CDE/cde/doc/C/guides/man/m3_ttmedia/load.sgm

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<RefMeta>
<RefEntryTitle>ttmedia_load</RefEntryTitle>
<ManVolNum>library call</ManVolNum>
</RefMeta>
<RefNameDiv>
<RefName><Function>ttmedia_load</Function></RefName>
<RefPurpose>send a Display, Edit or Compose request
</RefPurpose>
</RefNameDiv>
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<!-- (c) Copyright 1993, 1994, 1995 International Business Machines Corp.-->
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<RefSynopsisDiv>
<FuncSynopsis Remap="ANSI">
<FuncSynopsisInfo>#include &lt;Tt/tttk.h>
</FuncSynopsisInfo>
<FuncDef>Tt_message <Function>ttmedia_load</Function></FuncDef>
<ParamDef>Tt_message <Parameter>context</Parameter></ParamDef>
<ParamDef>Ttmedia_load_msg_cb <Parameter>cb</Parameter></ParamDef>
<ParamDef>void *<Parameter>clientdata</Parameter></ParamDef>
<ParamDef>Tttk_op <Parameter>op</Parameter></ParamDef>
<ParamDef>const char *<Parameter>media_type</Parameter></ParamDef>
<ParamDef>const unsigned char *<Parameter>contents</Parameter></ParamDef>
<ParamDef>int <Parameter>len</Parameter></ParamDef>
<ParamDef>const char *<Parameter>file</Parameter></ParamDef>
<ParamDef>const char *<Parameter>docname</Parameter></ParamDef>
<ParamDef>int <Parameter>send</Parameter></ParamDef>
</FuncSynopsis>
</RefSynopsisDiv>
<RefSect1>
<Title>DESCRIPTION</Title>
<Para>The
<Function>ttmedia_load</Function> function
is used to create and optionally send a Media Exchange request
to display, edit or compose a document.
</Para>
<Para>The
<Emphasis>cb</Emphasis> argument will be passed
<Emphasis>clientdata</Emphasis> when the reply is received, or when intermediate versions
of the document are checkpointed through
<Symbol Role="Message">Deposit</Symbol> requests.
The
<Symbol Role="Variable">op</Symbol> argument must be one of
<SystemItem Class="Constant">TTME_DISPLAY</SystemItem>, <SystemItem Class="Constant">TTME_EDIT</SystemItem> or
<SystemItem Class="Constant">TTME_COMPOSE</SystemItem>. The
<Emphasis>media_type</Emphasis> argument names the data format of the document, and is usually the
primary determinant of which application will be chosen to
handle the request.
The
<Emphasis>contents</Emphasis> and
<Emphasis>len</Emphasis> arguments specify the document; if they are
<SystemItem Class="Constant">NULL</SystemItem> and zero, respectively, and
<Symbol Role="Variable">file</Symbol> is not
<SystemItem Class="Constant">NULL</SystemItem>, then the document is assumed to be contained in
<Symbol Role="Variable">file</Symbol>. If
<Emphasis>docname</Emphasis> is not
<SystemItem Class="Constant">NULL</SystemItem>, then
<Function>ttmedia_load</Function> uses it as the title of the document.
If
<Emphasis>send</Emphasis> is True, the message is sent before being returned.
</Para>
<Para>The
<Symbol Role="Variable">context</Symbol> argument describes the environment to use.
If
<Symbol Role="Variable">context</Symbol> is not zero, messages created by
<Function>ttmedia_load</Function> inherit from
<Symbol Role="Variable">context</Symbol> all contexts whose slotname begins with the characters
<SystemItem Class="Constant">ENV_</SystemItem>.</Para>
<Para>The
<StructName Role="typedef">Ttmedia_load_msg_cb</StructName> argument is a callback defined as:
</Para>
<InformalExample Remap="indent">
<ProgramListing>Tt_message (*Ttmedia_load_msg_cb)(Tt_message <Emphasis>msg</Emphasis>,
        void *<Emphasis>clientdata</Emphasis>),
        Tttk_op <Symbol Role="Variable">op</Symbol>,
        unsigned char *<Emphasis>contents</Emphasis>,
        int <Emphasis>len</Emphasis>,
        char *<Symbol Role="Variable">file</Symbol>);
</ProgramListing>
</InformalExample>
<Para>The
<Emphasis>msg</Emphasis> argument is the
reply to the load request, or a
<Symbol Role="Message">Deposit</Symbol> request with a
<Emphasis>messageID</Emphasis> argument naming the identifier (see
&cdeman.tt.message.id;) of the load request.
In the latter case, the client
program becomes responsible for either failing or replying
to the request.
