Performance when frequently drawing CGPaths

Question

I am working on an iOS App that visualizes data as a line-graph. The graph is drawn as a CGPath in a fullscreen custom UIView and contains at most 320

Answer 1

Have you tried using UIBezierPath instead? UIBezierPath uses CGPath under-the-hood, but it'd be interesting to see if performance differs for some subtle reason. From Apple's Documentation:

For creating paths in iOS, it is recommended that you use UIBezierPath instead of CGPath functions unless you need some of the capabilities that only Core Graphics provides, such as adding ellipses to paths. For more on creating and rendering paths in UIKit, see “Drawing Shapes Using Bezier Paths.”

I'd would also try setting different properties on the CGContext, in particular different line join styles using CGContextSetLineJoin(), to see if that makes any difference.

Have you profiled your code using the Time Profiler instrument in Instruments? That's probably the best way to find where the performance bottleneck is actually occurring, even when the bottleneck is somewhere inside the system frameworks.