Re: NSBezierPath geometry question...

FROM : Keith Blount
DATE : Mon Apr 11 13:17:32 2005

Many thanks to you both for your replies.

This is in fact what I have been trying - going down
the right sides, then back up the left sides of the
rects, and then trying to round the corners using
appendBezierPathWithArcFromPoint... I have pasted the
code I have been trying at the bottom of this post. It
gets all the points correctly and rounds the corners,
but there are still some drawing glitches - in
particular, my radius calculation seems to result in
the top corners being more rounded than the bottom
ones, though I am not sure why.

Many thanks again,
Keith


The (not quite working properly) code:

NSLayoutManager *layoutManager = [self layoutManager];
   NSTextContainer *textContainer = [self
textContainer];
   unsigned rectCount;
   NSRectArray rectArray = [layoutManager
rectArrayForCharacterRange:charRange
                                       
withinSelectedCharacterRange:NSMakeRange(NSNotFound,0)
                                                     inTextContainer:textContainer
                                                           rectCount:&rectCount];
       
   int i;
   NSBezierPath *path = [NSBezierPath bezierPath];
   float radius = 6;
   
   NSMutableArray *corners = [NSMutableArray array];
   NSPoint textContainerOrigin = [self
textContainerOrigin];
   
   // Get right sides
   for (i=0; i<rectCount; i++)
   {
       // Get current rect and account for text container
       NSRect currRect =
NSOffsetRect(rectArray[i],textContainerOrigin.x,textContainerOrigin.y);
       
       NSPoint topPoint =
NSMakePoint(NSMaxX(currRect),currRect.origin.y);
       NSPoint bottomPoint =
NSMakePoint(NSMaxX(currRect),NSMaxY(currRect));
   
       // Make sure all points lie on the centre of a pixel

       topPoint.x = (int)topPoint.x;
       topPoint.x += 0.5;
       topPoint.y = (int)topPoint.y;
       topPoint.y += 0.5;
       bottomPoint.x = (int)bottomPoint.x;
       bottomPoint.x += 0.5;
       bottomPoint.y = (int)bottomPoint.y;
       bottomPoint.y += 0.5;
       [corners addObject:[NSValue
valueWithPoint:topPoint]];
       [corners addObject:[NSValue
valueWithPoint:bottomPoint]];
   }
   
   // Get left sides
   for (i=rectCount-1; i>=0; i--)
   {
       NSRect currRect =
NSOffsetRect(rectArray[i],textContainerOrigin.x,textContainerOrigin.y);
       
       NSPoint topPoint = currRect.origin;
       NSPoint bottomPoint =
NSMakePoint(currRect.origin.x,NSMaxY(currRect));

       topPoint.x = (int)topPoint.x;
       topPoint.x += 0.5;
       topPoint.y = (int)topPoint.y;
       topPoint.y += 0.5;
       bottomPoint.x = (int)bottomPoint.x;
       bottomPoint.x += 0.5;
       bottomPoint.y = (int)bottomPoint.y;
       bottomPoint.y += 0.5;
       [corners addObject:[NSValue
valueWithPoint:bottomPoint]];
       [corners addObject:[NSValue
valueWithPoint:topPoint]];
   }
   
   // Now try to draw the curve...
   NSPoint firstPoint = [[corners objectAtIndex:0]
pointValue];
   NSPoint lastPoint = [[corners objectAtIndex:[corners
count]-1] pointValue];
   NSPoint startPoint =
NSMakePoint((firstPoint.x+lastPoint.x)/2.0,(firstPoint.y+lastPoint.y)/2.0);
   [path moveToPoint:startPoint];
   for (i = 0; i < [corners count]; i++)
   {
       NSPoint currPoint = [[corners objectAtIndex:i]
pointValue];
       
       if (i < [corners count]-1)
       {
           NSPoint nextPoint = [[corners objectAtIndex:i+1]
pointValue];
           
           radius = MIN(6, 0.5 * (MIN(
KBDistanceBetweenPoints([path
currentPoint],currPoint),
                                       
KBDistanceBetweenPoints(currPoint,nextPoint))));
                                       
           [path appendBezierPathWithArcFromPoint:currPoint
toPoint:nextPoint radius:radius];
       }
       else
       {
           radius = MIN(6, 0.5 * (MIN(
KBDistanceBetweenPoints([path
currentPoint],currPoint),
                                       
KBDistanceBetweenPoints(currPoint,startPoint))));

           [path appendBezierPathWithArcFromPoint:currPoint
toPoint:startPoint radius:radius];
       }
   }
   
   [path closePath];


And this is the function used in radius calculation
above:

float KBDistanceBetweenPoints (NSPoint a, NSPoint b)
{
   float
   dX = a.x - b.x,
   dY = a.y - b.y;
   return (sqrt(dX*dX + dY*dY));
}


       
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