title: uiview animation is adding acceleration during animating
body: <p>I am working on the marquee text in ios using animation like below :</p>
  
  <p>First way:</p>
  
  <pre><code>-(void)startScrolling {
        CGRect rect ;
        rect                   =   self.titleView.frame;
        rect.origin.x          =   -self.titleView.frame.size.width;
        self.titleView.frame   =   rect;
        [UIView beginAnimations:@"" context:nil];
        [UIView setAnimationCurve:UIViewAnimationCurveLinear]; 
        [UIView setAnimationDuration:13];
        [UIView setAnimationDelegate:self];
        [UIView setAnimationDidStopSelector:@selector(startScrolling)];
  
        // Update end position
        CGRect rect ;
        rect                   =   self.titleView.frame;
        rect.origin.x          =   [[UIScreen mainScreen] bounds].size.width;
        self.titleView.frame   =   rect;
        [UIView commitAnimations];
  
  }
  </code></pre>
  
  <p>The second way:</p>
  
  <pre><code>      [UIView animateWithDuration:13
                              delay:0
                            options:UIViewAnimationOptionCurveLinear
                         animations:^{
                             CGRect rect ;
                             rect                   =   self.titleView.frame;
                             rect.origin.x          =   -self.titleView.frame.size.width;
                            self.titleView.frame    =   rect;
  
                   }
                        completion:^(BOOL finished) {
                            CGRect rect ;
                            rect                   =   self.titleView.frame;
                            rect.origin.x          =   [[UIScreen mainScreen] bounds].size.width;
                           self.titleView.frame    =   rect;
                           [self startScrolling];
                   }
   ];
  </code></pre>
  
  <p>The first way is working properly. and the issue for the second way is that acceleration is added during animating. Dont get it</p>
  
  <p>Why acceleration is added while using block. Searching over the internet but I am still getting stuck. Any ideas for this issue ?</p>