusArea set.
XIM_GEOMETRY (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
There is always a single Focus Window, even if some input fields have only one IC.
XIM_STR_CONVERSION (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 CARD16 XIMStringConversionPosition
2 unused
4 CARD32 XIMCaretDirection
#0 XIMForwardChar
#1 XIMBackwardChar
#2 XIMForwardWord
#3 XIMBackwardWord
#4 XIMCaretUp
#5 XIMCaretDown
#6 XIMNextLine
#7 XIMCPreviousLine
#8 XIMLineStart
#9 XIMLineEnd
#10 XIMAbsolutePosition
#11 XIMDontChange
2 CARD16 factor
2 CARD16 XIMStringConversionOperation
#0001 XIMStringConversionSubstitution
#0002 XIMStringConversionRetrieval
2 INT16 byte length to multiply the XIMStringConversionType
XIM_STR_CONVERSION
message may be used to start the string conversion from the IM Server.
XIM_STR_CONVERSION_REPLY (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 CARD32 XIMStringConversionFeedback
XIMSTRCONVTEXT XIMStringConversionText
XIM_STR_CONVERSION_REPLY
message returns the string to be converted and the feedback information array.
The IM Server sends
XIM_PREEDIT_START
message to call the XIMPreeditStartCallback function.
XIM_PREEDIT_START (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
The reply to this message must be sent synchronously. The reply forwards the return value from the callback function to the IM Server.
XIM_PREEDIT_START_REPLY (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 INT32 return value
XIM_PREEDIT_START_REPLY
message returns the input-context-ID to distinguish replies from multiple
IC's. The return value contains the return value of the function
XIMPreeditStartCallback.
The IM Server sends
XIM_PREEDIT_DRAW
message to call the XIMPreeditDrawCallback function.
XIM_PREEDIT_DRAW (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 INT32 caret
4 INT32 chg_first
4 INT32 chg_length
4 BITMASK32 status
#x0000001 no string
#x0000002 no feedback
2 n length of preedit string
n STRING8 preedit string
p unused, p = Pad(2+n)
2 m byte length of feedback array
2 unused
m LISTofXIMFEEDBACK feedback array
The fields "caret", "chg_first" and "chg_length" correspond to the fields of XIMPreeditDrawCallbackStruct. When the "no string" bit of the status field is set, the text field of XIMPreeditDrawCallbackStruct is NULL. When the "no feedback" bit of the status field is set, the text feedback field of XIMPreeditDrawCallbackStruct is NULL. When the above bits are not set, "preedit string" contains the preedit string to be displayed, and the feedback array contains feedback information.
The IM Server sends
XIM_PREEDIT_CARET
message to call the PreeditCaretCallback function.
XIM_PREEDIT_CARET (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 INT32 position
4 CARD32 direction
#0 XIMForwardChar
#1 XIMBackwardChar
#2 XIMForwardWord
#3 XIMBackwardWord
#4 XIMCaretUp
#5 XIMCaretDown
#6 XIMNextLine
#7 XIMCPreviousLine
#8 XIMLineStart
#9 XIMLineEnd
#10 XIMAbsolutePosition
#11 XIMDontChange
4 CARD32 style
#0 XIMInvisible
#1 XIMCPrimary
#2 XIMSecondary
Each entry corresponds to a field of XIMPreeditCaretCallbackStruct. Since this callback sets the caret position, its reply must be sent synchronously.
XIM_PREEDIT_CARET_REPLY (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 CARD32 position
The position is the value returned by the callback function after it has been called.
The IM Server sends
XIM_PREEDIT_DONE
message to call the XIMPreeditDoneCallback function.
XIM_PREEDIT_DONE (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
XIM_PREEDITSTATE (IM Server -> IM Library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 BITMASK32 XIMPreeditState
#x0000000 XIMPreeditUnknown
#x0000001 XIMPreeditEnable
#x0000002 XIMPreeditDisable
XIM_PREEDITSTATE
message is used to call the XIMPreeditStateNotifyCallback function.
The IM Server sends
XIM_STATUS_START
message to call the XIMStatusStartCallback function.
