# IBM Visualization Data Explorer Programmer's Reference

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## 17.4 Example 3: xapp.c

The third example which we will discuss is xapp.c. This sample program does not use the Data Explorer user interface at all; rather it creates its own (simple) user interface. The program communicates with Data Explorer entirely through the scripting language.

The interface presents the user with four buttons. Depending on which button is pressed, a different data file is imported. The maximum value in the data set is then computed and sent back to the DXLink application using a DXLOutput tool. The result is then displayed in a text widget created by the DXLink program.

    #include <Xm/Xm.h>
    #include <Xm/Form.h>
    #include <Xm/Label.h>
    #include <Xm/PushB.h>
    #include <Xm/ToggleB.h>
    #include <Xm/Text.h>
    #include "dx/dxl.h"
    void radio_cloudCB(Widget, XtPointer, XtPointer);
    void radio_rainCB(Widget, XtPointer, XtPointer);
    void radio_windCB(Widget, XtPointer, XtPointer);
    void radio_tempCB(Widget, XtPointer, XtPointer);
    void cloudhandler(DXLConnection *, const char *, const char *, void *);
    void rainhandler(DXLConnection *, const char *, const char *, void *);
    void windhandler(DXLConnection *, const char *, const char *, void *);
    void temphandler(DXLConnection *, const char *, const char *, void *);
    static String DefaultResources[] =
    {
        "*background:              #b4b4b4b4b4b4",
        "*foreground:              black",
    #ifdef sgi
        "*fontList:                 -adobe-helvetica*bold-r*14*=bold\n\
                                    -adobe-helvetica*medium-r*14*=normal\n\
                                    -adobe-helvetica*medium-o*14*=oblique",
    #else
        "*fontList:                 -adobe-helvetica*bold-r*14*=bold\
                                    -adobe-helvetica*medium-r*14*=normal\
                                    -adobe-helvetica*medium-o*14*=oblique",
    #endif
       "*XmToggleButton.selectColor:            CadetBlue",
        "*XmText.shadowThickness:                1",
        NULL
    };
    main(argc, argv)
    int argc;
    char *argv[];
    {
       Widget          toplevel, main_w, label, textfield, radio_box;
       Widget          radio_cloud, radio_rain, radio_temp, radio_wind;
       XtAppContext    app;
       XmString        xms;
       DXLConnection   *conn;
       int             n;
       Arg             wargs[50];
       /*
        *  Start the Data Explorer executive.
        */
       conn = DXLStartDX("dx -exonly",NULL);
       if (!conn)
        {
          printf("could not start dx");
          exit(0);
        }
       XtSetLanguageProc (NULL, NULL, NULL);
       toplevel = XtVaAppInitialize (&app, "Demos",
                                     NULL, 0, &argc, argv,
                                     DefaultResources, NULL);
       DXLInitializeXMainLoop(app, conn);
       /*
        * Create the user interface for this application
        */
       main_w = XtVaCreateManagedWidget("form",
                     xmFormWidgetClass, toplevel,
                     XmNwidth,    400,
                     XmNheight,   180,
                     XmNfractionBase, 5,
                     NULL);
       n = 0;
       XtSetArg(wargs[n], XmNtopAttachment, XmATTACH_FORM); n++;
       XtSetArg(wargs[n], XmNleftAttachment, XmATTACH_FORM); n++;
       XtSetArg(wargs[n], XmNleftOffset, 30); n++;
       radio_box = (Widget)XmCreateRadioBox(main_w, "choice", wargs, n);
       XtManageChild(radio_box);
       xms = XmStringCreateSimple("cloudwater");
       radio_cloud = XtVaCreateManagedWidget("radio_cloud",
                          xmToggleButtonWidgetClass, radio_box,
                          XmNlabelString, xms,
                          NULL);
       XmStringFree(xms);
       XtAddCallback(radio_cloud, XmNvalueChangedCallback,
                     (XtCallbackProc)radio_cloudCB,
                     (XtPointer)conn);
       xms = XmStringCreateSimple("rainwater");
       radio_rain = XtVaCreateManagedWidget("radio_rain",
                          xmToggleButtonWidgetClass, radio_box,
                          XmNlabelString, xms,
                          NULL);
       XmStringFree(xms);
       XtAddCallback(radio_rain, XmNvalueChangedCallback,
                     (XtCallbackProc)radio_rainCB,
                     (XtPointer)conn);
       xms = XmStringCreateSimple("temperature");
       radio_temp = XtVaCreateManagedWidget("radio_temp",
                          xmToggleButtonWidgetClass, radio_box,
                          XmNlabelString, xms,
                          NULL);
       XmStringFree(xms);
       XtAddCallback(radio_temp, XmNvalueChangedCallback,
                     (XtCallbackProc)radio_tempCB,
                     (XtPointer)conn);
