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Re: NSTabView Fix

From: Wolfgang Lux
Subject: Re: NSTabView Fix
Date: Sat, 24 Feb 2007 15:00:09 +0100

Andreas Höschler wrote:

and we need to make sure these two match in some way. And what I tried to do was just this. If I failed on doing so, please show me my > wrongs.

Create a tabView and add four tabViewItems. _selected_item will be 4. Then call selectedTabViewItem! Boohm!!!

So what? Fred's change looked okay to me (and still looks so). The point is just that NSTabView fails to initialize the _selected_item instance variable
properly. Adding the line
  _selected_item = NSNotFound;
in -initWithFrame: should fix this issue.

If NSNotFound is and will stay defined as -1 then YES! Can we build on that?

No, because 0x7fffffff != -1 :-) (see NSObject.h; it's the same on Cocoa). Anyway there is really no need to do so because the code (with two exceptions, see below) carefully checks whether _selected_item is NSNotFound before incrementing or
decrementing the instance variable.

The two methods were the check is absent are -selectNextTabViewItem: and
-selectPreviousTabViewItem:. These methods might be changed as follows

  - (void) selectNextTabViewItem: (id)sender
  #if 0
/* the check below does work because 0x80000000 is cast to unsigned and thus * greater than the number of items; nevertheless, checking explicitly for
     * NSNotFound improves code clarity */
    if ((unsigned)(_selected_item + 1) < [_items count])
if (_selected_item != NSNotFound && (unsigned)(_selected_item + 1) < [_items count]))
      [self selectTabViewItemAtIndex: _selected_item+1];

  - (void) selectPreviousTabViewItem: (id)sender
  #if 0
/* the check below works just because even NSNotFound-1 is greater than the index of any item in the tab view and therefore selectTabViewItemAtIndex: will set the selected item (redundantly) to nil (and thereby also _selected_item to NSNotFound); nevertheless, checking explicitly for
       NSNotFound improves code clarity. */
    if (_selected_item > 0)
    if (_selected_item != NSNotFound && _selected_item > 0)
      [self selectTabViewItemAtIndex: _selected_item-1];

Sorry (to Fred), I haven't looked for a fix for the fix yesterday. I just discovered that the modification broke my code and therefore rolled back to the older implementation. I suppose _selected_item = -1; in the init method will do the trick.

No, it won't. You have to use _selected_item = NSNotFound or you are going to
break other things in NSTabView.m.


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