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

BetterTouchTool 2.332 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Capture One 11.0.1.40 - RAW workflow sof...
Capture One is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 400 high-end cameras -- straight out of the box. It offers... Read more
Capture One 11.0.1.40 - RAW workflow sof...
Capture One is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 400 high-end cameras -- straight out of the box. It offers... Read more
GraphicConverter 10.5.4 - $39.95
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
Dash 4.1.3 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
Microsoft OneNote 16.9 - Free digital no...
OneNote is your very own digital notebook. With OneNote, you can capture that flash of genius, that moment of inspiration, or that list of errands that's too important to forget. Whether you're at... Read more
DEVONthink Pro 2.9.17 - Knowledge base,...
Save 10% with our exclusive coupon code: MACUPDATE10 DEVONthink Pro is your essential assistant for today's world, where almost everything is digital. From shopping receipts to important research... Read more
OmniGraffle 7.6 - Create diagrams, flow...
OmniGraffle helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use Graffle to... Read more
iFinance 4.3.7 - Comprehensively manage...
iFinance allows you to keep track of your income and spending -- from your lunchbreak coffee to your new car -- in the most convenient and fastest way. Clearly arranged transaction lists of all your... Read more
Opera 50.0.2762.58 - High-performance We...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more

Latest Forum Discussions

See All

Around the Empire: What have you missed...
Around this time every week we're going to have a look at the comings and goings on the other sites in Steel Media's pocket-gaming empire. We'll round up the very best content you might have missed, so you're always going to be up to date with the... | Read more »
Everything about Hero Academy 2: Part 4...
In this part of our Hero Academy 2 guide, we're going to have a look at some of the tactics you're going to need to learn if you want to rise up the ranks. We're going to start off slow, then get more advanced in the next section. [Read more] | Read more »
All the best games on sale for iPhone an...
Another week has flown by. Sometimes it feels like the only truly unstoppable thing is time. Time will make dust of us all. But before it does, we should probably play as many awesome mobile videogames as we can. Am I right, or am I right? [Read... | Read more »
The 7 best games that came out for iPhon...
Well, it's that time of the week. You know what I mean. You know exactly what I mean. It's the time of the week when we take a look at the best games that have landed on the App Store over the past seven days. And there are some real doozies here... | Read more »
Popular MMO Strategy game Lords Mobile i...
Delve into the crowded halls of the Play Store and you’ll find mobile fantasy strategy MMOs-a-plenty. One that’s kicking off the new year in style however is IGG’s Lords Mobile, which has beaten out the fierce competition to receive Google Play’s... | Read more »
Blocky Racing is a funky and fresh new k...
Blocky Racing has zoomed onto the App Store and Google Play this week, bringing with it plenty of classic kart racing shenanigans that will take you straight back to your childhood. If you’ve found yourself hooked on games like Mario Kart or Crash... | Read more »
Cytus II (Games)
Cytus II 1.0.1 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.1 (iTunes) Description: "Cytus II" is a music rhythm game created by Rayark Games. It's our fourth rhythm game title, following the footsteps of three... | Read more »
JYDGE (Games)
JYDGE 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Build your JYDGE. Enter Edenbyrg. Get out alive. JYDGE is a lawful but awful roguehate top-down shooter where you get to build your... | Read more »
Tako Bubble guide - Tips and Tricks to S...
Tako Bubble is a pretty simple and fun puzzler, but the game can get downright devious with its puzzle design. If you insist on not paying for the game and want to manage your lives appropriately, check out these tips so you can avoid getting... | Read more »
Everything about Hero Academy 2 - The co...
It's fair to say we've spent a good deal of time on Hero Academy 2. So much so, that we think we're probably in a really good place to give you some advice about how to get the most out of the game. And in this guide, that's exactly what you're... | Read more »

Price Scanner via MacPrices.net

Deals on clearance 15″ Apple MacBook Pros wit...
B&H Photo has clearance 2016 15″ MacBook Pros available for up to $800 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: – 15″ 2.7GHz Touch Bar MacBook Pro... Read more
Apple restocked Certified Refurbished 13″ Mac...
Apple has restocked a full line of Certified Refurbished 2017 13″ MacBook Airs starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: – 13″ 1.8GHz/8GB/128GB... Read more
How to find the lowest prices on 2017 Apple M...
Apple has Certified Refurbished 13″ and 15″ 2017 MacBook Pros available for $200 to $420 off the cost of new models. Apple’s refurbished prices are the lowest available for each model from any... Read more
The lowest prices anywhere on Apple 12″ MacBo...
Apple has Certified Refurbished 2017 12″ Retina MacBooks available for $200-$240 off the cost of new models. Apple will include a standard one-year warranty with each MacBook, and shipping is free.... Read more
Apple now offering a full line of Certified R...
Apple is now offering Certified Refurbished 2017 10″ and 12″ iPad Pros for $100-$190 off MSRP, depending on the model. An Apple one-year warranty is included with each model, and shipping is free: –... Read more
27″ iMacs on sale for $100-$130 off MSRP, pay...
B&H Photo has 27″ iMacs on sale for $100-$130 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 27″ 3.8GHz iMac (MNED2LL/A): $2199 $100 off MSRP – 27″ 3.... Read more
2.8GHz Mac mini on sale for $899, $100 off MS...
B&H Photo has the 2.8GHz Mac mini (model number MGEQ2LL/A) on sale for $899 including free shipping plus NY & NJ sales tax only. Their price is $100 off MSRP. Read more
Apple offers Certified Refurbished iPad minis...
Apple has Certified Refurbished 128GB iPad minis available today for $339 including free shipping. Apple’s standard one-year warranty is included. Their price is $60 off MSRP. Read more
Amazon offers 13″ 256GB MacBook Air for $1049...
Amazon has the 13″ 1.8GHz/256B #Apple #MacBook Air on sale today for $150 off MSRP including free shipping: – 13″ 1.8GHz/256GB MacBook Air (MQD42LL/A): $1049.99, $150 off MSRP Read more
9.7-inch 2017 WiFi iPads on sale starting at...
B&H Photo has 9.7″ 2017 WiFi #Apple #iPads on sale for $30 off MSRP for a limited time. Shipping is free, and pay sales tax in NY & NJ only: – 32GB iPad WiFi: $299, $30 off – 128GB iPad WiFi... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Data Center Site Selection and Strat...
# Apple Data Center Site Selection and Strategy Research Analyst Job Number: 83708609 Santa Clara Valley, California, United States Posted: 18-Jan-2018 Weekly Hours: Read more
Security Engineering Coordinator, *Apple* R...
# Security Engineering Coordinator, Apple Retail Job Number: 113237456 Santa Clara Valley, California, United States Posted: 18-Jan-2018 Weekly Hours: 40.00 **Job Read more
Firmware Engineer - *Apple* Accessories - A...
# Firmware Engineer - Apple Accessories Job Number: 113422485 Santa Clara Valley, California, United States Posted: 18-Jan-2018 Weekly Hours: 40.00 **Job Summary** Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.