TweetFollow Us on Twitter

Dec 01 Mac OS X

Volume Number: 17 (2001)
Issue Number: 12
Column Tag: Mac OS X

by Andrew Stone

Cocoamotion

Getting more for less with Cocoa.

Ever since ‘89 I’ve been developing with the precursor to Cocoa, NeXTStep & OpenStep. In each release, new features and new concepts have been added to the Application and related frameworks. making life even easier for the third party developer. The more reusable software components that Apple provides, the less code I have to write and maintain. Imagine being able to remove more and more code from your applications! Today I removed hundreds of lines of code in my Image drawing class by using the new NSImage drawing methods which respect the current transformation matrix.

This article goes over a few ways to eradicate code that you may have accrued by using new objects and new features in the old ones. We’ll look at a simplified Image drawing object, the NSStepper, and the fairly new drag methods in NSOutlineView and NSTableView.

NSImage Gets An Upgrade

Transformations

Before Mac OS X 10.0, NSImage would draw ignoring the current transformation matrix. Now this is fine if you have a simple list of graphics - but if you have nested layers of scaled, rotated, skewed groups, it’s a royal pain in the patooti to micromanage image drawing based on depth of a hierarchy!

For compatibility with older applications, the existing NSImage drawing methods such as compositeToPoint: alway draw with only the origin of the image transformed. The image itself is drawn ignoring scale and rotation transforms with the origin at the lower left. While it has been possible to draw with the current transform by getting one of the image’s representation and calling it’s draw method, two new methods have been added to NSImage that do this for you.

- (void)drawAtPoint:(NSPoint)point fromRect:(NSRect)fromRect operation:(NSCompositingOperation)op 
  fraction:(float)delta;
  
- (void)drawInRect:(NSRect)rect fromRect:(NSRect)fromRect operation:(NSCompositingOperation)op 
  fraction:(float)delta;

If you pass in NSZeroRect for the fromRect: parameter, then the whole image is used. For drawInRect:, the image will be scaled to fit in the destination rectangle as well as transformed with the context’s current transform. Please note that if you use these routines in a flipped view, you will need to ‘undo’ the negative y scale factor and adjust the origin before calling the new methods:

      // make a new transform:
                NSAffineTransform *t = [NSAffineTransform transform];
      
      // by scaling Y negatively, we effectively flip the image:
                [t scaleXBy:1.0 yBy:-1.0];
      
      // but we also have to translate it back by its height:
                [t translateXBy:0.0 yBy:-_bounds.size.height];
      
      // apply the transform:
                [t concat];

Now you can have groups of images that are scaled and skewed, and these transformations will automatically be correctly applied to the image when it is rendered. Total lines of code: 5. Number of lines of code replaced: 250. Improvement of rendering speed: 2x. Reliability and correctness were improved greatly.

Transparency:

Using these new methods, you can add a slider to your interface which controls the transparency of the image, because the new methods take a fractional dissolve, from 0.0 fully transparent to 1.0 fully opaque. Let’s say you store the amount of transparency as a float in _dissolve - then your call to render the image would be:

   // we have translated already to the origin of the image in its current group
   // _dissolve varies from 0 for no dissolve to 1 for fully transparent:
            [image drawInRect:NSMakeRect(0.0,0.0,_bounds.size.width,_bounds.size.height) 
            fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:1.0 - _dissolve];

PDF Optimization:

In 10.1 and earlier, there is an “over-optimization” bug in Apple’s implementation of the NSPDFImageRep whereby it draws from its bitmap cache in certain circumstances which are incorrect. For example, when you print, you want the full resolution PDF, not a standin bitmap image which will produce jaggies. Also, when you zoom in, you want the PDF to render beautifully at that scale. You might want to test if you are printing or saving or at a high level zoom, and render the image directly from the PDF data:

