TweetFollow Us on Twitter

Spaced Out

Volume Number: 18 (2002)
Issue Number: 12
Column Tag: Mac OS X

Spaced Out

Adding Paragraph Spacing to the Cocoa Text System

by Andrew C. Stone

One of my favorite Cocoa demos is to make a full featured word processor application in 5 minutes - complete with rulers, tabs, embedded graphics, line spacing, kerning, ligatures, baseline, colors, multi-font, automatic spell checking and more - (see http://www.stone.com/The_Cocoa_Files/Arise_Aqua_.html). Cocoa's powerful text system is a collection of classes that can meet almost any text need, and I highly recommend reading the documentation for these classes:,NSText and NSTextView (the display classes), NSTextStorage and NSAttributedString (how rich strings store all the attributes of unicode text), NSLayoutManager (manages an NSTextStorage and set of NSTextContainers which display in an NSTextView) and playing with the sample Text layout application available in the Developer distribution in /Developer/Examples/AppKit/TextSizingExample.

These full featured classes are getting more powerful with each major system release. In Mac OS X 10.2, a feature which was previously defined in the API was implemented in NSParagraphStyle:

ParagraphSpacing

- (float)paragraphSpacing

Returns the space added at the end of the paragraph to separate it from the following paragraph. This value is always nonnegative.

See Also: - lineSpacing - setParagraphSpacing: (NSMutableParagraphStyle)

Paragraph spacing is the additional distance between paragraphs (that is, whenever a <RETURN> appears in the text). This amount is in points (72 per inch) and by default is 0. It's added to any additional line spacing that applies to that paragraph style.

But, although the implementation is there, the interface is not. The ruler, which comes for free with NXTextView, and which contains controls for alignment, line spacing, and tabs, currently lacks any control for setting the paragraph spacing. This article will show you how to add a custom control to the standard text system ruler.


Figure 1: The standard text ruler in Mac OS X 10.2 doesn't have a paragraph spacing control.

Just using simple subclasses of NSTextView and NSLayoutManager, our page layout and web authoring application Create(R) can flow text through any size containers, place rich text along any path, apply neon and custom pattern effects to any text, and place text outside or inside of any path. Once Jaguar shipped, we could easily add paragraph spacing to our text - if we could figure out a way to add a new control to the ruler that automatically attaches itself to any NSTextView in an NSScrollView.

Like everything with Cocoa - if it's hard it's wrong. So finding an easy solution with modular application is the always the goal of any Cocoa programming challenge.

Our design imperatives include:

  • make it simple

  • make it small so it doesn't get in the way

  • make it a modular nib file

The solution has 3 parts - a user interface built in InterfaceBuilder, the create/update code in an NSLayoutManager subclass, and code in an NSTextView subclass which actually sets the spacing and maintains the undo stack.

So, I chose to make the narrowest UI possible - using the P symbol for paragraph and an NSStepper:


Figure 2: Create(R) adds a paragraph spacer next to the line spacing tools - P

The first problem is how do we get at the ruler to install the new device? It's owned by NSLayoutManager, which provides a method that returns this ruler view - so that seems like the most appropriate place to instantiate and update our own user interface addition which can set the paragraph spacing:

- (NSView *)rulerAccessoryViewForTextView:(NSTextView *)aTextView 
paragraphStyle:(NSParagraphStyle *)paraStyle ruler:(NSRulerView *)aRulerView enabled:(BOOL)flag

Returns the accessory NSView for aRulerView. This accessory contains tab wells, text alignment buttons, and so on. paraStyle is used to set the state of the controls in the accessory NSView; it must not be nil. If flag is YES the accessory view is enabled and accepts mouse and keyboard events; if NO it's disabled.

This method is invoked automatically by the NSTextView object using the layout manager. You should rarely need to invoke it, but you can override it to customize ruler support.

