Drawings in drawRect not being displayed correctly - cocoa-touch

Question

I want to implement freeform drawing in my app. First, I tried the code inside drawLayer:inContext: and it gave me the result I wanted.
Drawing in CALayer:
But when I decided to implement the code inside drawRect:, this happened:
Even if I draw inside the white space, the drawing is rendered outside as shown above. The code I used is exactly the same. I copy-pasted it from drawLayer:inContext: to drawRect:. I didn't change a thing, so why is this happening?
The Code:
CGContextSaveGState(ctx);
CGContextSetLineCap(ctx, kCGLineCapRound);
CGContextSetLineWidth(ctx, 1.0);
CGContextSetRGBStrokeColor(ctx, 1, 0, 0, 1);
CGContextBeginPath(ctx);
CGContextMoveToPoint(ctx, prevPoint.x, prevPoint.y);
for (NSValue *r in drawnPoints){
CGPoint pt = [r CGPointValue];
CGContextAddLineToPoint(ctx, pt.x, pt.y);
}
CGContextStrokePath(ctx);
CGContextRestoreGState(ctx);

Answer 1

I see you are using app in full screen mode where the view is centered and does not take full width of the screen.
It may be that CALayer has transform applied to it that translates the drawing from the left side of the screen to the center. This may not be the case with drawRect:. Try setting CGContext's transform matrix:
CGContextSaveGState(ctx);
CGFloat xOffset = CGRectGetMidX(screenFrame) - CGRectGetMidX(viewFrame);
CGContextTranslateCTM(ctx, xOffset, 0.0f);
// rest of drawing code
// ...
CGContextRestoreGState(ctx);