Re: Word selection and cursor placement

[Wolfgang Lux]

Andreas Höschler wrote:

> [...]
> > > • Selecting 'valueForKey' in
> > >
> > >         [self valueForKey:@"hostname"];
> > >
> > > and the pressing cursor left puts the cursor
> > > directly to the right of
> > > self which is wrong. The cursor should be placed
> > > between the space and
> > > valueForKey. The behaviour is even worse when
> > > leaving a selction to the
> > > right side. When self was selected this places the
> > > cursor between 's'
> > > and 'elf' which is totally wrong.
> >
> > NSTextView_actions.m: -moveLeft:
> >
> > > Hints where in the GNustep tree this can be
> > > corrected are greatly
> > > appreciated! Thanks!
>
> I belive the malfuntion actually is in NSLayoutManager

I don't think so. If you look carefully, you will notice that the  
logic implemented by the various -move methods which do not extend  
the current selection is incorrectly based on the result of [self  
_movementOrigin], which returns either the start or end of the  
current selection depending on whether the current selection affinity  
is NSSelectionAffinityUpstream or NSSelectionAffinityDownstream,  
respectively. The selection affinity should be taken only into  
account when the current selection is extended or reduced (i.e.,  
moveBackwardAndModifySelection: and friends).

Let's have a more detailed look at some of the methods. According to  
the NSTextView documentation, -moveBackward: and -moveForward: should  
collapse the selection to its beginning or end, respectively, if the  
selection is not empty and move the cursor only one character forward  
or backward otherwise. This suggests the following implementation of  
these two methods:

- (void) moveBackward: (id)sender
{
  NSRange range = [self selectedRange];

  if (range.length)
    [self _moveTo: range.location select: NO];
  else if (range.location)
    [self _moveTo: range.location - 1 select: NO];
}
- (void) moveForward: (id)sender
{
  NSRange range = [self selectedRange];

  if (range.length)
    [self _moveTo: NSMaxRange(range) select: NO];
  else if (range.location)
    [self _moveTo: range.location + 1 select: NO];
}

[Side note: These two methods should be bound to the keys Control-b  
and Control-f in DefaultKeyBindings.dict. At present, these two keys  
are bound to moveLeft: and moveRight:.]

Changing -moveLeft: and -moveRight: is a little bit more complicated  
because the selection should collapse to the left and right end,  
respectively. For languages with left-to-right text flow (i.e.,  
western languages), this ends will match the beginning and end of the  
selection, respectively. Yet, for languages with a right-to-left text  
flow (e.g. Hebrew or Arabic) the ends of the selection have to be  
reversed. I leave it as an exercise for someone more knowledgeable  
than me to fix this shortcoming in the following implementations of  
moveLeft: and moveRight:.

- (void) moveLeft: (id)sender
{
  NSRange range = [self selectedRange];

  if (range.length)
    // FIXME: this should be the *left* end of the selection
    [self _moveTo: range.location select: NO];
  else
    [self _move: GSInsertionPointMoveLeft
          distance: 0.0
          select: NO];
}

- (void) moveRight: (id)sender
{
  NSRange range = [self selectedRange];

  if (range.length)
    // FIXME: this should be the *right* end of the selection
    [self _moveTo: NSMaxRange(range) select: NO];
  else
    [self _move: GSInsertionPointMoveRight
          distance: 0.0
          select: NO];
}

I also leave it as an exercise to fix the -moveUp: and -moveDown:  
methods, which according to the documentation should move to the  
character immediately above the beginning and immediately below the  
end of the selection, respectively.

Similar fixes will be necessary in methods -moveWordForward: - 
moveWordBackward:, -moveToBeginningOfParagraph:, - 
moveToEndOfParagraph:, and maybe others. Look for [self  
_movementOrigin] to find other places that eventually need to be fixed.

Hope this helps,
Wolfgang