Let's Just Face it

We'll use InterfaceBuilder to create the interface and even the stub files for our new class, ParagraphSpacer:

    1. Launch Interface Builder

    2. File -> New..., Cocoa, "Empty", Click "New"

    3. Save this as "ParagraphSpacer.nib" in your project directory - also add it to your project when asked.

    4. Double-click the "File's Owner" icon in the folio window - NSObject will be selected in the Classes tab

    5. Control-Click NSObject and select "Create Subclass" - name it "ParagraphSpacer"

    6. Add two outlets: stepper and containerView by Control-Clicking ParagraphSpacer and choose "Add Outlet to ParagraphSpacer".

    7. Control-click ParagraphSpacer and choose "Create Files for Paragraph Spacer" - add these to your project

    8. Choose "Instances" tab, select "File's Owner", Info-> Custom Class, select "ParagraphSpacer"

    9. From the Tab icon on the Palette, drag a "Custom View" into the folio window

    10. Set the view's size with , Info -> Size, 26 wide by 28 tall

    11. Drag in "System Font Text", select all, delete, type P, Info -> Size 10 wide by 17 tall, locate on left

    12. Drag in an NSStepper from Slider Icon tab on Palette, adjust location as needed

    13. Connect the File's owner to the two instance variables - the stepper, and the view which holds the stepper and the static P text.

    14. Save ParagraphSpacer.nib

ParagraphSpacer

A very simple class which just returns its two instance variables.We need these to install the view into the Ruler view hierarchy and set the value of the stepper during updates:

/* ParagraphSpacer */
#import <Cocoa/Cocoa.h>
@interface ParagraphSpacer : NSObject
{
    IBOutlet id containerView;
    IBOutlet NSStepper *stepper;
}
- (NSStepper *)stepper;
- (NSView *)containerView;
@end
#import "ParagraphSpacer.h"
@implementation ParagraphSpacer
- (id) init {
    self = [super init];
    if (![NSBundle loadNibNamed:@"ParagraphSpacer.nib" owner:self])
   NSLog(@"couldn't load ParagraphSpacer\n");
        
        
    return self;
}
- (NSStepper *)stepper; {
    return stepper;
}
- (NSView *)containerView; {
    return containerView;
}
@end

SDLayoutManager

We just need to add one method to our NSLayoutManager subclass. Note that we call [super rulerAccessoryViewForTextView: ... ] to get the standard ruler provided for us, then we check to see if we have already initialized the paragraph spacer, and if not, proceed to create it, find it's proper position in the ruler and install it. We'll travel down the view hierarchy, looking at the subviews of each view. When we find a view with several subviews, then we know we're in the right place. When we find the view that starts far to the left, ie, not the tab well, but the NSBox which surrounds the alignment and line spacing controls, we'll place our control right next to it. We just have to hope that the ruler doesn't change drastically - if it does, it will probably have more controls in it, and our layout may be wrong.

Each time this method gets called, we'll set the target of the stepper to be the current text view with an action of changeParagraphSpacing:, and update the value of the stepper so that it sends the target the right value when incrementing or decrementing.

@interface SDLayoutManager : NSLayoutManager
{
  @private
    NSStepper *_paragraphStepper;
}
@implementation SDLayoutManager
- (NSView *)rulerAccessoryViewForTextView:(NSTextView *)view paragraphStyle:(NSParagraphStyle *)style 
ruler:(NSRulerView *)ruler enabled:(BOOL)isEnabled {

    NSView *accessory = [super rulerAccessoryViewForTextView:view paragraphStyle:style ruler:ruler 
    enabled:isEnabled];
    
    if (!_paragraphStepper) {
        ParagraphSpacer *spacer = [[ParagraphSpacer allocWithZone:[self zone]] init];
        NSView *viewToAdd = [spacer containerView];
        NSArray *subviews = [accessory subviews];
        NSView *viewToAddTo = accessory;
        unsigned int i, count = [subviews count];
        NSRect viewRect = [viewToAdd bounds];
        
        if (count == 1) {
            viewToAddTo = [subviews objectAtIndex:0];
            subviews = [[subviews objectAtIndex:0] subviews];
            count = [subviews count];
        }
        
