Problem with setNeedsDisplay:

 

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-(IBAction)rotateXAction:(id)sender
{
    NSLog(@"%@ \n",sender);
    BOOL yn = YES;
    _rotationX =  [_sliderX intValue];
    if(yn) printf("rotationX %d \n",_rotationX); // value o.k
    [self setNeedsDisplay:YES];
}