Preload a Core Text font descriptor if you are having performance issues in iOS 4.3

gistfile1.m

#import <CoreText/CoreText.h>

...

// preload
dispatch_queue_t queue = dispatch_queue_create("com.company.worker", NULL);
dispatch_async(queue, ^(void) {
    NSMutableDictionary *attributes = [NSMutableDictionary dictionary];
    [attributes setObject:@"Helvetica" forKey:(id)kCTFontFamilyNameAttribute];
    [attributes setObject:[NSNumber numberWithFloat:36.0f] forKey:(id)kCTFontSizeAttribute];
    CTFontDescriptorRef fontDesc = CTFontDescriptorCreateWithAttributes((CFDictionaryRef)attributes);
    CTFontRef matchingFont = CTFontCreateWithFontDescriptor(fontDesc, 36.0f, NULL);
    CFRelease(matchingFont);
    CFRelease(fontDesc);
});
dispatch_release(queue);

This code will preload core text by running this little block of code on a separate thread. You can add this to your UIAppDelegate

Is it necessary to spawn one separate thread per font/font-size used? For instance, I'm using Helvetica Neue Light and Helvetica Neue Ultra Light fonts, both with 16px font size, should I create one thread for both?

I tried with various combinations and it doesn't seem to really preload anything, there's still a delay when loading the first chunk of text. Loading times are much better after that. Any ideas?

Actually, it seems it's correctly preloading these fonts, because the delay before first text render is much better when the preloading code is active than when it's not. However, there is still a small delay left on first text render. Did you experience this too?