       xms = XmStringCreateSimple("wind");
       radio_wind = XtVaCreateManagedWidget("radio_wind",
                          xmToggleButtonWidgetClass, radio_box,
                          XmNlabelString, xms,
                          NULL);
       XmStringFree(xms);
       XtAddCallback(radio_wind, XmNvalueChangedCallback,
                     (XtCallbackProc)radio_windCB,
                     (XtPointer)conn);
       xms = XmStringCreateSimple("returned value:");
       label = XtVaCreateManagedWidget("label",
                     xmLabelWidgetClass,
                     main_w,
                     XmNtopAttachment,   XmATTACH_WIDGET,
                     XmNtopWidget,       radio_box,
                     XmNbottomAttachment,   XmATTACH_FORM,
                     XmNleftAttachment,  XmATTACH_FORM,
                     XmNlabelString, xms,
                     NULL);
       XmStringFree(xms);
       textfield = XtVaCreateManagedWidget("text",
                     xmTextWidgetClass,
                     main_w,
                     XmNtopAttachment,   XmATTACH_OPPOSITE_WIDGET,
                     XmNtopWidget,       label,
                     XmNleftAttachment,  XmATTACH_WIDGET,
                     XmNleftWidget,      label,
                     XmNrightAttachment,  XmATTACH_FORM,
                     XmNbottomAttachment,  XmATTACH_FORM,
                     NULL);
       /*
        * Set the handlers for the various parameters
        */
       DXLSetValueHandler(conn,"cloudmax", cloudhandler, textfield);
       DXLSetValueHandler(conn,"rainmax", rainhandler, textfield);
       DXLSetValueHandler(conn,"windmax", windhandler, textfield);
       DXLSetValueHandler(conn,"tempmax", temphandler, textfield);
       XtRealizeWidget (toplevel);
       XtAppMainLoop (app);
    }
    /*
     * The following are the handlers for data coming from DXLOutput. If
     * data is received by the handler, it is presented in a text widget.
     */
    void rainhandler(DXLConnection *conn, const char *name, const char *value,
                 void *data)
    {
       char string[100];
       Widget text_widget = (Widget)data;
       sprintf(string,"rainwater max value = %s", value);
       XmTextSetString(text_widget, string);
    }
    void cloudhandler(DXLConnection *conn, const char *name, const char *value,
                 void *data)
    {
       char string[100];
       Widget text_widget = (Widget)data;
       sprintf(string,"cloudwater max value = %s", value);
       XmTextSetString(text_widget, string);
    }
    void temphandler(DXLConnection *conn, const char *name, const char *value,
                 void *data)
    {
       char string[100];
       Widget text_widget = (Widget)data;
       sprintf(string,"temperature max value = %s", value);
       XmTextSetString(text_widget, string);
    }
    void windhandler(DXLConnection *conn, const char *name, const char *value,
                 void *data)
    {
       char string[100];
       Widget text_widget = (Widget)data;
       sprintf(string,"wind max value = %s", value);
       XmTextSetString(text_widget, string);
    }
    /*
     * The following are the callbacks for the buttons in the
     * user interface created above. In each case, some simple
     * script language commands are sent to the Data Explorer
     * executive. The maximum as computed by the Statistics
     * module is then input to the DXLOutput tool. The handlers
     * defined above wait for values to be received from
     * DXLOutput, and then present the result in the text widget.
     */
    void radio_cloudCB(Widget w, XtPointer xp1, XtPointer xp2)
    {
       DXLConnection *conn = (DXLConnection *)xp1;
       DXLSend(conn, "g = Import(\"/usr/share/dx/samples/data/cloudwater\");");
       DXLSend(conn, "mean,sd,var,min,max = Statistics(g);");
       DXLSend(conn, "DXLOutput(\"cloudmax\", max);");
    }
    void radio_rainCB(Widget w, XtPointer xp1, XtPointer xp2)
    {
       DXLConnection *conn = (DXLConnection *)xp1;
       DXLSend(conn, "g = Import(\"/usr/share/dx/samples/data/rainwater\");");
       DXLSend(conn, "mean,sd,var,min,max = Statistics(g);");
       DXLSend(conn, "DXLOutput(\"rainmax\", max);");
    }
    void radio_tempCB(Widget w, XtPointer xp1, XtPointer xp2)
    {
       DXLConnection *conn = (DXLConnection *)xp1;
       DXLSend(conn, "g = Import(\"/usr/share/dx/samples/data/temperature\");");
       DXLSend(conn, "mean,sd,var,min,max = Statistics(g);");
       DXLSend(conn, "DXLOutput(\"tempmax\", max);");
    }
    void radio_windCB(Widget w, XtPointer xp1, XtPointer xp2)
    {
       DXLConnection *conn = (DXLConnection *)xp1;
       DXLSend(conn, "g = Import(\"/usr/share/dx/samples/data/wind\");");
       DXLSend(conn, "mean,sd,var,min,max = Statistics(g);");
       DXLSend(conn, "DXLOutput(\"windmax\", max);");
    }

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