/** <title>NSTextView</title>

   <abstract>Categories which add user actions to NSTextView</abstract>

   Copyright (C) 1996, 1998, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.

   Originally moved here from NSTextView.m.

   Author: Scott Christley <scottc@net-community.com>
   Date: 1996

   Author: Felipe A. Rodriguez <far@ix.netcom.com>
   Date: July 1998

   Author: Daniel Bðhringer <boehring@biomed.ruhr-uni-bochum.de>
   Date: August 1998

   Author: Fred Kiefer <FredKiefer@gmx.de>
   Date: March 2000, September 2000

   Author: Nicola Pero <n.pero@mi.flashnet.it>
   Date: 2000, 2001, 2002

   Author: Pierre-Yves Rivaille <pyrivail@ens-lyon.fr>
   Date: September 2002

   Extensive reworking: Alexander Malmberg <alexander@malmberg.org>
   Date: December 2002 - February 2003

   This file is part of the GNUstep GUI Library.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with this library; see the file COPYING.LIB.
   If not, write to the Free Software Foundation,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
*/

#include <Foundation/NSNotification.h>
#include <Foundation/NSValue.h>
#include "AppKit/NSGraphics.h"
#include "AppKit/NSLayoutManager.h"
#include "AppKit/NSScrollView.h"
#include "AppKit/NSTextStorage.h"
#include "AppKit/NSTextView.h"

/*
These methods are for user actions, ie. they are normally called from
-doCommandBySelector: (which is called by the input manager) in response
to some key press or other user event.

User actions that modify the text must check that a modification is allowed
and make sure all necessary notifications are sent. This is done by sending
-shouldChangeTextInRange:replacementString: before making any changes, and
(if the change is allowed) -didChangeText after the changes have been made.

All actions from NSResponder that make sense for a text view  should be
implemented here, but this is _not_ the place to add new actions.

When changing attributes, the range returned by
rangeForUserCharacterAttributeChange or rangeForUserParagraphAttributeChange
should be used. If the location is NSNotFound, nothing should be done (in
particular, the typing attributes should _not_ be changed). Otherwise,
-shouldChangeTextInRange:replacementString: should be called, and if it
returns YES, the attributes of the range and the typing attributes should be
changed, and -didChangeText should be called.

In a non-rich-text text view, the typing attributes _must_always_ hold the
attributes of the text. Thus, the typing attributes must always be changed
in the same way that the attributes of the text are changed.

TODO: can the selected range's location be NSNotFound? when?

Not all user actions are here. Exceptions:

  -copy:
  -copyFont:
  -copyRuler:
  -paste:
  -pasteFont:
  -pasteRuler:
  -pasteAsPlainText:
  -pasteAsRichText:

  -checkSpelling:
  -showGuessPanel:

  -selectAll: (implemented in NSText)

Not all methods that handle user-induced text modifications are here.
Exceptions:
  (TODO)

  -insertText:
  -changeColor:
  -changeFont: (action method?)
  drag&drop handling methods
  (others?)

All other methods that modify text are for programmatic changes and do not
send -shouldChangeTextInRange:replacementString: or -didChangeText.

*/


/** First some helpers **/

@interface NSTextView (user_action_helpers)

-(void) _illegalMovement: (int)textMovement;

-(void) _changeAttribute: (NSString *)name
		 inRange: (NSRange)r
		   using: (id (*)(id))func;

@end


@implementation NSTextView (user_action_helpers)

- (void) _illegalMovement: (int)textMovement
{
  /* This is similar to [self resignFirstResponder], with the
     difference that in the notification we need to put the
     NSTextMovement, which resignFirstResponder does not.  Also, if we
     are ending editing, we are going to be removed, so it's useless
     to update any drawing.  Please note that this ends up calling
     resignFirstResponder anyway.  */
  NSNumber *number;
  NSDictionary *uiDictionary;

  if ((_tf.is_editable)
      && ([_delegate respondsToSelector:
		       @selector(textShouldEndEditing:)])
      && ([_delegate textShouldEndEditing: self] == NO))
    return;

  /* TODO: insertion point.
  doesn't the -resignFirstResponder take care of that?
  */

  number = [NSNumber numberWithInt: textMovement];
  uiDictionary = [NSDictionary dictionaryWithObject: number
			       forKey: @"NSTextMovement"];
  [[NSNotificationCenter defaultCenter]
    postNotificationName: NSTextDidEndEditingNotification
		  object: self
		userInfo: uiDictionary];
  /* The TextField will get the notification, and drop our first responder
   * status if it's the case ... in that case, our -resignFirstResponder will
   * be called!  */
  return;
}


