CGContext text drawing doesn't scale up on iPhone 4

Question

I am trying to create an app that scales up nicely on the iPhone 4. Currently most of it scales up perfectly, except for one crucial piece: the text that I draw inside a CALayer, inside its drawInContext: method. Here is my code:

- (void)drawInContext:(CGContextRef)context {
    UIGraphicsPushContext(context);

    CGContextSetGrayFillColor(context, 1.0f, 1.0f);
    CGContextFillRect(context, self.bounds);

    CGContextSetAllowsAntialiasing(context, true);
    CGContextSetShouldAntialias(context, true);

    CGContextSetAllowsFontSmoothing(context, true);
    CGContextSetShouldSmoothFonts(context, true);

    CGContextSetAllowsFontSubpixelQuantization(context, true);
    CGContextSetShouldSubpixelQuantizeFonts(context, true);

    CGContextTranslateCTM(context, 0.0f, self.frame.size.height);
    CGContextScaleCTM(context, 1.0f, -1.0f);

    CGContextSetFillColorWithColor(context, [[UIColor blackColor] CGColor]);
    CGContextSelectFont(context, "CardKit", 30.0f, kCGEncodingMacRoman);
    CGContextSetTextDrawingMode(context, kCGTextFill);
    CGContextShowText(context, "A", sizeof("A"));

    UIGraphicsPopContext();
}

This short produce crisp text on both devices, but unfortunately, it produces blurry text on both. Here is how it appears:

That image is taken at 100% zoom on the iPhone 4. What in the world? Any ideas how I can fix this?

Answer 1

Since you're dealing with CALayers, you need to set the contentsScale property of your layer to 2.0.

See this section in the iPhone Application programming guide for iOS 4.