Custom UIView's border drawing isn't smooth

I'm trying to draw a simple speech bubble using the following code:

@implementation SpeechBubbleView

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
       self.backgroundColor = [UIColor clearColor];
    }
    return self;
}

- (void)drawRect:(CGRect)rect {

   CGPoint triangleHeadPoint = CGPointMake(0, rect.size.height/2.0);
   float triangleHeight = 5;
   float triangleWidth = 10;

   float maxX = rect.size.width;
   float minX = 0.0;
   float maxY = rect.size.height;
   float minY = 0.0;

   float archTangentLine = 6.0;
   float archRadius = archTangentLine;

   float strokeWidth = 1.0;

   CGContextRef context = UIGraphicsGetCurrentContext();

   CGContextSetLineWidth(context, strokeWidth);   

   CGContextBeginPath(context);

   float currentX = triangleHeadPoint.x;
   float currentY = triangleHeadPoint.y;
   CGContextMoveToPoint(context, currentX, currentY);

   currentX += triangleWidth;
   currentY += (triangleHeight / 2.0);
   CGContextAddLineToPoint(context, currentX, currentY);

   currentY = maxY - archTangentLine;
   CGContextAddLineToPoint(context, currentX, currentY);

   currentY += archTangentLine;
   CGContextAddArcToPoint(context, currentX, currentY, currentX + archTangentLine, currentY, archRadius);

   currentX = maxX -开发者_JAVA技巧 archTangentLine;
   CGContextAddLineToPoint(context, currentX, currentY);

   currentX += archTangentLine;
   CGContextAddArcToPoint(context, currentX, currentY, currentX, currentY - archTangentLine, archRadius);

   currentY = minY + archTangentLine;
   CGContextAddLineToPoint(context, currentX, currentY);

   currentY -= archTangentLine;
   CGContextAddArcToPoint(context, currentX, currentY, currentX - archTangentLine, currentY, archRadius);

   currentX = minX + triangleWidth + archTangentLine;
   CGContextAddLineToPoint(context, currentX, currentY);

   currentX -= archTangentLine;
   CGContextAddArcToPoint(context, currentX, currentY, currentX, currentY + archTangentLine, archRadius);

   currentY = triangleHeadPoint.y - (triangleHeight / 2.0);
   CGContextAddLineToPoint(context, currentX, currentY);

   CGContextClosePath(context);

   [[UIColor whiteColor] setFill];
   [[UIColor blackColor] setStroke];

   CGContextDrawPath(context, kCGPathFillStroke);
}

@end

The result of this code is the following (not so pretty) image:

The drawing isn't as smooth as I was expecting it to be, the left side border is wider than the top, right and bottom sides, and the corners are wider than the adjacent lines.

I changed the fill color to black just to check and the result is as I was expecting:

Why does the border have a variable width? Is there a way to fix this and have a smooth border around the view?

Thanks in advance.

For future reference, I have found a way to improve the look of the border which will result in the following picture:

I simply made the border width very small (I used 0.2f) using the function CGContextSetLineWidth(context, 0.2f). And then added a shadow to the layer as following:

self.layer.shadowColor = [[UIColor blackColor] CGColor];
self.layer.shadowOffset = CGSizeMake(1.5f, 1.5f);
self.layer.shadowOpacity = 0.8f;
self.layer.shadowRadius = 1.0f;

And that's it!