- (void) _changeAttribute: (NSString *)name
		  inRange: (NSRange)r
		    using: (id (*)(id))func
{
  unsigned int i;
  NSRange e, r2;
  id current, new;

  if (![self shouldChangeTextInRange: r  replacementString: nil])
    return;

  [_textStorage beginEditing];
  for (i = r.location; i < NSMaxRange(r); )
    {
      current = [_textStorage attribute: name
				atIndex: i
			 effectiveRange: &e];

      r2 = NSMakeRange(i, NSMaxRange(e) - i);
      r2 = NSIntersectionRange(r2, r);
      i = NSMaxRange(e);

      new = func(current);
      if (new != current)
	{
	  if (!new)
	    {
	      [_textStorage removeAttribute: name
				      range: r2];
	    }
	  else
	    {
	      [_textStorage addAttribute: name
				   value: new
				   range: r2];
	    }
	}
    }
  [_textStorage endEditing];

  current = [_layoutManager->_typingAttributes objectForKey: name];
  new = func(current);
  if (new != current)
    {
      if (!new)
	{
	  [_layoutManager->_typingAttributes removeObjectForKey: name];
	}
      else
	{
	  [_layoutManager->_typingAttributes setObject: new  forKey: name];
	}
    }

  [self didChangeText];
}

@end


@implementation NSTextView (user_actions)

/* Helpers used with _changeAttribute:inRange:using:. */
static NSNumber *int_minus_one(NSNumber *cur)
{
  int value;

  if (cur)
    value = [cur intValue] - 1;
  else
    value = -1;

  if (value)
    return [NSNumber numberWithInt: value];
  else
    return nil;
}

static NSNumber *int_plus_one(NSNumber *cur)
{
  int value;

  if (cur)
    value = [cur intValue] + 1;
  else
    value = 1;

  if (value)
    return [NSNumber numberWithInt: value];
  else
    return nil;
}

static NSNumber *float_minus_one(NSNumber *cur)
{
  float value;

  if (cur)
    value = [cur floatValue] - 1;
  else
    value = -1;

  if (value)
    return [NSNumber numberWithFloat: value];
  else
    return nil;
}

static NSNumber *float_plus_one(NSNumber *cur)
{
  int value;

  if (cur)
    value = [cur floatValue] + 1;
  else
    value = 1;

  if (value)
    return [NSNumber numberWithFloat: value];
  else
    return nil;
}


- (void) subscript: (id)sender
{
  NSRange r = [self rangeForUserCharacterAttributeChange];

  if (r.location == NSNotFound)
    return;

  [self _changeAttribute: NSSuperscriptAttributeName
		 inRange: r
		   using: int_minus_one];
}

- (void) superscript: (id)sender
{
  NSRange r = [self rangeForUserCharacterAttributeChange];

  if (r.location == NSNotFound)
    return;

  [self _changeAttribute: NSSuperscriptAttributeName
		 inRange: r
		   using: int_plus_one];
}

- (void) lowerBaseline: (id)sender
{
  NSRange r = [self rangeForUserCharacterAttributeChange];

  if (r.location == NSNotFound)
    return;

  [self _changeAttribute: NSBaselineOffsetAttributeName
		 inRange: r
		   using: float_plus_one];
}

- (void) raiseBaseline: (id)sender
{
  NSRange r = [self rangeForUserCharacterAttributeChange];

  if (r.location == NSNotFound)
    return;

  [self _changeAttribute: NSBaselineOffsetAttributeName
		 inRange: r
		   using: float_minus_one];
}

- (void) unscript: (id)sender
{
  NSRange aRange = [self rangeForUserCharacterAttributeChange];

  if (aRange.location == NSNotFound)
    return;

  if (![self shouldChangeTextInRange: aRange
		   replacementString: nil])
    return;

  if (aRange.length)
    {
      [_textStorage beginEditing];
      [_textStorage removeAttribute: NSSuperscriptAttributeName
			      range: aRange];
      [_textStorage removeAttribute: NSBaselineOffsetAttributeName
			      range: aRange];
      [_textStorage endEditing];
    }

