Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!munnari.oz.au!uhccux!galileo!denault
From: denault@galileo.ifa.hawaii.edu (Tony Denault)
Newsgroups: comp.windows.x
Subject: Re:  XView scrolling list usage
Message-ID: <10351@uhccux.uhcc.Hawaii.Edu>
Date: 20 Nov 90 20:57:24 GMT
References: <9011200021.AA02255@zia.aoc.nrao.edu> <5873@pizza.cam.nist.gov>
Sender: news@uhccux.uhcc.Hawaii.Edu
Organization: Institute For Astronomy, Hawaii
Lines: 87

>
>I would like to change the contents of the list with one call to xv_set().
>And since my lists will have differing number of items, I was looking for a
>way to do this without knowing at compile time how many items are in the
>list.
>

Many months ago I posted a request similar to your. I want to
be able to update a scroll list quickly. Using the xv_set() calls
to delete and insert items in the list was too slow, because 
xview redraws the panel item on each xv_set() call.

Someone posted a solution ( author unknown, sorry I lost the orginal file )
which I use to set the contents of the scrolling list using an argv-style 
array of strings. I am posting this function.

/*----------------------------------------------------------------------------
 * scrolling_list_update:
 *
 *   Given a scrolling list and an argv-style array of strings,
 *   update the contents of the scrolling list.
 *----------------------------------------------------------------------------
 */
void scrolling_list_update(list, argc, argv)
Xv_opaque   list;
int      argc;
char      **argv;
{
   register int   i, j;
   char      **avlist;
   int      rows = xv_get(list, PANEL_LIST_NROWS);
 
   /*
    * Copy the string information to an avlist.
    */
   if (argc > 0) {
      /*
       * Allocate memory for the list and fill it in.
       */
      avlist = (char **) malloc((argc + 3) * sizeof (char *));
      avlist[0] = (char *) PANEL_LIST_STRINGS;
      for (i = 0; i < argc; i++)
         avlist[i + 1] = argv[i];
      avlist[++i] = (char *) NULL;   /* NULL-terminate strings */
      avlist[++i] = (char *) NULL;   /* NULL-terminate avlist */

      /*
       * Set the scrolling list and free the avlist.
       */
      xv_set(list, ATTR_LIST, avlist, NULL);
      free((char *) avlist);
   }
   /*
    * This should not be necessary, but ... clear any entries
    * in excess of the new entries.
    */
   if (rows > argc) {
      /*
       * Set up an avlist with PANEL_LIST_DELETE,index pairs. The
       * panel entries are deleted from bottom (high index) to
       * top (low index) which might reduce copying of entries.
       */
      avlist = (char **) malloc(((rows-argc)*2+1) * sizeof (char *));
      for (j = 0, i = rows - 1; i >= argc; i--) {
         avlist[j++] = (char *) PANEL_LIST_DELETE;
         avlist[j++] = (char *) i;
      }
      avlist[j] = (char *) NULL;   /* NULL-terminate avlist */

      /*
       * Delete the excess entries and free the avlist.
       */
      xv_set(list, ATTR_LIST, avlist, NULL);
      free((char *) avlist);
   }
}


/------------------------------------------------------------------------\
| Tony Denault, Institute for Astronomy,  | denault@uhifa.ifa.hawaii.edu |
| 2680 Woodlawn Drive, Honolulu, HI 96789 |               (808) 956-6097 |
\------------------------------------------------------------------------/
--
/------------------------------------------------------------------------\
| Tony Denault, Institute for Astronomy,  | denault@uhifa.ifa.hawaii.edu |
| 2680 Woodlawn Drive, Honolulu, HI 96789 |               (808) 956-6097 |
\------------------------------------------------------------------------/