Why does the font of my UITextField change when editing?

My UITextField's font 开发者_Go百科gets lighter when it is being edited, and bolder whenever editing finishes. These images should illustrate the problem:

Can anyone explain why this is, and how to stop it?

This is all the code I've got for it - first my UITextField subclass (which is just there to add margins):

@interface RLTextField : UITextField {    
}
@end

@implementation RLTextField

- (CGRect)editingRectForBounds:(CGRect)bounds
{
    CGRect editingRect = CGRectMake(bounds.origin.x+35, bounds.origin.y-5, bounds.size.width, bounds.size.height);
    return editingRect;
}

- (CGRect)textRectForBounds:(CGRect)bounds
{
    CGRect editingRect = CGRectMake(bounds.origin.x+35, bounds.origin.y-5, bounds.size.width, bounds.size.height);
    return editingRect;
}
@end

And then where it's actually added in my viewController:

- (void)viewDidLoad
{   
    CGRect noteTitleTextFrame  = CGRectMake(self.view.bounds.origin.x, 
                                            self.view.bounds.origin.y+10, 
                                            self.view.bounds.size.width, 
                                            44);
    RLTextField *textField = [[RLTextField alloc] initWithFrame:noteTitleTextFrame];
    self.nameTextField = textField; [textField release];
    self.nameTextField.delegate = self;
    self.nameTextField.borderStyle = UITextBorderStyleNone;    
    self.nameTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentBottom;
    self.nameTextField.font = [UIFont fontWithName:@"Courier" size:21];
    [self.view addSubview:self.nameTextField]; 
}

checked your code.... and there only one word for that WTF....!
I don't know what's wrong with that but there is a solution for that and it's

self.nameTextField.font = [UIFont fontWithName:@"Courier New" size:21];

just change the font name. This will work.. cheers :)
By the way you probably found a bug or may be not that's why apple has added "Courier New".
I don't know...