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

BusyContacts 1.6.4 - 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
Steam 4.0 - Multiplayer and communicatio...
Steam is a digital distribution, digital rights management, multiplayer and communications platform developed by Valve Corporation. It is used to distribute a large number of games and related media... Read more
OmniGraffle Pro 7.19.3 - Create diagrams...
OmniGraffle Pro 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... Read more
OmniGraffle 7.19.3 - Create diagrams, fl...
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
Hopper Disassembler 5.3.3- - Binary disa...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
calibre 5.35.0 - Complete e-book library...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
Sound Studio 4.10.0 - Robust audio recor...
Sound Studio lets you easily record and professionally edit audio on your Mac. Easily rip vinyls and digitize cassette tapes, or record lectures and voice memos. Prepare for live shows with live... Read more
Sparkle Pro 4.0 - Visual website creator...
Sparkle Pro will change your mind if you thought building websites wasn't for you. Sparkle is the intuitive site builder that lets you create sites for your online portfolio, team or band pages, or... Read more
Dropbox 140.4.1951 - Cloud backup and sy...
Dropbox for Mac is a file hosting service that provides cloud storage, file synchronization, personal cloud, and client software. It is a modern workspace that allows you to get to all of your files... Read more
FotoMagico 6.0.5 - Powerful slideshow cr...
FotoMagico lets you create professional slideshows from your photos and music with just a few, simple mouse clicks. It sports a very clean and intuitive yet powerful user interface. High image... Read more

Latest Forum Discussions

See All

Best iPhone Game Updates: ‘Garena Free F...
Hello everyone, and welcome to the week! It’s time once again for our look back at the noteworthy updates of the last seven days. I got busted last week for not including the obligatory free-to-play matching puzzle game update of the week, and my... | Read more »
‘Horizon Chase’ China Spirit DLC Release...
Following the release of the excellent reveal of the Horizon Chase Senna Forever expansion, the game will be getting a new DLC on mobile platforms today. Today, the Horizon Chase China Spirit DLC pack will release on iOS and Android bringing in 9... | Read more »
‘PUZZLED’ from SNK and Hamster Is Out No...
Following ZED BLADE ACA NeoGeo earlier this month, SNK has brought over another game in the ACA NeoGeo series to both iOS and Android in the form of PUZZLED. SNK and Hamster originally brought the series to mobile with Samurai Shodown IV, Alpha... | Read more »
A House Full of Covid – The TouchArcade...
It’s been a rough week as both of our young children tested positive for Covid, and since recording this early on Friday my wife has tested positive now too. Thankfully the kids seemed to recover fairly quickly and are mostly back to normal, and I... | Read more »
TouchArcade Game of the Week: ‘Krispee S...
Krispee Street is a new hidden object game from Frosty Pop that is based on their popular and almost painfully sweet webcomic Krispee. This is one of the latest titles to be added to the Netflix Games catalog, which means you’ll need to log into... | Read more »
SwitchArcade Round-Up: ‘Escape Lala’, ‘B...
Hello gentle readers, and welcome to the SwitchArcade Round-Up for January 21st, 2022. In today’s article, we’ve got a lot of new releases. A lot. There were eight on the schedule when I went to bed last night. There were twenty-four when I woke up... | Read more »
Beta Testers Needed for Huge Version 2.0...
Ya’ll remember Dungeon Raid, right? The phenomenal matching RPG hybrid that launched on mobile more than a decade ago, but was more or less abandoned by its developer only to die a slow death on the App Store before the 32-bit Appocalypse finally... | Read more »
‘Ark Legends’ Gives Players a Chance to...
It’s Airpods and Amazon gift cards galore as Melting Games opens pre-registration for Ark Legends. The upcoming mobile RPG is giving away tons of in-game goodies such as gold, energy, iron core, hero summon chest and rare iron core to players who... | Read more »
‘Nickelodeon Extreme Tennis’ Out Now on...
Nickelodeon Extreme Tennis () from Old Skull Games and Nickelodeon is this week’s new Apple Arcade release. Nickelodeon Extreme Tennis features characters from old and new Nickelodeon shows including SpongeBob, TMNT, and many more. The tennis game... | Read more »
SwitchArcade Round-Up: ‘RPGolf Legends’,...
Hello gentle readers, and welcome to the SwitchArcade Round-Up for January 20th, 2022. In today’s article, we’ve got a massive amount of new releases to check out. We’ve got summaries of all of them, from heaven to hell. We also have the lists of... | Read more »