XIM_STATUS_START (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
The IM Server sends
XIM_STATUS_DRAW
message to call the XIMStatusDrawCallback function.
XIM_STATUS_DRAW (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 CARD32 type
#0 XIMTextType
#1 XIMBitmapType
If type is XIMTextType, the arguments continue as follows.
4 BITMASK32 status
#x0000001 no string
#x0000002 no feedback
2 n length of status string
n STRING8 status string
p unused, p = Pad(2+n)
2 m byte length of feedback array
2 unused
m LISTofXIMFEEDBACK feedback array
If type is XIMBitmapType, the arguments continue as follows.
4 PIXMAP pixmap data
The field "type" corresponds to the field in XIMStatusDrawCallbackStruct.
The IM Server sends
XIM_STATUS_DONE
message to call the XIMStatusDoneCallback function.
XIM_STATUS_DONE (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
This document represents the culmination of several years of debate and experiments done under the auspices of the MIT X Consortium i18n working group. Although this was a group effort, the author remains responsible for any errors or omissions.
We would like to thank to all members of this group. And we would like to make special thanks to the following people (in alphabetical order) for their participation in the IM Protocol design, Hector Chan, Takashi Fujiwara, Yoshio Horiuchi, Makoto Inada, Hiromu Inukai, Mickael Kung, Seiji Kuwari, Franky Ling, Hiroyuki Machida, Hiroyuki Miyamoto, Frank Rojas, Bob Scheifler, Makiko Shimamura, Shoji Sugiyama, Hidetoshi Tajima, Masaki Takeuchi, Makoto Wakamatsu, Masaki Wakao, Nobuyuki Tanaka, Shigeru Yamada, Katsuhisa Yano, Jinsoo Yoon.
Extension opcodes and packet names (e.g.
XIM_EXT_SET_EVENT_MASK
) for additional extensions may be registered with X Consortium.
The following is a commonly well-known extended packet.
(1) Extension to manipulate the event handling\fP
XIM_EXT_SET_EVENT_MASK
message specifies the set of event masks that the IM library should manipulate.
XIM_EXT_SET_EVENT_MASK (IM Server -> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
4 EVENTMASK filter-event-mask (*1)
4 EVENTMASK intercept-event-mask (*2)
4 EVENTMASK select-event-mask (*3)
4 EVENTMASK forward-event-mask (*4)
4 EVENTMASK synchronous-event-mask (*5)
(*1) Specify the events to be neglected by the IM library via XFilterEvent.
(*2) Specify the events to be deselected by the IM library with XSelectInput.
(*3) Specify the events to be selected by the IM library with XSelectInput.
(*4) Specify all the events to be forwarded to the IM Server by the IM library.
(*5) Specify the events to be forwarded with synchronous flag on by the IM library.
The IM library must reply
XIM_SYNC_REPLY
message to the IM Server. This request is valid after the ic is created.
(2) Extension for improvement of performance.
The following requests may be used for improvement of performance.
XIM_EXT_FORWARD_KEYEVENT
message may be used instead of
XIM_FORWARD_EVENT
message.
XIM_EXT_FORWARD_KEYEVENT (IM Server <--> IM library)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 BITMASK16 flag
#0001 synchronous
2 CARD16 sequence number
1 BYTE xEvent.u.u.type
1 BYTE keycode
2 CARD16 state
4 CARD32 time
4 CARD32 window
XIM_EXT_MOVE
message may be used to change the spot location instead of
XIM_SET_IC_VALUES
message.
It is effective only if the client specified XIMPreeditPosition.
XIM_EXT_MOVE (IM library -> IM Server)
2 CARD16 input-method-ID
2 CARD16 input-context-ID
2 INT16 X
2 INT16 Y
XIM_EXT_MOVE
message is a asynchronous request.
The list of transport specific IM Server address format registered
The following format represents the ATOM contained in
XIM_SERVERS
property and the string returned from the request converting
selection target LOCALES and TRANSPORT.
"{category=[value,...]}..."
