The XIM Transport Specification
Revision 0.1
Takashi Fujiwara
FUJITSU LIMITED
X Version 11, Release 7.7
Copyright © 1994 FUJITSU LIMITED
Permission to use, copy, modify, and distribute this documentation for any
purpose and without fee is hereby granted, provided that the above copyright
notice and this permission notice appear in all copies. Fujitsu makes no
representations about the suitability for any purpose of the information in
this document. This documentation is provided as is without express or implied
warranty.
Copyright © 1994 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
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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 Open Group.
This specification describes the transport layer interfaces between Xlib and IM
Server, which makes various channels usable such as X protocol or TCP/IP,
DECnet and etc.
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Table of Contents
1. X Transport Specification
Introduction
Initialization
Registering structure to initialize
Initialization function
The interface/transport layer functions
Opening connection
Closing connection
Writing data
Reading data
Flushing buffer
Registering asynchronous data handler
Calling dispatcher
Sample implementations for the Transport Layer
X Transport
References
List of Tables
1.1. The Transport Layer Functions
1.2. The ClientMessage sent to the IMS window.
1.3. The ClientMessage sent by IM Server.
1.4. The read/write method and the major/minor-transport-version
1.5. The ClientMessage event's format (first or middle)
1.6. The ClientMessage event's format (only or last)
1.7. The XChangeProperty event's format
1.8. The ClientMessage event's format to send Atom of property
1.9. The ClientMessage event's format (first or middle)
1.10. The ClientMessage event's format (only or last)
1.11. The XChangeProperty event's format
1.12. The ClientMessage event's format to send Atom of property
Chapter 1. X Transport Specification
Table of Contents
Introduction
Initialization
Registering structure to initialize
Initialization function
The interface/transport layer functions
Opening connection
Closing connection
Writing data
Reading data
Flushing buffer
Registering asynchronous data handler
Calling dispatcher
Sample implementations for the Transport Layer
X Transport
References
Introduction
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 implements overall function of XIM and calls the interface layer
protocol functions when it needs to communicate to IM Server.
layer
The separates the implementation of the transport layer from the protocol
interface layer, in other words, it provides implementation independent hook
layer for the transport layer functions.
The handles actual data communication with IM Server. It is done by a set
transport of several functions named transporters.
layer
This specification describes the interface layer and the transport layer, which
makes various communication channels usable such as X protocol or, TCP/IP,
DECnet, STREAM, etc., and provides the information needed for adding another
new transport layer. In addition, sample implementations for the transporter
using the X connection is described in section 4.
Initialization
Registering structure to initialize
The structure typed as TransportSW contains the list of the transport layer the
specific implementations supports.
typedef struct {
char *transport_name;
Bool (*config);
} TransportSW;
transport_name name of transport^[a]
config initial configuration function
^[a] Refer to "The Input Method Protocol: Appendix B
A sample entry for the Xlib supporting transporters is shown below:
TransportSW _XimTransportRec[] = {
/* char *:
* transport_name, Bool (*config)()
*/
"X", _XimXConf,
"tcp", _XimTransConf,
"local", _XimTransConf,
"decnet", _XimTransConf,
"streams", _XimTransConf,
(char *)NULL, (Bool (*)())NULL,
};
Initialization function
The following function will be called once when Xlib configures the transporter
functions.
Bool (*config)(XIM im, char *transport_data);
im Specifies XIM structure address.
transport_data Specifies the data specific to the transporter, in IM Server
address.^[1]
This function must setup the transporter function pointers.
The actual config function will be chosen by IM Server at the pre-connection
time, matching by the transport_name specified in the _XimTransportRec array;
The specific members of XimProto structure listed below must be initialized so
that point they appropriate transporter functions.
If the specified transporter has been configured successfully, this function
returns True. There is no Alternative Entry for config function itself.
The structure XimProto contains the following function pointers:
Bool (*connect)(); /* Open connection */
Bool (*shutdown)(); /* Close connection */
Bool (*write)(); /* Write data */
Bool (*read)(); /* Read data */
Bool (*flush)(); /* Flush data buffer */
Bool (*register_dispatcher)(); /* Register asynchronous data handler */
Bool (*call_dispatcher)(); /* Call dispatcher */
These functions are called when Xlib needs to communicate the IM Server. These
functions must process the appropriate procedure described below.
