handle text output in OpenMaple - Maple Help

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textCallBack - handle text output in OpenMaple

Calling Sequence

textCallBack(data, tag, output)




user_data pointer passed to StartMaple (Long)



code indicating kind of text (Long)



output string (byte array pointer)



This OpenMaple function is part of the MapleCallBack structure passed as an argument to StartMaple.


The textCallBack function is called with typical (non-exceptional) Maple output. The output that Maple generates, for example, an intermediate result or the output from a printf statement, is passed to the textCallBack function.


The prototype for the function that you can assign to the entry in the MapleCallBack must resemble the following.

Sub TextCallBack(ByVal data As Long,

     ByVal tag As Integer,

     ByVal Output As Long)


The tag parameter indicates the type of Maple output. The tag parameter can take one of the following values (as defined in maplec.h).


A line-printed (1-D) Maple expression or statement.




Diagnostic output (high printlevel or trace output).




Miscellaneous output, for example, from the Maple


printf function.




Response to a Maple quit, done, or stop command.




A warning message generated during a computation.




An error message generated during parsing or


processing. This is generated only if you


do not specify an errorCallBack function.




Kernel resource usage status (a "bytes used"


message). This is generated only if you


do not specify a statusCallBack function.




Output from the Maple debugger.




The output parameter contains the output of the type indicated by the tag parameter. Each output string can be arbitrarily long.  Most output obeys interface(screenwidth), which is initially set to infinity.  Some output is not line-broken, including output generated by printf (which controls its own formatting).


A single result may be split into multiple calls to the textCallBack function. In particular, this can happen when interfacescreenwidth is not infinity.  It is also true for formatted output like that generated by accessing help.  A single command can generate many calls with different output tags.


The data parameter contains the same data as passed to StartMaple in the user_data parameter.


 Public Sub TextCallBack2(ByVal data As Long, ByVal tag As Integer, _

         ByVal Output As Long)

    Dim OutputString As String

    OutputString = MaplePointerToString(Output)

    If tag = MAPLE_TEXT_HELP Then

        Write #2, OutputString


        Write #1, OutputString

    End If

 End Sub

 ' assignment to MapleCallback entry

 cb.lpTextCallBack = GetProc(AddressOf TextCallBack)

 ' test statement that will invoke the TextCallBack

 EvalMapleStatement kv, "x^2+3*x+1;"

 EvalMapleStatement kv, "help(int);"

See Also

callBackCallBack, errorCallBack, interface, OpenMaple, OpenMaple/VB/API, OpenMaple/VB/Examples, queryInterrupt, readLineCallBack, redirectCallBack, StartMaple, statusCallBack, streamCallBack

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