      // if image is a pdf, and we are printing or saving or need the actual data:

            if (needToUseRealPDFData) {
          // grab the image’s best representation, the actual NSPDFImageRep:
                NSPDFImageRep *rep = [_image bestRepresentationForDevice:nil];
         // ask it to draw within our bounds:
                [rep drawInRect:NSMakeRect(0.0,0.0,_bounds.size.width,_bounds.size.height)];
            } else 
                  [image drawInRect:NSMakeRect(0.0,0.0,_bounds.size.width,_bounds.size.height) 
                  fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:1.0 - _dissolve];

The trick to get zoomed PDF to render onscreen at full quality is to multiply the size of the PDF image to the zoom:

   // helper method to return an integral size of an image, based on the zoom:
   
    - (NSSize)sizeForZoom:(float)zoom {
       NSSize s = [_image size];
       if (zoom == 1.0 || zoom == 0.0) return s;
       // images cannot be fractional sizes, so we round down:
       return NSMakeSize(floor(s.width * zoom), floor(s.height * zoom));
    }
    
          // Before drawing the image, we check if we are zoomed:
         // if our image is a PDF, and we’re drawing to screen, get a bigger image:
         
            if (_isPDF &&  [[NSGraphicsContext currentContext] isDrawingToScreen]  &&  zoom != 1.0) {
                NSSize s = [self sizeForZoom:zoom];
                if (_zoomedPDFImage == nil) {
                    _zoomedPDFImage = [_image copyWithZone:[self zone]];
             }
             if ( !NSEqualSizes([_zoomedPDFImage size], s))
                    [_zoomedPDFImage setSize:s];
                image = _zoomedPDFImage;
            } else {
                image = _image;
            }

NSStepper

An NSStepper provides what is known in Carbon as ‘little arrows’. These are common controls for date and time entries, but are also useful for any UI component that has values which can be “tweaked” a little bit. For example, we use them in Create to allow small adjustments to scale:


The ‘little arrows’ are a new addition to Cocoa, but have been around Carbon for awhile.

Like most control subclasses, NSStepper relies on the behavior of its custom NSStepperCell for its functionality. You don’t even need to know to this to use the stepper because the control has cover methods for the standard cell methods. Besides methods familiar from slider controls (setMaxValue:, setMinValue:, setAutorepeat:), the NSStepper allows you to set the granularity of an increment (or a decrement if the lower arrow is clicked) with setIncrement:.

You can also set whether the values loop around (as would be true in the case of rotation stepper) or not with setValueWraps:. In the example of a scale slider, for example, it makes no sense to go from the maximum value to the minimum value with one click!

Using the NSStepper in your interface consists of two parts: initializing the stepper for your requirements and keeping the value of the stepper in synch with data model, since it needs to know the original value in order to increment or decrement the value. You can initialize the stepper when loading the UI components for the first itme or directly in Interface Builder. This example is for a rotational slider: When loading the UI components the first time, you might initialize the values of the stepper, in this example, for a rotational slider. You can also set these values directly in Interface Builder, or programmatically in the File Owner’s class in awakeFromNib, which is called by the nib loading mechanism if this method exists:

- (void)awakeFromNib {
   [stepper setMinValue:0.0];
   [stepper setMaxValue:360.0];
   [stepper setIncrement:1.0];
   [stepper setValueWraps:YES];
   [stepper setAutorepeat:YES];
       // target/action set in IB
}

When inspecting a graphic that can be rotated, you reload the stepper with the current value of the graphic’s rotation:

   double currentRotation = [graphic rotation];
    [circularSlider setDoubleValue: currentRotation];
      [rotationStepper setDoubleValue: currentRotation];
   ...

The stepper handles all mousedowns and it knows whether it needs to increment or decrement the value. Let’s say you have connected the stepper to an action “incrementDecrementAction:”: The stepper has set its internal value to its incremented or decremented value, depending where the user clicked.

- (void)incrementDecrementAction:(id)aStepper {
    [self setSomeValue:[aStepper doubleValue]];  
      // take the value from the stepper
    [self reloadInspectingUI];   
         // update textfields, sliders, etc with new values 
}

The NSStepper is an excellent addition to the Cocoa developer’s toolkit, and both saves some lines of code as well as provide a standard mechanism for tweaking UI values.