The interface/transport layer functions
Following functions are used for the transport interface.
Table 1.1. The Transport Layer Functions
┌─────────────────────────────────┬─────────────────────────────────┬───────┐
│Alternate Entry (Interface Layer)│XimProto member (Transport Layer)│Section│
├─────────────────────────────────┼─────────────────────────────────┼───────┤
│_XimConnect │connect │3.1 │
├─────────────────────────────────┼─────────────────────────────────┼───────┤
│_XimShutdown │shutdown │3.2 │
├─────────────────────────────────┼─────────────────────────────────┼───────┤
│_XimWrite │write │3.3 │
├─────────────────────────────────┼─────────────────────────────────┼───────┤
│_XimRead │read │3.4 │
├─────────────────────────────────┼─────────────────────────────────┼───────┤
│_XimFlush │flush │3.5 │
├─────────────────────────────────┼─────────────────────────────────┼───────┤
│_XimRegisterDispatcher │register_dispatcher │3.6 │
├─────────────────────────────────┼─────────────────────────────────┼───────┤
│_XimCallDispatcher │call_dispatcher │3.7 │
└─────────────────────────────────┴─────────────────────────────────┴───────┘
The Protocol layer calls the above functions using the Alternative Entry in the
left column. The transport implementation defines XimProto member function in
the right column. The Alternative Entry is provided so as to make easier to
implement the Protocol Layer.
Opening connection
When XOpenIM is called, the following function is called to connect with the IM
Server.
Bool (*connect)(XIM im);
im Specifies XIM structure address.
This function must establishes the connection to the IM Server. If the
connection is established successfully, this function returns True. The
Alternative Entry for this function is:
Bool _XimConnect(XIM im);
im Specifies XIM structure address.
Closing connection
When XCloseIM is called, the following function is called to disconnect the
connection with the IM Server. The Alternative Entry for this function is:
Bool (*shutdown)(XIM im);
im Specifies XIM structure address.
This function must close connection with the IM Server. If the connection is
closed successfully, this function returns True. The Alternative Entry for this
function is:
Bool _XimShutdown(XIM im);
im Specifies XIM structure address.
Writing data
The following function is called, when Xlib needs to write data to the IM
Server.
Bool _XimWrite(XIM im, INT16 len, XPointer data);
im Specifies XIM structure address.
len Specifies the length of writing data.
data Specifies the writing data.
This function writes the data to the IM Server, regardless of the contents. The
number of bytes is passed to len. The writing data is passed to data. If data
is sent successfully, the function returns True. Refer to "The Input Method
Protocol" for the contents of the writing data. The Alternative Entry for this
function is:
Bool _XimWrite(XIM im, INT16 len, XPointer data);
im Specifies XIM structure address.
len Specifies the length of writing data.
data Specifies the writing data.
Reading data
The following function is called when Xlib waits for response from IM server
synchronously.
Bool _XimRead(XIM im, XPointer read_buf, int buf_len, int *ret_len);
im Specifies XIM structure address.
read_buf Specifies the buffer to store data.
buf_len Specifies the size of the buffer
ret_len Specifies the length of stored data.
This function stores the read data in read_buf, which size is specified as
buf_len. The size of data is set to ret_len. This function return True, if the
data is read normally or reading data is completed.
The Alternative Entry for this function is:
Bool _XimRead(XIM im, INT16 *ret_len, XPointer buf, int buf_len, Bool
(*predicate)(), XPointer predicate_arg);
im Specifies XIM structure address.
ret_len Specifies the size of the data buffer.
buf Specifies the buffer to store data.
buf_len Specifies the length of buffer.
predicate Specifies the predicate for the XIM data.
predicate_arg Specifies the predicate specific data.
The predicate procedure indicates whether the data is for the XIM or not. len
This function stores the read data in buf, which size is specified as buf_len.
The size of data is set to ret_len. If preedicate() returns True, this function
returns True. If not, it calls the registered callback function.