In either case,
<Emphasis>msg</Emphasis> should be destroyed after being processed.
</Para>
<Para>The
<Symbol Role="Variable">op</Symbol> argument is the
op of
<Emphasis>msg</Emphasis>. It must be either
<SystemItem Class="Constant">TTME_DEPOSIT</SystemItem> or the
<Symbol Role="Variable">op</Symbol> passed to
&cdeman.ttmedia.load;.</Para>
<Para>The
<Emphasis>contents</Emphasis>, <Emphasis>len</Emphasis> and
<Symbol Role="Variable">file</Symbol> arguments represent the
contents of the arriving document.
If
<Emphasis>len</Emphasis> is zero, then the document is contained in
<Symbol Role="Variable">file</Symbol>. If
<Emphasis>contents</Emphasis> or
<Symbol Role="Variable">file</Symbol> are non-
<SystemItem Class="Constant">NULL</SystemItem>, they can be freed using
<Function>tt_free</Function>.</Para>
<Para>The
<Emphasis>clientdata</Emphasis> argument is the
<Emphasis>clientdata</Emphasis> passed to
<Function>ttmedia_load</Function>.</Para>
</RefSect1>
<RefSect1>
<Title>RETURN VALUE</Title>
<Para>Upon successful completion, the
<Function>ttmedia_load</Function> function returns the request it was asked to build;
otherwise, it returns an error pointer.
The application can use
&cdeman.tt.ptr.error; to extract one of the following
<StructName Role="typedef">Tt_status</StructName> values from the returned handle:
</Para>
<VariableList>
<VarListEntry>
<Term>TT_ERR_NOMEM</Term>
<ListItem>
<Para>There is insufficient memory available to perform the function.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>TT_ERR_NOMP</Term>
<ListItem>
<Para>The
&cdeman.ttsession; process is not running and the ToolTalk service cannot restart it.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>TT_ERR_OVERFLOW</Term>
<ListItem>
<Para>The ToolTalk service has more active messages than it can handle.
(The maximum number of active messages is
implementation specific, but is at least 2000.)
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>TT_ERR_PROCID</Term>
<ListItem>
<Para>The specified process identifier is out of date or invalid.
</Para>
</ListItem>
</VarListEntry>
</VariableList>
</RefSect1>
<RefSect1>
<Title>APPLICATION USAGE</Title>
<Para>After the request created by
<Function>ttmedia_load</Function> is sent, the application will probably want to use
<Function>ttdt_subcontract_manage</Function> immediately afterwards to manage the standard interactions with the
handler of the request.
</Para>
<Para>A
<StructName Role="typedef">Ttmedia_load_msg_cb</StructName> callback should return
<SystemItem Class="Constant">NULL</SystemItem> if it processes
<Emphasis>msg</Emphasis> successfully, or a
<Function>tt_error_pointer</Function> cast to
<StructName Role="typedef">Tt_message</StructName> if processing results in an error.
It should return the
<Emphasis>msg</Emphasis> if it does not consume it, in which case
the ToolTalk service
will pass
<SystemItem Class="Constant">TT_CALLBACK_CONTINUE</SystemItem> down the call stack, so that
<Emphasis>msg</Emphasis> will be offered to other callbacks or (more likely) be returned
from
&cdeman.tt.message.receive;. Applications will rarely want
<Emphasis>msg</Emphasis> to get processed by other callbacks or in the main event loop.
</Para>
</RefSect1>
<RefSect1>
<Title>EXAMPLES</Title>
<Para>This is the typical algorithm of a
<StructName Role="typedef">Ttmedia_load_msg_cb</StructName>:</Para>
<InformalExample Remap="indent">
<ProgramListing>Tt_message
myLoadMsgCB(Tt_message  msg,
        void           *clientData,
        Tttk_op         op,
        unsigned char  *contents,
        int             len,
        char           *file)
{
        if (len > 0) {
                /* Replace data with len bytes in contents */
        } else if (file != 0) {
                /* Replace data with data read from file */
        }
        if (op == TTME_DEPOSIT) {
                tt_message_reply(msg);
        }
        tttk_message_destroy(msg);
        return 0;
}
</ProgramListing>
</InformalExample>
</RefSect1>
<RefSect1>
<Title>SEE ALSO</Title>
<Para>&cdeman.Tt.tttk.h;, &cdeman.ttmedia.load.reply;, &cdeman.ttmedia.ptype.declare;, &cdeman.ttmedia.Deposit;, &cdeman.tt.free;, &cdeman.tt.message.receive;.</Para>
</RefSect1>
</RefEntry>
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