Volume 6A: Motif Programming Manual

13.3.6 An Example

In this section, we pull together all of the functions we have described in the preceding sections. This example builds

on alpha_list.c, the program that adds items that are input by the user to a ScrolledList in alphabetical order. Using

another Text widget, the user can also search for items in the list. The searching method uses regular expression

pattern−matching functions intrinsic to UNIX systems. the source code shows the new application.

XtSetLanguageProc() is only available in X11R5; there is no corresponding function in X11R4.

XmStringCreateLocalized() is only available in Motif 1.2; XmStringCreateSimple() is the

corresponding function in Motif 1.1. XmFONTLIST_DEFAULT_TAG replaces XmSTRING_DEFAULT_CHARSET in

Motif 1.2.

/* search_list.c −− search for items in a List and select them */

#include <stdio.h>

#include <Xm/List.h>

#include <Xm/LabelG.h>

#include <Xm/Label.h>

#include <Xm/RowColumn.h>

#include <Xm/PanedW.h>

#include <Xm/TextF.h>

main(argc, argv)

int argc;

char *argv[];

{

Widget toplevel, rowcol, list_w, text_w;

XtAppContext app;

Arg args[5];

int n = 0;

XmString label;

void add_item(), search_item();

XtSetLanguageProc (NULL, NULL, NULL);

toplevel = XtVaAppInitialize (&app, "Demos", NULL, 0,

&argc, argv, NULL, NULL);

rowcol = XtVaCreateWidget ("rowcol",

xmPanedWindowWidgetClass, toplevel, NULL);

label = XmStringCreateLocalized ("List:");

XtVaCreateManagedWidget ("list_lable", xmLabelWidgetClass, rowcol,

XmNlabelString, label,

NULL);

XmStringFree (label);

XtSetArg (args[n], XmNvisibleItemCount, 10); n++;

XtSetArg (args[n], XmNselectionPolicy, XmEXTENDED_SELECT); n++;

list_w = XmCreateScrolledList (rowcol, "scrolled_list", args, n);

XtManageChild (list_w);

label = XmStringCreateLocalized ("Add:");

XtVaCreateManagedWidget ("add_label", xmLabelWidgetClass, rowcol,

XmNlabelString, label,

NULL);

XmStringFree (label);

text_w = XtVaCreateManagedWidget ("add_text",

xmTextFieldWidgetClass, rowcol,

XmNcolumns, 25,

NULL);

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XtAddCallback (text_w, XmNactivateCallback, add_item, list_w);

label = XmStringCreateLocalized ("Search:");

XtVaCreateManagedWidget ("search_label", xmLabelWidgetClass, rowcol,

XmNlabelString, label,

NULL);

XmStringFree (label);

text_w = XtVaCreateManagedWidget ("search_text",

xmTextFieldWidgetClass, rowcol,

XmNcolumns, 25,

NULL);

XtAddCallback (text_w, XmNactivateCallback, search_item, list_w);

XtManageChild (rowcol);

XtRealizeWidget (toplevel);

XtAppMainLoop (app);

}

/* Add item to the list in alphabetical order. Perform binary

* search to find the correct location for the new item position.

* This is the callback routine for the Add: TextField widget.

*/

void

add_item(text_w, client_data, call_data)

Widget text_w;

XtPointer client_data;

XtPointer call_data;

{

Widget list_w = (Widget) client_data;

char *text, *newtext = XmTextFieldGetString (text_w);

XmString str, *strlist;

int u_bound, l_bound = 0;

if (!newtext || !*newtext) {

/* non−null strings must be entered */

XtFree (newtext);

return;

}

XtVaGetValues (list_w,

XmNitemCount, &u_bound,

XmNitems, &strlist,

NULL);

u_bound−−;

/* perform binary search */

while (u_bound >= l_bound) {

int i = l_bound + (u_bound − l_bound)/2;

if (!XmStringGetLtoR (strlist[i], XmFONTLIST_DEFAULT_TAG, &text))

break;

if (strcmp (text, newtext) > 0)

u_bound = i−1; /* newtext comes before item */

else

l_bound = i+1; /* newtext comes after item */

XtFree (text);

}

str = XmStringCreateLocalized (newtext);

XtFree (newtext);

/* positions indexes start at 1, so increment accordingly */

XmListAddItemUnselected (list_w, str, l_bound+1);

XmStringFree (str);

XmTextFieldSetString (text_w, "");

}

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/* find the item in the list that matches the specified pattern */

void

search_item(text_w, client_data, call_data)

Widget text_w;

XtPointer client_data;

XtPointer call_data;

{

Widget list_w = (Widget) client_data;

char *exp, *text, *newtext = XmTextFieldGetString (text_w);

XmString *strlist, *selectlist = NULL;

int matched, cnt, j = 0;

#ifndef SYSV

extern char *re_comp();

#endif /* SYSV */

if (!newtext || !*newtext) {

/* non−null strings must be entered */

XtFree (newtext);

return;

}

/* compile expression into pattern matching library */

#ifdef SYSV

if (!(exp = regcmp (newtext, NULL))) {

printf ("Error with regcmp(%s)0, newtext);

XtFree (newtext);

return;

}

#else /* BSD */

if (exp = re_comp (newtext)) {

printf ("Error with re_comp(%s): %s0, newtext, exp);

XtFree (newtext);

return;

}

#endif /* SYSV */

/* get all the items in the list ... we're going to search each one */

XtVaGetValues (list_w,

XmNitemCount, &cnt,

XmNitems, &strlist,

NULL);

while (cnt−−) {

/* convert item to C string */

if (!XmStringGetLtoR (strlist[cnt], XmFONTLIST_DEFAULT_TAG, &text))

break;

/* do pattern match against search string */

#ifdef SYSV

/* returns NULL if match failed */

matched = regex (exp, text, NULL) != NULL;

#else /* BSD */

/* −1 on error, 0 if no−match, 1 if match */

matched = re_exec (text) > 0;

#endif /* SYSV */

if (matched) {

selectlist = (XmString *) XtRealloc (selectlist,

(j+1) * (sizeof (XmString *)));

selectlist[j++] = XmStringCopy (strlist[cnt]);

}

XtFree (text);

}

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#ifdef SYSV

free (exp); /* this must be freed for regcmp() */

#endif /* SYSV */

XtFree (newtext);

/* set the actual selected items to be those that matched */

XtVaSetValues (list_w,

XmNselectedItems, selectlist,

XmNselectedItemCount, j,

NULL);

while (j−−)

XmStringFree (selectlist[j]);

XmTextFieldSetString (text_w, "");

}

The output of this program is shown in the figure. The TextField widget that is used to search for items in the List

widget works identically to the one that is used to add new items. Its callback routine, search_item(), searches

the list for the specified pattern. The version of UNIX you are running (System V or BSD) dictates which kind of

regular expression matching is done. System V machines use the function regcmp() to compile the pattern and

regex() to search for the pattern within another string, while BSD UNIX systems use the functions re_comp()

and re_exec() to do the same thing. Systems that support both BSD and System V may support one, the other, or

both methods of regular expression handling. You should consult your system's documentation for more information

on these functions.

The items in the list are retrieved using XtVaGetValues() and the strlist parameter. This variable points to

the internal list used by the List widget, so it is important that we do not change any of these elements or free these

pointers when we are through with them. Changing the value of XmNselectedItems causes the internal list to

change. Since the internal list is referenced by strlist, it is important to copy any values that we want to use

elsewhere. If the pattern matches a list item, the item is copied using XmStringCopy() and is later added to the

List's XmNselectedItems.

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