The subject of this post is the NSScroller class, since I recently needed to work with it and I found the documentation lacking and a bit out of date. Further, I couldn’t find much about the class on the web, and most of the comments involved sub-classing the control, which really isn’t a good idea. So here is what I’ve learned about NSScroller.

You almost never need to use NSScroller in your code, because NSScrollView will do everything you need. Also, consider using NSSlider instead.

So, you’ve thought about your UI design, and decided that a scroller really is the way to go. So, fire up Interface Builder, open your window, and drag a scroller instance from the palette to your window.

What’s that?

You can’t find the scroller objects in IB? That’s because they’re not there; you’ll have to create the scroller in code. It’s really not that hard. First, figure out where you want the scroller to live on the screen. You’ll need the x,y co-ordinates of the bottom left corner. Now, make a rect with those co-ordinates and the width and length of the scroller you want.

For my horizontal scroller, it looks like this

-(void)awakeFromNib
{
    NSRect winRect = [window frame];
    NSRect scrollFrame = NSMakeRect(20.0, 20.0,
        winRect.size.width -40.0,[NSScroller scrollerWidth] );
    hScroller = [[NSScroller alloc] initWithFrame:scrollFrame];

Here, hScroller is a property so that you can get at it from other places in your code.

Now, there are a few setup steps that are necessary for the scroller to appear in the window.

    // Proportion is the amount of the scroller that
    // the knob takes up,
    // the width of the knob for a horizontal scroller,
    //  or the height for a vertical scroller.
    [hScroller setKnobProportion:0.05];
    // the scroller double value is the position of
    // the knob on the slider, with a range of
    // 0.0 to 1.0
    [hScroller setDoubleValue:0.5];
    [hScroller setEnabled:YES];
    [[window contentView] addSubview:hScroller];

The setEnabled message is necessary because the control defaults to disabled. I suspect this is for the scrollview implementation.

Now, if you run your program, you’ll see a scroller that you can interact with. The arrows work, and sliding the knob works. The next step is dealing with the interactions in code. You need to connect the scroller action to the controller.

So, back in the awakeFromNib method, add two more lines.

SEL mySelector = NSSelectorFromString(@"scrollAction:");
	[hScroller setAction:mySelector];

And that’s it; setup complete.

Now, to handle the messages sent by the scroller, you need to implement the scrollAction method. The trick seems to be to read the hitPart property to figure out which part on the scroller was clicked. Here is a sample handler:

- (IBAction)scrollAction:(id)sender
{
  switch ([hScroller hitPart]) {
  case NSScrollerNoPart:
    break;
  case NSScrollerDecrementPage:
    NSLog(@"decrementPage");
    break;
  case NSScrollerKnob:
    NSLog(@"scrollerKnob, value= %f",[hScroller doubleValue]);
    break;
  case NSScrollerIncrementPage:
    NSLog(@"incrementPage");
    break;
  case NSScrollerDecrementLine:
    NSLog(@"decrementLine");
    break;
  case NSScrollerIncrementLine:
    NSLog(@"incrementLine");
    break;
  case NSScrollerKnobSlot:
    NSLog(@"knobSlot, value= %f",[hScroller doubleValue]);
    break;
  default:
    break;
  }
}

Now, when you get a page or line change you’ll need to adjust the doubleValue accordingly, to reposition the knob.

By experimenting with these messages you should be able to adapt the scroller to suit your needs.

One last thing: the top of the Apple documentation states that setFloatValue:knobProportion: is a commonly used method, but further on down you’ll learn that it is, in fact, deprecated. You should be using setDoubleValue: and setKnobProportion instead.

That’s it. If you have any questions, or anything to add, please let me know in the comments.

He pulled up my existing Rogers account, looked at the screen, and said, “You’re not eligible.”

“Wha?”

“You got a new handset last September. You’re not eligible for a hardware upgrade yet.”

“I don’t want a hardware upgrade. I want to buy an iPhone, and put it on my existing plan. And pay more for the data plan.”

“Well, you can’t. I can’t sell it to you.”

“That’s crazy. You’re saying you won’t sell me the phone? Isn’t there some sort of penalty I can pay to get the hardware?”

“Nope. I can’t sell it to you. There’s nothing I can do.”

I went home, and called Rogers “Customer Service”. The first call ended abruptly as the agent put me on hold and I got disconnected. The second agent repeated what I heard in the store and said that the only thing I could do would be to cancel my existing contract, pay the $200 early termination fee, and start over from scratch. Oh, and lose my existing cell phone number in the process.

Now, I’ve been a Rogers customer for almost seven years. Any other business that had you as a paying customer for that long would be failing over themselves to keep your business. Anyone serious about customer retention would have offered existing customers first dibs on the iPhone. But not Rogers. They seem much more interested in signing new customers than keeping old ones.

I’ve had better treatment from credit card companies. Now that’s saying something.

John Gruber

Daniel Jalkut

Wil Shipley

Jacqui Cheng

Clint Ecker

Kevin Hocter

Scotty

Andy Matuschak

Jeff Biggus

Mike Lee

Ash Ponders

Brian Webster

Mike Ash

Cathy Shive

Brian Criscuolo

The Guys at Karelia

and

Sanjay Samani

In the evenings I plan on hitting as many gatherings as possible; to shmooz and learn new and better ways to market the program. To that end I’ve started compiling the WWDC party list on Google Calendar. You can subscribe to it, or download the iCal version to your Mac or iPhone.

Here’s the link.

Please let me know of any other gatherings, and I’ll add them to the calendar.

As always, I’d love to hear feedback on this new feature; what works for you and what doesn’t, so that I can continue to improve the program.

Anyway, it’s out, so grab a copy and tell your friends.

With the group expanded, the Summary View looks like this:

If you have a lot of categories, and you’re not interested in the details at the moment, you can collapse the group:

and the Summary View will summarize the group for you:

Once again, I’m looking for beta testers. Because this update changes the structure of the data files, you will have to back up your data (but you do that anyway, don’t you?) and keep a copy of Horizon 1.3.5 around, just to be safe. If you’re interested in testing this version, drop me an email at the contact address and let me know. I’ll send you the link to the beta version. Thanks to everyone who helped test last time, and thanks in advance to everyone who can help with this version.

The second piece of news is that, for today only, Horizon is available at 20% off the usual price of $29.95 U.S. As part of the MacSanta campaign, you can use the coupon code ‘MACSANTA07′ in the built-in store to get the discount. You might want to visit the MacSanta store as well, to see the other great software deals.