Question

See the image below (I sat a breakpoint on CGPostError). Is there anything to do with this error?? In console the following message was printed out:
<Error>: doClip: empty path

We’re building an iPad app and uses webkit to display custom ads.

Answer 1

Look for clipping functions with empty paths, like CGContextClip(). In this case, the errors appears harmless and the “fix” appears equally harmless. From Apple’s docs,

Parameters
c
A graphics context that contains a path. If the context does not have a current path, the function does nothing.

http://developer.apple.com/library/mac/#documentation/GraphicsImaging/Reference/CGContext/Reference/reference.html

If you really want to prevent logging the error, you should probably check the context before calling CGContextClip(...) or similar functions:

if (!CGContextIsPathEmpty(c))
{
    CGContextClip(c);
}