The following categories are currently registered.
server;: IM Server name (used for XIM_SERVERS)locale;: XPG4 locale name (LOCALES)transport;: transport-specific name (TRANSPORT)
The preregistered formats for transport-specific names are as follows:
TCP/IP Names
The following syntax should be used for system internal domain names:
<local name> ::= "local/"<hostname>":"<pathname>
Where <pathname> is a path name of socket address.
IM Server's name should be set to <pathname> to run multiple IM Server at the same time
The following syntax should be used for Internet domain names:
<TCP name> ::= "tcp/"<hostname>":"<ipportnumber>
where <hostname> is either symbolic (such as expo.lcs.mit.edu) or numeric decimal (such as 18.30.0.212). The <ipportnumber> is the port on which the IM Server is listening for connections. For example:
tcp/expo.lcs.mit.edu:8012 tcp/18.30.0.212:7890
DECnet Names
The following syntax should be used for DECnet names:
<DECnet name> ::= "decnet/"<nodename>"::IMSERVER$"<objname>
where <nodename> is either symbolic (such as SRVNOD) or the numeric decimal form of the DECnet address (such as 44.70). The <objname> is normal, case-insensitive DECnet object name. For example:
DECNET/SRVNOD::IMSERVER$DEFAULT decnet/44.70::IMSERVER$other
X Names
The following syntax should be used for X names:
<X name> ::= "X/"
If a given category has multiple values, the value is evaluated in order of setting.
Major Protocol number
XIM_CONNECT #001 XIM_CONNECT_REPLY #002 XIM_DISCONNECT #003 XIM_DISCONNECT_REPLY #004 XIM_AUTH_REQUIRED #010 XIM_AUTH_REPLY #011 XIM_AUTH_NEXT #012 XIM_AUTH_SETUP #013 XIM_AUTH_NG #014 XIM_ERROR #020 XIM_OPEN #030 XIM_OPEN_REPLY #031 XIM_CLOSE #032 XIM_CLOSE_REPLY #033 XIM_REGISTER_TRIGGERKEYS #034 XIM_TRIGGER_NOTIFY #035 XIM_TRIGGER_NOTIFY_REPLY #036 XIM_SET_EVENT_MASK #037 XIM_ENCODING_NEGOTIATION #038 XIM_ENCODING_NEGOTIATION_REPLY #039 XIM_QUERY_EXTENSION #040 XIM_QUERY_EXTENSION_REPLY #041 XIM_SET_IM_VALUES #042 XIM_SET_IM_VALUES_REPLY #043 XIM_GET_IM_VALUES #044 XIM_GET_IM_VALUES_REPLY #045 XIM_CREATE_IC #050 XIM_CREATE_IC_REPLY #051 XIM_DESTROY_IC #052 XIM_DESTROY_IC_REPLY #053 XIM_SET_IC_VALUES #054 XIM_SET_IC_VALUES_REPLY #055 XIM_GET_IC_VALUES #056 XIM_GET_IC_VALUES_REPLY #057 XIM_SET_IC_FOCUS #058 XIM_UNSET_IC_FOCUS #059 XIM_FORWARD_EVENT #060 XIM_SYNC #061 XIM_SYNC_REPLY #062 XIM_COMMIT #063 XIM_RESET_IC #064 XIM_RESET_IC_REPLY #065 XIM_GEOMETRY #070 XIM_STR_CONVERSION #071 XIM_STR_CONVERSION_REPLY #072 XIM_PREEDIT_START #073 XIM_PREEDIT_START_REPLY #074 XIM_PREEDIT_DRAW #075 XIM_PREEDIT_CARET #076 XIM_PREEDIT_CARET_REPLY #077 XIM_PREEDIT_DONE #078 XIM_STATUS_START #079 XIM_STATUS_DRAW #080 XIM_STATUS_DONE #081 XIM_PREEDITSTATE #082 (*) The IM Server's extension protocol number should be more than #128.
(1) FrontEnd Method
FrontEnd method is recognized as a performance acceleration by the trade off of the variety of the reliability.
