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

Together 3.4.6 - Store and organize all...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Smart storage. With simple drag-and-drop functionality,... Read more
Monosnap 3.1.0 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Capture: Capture full screen, just part of the screen, or a selected window Make your crop area pixel perfect with... Read more
Cocktail 8.5.1 - General maintenance and...
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
Vienna 3.0.6 :5eaf312: - RSS and Atom ne...
Vienna is a freeware and Open-Source RSS/Atom newsreader with article storage and management via a SQLite database, written in Objective-C and Cocoa, for the OS X operating system. It provides... Read more
Kodi 15.1.rc1 - Powerful media center to...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
Bookends 12.5.8 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Access the power of Bookends directly from Mellel, Nisus Writer Pro, or MS Word (... Read more
Chromium 44.0.2403.125 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 44.0.2403.125: This release contains a number... Read more
iMazing 1.2.2 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Audio Hijack 3.2.0 - Record and enhance...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
FontExplorer X Pro 5.0.1 - Font manageme...
FontExplorer X Pro is optimized for professional use; it's the solution that gives you the power you need to manage all your fonts. Now you can more easily manage, activate and organize your... Read more

Card King: Dragon Wars - Tips, Tricks an...
[Read more] | Read more »
Pac-Man Championship Edition DX has brou...
Bandai Namco has released Pac-Man Championship Edition DX on iOS and Android, which features the classic arcade gameplay that we've all grown to love. Pac-Man Championship Edition DX can be enjoyed in much shorter bursts than the arcade versions... | Read more »
Cosmonautica (Games)
Cosmonautica 1.1 Device: iOS Universal Category: Games Price: $6.99, Version: 1.1 (iTunes) Description: Cast off! Are you ready for some hilarious adventures in outer space? | Read more »
Rescue humanity from a Demon horde in An...
Angel Stone is Fincon's follow up to the massively successful Hello Hero and is out now on iOS and Android. You play as a member of The Resistance, a group of mighty human warriors who have risen up in defiance of the Demon horde threatening to... | Read more »
Gallery Doctor (Photography)
Gallery Doctor 1.0 Device: iOS iPhone Category: Photography Price: $2.99, Version: 1.0 (iTunes) Description: Free up valuable iCloud and iPhone storage with Gallery Doctor, the only iPhone cleaner that automatically identifies the... | Read more »
You Against Me (Games)
You Against Me 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: A simple game… You. Me. Claim, steal, lock, score, win! | Read more »
Yep, it's True - Angry Birds 2 is O...
The not exactly rumors were true and the birds are back. Angry Birds 2 has come to the App Store and the world will... well I suppose it'll still be the same, but now we have more bird-flinging options! [Read more] | Read more »
You Could Design Your Own Card for Chain...
If you've ever wanted to create your own item, weapon, trap, or even monster for Chainsaw Warrior: Lords of the Night, this is your chance. Auroch Digital is currently holding a contest so that fans can fight to the death (not really) to see which... | Read more »
Bitcoin Billionaire is Going Back in Tim...
If you thought you managed to buy everything there is to buy in Bitcoin Billionaire and make all the money, well you though wrong. Those of you who made it far enough might remember investing in time travel - and it looks like that investment is... | Read more »
Domino Drop (Games)
Domino Drop 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Domino Drop is a delightful new puzzle game with dominos and gravity!Learn how to play it in a minute, master it day by day.Your... | Read more »

Price Scanner via MacPrices.net

27-inch 3.5GHz 5K iMac on sale for $81 off MS...
Adorama has the 27″ 3.5GHz 5K iMac on sale for $2218, $81 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax in NY & NJ... Read more
Back-to-School with Tablet and Smartphone Acc...
Belkin helps you prepare for the coming school year with a wide variety of the latest mobile and tablet accessories to outfit both grade school and college students. The line-up includes charging... Read more
11-inch MacBook Airs on sale for $100 off MSR...
Best Buy has 11-inch MacBook Airs on sale for $100 off MSRP. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary: - 11″ 1.6GHz... Read more
iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
Sale! 13-inch MacBook Pros on sale for $100 o...
B&H Photo has 13″ MacBook Pros on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.5GHz/500GB MacBook Pro: $999.99 save $100 - 13″ 2.7GHz/128GB Retina... Read more
Sale! Save $100 on 13-inch MacBook Airs this...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model.... Read more
Worldwide Tablet Market Decline Continues, Ap...
The worldwide tablet market declined -7.0% year-over-year in the second quarter of 2015 (2Q15) with shipments totaling 44.7 million units according to preliminary data from the International Data... Read more
TP-LINK TL-PA8030P KIT Powerline Featuring Ho...
Consumer and business networking products provider TP-LINK is now shipping its TL-PA8030P KIT AV1200 3-Port Gigabit Passthrough Powerline Starter Kit that expands your home’s network over its... Read more
Apple refurbished iPad Air 2s available for u...
The Apple Store has Apple Certified Refurbished iPad Air 2s available for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: - 128GB... Read more
Updated Apple iPad Price Trackers
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers. Read more

Jobs Board

*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
Infrastructure Engineer - *Apple* /Mac - Hil...
Infrastructure Engineer - Apple /Mac Job Code: 1608 # of openings: 1 Description Our fortune 500 client is looking to hire an experienced Infrastructure Engineer to join Read more
Executive Administrative Assistant, *Apple*...
…supporting presentation development for senior leadership. * User experience with Apple hardware and software is preferred. Additional Requirements The following list Read more
*Apple* Bus Company is now hirin - Apple Bus...
Apple Bus Company is now hiring school bus drivers in the Pettis County area. Class B CDL preferred. Free training provided. No nights or weekends required. Flexible Read more
*Apple* Certified Mac Technician - Updated 6...
…and friendly, hands-on technical support to customers troubleshooting and repairing Apple /Mac products with courtesy, speed and skill. Use your problem-solving skills Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.