  [_layoutManager->_typingAttributes removeObjectForKey: NSSuperscriptAttributeName];
  [_layoutManager->_typingAttributes removeObjectForKey: NSBaselineOffsetAttributeName];
  [self didChangeText];
}


- (void) underline: (id)sender
{
  BOOL doUnderline = YES;
  NSRange aRange = [self rangeForUserCharacterAttributeChange];

  if (aRange.location == NSNotFound)
    return;

  if ([[_textStorage attribute: NSUnderlineStyleAttributeName
		     atIndex: aRange.location
		     effectiveRange: NULL] intValue])
    doUnderline = NO;

  if (aRange.length)
    {
      if (![self shouldChangeTextInRange: aRange
		 replacementString: nil])
	return;
      [_textStorage beginEditing];
      [_textStorage addAttribute: NSUnderlineStyleAttributeName
		    value: [NSNumber numberWithInt: doUnderline]
		    range: aRange];
      [_textStorage endEditing];
      [self didChangeText];
    }

  [_layoutManager->_typingAttributes
      setObject: [NSNumber numberWithInt: doUnderline]
      forKey: NSUnderlineStyleAttributeName];
}


- (void) useStandardKerning: (id)sender
{
  NSRange aRange = [self rangeForUserCharacterAttributeChange];

  if (aRange.location == NSNotFound)
    return;
  if (![self shouldChangeTextInRange: aRange
	    replacementString: nil])
    return;

  [_textStorage removeAttribute: NSKernAttributeName
		range: aRange];
  [_layoutManager->_typingAttributes removeObjectForKey: NSKernAttributeName];
  [self didChangeText];
}

- (void) turnOffKerning: (id)sender
{
  NSRange aRange = [self rangeForUserCharacterAttributeChange];

  if (aRange.location == NSNotFound)
    return;
  if (![self shouldChangeTextInRange: aRange
	    replacementString: nil])
    return;

  [_textStorage addAttribute: NSKernAttributeName
		value: [NSNumber numberWithFloat: 0.0]
		range: aRange];
  [_layoutManager->_typingAttributes setObject: [NSNumber numberWithFloat: 0.0]
    forKey: NSKernAttributeName];
  [self didChangeText];
}

- (void) loosenKerning: (id)sender
{
  NSRange r = [self rangeForUserCharacterAttributeChange];

  if (r.location == NSNotFound)
    return;

  [self _changeAttribute: NSKernAttributeName
		 inRange: r
		   using: float_plus_one];
}

- (void) tightenKerning: (id)sender
{
  NSRange r = [self rangeForUserCharacterAttributeChange];

  if (r.location == NSNotFound)
    return;

  [self _changeAttribute: NSKernAttributeName
		 inRange: r
		   using: float_minus_one];
}

- (void) turnOffLigatures: (id)sender
{
  NSRange aRange = [self rangeForUserCharacterAttributeChange];

  if (aRange.location == NSNotFound)
    return;

  if (![self shouldChangeTextInRange: aRange
	    replacementString: nil])
    return;
  [_textStorage addAttribute: NSLigatureAttributeName
		value: [NSNumber numberWithInt: 0]
		range: aRange];
  [_layoutManager->_typingAttributes setObject: [NSNumber numberWithInt: 0]
    forKey: NSLigatureAttributeName];
  [self didChangeText];
}

- (void) useStandardLigatures: (id)sender
{
  NSRange aRange = [self rangeForUserCharacterAttributeChange];

  if (aRange.location == NSNotFound)
    return;

  if (![self shouldChangeTextInRange: aRange
	    replacementString: nil])
    return;
    
  [_textStorage removeAttribute: NSLigatureAttributeName
		range: aRange];
  [_layoutManager->_typingAttributes removeObjectForKey: NSLigatureAttributeName];
  [self didChangeText];
}

- (void) useAllLigatures: (id)sender
{
  NSRange aRange = [self rangeForUserCharacterAttributeChange];

  if (aRange.location == NSNotFound)
    return;

  if (![self shouldChangeTextInRange: aRange
	    replacementString: nil])
    return;
  [_textStorage addAttribute: NSLigatureAttributeName
		value: [NSNumber numberWithInt: 2]
		range: aRange];
  [_layoutManager->_typingAttributes setObject: [NSNumber numberWithInt: 2]
    forKey: NSLigatureAttributeName];
  [self didChangeText];
}