In order to use the FrontEnd method, the IM library must query the IM
Server to see if the FrontEnd extension is available. The query is
made by using the
XIM_QUERY_EXTENSION
message. The IM Server may send
XIM_EXT_SET_EVENT_MASK
message with intercept-event-mask, forward-event-mask, and
synchronous-event-mask values set after replying
XIM_QUERY_EXTENSION_REPLY
message.
FrontEnd method can be implemented in a couple of ways depending on
how the IM Server utilize
XIM_EXT_SET_EVENT_MASK
message.
One approach is to update both of the input mask and the filter-event-mask depending on the preeidting state. The sample protocol sequence using the static event flow is as follows:
To pursuit a maximum performance regardless of the preediting mode, the IM Server may use the dynamic event flow with the following sample protocol sequence.
This method can reduce the XIM protocol traffic dramatically by updating intercept-event-mask and select-event-mask accordingly. The tradeoff of this performance improvement is that the key events may be lost or disordered in some particular situation, such as when the user types the keyboard in following sequence really fast:
<preediting on key>"some strings"<preediting off key>"another string"
Since this method requires the input mask updates to the both the IM Server and Xlib when turning on and off the preediting, and there is a time lag till the requests take effect when two client issues the input mask updates simultaneously.
Another approach of the FrontEnd method is to update the filter-event-mask
depending on the preediting state and not to update the input mask.
The IM Server must register both of the preediting on key list and off key
list by
XIM_REGISTER_TRIGGERKEYS
message.
In this method, Both the IM Server and the IM client select the same
events on the same client's window, so that the events are delivered
to both of the IM Server and the client. The preediting on and off
states are expressed by whether the key events are filtered or not.
The sample protocol sequence are as follows:
<<Using static event flow>>
<<Using the dynamic event flow>>
This method does not have the problem of the time lag when going across the preediting on and off mode, however, the amount of the performance acceleration is not as good as the method described above.
In general, the FrontEnd method requires some synchronization to some of the X protocols, such as the ChangeWindowAttribute protocol for the event mask change or the GrabKey protocol, since it relies on the X's principal event dispatching mechanism. Any X protocol bindings do not consider the synchronization might cause some mis-synchronization between the IM clients and the IM Server.
(2) Transport Layer
The Xlib XIM implementation is layered into three functions, a protocol layer, an interface layer and a transport layer. The purpose of this layering is to make the protocol independent of transport implementation. Each function of these layers are:
The protocol layer | implements overall function of XIM and calls the interface layer functions when it needs to communicate to IM Server. |
The interface layer | separates the implementation of the transport layer from the protocol layer, in other words, it provides implementation independent hook for the transport layer functions. |
The transport layer | handles actual data communication with IM Server. It is done by a set of several functions named transporters. |
The interface layer and the transport layer make various communication channels usable such as X Protocol, TCP/IP, DECnet or STREAM. The following is a sample implementation for the transporter using the X connection. Refer to "xtrans" for the transporter using Socket Transport.
At the beginning of the X Transport connection for the XIM transport mechanism, two different windows must be created either in an Xlib XIM or in an IM Server, with which the Xlib and the IM Server exchange the XIM transports by using the ClientMessage events and Window Properties. In the following, the window created by the Xlib is referred as the "client communication window", and on the other hand, the window created by the IM Server is referred as the "IMS communication window".
Connection
In order to establish a connection, a communication window is created. A ClientMessage in the following event's format is sent to the owner window of XIM_SERVER selection, which the IM Server has created.
Refer to "The Input Method Protocol" for the XIM_SERVER atom.
Table D.1. The ClientMessage sent to the IMS window.
| Structure Member | Contents | |
|---|---|---|
| int | type | ClientMessage |
| u_long | serial | Set by the X Window System |
| Bool | send_event | Set by the X Window System |
| Display | *display | The display to which connects |
| Window | window | IMS Window ID |
| Atom | message_type | XInternAtom(display, "_XIM_XCONNECT", False) |
| int | format | 32 |
| long | data.l[0] | client communication window ID |
| long | data.l[1] | client-major-transport-version (*1) |
| long | data.l[2] | client-major-transport-version (*1) |
In order to establish the connection (to notify the IM Server communication window), the IM Server sends a ClientMessage in the following event's format to the client communication window.