Price Scanner via MacPrices.net

Verizon’s 2022 iPad promo: $100-$310 off any...
Verizon has cellular-capable iPads on sale for $100-$310 off MSRP when purchased with an Unlimited service plan. Sale price is applied to your account monthly over a 24 or 30 month period, depending... Read more
Sunday Sale: Apple AirPods are on sale for up...
Amazon has Apple AirPods on sale for $10-$100 off MSRP today, depending on the model. All are in stock today with free delivery: – AirPods Max headphones (Blue): $449 $100 off MSRP – AirPods Max... Read more
These Apple resellers are offering 13″ M1 Mac...
Apple resellers are offering discounts on 13″ MacBook Pros with M1 Apple Silicon processors ranging up to $150 off MSRP. Here’s where to get one today: (1): Apple’s 13″ MacBook Pros with M1 Apple... Read more
Amazon lowers prices on select 13″ M1 MacBook...
Amazon has select Apple 13″ M1 MacBook Airs on sale for $150 off MSRP this weekend, starting at only $849. Their prices are the lowest available for new MacBook Airs today. Stock may come and go, so... Read more
Apple has 13″ M1 MacBook Airs back in stock s...
Apple has restocked a full line of 13″ M1 MacBook Airs, Certified Refurbished, starting at only $849 and up to $190 off original MSRP. These are the cheapest M1-powered MacBooks for sale today at... Read more
In stock and on sale! 16″ 10-Core M1 Pro MacB...
Amazon has new 16″ 10-Core/512GB M1 Pro MacBook Pros in stock today and on sale for $50 off MSRP including free shipping. Their prices are the lowest available for new M1 Pro 16″ MacBook Pro from any... Read more
Deal Alert!: 14″ M1 Pro with 10-Core CPU in s...
Amazon has the new 14″ M1 Pro MacBook Pro with a 10-Core CPU and 16-Core GPU in stock today and on sale for $2299.99 including free shipping. Their price is $200 off Apple’s standard MSRP, and it’s... Read more
Apple has 24-inch M1 iMacs (8-Core CPU/8-Core...
Apple has restocked a wide array of 24-inch M1 iMacs with 8-Core CPUs and 8-Core GPUs in their Certified Refurbished store. Models are available starting at only $1269 and range up to $260 off... Read more
Select 24″ M1 iMacs are on sale for $100 off...
Sales of Apple’s new 24″ M1 iMacs have been rare since its introduction, perhaps due to global supply issues. However, B&H is offering a $100 discount on select 24″ iMacs, and they’re in stock... Read more
M1 Mac minis are back in stock today at Apple...
Apple has M1-powered Mac minis available in their Certified Refurbished section starting at only $589 and up to $140 off MSRP. Each mini comes with Apple’s one-year warranty, and shipping is free: –... Read more

Jobs Board

Registered Nurse (RN) Employee Health PSJH -...
…is calling for a Registered Nurse (RN) Employee Health PSJH to our location in Apple Valley, CA.** We are seeking a Registered Nurse (RN) Employee Health PSJH to be Read more
Systems Administrator - Pearson (United State...
…and troubleshoot Windows operating systems (workstation and server), laptop computers, Apple iPads, Chromebooks and printers** + **Administer and troubleshoot all Read more
IT Assistant Level 1- IT Desktop Support Anal...
…providing tier-1 or better IT help desk support in a large Windows and Apple environment * Experience using IT Service Desk Management Software * Knowledge of IT Read more
Human Resources Business Partner PSJH - Provi...
…**is calling a** **Human Resources Business Partner, PSJH** **to our location in Apple Valley, CA.** **Applicants that meet qualifications will receive a text with Read more
Manager Community Health Investment Programs...
…is calling a Manager Community Health Investment Programs PSJH to our location in Apple Valley, CA.** **Qualified candidates will be invited to do a self-paced video Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.