- (void) toggleTraditionalCharacterShape: (id)sender
{
  // TODO
  NSLog(@"Method %s is not implemented for class %s",
	"toggleTraditionalCharacterShape:", "NSTextView");
}


- (void) insertNewline: (id)sender
{
  if (_tf.is_field_editor)
    {
      [self _illegalMovement: NSReturnTextMovement];
      return;
    }

  [self insertText: @"\n"];
}

- (void) insertTab: (id)sender
{
  if (_tf.is_field_editor)
    {
      [self _illegalMovement: NSTabTextMovement];
      return;
    }

  [self insertText: @"\t"];
}

- (void) insertBacktab: (id)sender
{
  if (_tf.is_field_editor)
    {
      [self _illegalMovement: NSBacktabTextMovement];
      return;
    }

  /* TODO */
  //[self insertText: @"\t"];
}


- (void) deleteForward: (id)sender
{
  NSRange range = [self rangeForUserTextChange];
  
  if (range.location == NSNotFound)
    {
      return;
    }
  
  /* Manage case of insertion point - implicitly means to delete following 
     character */
  if (range.length == 0)
    {
      if (range.location != [_textStorage length])
	{
	  /* Not at the end of text -- delete following character */
	  range.length = 1;
	}
      else
	{
	  /* At the end of text - TODO: Make beeping or not beeping
	     configurable vie User Defaults */
	  NSBeep ();
	  return;
	}
    }
  
  if (![self shouldChangeTextInRange: range  replacementString: @""])
    {
      return;
    }

  [_textStorage beginEditing];
  [_textStorage deleteCharactersInRange: range];
  [_textStorage endEditing];
  [self didChangeText];
}

- (void) deleteBackward: (id)sender
{
  NSRange range = [self rangeForUserTextChange];
  
  if (range.location == NSNotFound)
    {
      return;
    }
  
  /* Manage case of insertion point - implicitly means to delete
     previous character */
  if (range.length == 0)
    {
      if (range.location != 0)
	{
	  /* Not at the beginning of text -- delete previous character */
	  range.location -= 1;
	  range.length = 1;
	}
      else
	{
	  /* At the beginning of text - TODO: Make beeping or not
	     beeping configurable via User Defaults */
	  NSBeep ();
	  return;
	}
    }
  
  if (![self shouldChangeTextInRange: range  replacementString: @""])
    {
      return;
    }

  [_textStorage beginEditing];
  [_textStorage deleteCharactersInRange: range];
  [_textStorage endEditing];
  [self didChangeText];
}


/*
TODO: find out what affinity is supposed to mean

My current assumption:

Affinity deals with which direction we are selecting in, ie. which end of
the selected range is the moving end, and which is the anchor.

NSSelectionAffinityUpstream means that the minimum index of the selected
range is moving (ie. _selected_range.location).

NSSelectionAffinityDownstream means that the maximum index of the selected
range is moving (ie. _selected_range.location+_selected_range.length).

Thus, when moving and selecting, we use the affinity to find out which end
of the selected range to move, and after moving, we compare the character
index we moved to with the anchor and set the range and affinity.


The affinity is important when making keyboard selection have sensible
behavior. Example:

If, in the string "abcd", the insertion point is between the "c" and the "d"
(selected range is (3,0)), and the user hits shift-left twice, we select
the "c" and "b" (1,2) and set the affinity to NSSelectionAffinityUpstream.
If the user hits shift-right, only the "c" will be selected (2,1).

If the insertion point is between the "a" and the "b" (1,0) and the user hits
shift-right twice, we again select the "b" and "c" (1,2), but the affinity
is NSSelectionAffinityDownstream. If the user hits shift-right, the "d" is
added to the selection (1,3).