Table D.2. The ClientMessage sent by the IM Server.
| Structure Member | Contents | |
|---|---|---|
| int | type | ClientMessage |
| u_long | serial | Set by the X Window System |
| Bool | send_event | Set by the X Window System |
| Display | *display | The display to which connects |
| Window | window | client communication window ID |
| Atom | message_type | XInternAtom(display, "_XIM_XCONNECT", False) |
| int | format | 32 |
| long | data.l[0] | IMS communication window ID |
| long | data.l[1] | server-major-transport-version (*1) |
| long | data.l[2] | server-minor-transport-version (*1) |
| long | data.l[3] | dividing size between ClientMessage and Property (*2) |
(*1) major/minor-transport-version
The read/write method is decided by the combination of major/minor-transport-version, as follows:
Table D.3. The read/write method and the major/minor-transport-version
| Transport-version | read/write | |
|---|---|---|
| major | minor | |
| 0 | 0 | only-CM & Property-with-CM |
| 1 | only-CM & multi-CM | |
| 2 | only-CM & multi-CM & Property-with-CM | |
| 1 | 0 | PropertyNotify |
| 2 | 0 | only-CM & PropertyNotify |
| 1 | only-CM & multi-CM & PropertyNotify | |
only-CM : data is sent via a ClientMessage
multi-CM : data is sent via multiple ClientMessages
Property-with-CM : data is written in Property, and its Atom
is send via ClientMessage
PropertyNotify : data is written in Property, and its Atom
is send via PropertyNotify
The method to decide major/minor-transport-version is as follows:
The client sends 0 as major/minor-transport-version to the IM Server. The client must support all methods in Table D-3. The client may send another number as major/minor-transport-version to use other method than the above in the future.
The IM Server sends its major/minor-transport-version number to the client. The client sends data using the method specified by the IM Server.
If major/minor-transport-version number is not available, it is regarded as 0.
(*2) dividing size between ClientMessage and Property
If data is sent via both of multi-CM and Property, specify the dividing size between ClientMessage and Property. The data, which is smaller than this size, is sent via multi-CM (or only-CM), and the data, which is lager than this size, is sent via Property.
read/write
The data is transferred via either ClientMessage or Window Property in the X Window System.
Format for the data from the Client to the IM Server
ClientMessage
If data is sent via ClientMessage event, the format is as follows:
Table D.4. The ClientMessage event's format (first or middle)
| Structure Member | Contents | |
|---|---|---|
| int | type | ClientMessage |
| u_long | serial | Set by the X Window System |
| Bool | send_event | Set by the X Window System |
| Display | *display | The display to which connects |
| Window | window | IMS communication window ID |
| Atom | message_type | XInternAtom(display, "_XIM_MOREDATA", False) |
| int | format | 8 |
| char | data.b[20] | (read/write DATA : 20 byte) |
Table D.5. The ClientMessage event's format (only or last)
| Structure Member | Contents | |
|---|---|---|
| int | type | ClientMessage |
| u_long | serial | Set by the X Window System |
| Bool | send_event | Set by the X Window System |
| Display | *display | The display to which connects |
| Window | window | IMS communication window ID |
| Atom | message_type | XInternAtom(display, "_XIM_PROTOCOL", False) |
| int | format | 8 |
| char | data.b[20] | (read/write DATA : MAX 20 byte) (*1) |
(*1) If the data is smaller than 20 byte, all data other than available data must be 0.
Property
In the case of large data, data will be sent via the Window Property for the efficiency. There are the following two methods to notify Property, and transport-version is decided which method is used.
The XChangeProperty function is used to store data in the client communication window, and Atom of the stored data is notified to the IM Server via ClientMessage event.
The XChangeProperty function is used to store data in the client communication window, and Atom of the stored data is notified to the IM Server via PropertyNotify event.