        _paragraphStepper = [spacer stepper];
        
        for (i = 0; i < count; i++) {
            NSView *v = [subviews objectAtIndex:i];
            NSRect r = [v frame];
            if (r.origin.x < 10.0) {   // it's the box containing the left controls)
                viewRect.origin.x = r.origin.x + r.size.width;
                viewRect.origin.y = 0.0;
                [viewToAdd setFrame:viewRect];
                [viewToAddTo addSubview:viewToAdd];
            }
        }
    }
    [_paragraphStepper setDoubleValue:style? [style paragraphSpacing] : 0.0];
    [_paragraphStepper setTarget:view];
    [_paragraphStepper setAction:@selector(changeParagraphSpacing:)];
    
    return accessory;
}
@end

SDTextView

If you don't want to subclass NSTextView, you could instead add the changeParagraphSpacing: method to a category of NSTextView. This is not the case with the NSLayoutManager subclass, because we need to call super's implementation of rulerAccessoryViewForTextView:paragraphStyle:ruler:enabled:.

The main reason we place this code in NSTextView or a subclass is so we get the free automatic undo associated with Text. To do that, we alert the text system that there will be changes in a certain range with shouldChangeTextInRange: replacementString: with a replacement string of "nil" , which means other attributes are changing, but not any characters. Then, we walk over text paragraph style by paragraph style, setting the paragraph spacing to the value determined by the stepper (up or down a point from the first style in the selection). Note that if there are no paragraph attributes, one is added.

Finally, we alert the text that we are done changing it with didChangeText, and we add a custom action name so the menu will say "Undo Paragraph Spacing" and "Redo Paragraph Spacing".

@interface SDTextView: NSTextView
{}
@end
@implementation SDTextView
- (void)changeParagraphSpacing:(id)sender {
    double value = [sender doubleValue];
    NSRange range = [self rangeForUserParagraphAttributeChange];
    if (range.length > 0) {
        NSRange remainingRange = range;
        NSTextStorage *storage = [self textStorage];
        [self shouldChangeTextInRange:range replacementString:nil];
        while (remainingRange.length > 0) {
                NSRange effectiveRange;
                NSParagraphStyle *para = [storage attribute:NSParagraphStyleAttributeName 
                atIndex:remainingRange.location longestEffectiveRange:&effectiveRange 
                inRange:remainingRange];
        
                if (para == nil) {
                    para = [[[NSMutableParagraphStyle alloc] init] autorelease];
                    [para setParagraphStyle:[NSParagraphStyle defaultParagraphStyle]];
                } else para = [[para mutableCopyWithZone:[self zone]]autorelease];
                
                [para setParagraphSpacing:value];
                [storage addAttribute:NSParagraphStyleAttributeName value:para range:remainingRange];
    
                if (NSMaxRange(effectiveRange) < NSMaxRange(remainingRange)) {
                    remainingRange.length = NSMaxRange(remainingRange) - NSMaxRange(effectiveRange);
                    remainingRange.location = NSMaxRange(effectiveRange);
                } else {
                    break;
                }
        }
            [self didChangeText];
            [[self undoManager] setActionName:NSLocalizedStringFromTable(@"Paragraph Spacing",
            @"Muktinath",@"change of space between paragraphs")];
    
    }
}
@end

All Together Now

Your final task is just to be sure you create your text system with the special SDLayoutManager. If you have a shared text editor, it might look something like this:

static NSTextView *newEditor(TextArea *self) {
    SDTextView *tv;
    NSTextContainer *tc;
    // This method returns an NSTextView whose SDLayoutManager has a refcount of 1.  It is 
    the caller's responsibility to release the SDLayoutManager.  This function is only for the use of
    the following method.
    