*/

- (unsigned int) _movementOrigin
{
  NSRange range = [self selectedRange];

  if ([self selectionAffinity] == NSSelectionAffinityUpstream)
    return range.location;
  else
    return NSMaxRange(range);
}

- (unsigned int) _movementEnd
{
  NSRange range = [self selectedRange];

  if ([self selectionAffinity] == NSSelectionAffinityDownstream)
    return range.location;
  else
    return NSMaxRange(range);
}

- (void) _moveTo: (unsigned int)cindex
	  select: (BOOL)select
{
  if (select)
    {
      unsigned int anchor = [self _movementEnd];

      if (anchor < cindex)
	{
	  [self setSelectedRange: NSMakeRange(anchor, cindex - anchor)
			affinity: NSSelectionAffinityDownstream
		  stillSelecting: NO];
	  [self scrollRangeToVisible: NSMakeRange(anchor, cindex - anchor)];
	}
      else
 	{
	  [self setSelectedRange: NSMakeRange(cindex, anchor - cindex)
			affinity: NSSelectionAffinityUpstream
		  stillSelecting: NO];
	  [self scrollRangeToVisible: NSMakeRange(cindex, anchor - cindex)];
	}
    }
  else
    {
      [self setSelectedRange: NSMakeRange(cindex, 0)];
      [self scrollRangeToVisible: NSMakeRange(cindex, 0)];
    }
}

- (void) _move: (GSInsertionPointMovementDirection)direction
      distance: (float)distance
	select: (BOOL)select
{
  unsigned int cindex;
  int new_direction;

  if (direction == GSInsertionPointMoveUp ||
      direction == GSInsertionPointMoveDown)
    {
      new_direction = 2;
    }
  else if (direction == GSInsertionPointMoveLeft ||
	   direction == GSInsertionPointMoveRight)
    {
      new_direction = 1;
    }
  else
    {
      new_direction = 0;
    }

  cindex = [self _movementOrigin];
  if (new_direction != _currentInsertionPointMovementDirection ||
      !new_direction)
    {
      _originalInsertionPointCharacterIndex = cindex;
    }

  cindex = [_layoutManager characterIndexMoving: direction
	      fromCharacterIndex: cindex
	      originalCharacterIndex: _originalInsertionPointCharacterIndex
	      distance: distance];
  [self _moveTo: cindex
	 select: select];
  /* Setting the selected range will clear out the current direction, but
  not the index. Thus, we always set the direction here. */
  _currentInsertionPointMovementDirection = new_direction;
}


/*
Insertion point movement actions.

TODO: some of these used to do nothing if self is a field editor. should
check if there was a reason for that.
*/

- (void) moveUp: (id)sender
{
  [self _move: GSInsertionPointMoveUp
	distance: 0.0
	select: NO];
}

- (void) moveUpAndModifySelection: (id)sender
{
  [self _move: GSInsertionPointMoveUp
	distance: 0.0
	select: YES];
}

- (void) moveDown: (id)sender
{
  [self _move: GSInsertionPointMoveDown
	distance: 0.0
	select: NO];
}

- (void) moveDownAndModifySelection: (id)sender
{
  [self _move: GSInsertionPointMoveDown
	distance: 0.0
	select: YES];
}

- (void) moveLeft: (id)sender
{
  [self _move: GSInsertionPointMoveLeft
	distance: 0.0
	select: NO];
}

- (void) moveRight: (id)sender
{
  [self _move: GSInsertionPointMoveRight
	distance: 0.0
	select: NO];
}


- (void) moveBackward: (id)sender
{
  unsigned int to = [self _movementOrigin];

  if (to == 0)
    return;
  to--;
  [self _moveTo: to
	 select: NO];
}

- (void) moveBackwardAndModifySelection: (id)sender
{
  unsigned int to = [self _movementOrigin];

  if (to == 0)
    return;
  to--;
  [self _moveTo: to
	 select: YES];
}

- (void) moveForward: (id)sender
{
  unsigned int to = [self _movementOrigin];

  if (to == [_textStorage length])
    return;
  to++;
  [self _moveTo: to
	 select: NO];
}
- (void) moveForwardAndModifySelection: (id)sender
{
  unsigned int to = [self _movementOrigin];

  if (to == [_textStorage length])
    return;
  to++;
  [self _moveTo: to
	 select: YES];
}

- (void) moveWordBackward: (id)sender
{
  unsigned int newLocation;

  newLocation = [_textStorage nextWordFromIndex: [self _movementOrigin]
			      forward: NO];
  [self _moveTo: newLocation
	 select: NO];
}

- (void) moveWordBackwardAndModifySelection: (id)sender
{
  unsigned int newLocation;
  
  newLocation = [_textStorage nextWordFromIndex: [self _movementOrigin]
			      forward: NO];
  [self _moveTo: newLocation
	 select: YES];
}