The procedure and its arguments are:
void (*predicate)(XIM im, INT16 len, XPointer data, XPointer predicate_arg);
im Specifies XIM structure address.
len Specifies the size of the data buffer.
data Specifies the buffer to store data.
predicate_arg Specifies the predicate specific data.
Flushing buffer
The following function is called when Xlib needs to flush the data.
void (*flush)(XIM im);
im Specifies XIM structure address.
This function must flush the data stored in internal buffer on the transport
layer. If data transfer is completed, the function returns True. The
Alternative Entry for this function is:
void _XimFlush(XIM im);
im Specifies XIM structure address.
Registering asynchronous data handler
Xlib needs to handle asynchronous response from IM Server. This is because some
of the XIM data occur asynchronously to X events.
Those data will be handled in the Filter, and the Filter will call asynchronous
data handler in the protocol layer. Then it calls dispatchers in the transport
layer. The dispatchers are implemented by the protocol layer. This function
must store the information and prepare for later call of the dispatchers using
_XimCallDispatcher.
When multiple dispatchers are registered, they will be called sequentially in
order of registration, on arrival of asynchronous data. The register_dispatcher
is declared as following:
Bool (*register_dispatcher)(XIM im, Bool (*dispatcher)(), XPointer call_data);
im Specifies XIM structure address.
dispatcher Specifies the dispatcher function to register.
call_data Specifies a parameter for the dispatcher.
The dispatcher is a function of the following type:
Bool (*dispatcher)(XIM im, INT16 len, XPointer data, XPointer call_data);
im Specifies XIM structure address.
len Specifies the size of the data buffer.
data Specifies the buffer to store data.
call_data Specifies a parameter passed to the register_dispatcher.
The dispatcher is provided by the protocol layer. They are called once for
every asynchronous data, in order of registration. If the data is used, it must
return True. otherwise, it must return False.
If the dispatcher function returns True, the Transport Layer assume that the
data has been processed by the upper layer. The Alternative Entry for this
function is:
Bool _XimRegisterDispatcher(XIM im, Bool (*dispatcher)(), XPointer call_data);
im Specifies XIM structure address.
dispatcher Specifies the dispatcher function to register.
call_data Specifies a parameter for the dispatcher.
Calling dispatcher
The following function is used to call the registered dispatcher function, when
the asynchronous response from IM Server has arrived.
Bool (*call_dispatcher)(XIM im, INT16 len, XPointer data);
im Specifies XIM structure address.
len Specifies the size of data buffer.
data Specifies the buffer to store data.
The call_dispatcher must call the dispatcher function, in order of their
registration. len and data are the data passed to register_dispatcher.
The return values are checked at each invocation, and if it finds True, it
immediately return with true for its return value.
It is depend on the upper layer whether the read data is XIM Protocol packet
unit or not. The Alternative Entry for this function is:
Bool _XimCallDispatcher(XIM im, INT16 len, XPointer call_data);
Sample implementations for the Transport Layer
Sample implementations for the transporter using the X connection is described
here.