Drag & Drop Support in NSTableView and NSOutlineView

The refinement of the Application framework is an ongoing process. For example, a few years ago we had to write our own code for drag and drop row reordering of table views and outlineviews (http://www.stone.com/GIFfun/GIFfunSource/Row_Moving_Protocol.html). Now, that code can be thrown away, and you can use the exposed API to accomplish this:

typedef enum { NSTableViewDropOn, NSTableViewDropAbove } NSTableViewDropOperation;

// In drag and drop, used to specify a dropOperation. For example, given a table with N rows 
(numbered with row 0 at the top visually), a row of N-1 and operation of NSTableViewDropOn would 
specify a drop on the last row. To specify a drop below the last row, one would use a row of N and 
NSTableViewDropAbove for the operation.

- (BOOL)tableView:(NSTableView *)tv writeRows:(NSArray*)rows toPasteboard:(NSPasteboard*)pboard;
    // This method is called after it has been determined that a drag should begin, but before the drag 
    has been started.  To refuse the drag, return NO.  To start a drag, return YES and place the drag 
    data onto the pasteboard (data, owner, etc...).  The drag image and other drag related information 
    will be set up and provided by the table view once this call returns with YES.  The rows array is 
    the list of row numbers that will be participating in the drag.

- (NSDragOperation)tableView:(NSTableView*)tv validateDrop:(id )info 
   proposedRow:(int)row proposedDropOperation:(NSTableViewDropOperation)op;
   
    // This method is used by NSTableView to determine a valid drop target.  Based on the mouse 
    position, the table view will suggest a proposed drop location.  This method must return a value 
    that indicates which dragging operation the data source will perform.  The data source may 
    “re-target” a drop if desired by calling setDropRow:dropOperation: and returning something other 
    than NSDragOperationNone.  One may choose to re-target for various reasons (eg. for better visual 
    feedback when inserting into a sorted position).

- (BOOL)tableView:(NSTableView*)tv acceptDrop:(id )info row:(int)row 
   dropOperation:(NSTableViewDropOperation)op;
    // This method is called when the mouse is released over an outline view that previously decided to 
    allow a drop via the validateDrop method.  The data source should incorporate the data from the 
    dragging pasteboard at this time.

Our free application, GIFfun, allows users to reorder the individual images that make up the final animated GIF. Here’ s a sample implementation of the Drag and Drop support in an NSTableView:

static int _moveRow = 0;

- (BOOL)tableView:(NSTableView *)tv writeRows:(NSArray*)rows toPasteboard:(NSPasteboard*)pboard 
{
    int count = [gifFileArray count];
    int rowCount = [rows count];
    if (count < 2) return NO; 

    [pboard declareTypes:[NSArray arrayWithObject:GifInfoPasteBoard] owner:self];
    [pboard setPropertyList:rows forType:GifInfoPasteBoard];
    _moveRow = [[rows objectAtIndex:0]intValue];
    return YES;
}

- (unsigned int)tableView:(NSTableView*)tv validateDrop:(id )info 
   proposedRow:(int)row proposedDropOperation:(NSTableViewDropOperation)op 
{
    if (row != _moveRow) {
        if (op==NSTableViewDropAbove) {
            return NSDragOperationAll;
        }
        return NSDragOperationNone;
    }
    return NSDragOperationNone;
}

- (BOOL)tableView:(NSTableView*)tv acceptDrop:(id )info row:(int)row 
   dropOperation:(NSTableViewDropOperation)op 
{
   BOOL result = [self tableView:tableView didDepositRow:_moveRow at:(int)row];
   [tableView reloadData];
   return result;
}

// here we actually do the management of the data model:

