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From: denault@wirth.ifa.hawaii.EDU (Anthony Denault)
Newsgroups: comp.windows.x
Subject: Re: Help with XView`s PANEL_LIST
Message-ID: <9101222032.AA00452@wirth.ifa.hawaii.edu>
Date: 22 Jan 91 20:32:36 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 84

> 1.  I'm xv_create(ing) a PANEL_LIST.  Whenever I insert or delete items,
>it appears as if OW redraws the entire list.  This causes a "flashing"
>that is very annoying (especially since I update the list frequently).
>I'm hoping that there is a way around this... Any clues?

 
I got this function from the net. Original author is not knowned. It sets the
contents of a scrolling list from a list of string in an argc-style parameter.
 
Since it update the entire list at once, there is no "flashing" for each 
insert or delete. (There is only 1 re-draw of the list).

 
/*----------------------------------------------------------------------------
 * 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
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| Tony Denault, Institute for Astronomy,  | denault@uhifa.ifa.hawaii.edu |
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