Looping through windows on a screen

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Tue, 2014-11-04 16:00
#1
JosDuchIt
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Looping through windows on a screen

When looping through windows on a screen with the code below, and searching for a non-existing windowtitle, i get a crash? No problem when the title exists (CS) 

  1. struct Window * GetWindow( STRPTR screenname, STRPTR windowabbrev ) {
  2. 	struct Screen *nxtscreen, *scr;
  3. 	struct Window *win, *selwin;
  4. 	int lgtwt, lgtabbr;
  5. 	char wtshort[31];
  6.  	BOOL winfound =FALSE;
  7. 	lgtabbr = strlen(windowabbrev);
  8. 	if (screenname[0] == 0 ) 
  9. 	{
  10. 		scr = LockPubScreen(NULL);
  11. 	}
  12. 	else scr = LockPubScreen(screenname); 
  13. 	if (!(scr )) return (NULL); /// NULL Default public screen , mopstly WB screen 
  14. 	win = scr->FirstWindow;
  15. 	while (win) 
  16. 	{  
  17. 		lgtwt = strlen(win->Title); /// ########crash here when all windows looped through
  18. 		if (lgtwt >= lgtabbr) 
  19. 		{
  20. 			strncpy (wtshort, (char *)win->Title, lgtabbr);
  21. 			wtshort[lgtabbr]=0;
  22. 			if (strcmp(wtshort, windowabbrev) == 0) {
  23. 				winfound=TRUE;
  24. 				break;
  25. 			}
  26. 		}
  27. 		win = win->NextWindow;
  28. 	}
  29. 	if (winfound) 
  30. 	{
  31. 		PutStr("found");
  32. 		UnlockPubScreen(screenname, scr);
  33. 		return (win);
  34. 	}
  35. 	else 
  36. 	{
  37. 		UnlockPubScreen(screenname, scr);
  38. 		return (NULL); 
  39. 	}
  40. }

What is wring with the loop?
Why doesn't it stop when win is NULL ??

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Tue, 2014-11-04 17:59
OldFart
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Joined: 2010-11-30 14:09
I'm not exactly sure as it

I'm not exactly sure as it has been a while since I last touched this issue (my MicroA1 broke down 2 years ago...), but if I remember correctly, some windows have no titlestring, hence win->Title is NULL.

Maybe this helps:

  1. struct Window * GetWindow(STRPTR screenname, STRPTR windowabbrev)
  2. {
  3.   struct Window *win = NULL;
  4.  
  5.   struct Screen *scr;
  6.  
  7.   if (
  8.       (screenname    != NULL) &&
  9.       (screenname[0] == 0)
  10.      )
  11.    {
  12.     scr = LockPubScreen(NULL);
  13.    }
  14.   else
  15.    {
  16.     scr = LockPubScreen(screenname); 
  17.    }
  18.  
  19.   if (scr)
  20.    {
  21.     BOOL winfound = FALSE;
  22.     int lgtwt,
  23.         lgtabbr = strlen(windowabbrev);
  24.     char wtshort[31];
  25.  
  26.     win = scr->FirstWindow;
  27.  
  28.     while (
  29.            (win      != NULL) &&
  30.            (winfound == FALSE)
  31.           )
  32.      {
  33.       if (win->Title != NULL)
  34.        {
  35.         lgtwt = strlen(win->Title);
  36.  
  37.         if (lgtwt >= lgtabbr) 
  38.          {
  39.           strncpy (wtshort, (char *)win->Title, lgtabbr);
  40.           wtshort[lgtabbr] = 0;
  41.  
  42.           if (strcmp(wtshort, windowabbrev) == 0)
  43.            {
  44.             winfound = TRUE;
  45.            }
  46.          }
  47.        }
  48.  
  49.       win = win->NextWindow;
  50.      }
  51.  
  52.     if (winfound == TRUE) 
  53.      {
  54.       PutStr("found");
  55.      }
  56.  
  57.     UnlockPubScreen(screenname, scr);
  58.    }
  59.  
  60.   return (win);
  61. }

Try it.

Added an extra safeguard and removed some superfluous code. I'm sorry this being a nasty habbit of mine.

OldFart

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Tue, 2014-11-04 18:30
(Reply to #2)
thomas
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Joined: 2011-05-16 14:23
@OldFart: your routine does

@OldFart: your routine does not return the window which matches the title but the next one.

Here is a shorter one and it works (tested):

  1. struct Window *get_window (STRPTR screenname, STRPTR windowabbrev)
  2.  
  3. {
  4. struct Window *win = NULL;
  5.  
  6. if (windowabbrev)
  7. 	{
  8. 	long abbrlen = strlen(windowabbrev);
  9. 	struct Screen *scr;
  10.  
  11. 	if (scr = LockPubScreen (screenname && !screenname[0] ? NULL : screenname))
  12. 		{
  13. 		for (win = scr->FirstWindow; win; win = win->NextWindow)
  14. 			{
  15. 			if (win->Title && !Strnicmp(win->Title,windowabbrev,abbrlen))
  16. 				break;
  17. 			}
  18.  
  19. 		UnlockPubScreen (NULL,scr);
  20. 		}
  21. 	}
  22.  
  23. return (win);
  24. }

Note: I intentionally use Strnicmp which does not care about upper/lower case. You can as well use strncmp if case matters.

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Tue, 2014-11-04 21:52
(Reply to #3)
JosDuchIt
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Joined: 2012-01-08 20:57
@OldFart &Thomas Thanks for

@OldFart &Thomas

Thanks for the help
Works OK now

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