-  (BOOL)tableView:(NSTableView *)tv didDepositRow:(int)rowToMove at:(int)newPosition
{
   if (rowToMove != -1 && newPosition != -1) {
      id object = [gifFileArray objectAtIndex:rowToMove];
      if (newPosition < [gifFileArray count] - 1) {
         [gifFileArray removeObjectAtIndex:rowToMove];
         [gifFileArray insertObject:object atIndex:newPosition];
      } else {
         [gifFileArray removeObjectAtIndex:rowToMove];
         [gifFileArray addObject:object];
      }
      return YES;   // ie reload
   }
   return NO;
}

These few lines listed replace the 650 lines of code from SDTableView.h, SDTableView.m and SDMovingRowsProtocol.h. The complete source code to GIFfun is available at http://www.stone.com/GIFfun/.

Adding Features By Doing Nothing

And, if my Zen slacker coding model isn’t convincing enough, consider how you can add new features by doing nothing!

If you are using the Model-View-Controller pattern and taking advantage of the NSDocument architecture, then the introduction of Mac OS X 10.1 brought you new features, without you doing anything. Because your application links at runtime with the current version of the Application and Foundation frameworks, new features available in the kits become available to your users.

10.1 adds Hidden file extensions (which is way more Mac-like than the UNIX file extensions), ability to track documents, folders, and volumes which are renamed, and ability to save documents in a way which preserves aliases to the documents and additional document info such as maintaining file permissions, creation date, and icon settings.

Some of these features do require that you recompile your application, because the Apple engineers wanted to provide full backwards binary compatibility in programs that were linked against the Mac OS 10.0 version of the Cocoa framework.

Conclusion

Software is a process not a product, and therefore it is never finished! The frameworks that Cocoa developers rely on are continually being refined and improved, so it’s very important to carefully read the Release Notes found in /Developer/Documentation/ReleaseNotes, especially AppKit.html and Foundation.html. Always check for new functionality which can replace your home-rolled versions, thus making your application more compact and reducing the code base that you need to support.


Andrew Stone andrew@stone.com is the chief executive haquer at Stone Design Corp http://www.stone.com and divides his time between raising children, llamas & cane and writing applications for Mac OS X.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Duplicate Annihilator 5.7.5 - Find and d...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator... Read more
BusyContacts 1.0.2 - Fast, efficient con...
BusyContacts is a contact manager for OS X that makes creating, finding, and managing contacts faster and more efficient. It brings to contact management the same power, flexibility, and sharing... Read more
Capture One Pro 8.2.0.82 - RAW workflow...
Capture One Pro 8 is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 300 high-end cameras -- straight out of the box. It... Read more
Backblaze 4.0.0.872 - Online backup serv...
Backblaze is an online backup service designed from the ground-up for the Mac.With unlimited storage available for $5 per month, as well as a free 15-day trial, peace of mind is within reach with... Read more
Little Snitch 3.5.2 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more
Monolingual 1.6.4 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. If you use your computer in only one (human) language, you... Read more
CleanApp 5.0 - Application deinstaller a...
CleanApp is an application deinstaller and archiver.... Your hard drive gets fuller day by day, but do you know why? CleanApp 5 provides you with insights how to reclaim disk space. There are... Read more
Fantastical 2.0 - Create calendar events...
Fantastical is the Mac calendar you'll actually enjoy using. Creating an event with Fantastical is quick, easy, and fun: Open Fantastical with a single click or keystroke Type in your event details... Read more
Cocktail 8.2 - General maintenance and o...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
Skype 7.6.0.409 - Voice-over-internet ph...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more