    SDLayoutManager *lm = [[SDLayoutManager allocWithZone:NULL] init];
    tv = [[SDTextView allocWithZone:NULL] initWithFrame:NSMakeRect(0.0, 0.0, 100.0, 100.0) 
    textContainer:nil];
    
    tc = [[NSTextContainer allocWithZone:NULL] initWithContainerSize:NSMakeSize(1.0e6, 1.0e6)];
    [lm addTextContainer:tc];
    [tc release];
     
    [tc setTextView:tv];
    [tv release];
    return tv;
}


Figure 3: The new text ruler with paragraph spacing stepper installed.

Conclusion

The Cocoa text system just keeps getting better. And sometimes there are features that are still hidden from the user interface, such as paragraph spacing in Jaguar 10.2. With a little Cocoa magic, it's easy to install your own custom controls and add more functionality to the standard text object.


Andrew Stone, CEO of Stone Design, www.stone.com, has been the principal architect of several solar houses and over a dozen Cocoa applications shipping for Mac OS X.

 
AAPL
$97.67
Apple Inc.
+0.64
MSFT
$44.50
Microsoft Corpora
+0.10
GOOG
$589.02
Google Inc.
-4.33

MacTech Search:
Community Search:

Software Updates via MacUpdate

TinkerTool 5.3 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more
Audio Hijack Pro 2.11.0 - Record and enh...
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 with Audio Hijack... Read more
Intermission 1.1.1 - Pause and rewind li...
Intermission allows you to pause and rewind live audio from any application on your Mac. Intermission will buffer up to 3 hours of audio, allowing users to skip through any assortment of audio... Read more
Autopano Giga 3.6 - Stitch multiple imag...
Autopano Giga allows you to stitch 2, 20, or 2,000 images. Version 3.0 integrates impressive new features that will definitely make you adopt Autopano Pro or Autopano Giga: Choose between 9... Read more
Airfoil 4.8.7 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Microsoft Remote Desktop 8.0.8 - Connect...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
xACT 2.30 - Audio compression toolkit. (...
xACT stands for X Aaudio Compression Toolkit, an application that encodes and decodes FLAC, SHN, Monkey’s Audio, TTA, Wavpack, and Apple Lossless files. It also can encode these formats to MP3, AAC... Read more
Firefox 31.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals... Read more
Little Snitch 3.3.3 - Alerts you to outg...
Little Snitch gives you control over your private outgoing data. Track background activityAs soon as your computer connects to the Internet, applications often have permission to send any... Read more
Thunderbird 31.0 - Email client from Moz...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more

Latest Forum Discussions

See All

Reddme for iPhone - The Reddit Client (...
Reddme for iPhone - The Reddit Client 1.0 Device: iOS iPhone Category: News Price: $.99, Version: 1.0 (iTunes) Description: Reddme for iPhone is an iOS 7-optimized Reddit client that offers a refreshing new way to experience Reddit... | Read more »
Jacob Jones and the Bigfoot Mystery : Ep...
Jacob Jones and the Bigfoot Mystery : Episode 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Jacob Jones is back in Episode 2 of one of Apples 'Best of 2013' games and an App Store... | Read more »
New Trailer For Outcast Odyssey, A New K...
New Trailer For Outcast Odyssey, A New Kind of Card Battler Posted by Jennifer Allen on July 25th, 2014 [ permalink ] Out this Fall is a new kind of card battle game: Outcast Odyssey. | Read more »
Garfield: Survival of the Fattest Coming...
Garfield: Survival of the Fattest Coming to iOS this Fall Posted by Jennifer Allen on July 25th, 2014 [ permalink ] Who loves lasagna? Me. Also everyone’s favorite grumpy fat cat, Garfield. | Read more »
Happy Flock Review
Happy Flock Review By Andrew Fisher on July 25th, 2014 Our Rating: :: HERD IT ALL BEFOREUniversal App - Designed for iPhone and iPad Underneath the gloss of Happy Flock’s visuals is a game of very little substance. It’s cute, but... | Read more »
Square Register Updates Adds Offline Pay...
Square Register Updates Adds Offline Payments Posted by Ellis Spice on July 25th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Looking For Group – Hearthstone’s Curse...
For the first time since its release (which has thankfully been a much shorter window for iPad players than their PC counterparts), Blizzard’s wildly successful Hearthstone: Heroes of Warcraft CCG is sporting some brand new content: the single... | Read more »
Poptile Review
Poptile Review By Jennifer Allen on July 25th, 2014 Our Rating: :: SIMPLY FUNUniversal App - Designed for iPhone and iPad Simple yet a little bit glorious, Poptile is a satisfying entertaining puzzle game with oodles of the ‘one... | Read more »
Modern Combat 5: Blackout Review
Modern Combat 5: Blackout Review By Brittany Vincent on July 25th, 2014 Our Rating: :: LESS QQ, MORE PEW PEWUniversal App - Designed for iPhone and iPad The fifth entry into the blockbuster Modern Combat series is what mobile... | Read more »
Watch and Share Mobile Gameplay Videos W...
Watch and Share Mobile Gameplay Videos With Kamcord Posted by Jennifer Allen on July 25th, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »

Price Scanner via MacPrices.net

iMacs on sale for $150 off MSRP, $250 off for...
Best Buy has iMacs on sale for up to $160 off MSRP for a limited time. Choose free home shipping or free instant local store pickup (if available). Prices are valid for online orders only, in-store... Read more
Mac minis on sale for $100 off MSRP, starting...
Best Buy has Mac minis on sale for $100 off MSRP. Choose free shipping or free instant local store pickup. Prices are for online orders only, in-store prices may vary: 2.5GHz Mac mini: $499.99 2.3GHz... Read more
Global Tablet Market Grows 11% in Q2/14 Notwi...
Worldwide tablet sales grew 11.0 percent year over year in the second quarter of 2014, with shipments reaching 49.3 million units according to preliminary data from the International Data Corporation... Read more
New iPhone 6 Models to Have Staggered Release...
Digitimes’ Cage Chao and Steve Shen report that according to unnamed sources in Apple’s upstream iPhone supply chain, the new 5.5-inch iPhone will be released several months later than the new 4.7-... Read more
New iOS App Helps People Feel Good About thei...
Mobile shoppers looking for big savings at their favorite stores can turn to the Goodshop app, a new iOS app with the latest coupons and deals at more than 5,000 online stores. In addition to being a... Read more
Save on 5th generation refurbished iPod touch...
The Apple Store has Apple Certified Refurbished 5th generation iPod touches available starting at $149. Apple’s one-year warranty is included with each model, and shipping is free. Many, but not all... Read more
What Should Apple’s Next MacBook Priority Be;...
Stabley Times’ Phil Moore says that after expanding its iMac lineup with a new low end model, Apple’s next Mac hardware decision will be how it wants to approach expanding its MacBook lineup as well... Read more
ArtRage For iPhone Painting App Free During C...
ArtRage for iPhone is currently being offered for free (regularly $1.99) during Comic-Con San Diego #SDCC, July 24-27, in celebration of the upcoming ArtRage 4.5 and other 64-bit versions of the... Read more
With The Apple/IBM Alliance, Is The iPad Now...
Almost since the iPad was rolled out in 2010, and especially after Apple made a 128 GB storage configuration available in 2012, there’s been debate over whether the iPad is a serious tool for... Read more
MacBook Airs on sale starting at $799, free s...
B&H Photo has the new 2014 MacBook Airs on sale for up to $100 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Sr. Project Manager for *Apple* Campus 2 -...
…the design and construction of one building or building components of the New Apple Campus located in Cupertino, CA. They will provide project management oversight for Read more
WW Sales Program Manager, *Apple* Online St...
**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* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.