The arguments of the XChangeProperty are as follows:
Table D.6. The XChangeProperty event's format
| Argument | Contents | |
|---|---|---|
| Display | *display | The display to which connects |
| Window | window | IMS communication window ID |
| Atom | property | read/write property Atom (*1) |
| Atom | type | XA_STRING |
| int | format | 8 |
| int | mode | PropModeAppend |
| u_char | *data | read/write DATA |
| int | nelements | length of DATA |
The read/write property ATOM allocates the following strings by
XInternAtom.
"_clientXXX"
The client changes the property with the mode of PropModeAppend and the IM Server will read it with the delete mode i.e. (delete = True).
If Atom is notified via ClientMessage event, the format of the ClientMessage is as follows:
Table D.7. The ClientMessage event's format to send Atom of property
| Structure Members | Contents | |
|---|---|---|
| int | type | ClientMessage |
| u_long | serial | Set by the X Window System |
| Bool | send_event | Set by the X Window System |
| Display | *display | The display to which connects |
| Window | window | IMS communication window ID |
| Atom | message_type | XInternAtom(display, "_XIM_PROTOCOL", False) |
| int | format | 32 |
| long | data.l[0] | length of read/write property Atom |
| long | data.l[1] | read/write property Atom |
Format for the data from the IM Server to the Client
ClientMessage
The format of the ClientMessage is as follows:
Table D.8. The ClientMessage event's format (first or middle)
| Structure Members | Contents | |
|---|---|---|
| int | type | ClientMessage |
| u_long | serial | Set by the X Window System |
| Bool | send_event | Set by the X Window System |
| Display | *display | The display to which connects |
| Window | window | client communication window ID |
| Atom | message_type | XInternAtom(display, "_XIM_MOREDATA", False) |
| int | format | 8 |
| char | data.b[20] | (read/write DATA : 20 byte) |
Table D.9. The ClientMessage event's format (only or last)
| Structure Members | Contents | |
|---|---|---|
| int | type | ClientMessage |
| u_long | serial | Set by the X Window System |
| Bool | send_event | Set by the X Window System |
| Display | *display | The display to which connects |
| Window | window | client communication window ID |
| Atom | message_type | XInternAtom(display, "_XIM_PROTOCOL", False) |
| int | format | 8 |
| char | data.b[20] | (read/write DATA : MAX 20 byte) (*1) |
(*1) If the data size is smaller than 20 bytes, all data other than available data must be 0.
Property
In the case of large data, data will be sent via the Window Property for the efficiency. There are the following two methods to notify Property, and transport-version is decided which method is used.
The XChangeProperty function is used to store data in the IMS communication window, and Atom of the property is sent via the ClientMessage event.
The XChangeProperty function is used to store data in the IMS communication window, and Atom of the property is sent via PropertyNotify event.
The arguments of the XChangeProperty are as follows:
Table D.10. The XChangeProperty event's format
| Argument | Contents | |
|---|---|---|
| Display | *display | The display which to connects |
| Window | window | client communication window ID |
| Atom | property | read/write property Atom (*1) |
| Atom | type | XA_STRING |
| int | format | 8 |
| int | mode | PropModeAppend |
| u_char | *data | read/write DATA |
| int | nelements | length of DATA |
(*1) The read/write property ATOM allocates some strings, which are not
allocated by the client, by XInternAtom.
The IM Server changes the property with the mode of PropModeAppend and the client reads it with the delete mode, i.e. (delete = True).
If Atom is notified via ClientMessage event, the format of the ClientMessage is as follows:
Table D.11. The ClientMessage event's format to send Atom of property
| Structure Member | Contents | |
|---|---|---|
| int | type | ClientMessage |
| u_long | serial | Set by the X Window System |
| Bool | send_event | Set by the X Window System |
| Display | *display | The display to which connects |
| Window | window | client communication window ID |
| Atom | message_type | XInternAtom(display, "_XIM_PROTOCOL", False) |
| int | format | 32 |
| long | data.l[0] | length of read/write property ATOM |
| long | data.l[1] | read/write property ATOM |
Closing Connection
If the client disconnect with the IM Server, shutdown function should free the communication window properties and etc..