Fast & Furious: Legacy's Creati...
| Read more »
N-Fusion and 505's Ember is Totally...
| Read more »
These are All the Apple Watch Apps and G...
The Apple Watch is less than a month from hitting store shelves, and once you get your hands on it you're probably going to want some apps and games to install. Fear not! We've compiled a list of all the Apple Watch apps and games we've been able to... | Read more »
Appy to Have Known You - Lee Hamlet Look...
Being at 148Apps these past 2 years has been an awesome experience that has taught me a great deal, and working with such a great team has been a privilege. Thank you to Rob Rich, and to both Rob LeFebvre and Jeff Scott before him, for helping me... | Read more »
Hands-On With Allstar Heroes - A Promisi...
Let’s get this out of the way quickly. Allstar Heroes looks a lot like a certain other recent action RPG release, but it turns out that while it’s not yet available here, Allstar Heroes has been around for much longer than that other title. Now that... | Read more »
Macho Man and Steve Austin Join the Rank...
WWE Immortals, by Warner Bros. Interactive Entertainment and WWE, has gotten a superstar update. You'll now have access to Macho Man Randy Savage and Steve Austin. Both characters have two different versions: Macho Man Randy Savage Renegade or Macho... | Read more »
Fearless Fantasy is Fantastic for the iF...
I actually had my first look at Fearless Fantasy last year at E3, but it was on a PC so there wasn't much for me to talk about. But now that I've been able to play with a pre-release version of the iOS build, there's quite a bit for me to talk... | Read more »
MLB Manager 2015 (Games)
MLB Manager 2015 5.0.14 Device: iOS Universal Category: Games Price: $4.99, Version: 5.0.14 (iTunes) Description: Guide your favorite MLB franchise to glory! MLB Manager 2015, officially licensed by MLB.com and based on the award-... | Read more »
Breath of Light (Games)
Breath of Light 1.0.1421 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.1421 (iTunes) Description: Hold a quiet moment. Breath of Light is a meditative and beautiful puzzle game with a hypnotic soundtrack by... | Read more »
WWE WrestleMania Tags into the App Store
Are You ready to rumble? The official WWE WrestleMania app, by World Wrestling Entertainment, is now available. Now you can get all your WrestleMania info in one place before anyone else. The app offers details on superstar signings, interactive... | Read more »

Price Scanner via MacPrices.net

Apple offering refurbished 27-inch 5K iMacs f...
The Apple Store is offering Apple Certified Refurbished 27″ 3.5GHz 5K iMacs for $2119 including free shipping. Their price is $380 off the price of new models, and it’s the lowest price available for... Read more
16GB iPad mini on sale for $199, save $50
Walmart has 16GB iPad minis (1st generation) available for $199.99 on their online store, including free shipping. Their price is $50 off MSRP. Online orders only. Read more
New 128GB MacBook Airs on sale for $50 off MS...
 B&H Photo has 128GB 11″ and 13″ 2015 MacBook Airs on sale today for $50 off MSRP including free shipping plus NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air (Model #MJVM2LL/A): $849 $50 off... Read more
13-inch 2.6GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished 13″ 2.6GHz/128GB Retina MacBook Pros available for $979 including free shipping. Original MSRP for this model was $1299. Read more
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store is offering Apple Certified Refurbished Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more
Samsung Galaxy S 6 and Galaxy S 6 edge U.S. P...
Samsung Electronics America, Inc. has announced the Galaxy S 6 and Galaxy S 6 edge will be available in the U.S. beginning April 10, with pre-orders being accepted now. “We have completely reimagined... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
Save up to $80 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $80 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549.99 $50 off - 128GB iPad... Read more
iMacs on sale for up to $205 off MSRP
B&H Photo has 21″ and 27″ iMacs on sale for up to $205 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $1019 $80 off - 21″ 2.7GHz iMac: $1189 $110 off - 21″ 2.9GHz... Read more
Färbe Technik Offers iPhone Battery Charge LI...
Färbe Technik, which manufactures and markets of mobile accessories for Apple, Blackberry and Samsung mobile devices, is offering tips on how to keep your iPhone charged while in the field: •... Read more

Jobs Board

DevOps Software Engineer - *Apple* Pay, iOS...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Lead *Apple* Solutions Consultant - Retail...
**Job Summary** Job Summary The Lead ASC is an Apple employee who serves as the Apple business manager and influencer in a hyper-business critical Reseller's store Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.