- (void) moveWordForward: (id)sender
{
  unsigned newLocation;

  newLocation = [_textStorage nextWordFromIndex: [self _movementOrigin]
			      forward: YES];
  [self _moveTo: newLocation
	 select: NO];
}

- (void) moveWordForwardAndModifySelection: (id)sender
{
  unsigned newLocation;

  newLocation = [_textStorage nextWordFromIndex: [self _movementOrigin]
			      forward: YES];
  [self _moveTo: newLocation
	 select: YES];
}

- (void) moveToBeginningOfDocument: (id)sender
{
  [self _moveTo: 0
	 select: NO];
}

- (void) moveToEndOfDocument: (id)sender
{
  [self _moveTo: [_textStorage length]
	 select: NO];
}

- (void) moveToBeginningOfParagraph: (id)sender
{
  NSRange aRange;
  
  aRange = [[_textStorage string] lineRangeForRange: 
				      NSMakeRange([self _movementOrigin], 0)];
  [self _moveTo: aRange.location
	 select: NO];
}

- (void) moveToEndOfParagraph: (id)sender
{
  NSRange aRange;
  unsigned newLocation;
  unsigned maxRange;
  
  aRange = [[_textStorage string] lineRangeForRange: 
				      NSMakeRange([self _movementOrigin], 0)];
  maxRange = NSMaxRange (aRange);

  if (maxRange == 0)
    {
      /* Beginning of text is special only for technical reasons -
	 since maxRange is an unsigned, we can't safely subtract 1
	 from it if it is 0.  */
      newLocation = maxRange;
    }
  else if (maxRange == [_textStorage length])
    {
      /* End of text is special - we want the insertion point to
	 appear *after* the last character, which means as if before
	 the next (virtual) character after the end of text ... unless
	 the last character is a newline, and we are trying to go to
	 the end of the line which is displayed as the
	 one-before-the-last.  Please note (maxRange - 1) is a valid
	 char since the maxRange == 0 case has already been
	 eliminated.  */
      unichar u = [[_textStorage string] characterAtIndex: (maxRange - 1)];
      if (u == '\n'  ||  u == '\r')
	{
	  newLocation = maxRange - 1;
	}
      else
	{
	  newLocation = maxRange;
	}
    }
  else
    {
      /* Else, we want the insertion point to appear before the last
	 character in the paragraph range.  Normally the last
	 character in the paragraph range is a newline.  */
      newLocation = maxRange - 1;
    }

  if (newLocation < aRange.location)
    {
      newLocation = aRange.location;
    }

  [self _moveTo: newLocation
	 select: NO];
}


/* TODO: this is only the beginning and end of lines if lines are horizontal
and layout is left-to-right */
- (void) moveToBeginningOfLine: (id)sender
{
  [self _move: GSInsertionPointMoveLeft
	distance: 1e8
	select: NO];
}
- (void) moveToEndOfLine: (id)sender
{
  [self _move: GSInsertionPointMoveRight
	distance: 1e8
	select: NO];
}

/**
 * Tries to move the selection/insertion point down one page of the
 * visible rect in the receiver while trying to maintain the
 * horizontal position of the last vertical movement.
 * If the receiver is a field editor, this method returns immediatly. 
 */
- (void) pageDown: (id)sender
{
  float    scrollDelta;
  float    oldOriginY;
  float    newOriginY;

  /*
   * Scroll; also determine how far to move the insertion point.
   */
  oldOriginY = NSMinY([self visibleRect]);
  [[self enclosingScrollView] pageDown: sender];
  newOriginY = NSMinY([self visibleRect]);
  scrollDelta = newOriginY - oldOriginY;

  if (scrollDelta == 0)
    {
      /* TODO/FIXME: If no scroll was done, it means we are in the
       * last page of the document already - should we move the
       * insertion point to the last line when the user clicks
       * 'PageDown' in that case ?
       */
      return;
    }

  [self _move: GSInsertionPointMoveDown
	distance: scrollDelta
	select: NO];
}

/**
 * Tries to move the selection/insertion point up one page of the
 * visible rect in the receiver while trying to maintain the
 * horizontal position of the last vertical movement.
 * If the receiver is a field editor, this method returns immediatly. 
 */
- (void) pageUp: (id)sender
{
  float    scrollDelta;
  float    oldOriginY;
  float    newOriginY;

