Re: Doubleclicking NSTextView

[Wolfgang Lux]

Andreas Höschler wrote:

> - (void)mouseDown:(NSEvent *)theEvent
> {
> ...
> +  if (startIndex != (unsigned)-1 && startIndex > 0)
> +     {
> +     NSString *string = [self string];
> +     if ([string characterAtIndex:startIndex - 1] == '\n')  
> startIndex--;
> +     }
> ...
> }

Unfortunately, this change is not correct (if you double click on the  
beginning of a line the previous line will be selected). In fact, it  
merely tries to work around the problem that -characterIndexForPoint:  
returns a wrong result in the first place. A better fix for the whole  
problem is below.

> - (NSRange)selectionRangeForProposedRange:(NSRange) 
> proposedCharRange granularity:(NSSelectionGranularity)gr
> {
> ...
> +      switch (gr)
> +        {
> +        case NSSelectByCharacter:
> +            break;
> +        default:
> +            return [string lineRangeForRange:proposedCharRange];
> +            break;
> +        }
> ...
> )

I do not really understand this change and could not find an example  
where it makes a difference.

Okay, now for a better solution of the problem. First of all,  
NSLayoutManager's - 
glyphIndexForPoint:inTextContainer:fractionOfDistanceThroughGlyph: is  
returning wrong information here because it ignores characters which  
are not shown and control characters when computing the position even  
though such characters are relevant for layout. In particular, if you  
click after the last character of a line, the method returns the  
index of the last character in the line and fraction 1 rather than  
the index of the newline character (and fraction 1). The following  
patch corrects this. Incidentally, the same applies to tab  
characters. Without this fix, if you click in the space of a tab  
character, the method returns the index of the character *before* the  
tab character (unless it is the first character in the line) and not  
that of the tab character.

--- Source/NSLayoutManager.m    (Revision 25440)
+++ Source/NSLayoutManager.m    (Arbeitskopie)
@@ -696,11 +696,10 @@
       last_visible = lf->pos;
       for (j = lp->pos - glyph_pos; j + glyph_pos < lp->pos + lp- 
>length;)
        {
-         if (r->glyphs[j].isNotShown || r->glyphs[j].g == NSControlGlyph ||
-             !r->glyphs[j].g)
+         if (!r->glyphs[j].g)
            {
              GLYPH_STEP_FORWARD(r, j, glyph_pos, char_pos)
-               continue;
+             continue;
            }
          last_visible = j + glyph_pos;

The other part of the problem is that we do not want NSTextView's - 
characterIndexForPoint: method to increment the position even if  
fraction is greater than 0.5 if the new position is in the next line.  
This is fixed by the patch below. In addition, - 
characterIndexForPoint: is not correct according to the Mac OS X  
documentation (and the implementation) because - 
characterIndexForPoint: expects a point in screen coordinates rather  
than view coordinates. Therefore, I have take the liberty to  
introduce a new private method  
_characterIndexForPoint:respectFraction: to compute the index in view  
coordinates. Unless respectFraction is NO, the index is incremented  
to match the closest character on the same line. Note that - 
characterIndexForPoint: passes NO for this parameter, which is  
compatible with the Mac OS X implementation of this method.

--- NSSource/NSTextView.m       (Revision 25440)
+++ NSSource/NSTextView.m       (Arbeitskopie)
@@ -1793,7 +1793,8 @@
TODO: make sure this is only called when _layoutManager is known non- 
nil,
or add guards
*/
-- (unsigned int) characterIndexForPoint: (NSPoint)point
+- (unsigned int) _characterIndexForPoint: (NSPoint)point
+                        respectFraction: (BOOL)respectFraction
{
   unsigned     index;
   float                fraction;
@@ -1808,13 +1809,21 @@
     return (unsigned int)-1;
   index = [_layoutManager characterIndexForGlyphAtIndex: index];
-  if (fraction > 0.5 && index < [_textStorage length])
+  if (respectFraction && fraction > 0.5 && index < [_textStorage  
length] &&
+      [[_textStorage string] characterAtIndex:index] != '\n')
     {
       index++;
     }
   return index;
}
+- (unsigned int) characterIndexForPoint: (NSPoint)point
+{
+  point = [[self window] convertScreenToBase:point];
+  point = [self convertPoint:point fromView:nil];
+  return [self _characterIndexForPoint:point respectFraction:NO];
+}
+
- (NSRange) markedRange
{
   return NSMakeRange(NSNotFound, 0);
@@ -4267,7 +4276,8 @@
       dragPoint = [sender draggingLocation];
       dragPoint = [self convertPoint: dragPoint fromView: nil];
-      dragIndex = [self characterIndexForPoint: dragPoint];
+      dragIndex = [self _characterIndexForPoint: dragPoint
+                               respectFraction: YES];
       dragRange = NSMakeRange (dragIndex, 0);
       range = [self selectionRangeForProposedRange: dragRange
@@ -4302,7 +4312,8 @@
       dragPoint = [sender draggingLocation];
       dragPoint = [self convertPoint: dragPoint fromView: nil];
-      dragIndex = [self characterIndexForPoint: dragPoint];
+      dragIndex = [self _characterIndexForPoint: dragPoint
+                               respectFraction: YES];
       dragRange = NSMakeRange (dragIndex, 0);
       range = [self selectionRangeForProposedRange: dragRange
@@ -4416,7 +4427,8 @@
      possible) */
   startPoint = [self convertPoint: [theEvent locationInWindow]  
fromView: nil];
-  startIndex = [self characterIndexForPoint: startPoint];
+  startIndex = [self _characterIndexForPoint: startPoint
+                            respectFraction: [theEvent clickCount] == 1];
   if (startIndex == (unsigned int)-1)
     {
@@ -4620,7 +4632,8 @@
        point = [self convertPoint: [lastEvent locationInWindow]
                  fromView: nil];
-       proposedRange = MakeRangeFromAbs([self characterIndexForPoint: point],
+       proposedRange = MakeRangeFromAbs([self _characterIndexForPoint: point
+                                                      respectFraction: YES],
                                         startIndex);
        chosenRange = [self selectionRangeForProposedRange: proposedRange
                        granularity: granularity];

Regards
Wolfgang