X 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 1.2. 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_CONNECT", false)│
├───────┼────────────┼───────────────────────────────────────────┤
│int │format │32 │
├───────┼────────────┼───────────────────────────────────────────┤
│long │data.1[0] │client communication window ID │
├───────┼────────────┼───────────────────────────────────────────┤
│long │data.1[1] │client-major-transport-version(*1) │
├───────┼────────────┼───────────────────────────────────────────┤
│long │data.1[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 1.3. The ClientMessage sent by 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 │IMS Window ID │
├───────┼────────────┼────────────────────────────────────────────────────┤
│Atom │message_type│XInternAtom(display, "_XIM_CONNECT", false) │
├───────┼────────────┼────────────────────────────────────────────────────┤
│int │format │32 │
├───────┼────────────┼────────────────────────────────────────────────────┤
│long │data.1[0] │client communication window ID │
├───────┼────────────┼────────────────────────────────────────────────────┤
│long │data.1[1] │client-major-transport-version(*1) │
├───────┼────────────┼────────────────────────────────────────────────────┤
│long │data.1[2] │client-major-transport-version(*1) │
├───────┼────────────┼────────────────────────────────────────────────────┤
│long │data.1[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 1.4. The read/write method and the major/minor-transport-version
┌─────────────────┬─────────────────────────────────────┐
│Transport-version│ read/write │
├────────┬────────┼─────────────────────────────────────┤
│ major │ minor │ │
├────────┼────────┼─────────────────────────────────────┤
│ │0 │only-CM & Property-with-CM │
│ ├────────┼─────────────────────────────────────┤
│0 │1 │only-CM & multi-CM │
│ ├────────┼─────────────────────────────────────┤
│ │2 │only-CM & multi-CM & Property-with-CM│
├────────┼────────┼─────────────────────────────────────┤
│1 │0 │PropertyNotify │
├────────┼────────┼─────────────────────────────────────┤
│ │0 │only-CM & PropertyNotify │
│2 ├────────┼─────────────────────────────────────┤
│ │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 4-3. 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 1.5. 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 Window ID │
├───────┼────────────┼────────────────────────────────────────────┤
│Atom │message_type│XInternAtom(display, "_XIM_MOREDATA", False)│
├───────┼────────────┼────────────────────────────────────────────┤
│int │format │8 │
├───────┼────────────┼────────────────────────────────────────────┤
│char │data.b[20] │(read/write DATA : 20 byte) │
└───────┴────────────┴────────────────────────────────────────────┘
Table 1.6. 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 Window ID │
├────────┼──────────────┼─────────────────────────────────────────────────────┤
│Atom │message_type │XInternAtom(display, "_XIM_PROTOCOL", False) │
├────────┼──────────────┼─────────────────────────────────────────────────────┤
│int │format │8 │
├────────┼──────────────┼─────────────────────────────────────────────────────┤
│char │data.b[20] │(read/write DATA : MAX 20 byte) ^[a] │
├────────┴──────────────┴─────────────────────────────────────────────────────┤
│^[a] If the data 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 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 1.7. 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)│
├───────┼─────────┼─────────────────────────────┤
│int │format │8 │
├───────┼─────────┼─────────────────────────────┤
│int │mode │PropModeAppend │
├───────┼─────────┼─────────────────────────────┤
│u_char │*data │read/write DATA │
├───────┼─────────┼─────────────────────────────┤
│int │nelements│length of DATA │
└───────┴─────────┴─────────────────────────────┘
(*1) 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 1.8. 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 │IMS Window ID │
├───────┼────────────┼────────────────────────────────────────────┤
│Atom │message_type│XInternAtom(display, "_XIM_PROTOCOL", False)│
├───────┼────────────┼────────────────────────────────────────────┤
│int │format │8 │
├───────┼────────────┼────────────────────────────────────────────┤
│long │data.1[0] │length of read/write property Atom │
├───────┼────────────┼────────────────────────────────────────────┤
│long │data.1[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 1.9. 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 Window ID │
├───────┼────────────┼────────────────────────────────────────────┤
│Atom │message_type│XInternAtom(display, "_XIM_MOREDATA", False)│
├───────┼────────────┼────────────────────────────────────────────┤
│int │format │8 │
├───────┼────────────┼────────────────────────────────────────────┤
│char │data.b[20] │(read/write DATA : 20 byte) │
└───────┴────────────┴────────────────────────────────────────────┘
Table 1.10. 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 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 1.11. 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)│
├───────┼─────────┼─────────────────────────────┤
│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 1.12. 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 │IMS Window ID │
├───────┼────────────┼────────────────────────────────────────────┤
│Atom │message_type│XInternAtom(display, "_XIM_PROTOCOL", False)│
├───────┼────────────┼────────────────────────────────────────────┤
│int │format │8 │
├───────┼────────────┼────────────────────────────────────────────┤
│long │data.1[0] │length of read/write property Atom │
├───────┼────────────┼────────────────────────────────────────────┤
│long │data.1[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..
References
[1] Masahiko Narita and Hideki Hiura, "The Input Method Protocol"
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^[1] Refer to "The Input Method Protocol: Appendix B
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