As was suggested to me in a prior StackOverflow question, I'm trying to improve my drawing method for letting my user draw lines/dots into a UIView. I'm now trying to draw using a CAShapeLayer instead of dispatch_async. This all works correctly, however, drawing into the CAShapeLayer continuously while touches are moving becomes slow and the path lags behind, whereas my old (inefficient I was told) code worked beautifully smooth and fast. You can see my old code commented out below.
Is there any way to improve the performance for what I want to do? Maybe I'm overthinking something.
I'd appreciate any help offered.
Code:
@property (nonatomic, assign) NSInteger center;
@property (nonatomic, strong) CAShapeLayer *drawLayer;
@property (nonatomic, strong) UIBezierPath *drawPath;
@property (nonatomic, strong) UIView *drawView;
@property (nonatomic, strong) UIImageView *drawingImageView;
CGPoint points[4];
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
self.center = 0;
points[0] = [touch locationInView:self.drawView];
if (!self.drawLayer)
{
CAShapeLayer *layer = [CAShapeLayer layer];
layer.lineWidth = 3.0;
layer.lineCap = kCALineCapRound;
layer.strokeColor = self.inkColor.CGColor;
layer.fillColor = [[UIColor clearColor] CGColor];
[self.drawView.layer addSublayer:layer];
self.drawView.layer.masksToBounds = YES;
self.drawLayer = layer;
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
self.center++;
points[self.center] = [touch locationInView:self.drawView];
if (self.center == 3)
{
UIBezierPath *path = [UIBezierPath bezierPath];
points[2] = CGPointMake((points[1].x + points[3].x)/2.0, (points[1].y + points[3].y)/2.0);
[path moveToPoint:points[0]];
[path addQuadCurveToPoint:points[2] controlPoint:points[1]];
points[0] = points[2];
points[1] = points[3];
self.center = 1;
[self drawWithPath:path];
}
}
- (void)drawWithPath:(UIBezierPath *)path
{
if (!self.drawPath)
{
self.drawPath = [UIBezierPath bezierPath];
}
[self.drawPath appendPath:path];
self.drawLayer.path = self.drawPath.CGPath;
[self.drawLayer setNeedsDisplay];
// Below code worked faster and didn't lag behind at all really
/*
dispatch_async(dispatch_get_main_queue(),
^{
UIGraphicsBeginImageContextWithOptions(self.drawingImageView.bounds.size, NO, 0.0);
[self.drawingImageView.image drawAtPoint:CGPointZero];
[self.inkColor setStroke];
[path stroke];
self.drawingImageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
});
*/
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
if (self.center == 0)
{
UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:points[0]];
[path addLineToPoint:points[0]];
[self drawWithPath:path];
}
self.drawLayer = nil;
self.drawPath = nil;
}