  /*
   * Scroll; also determine how far to move the insertion point.
   */
  oldOriginY = NSMinY([self visibleRect]);
  [[self enclosingScrollView] pageUp: sender];
  newOriginY = NSMinY([self visibleRect]);
  scrollDelta = newOriginY - oldOriginY;

  if (scrollDelta == 0)
    {
      /* TODO/FIXME: If no scroll was done, it means we are in the
       * first page of the document already - should we move the
       * insertion point to the first line when the user clicks
       * 'PageUp' in that case ?
       */
      return;
    }


  [self _move: GSInsertionPointMoveUp
	distance: -scrollDelta
	select: NO];
}

- (void) scrollLineDown: (id)sender
{
  // TODO
  NSLog(@"Method %s is not implemented for class %s",
	"scrollLineDown:", "NSTextView");
}

- (void) scrollLineUp: (id)sender
{
  // TODO
  NSLog(@"Method %s is not implemented for class %s",
	"scrollLineUp:", "NSTextView");
}

- (void) scrollPageDown: (id)sender
{
  // TODO
  NSLog(@"Method %s is not implemented for class %s",
	"scrollPageDown:", "NSTextView");
}

- (void) scrollPageUp: (id)sender
{
  // TODO
  NSLog(@"Method %s is not implemented for class %s",
	"scrollPageUp:", "NSTextView");
}


/* -selectAll: inherited from NSText  */

- (void) selectLine: (id)sender
{
  unsigned int start, end, cindex;

  cindex = [self _movementOrigin];
  start = [_layoutManager characterIndexMoving: GSInsertionPointMoveLeft
	     fromCharacterIndex: cindex
	     originalCharacterIndex: cindex
	     distance: 1e8];
  end = [_layoutManager characterIndexMoving: GSInsertionPointMoveRight
	   fromCharacterIndex: cindex
	   originalCharacterIndex: cindex
	   distance: 1e8];
  [self setSelectedRange: NSMakeRange(start, end - start)];
}


/* The following method is bound to 'Control-t', and must work like
 * pressing 'Control-t' inside Emacs.  For example, say that I type
 * 'Nicoal' in a NSTextView.  Then, I press 'Control-t'.  This should
 * swap the last two characters which were inserted, thus swapping the
 * 'a' and the 'l', and changing the text to read 'Nicola'.  */
/*
TODO: description incorrect. should swap characters on either side of the
insertion point. (see also: miswart)
*/
- (void) transpose: (id)sender
{
  NSRange range = [self selectedRange];
  NSString *string;
  NSString *replacementString;
  unichar chars[2];

  /* Do nothing if we are at beginning of text.  */
  if (range.location < 2)
    {
      return;
    }

  range = NSMakeRange(range.location - 2, 2);

  /* Get the two chars and swap them.  */
  string = [_textStorage string];
  chars[1] = [string characterAtIndex: range.location];
  chars[0] = [string characterAtIndex: (range.location + 1)];

  /* Replace the original chars with the swapped ones.  */
  replacementString = [NSString stringWithCharacters: chars  length: 2];

  if ([self shouldChangeTextInRange: range
	replacementString: replacementString])
    {
      [self replaceCharactersInRange: range
        withString: replacementString];
      [self didChangeText];
    }
}

- (void) delete: (id)sender
{
  [self deleteForward: sender];
}


/* Helper for -align*: */
- (void) _alignUser: (NSTextAlignment)alignment
{
  NSRange r = [self rangeForUserParagraphAttributeChange];

  if (r.location == NSNotFound)
    return;
  if (![self shouldChangeTextInRange: r
	 replacementString: nil])
    return;

  [self setAlignment: alignment
    range: r];
  [self didChangeText];
}

- (void) alignCenter: (id)sender
{
  [self _alignUser: NSCenterTextAlignment];
}

- (void) alignLeft: (id)sender
{
  [self _alignUser: NSLeftTextAlignment];
}

- (void) alignRight: (id)sender
{
  [self _alignUser: NSRightTextAlignment];
}

- (void) alignJustified: (id)sender
{
  [self _alignUser: NSJustifiedTextAlignment];
}

- (void) toggleContinuousSpellChecking: (id)sender
{
  [self setContinuousSpellCheckingEnabled: 
	    ![self isContinuousSpellCheckingEnabled]];
}

- (void) toggleRuler: (id)sender
{
  [self setRulerVisible: !_tf.is_ruler_visible];
}

@end