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
$524.94
Apple Inc.
+5.93
MSFT
$40.01
Microsoft Corpora
-0.39
GOOG
$536.10
Google Inc.
-20.44

MacTech Search:
Community Search:

Software Updates via MacUpdate

Tweetbot 1.5.1 - Popular iOS twitter cli...
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Mac DVDRipper Pro 4.1.7 - Copy, backup,...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more
PDFpenPro 6.2 - Advanced PDF toolkit for...
PDFpenPro allows users to edit PDF's easily. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Create... Read more
PDFpen 6.2 - Edit and annotate PDFs with...
PDFpen allows users to easily edit PDF's. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Features... Read more
Monolingual 1.5.9 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. It requires a 64-bit capable Intel-based Mac and at least... Read more
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
Starcraft II: Wings of Liberty 1.1.1.180...
Download the patch by launching the Starcraft II game and downloading it through the Battle.net connection within the app. Starcraft II: Wings of Liberty is a strategy game played in real-time. You... Read more
Sibelius 7.5.0 - Music notation solution...
Sibelius is the world's best-selling music notation software for Mac. It is as intuitive to use as a pen, yet so powerful that it does most things in less than the blink of an eye. The demo includes... Read more
Typinator 5.9 - Speedy and reliable text...
Typinator turbo-charges your typing productivity. Type a little. Typinator does the rest. We've all faced projects that require repetitive typing tasks. With Typinator, you can store commonly used... Read more
MYStuff Pro 2.0.16 - Create inventories...
MYStuff Pro is the most flexible way to create detail-rich inventories for your home or small business. Add items to MYStuff by dragging and dropping existing information, uploading new images, or... Read more

Latest Forum Discussions

See All

Have a Special Dead Trigger 2 Easter Bas...
Have a Special Dead Trigger 2 Easter Basket Full of Goodies, Courtesy of Madfinger Games Posted by Rob Rich on April 18th, 2014 [ permalink ] Dead Trigger 2 | Read more »
Zynga Launches Brand New Farmville Exper...
Zynga Launches Brand New Farmville Experience with Farmville 2: Country Escape Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
David. Review
David. Review By Cata Modorcea on April 18th, 2014 Our Rating: :: MINIMALISTIC IN A DIFFERENT WAYUniversal App - Designed for iPhone and iPad David is a minimalistic game wrapped inside of a soothing atmosphere in which the hero... | Read more »
Eyefi Unveils New Eyefi Cloud Service Th...
Eyefi Unveils New Eyefi Cloud Service That Allows Users to Share Media Across Personal Devices Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
Tales from the Dragon Mountain: The Lair...
Tales from the Dragon Mountain: The Lair Review By Jennifer Allen on April 18th, 2014 Our Rating: :: STEADY ADVENTURINGiPad Only App - Designed for the iPad Treading a safe path, Tales from the Dragon Mountain: The Lair is a... | Read more »
Yahoo Updates Flickr App with Advanced E...
Yahoo Updates Flickr App with Advanced Editing Features and More Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
My Incredible Body - A Kid's App to...
My Incredible Body - A Kid's App to Learn about the Human Body 1.1.00 Device: iOS Universal Category: Education Price: $2.99, Version: 1.1.00 (iTunes) Description: Wouldn’t it be cool to look inside yourself and see what was going on... | Read more »
Trials Frontier Review
Trials Frontier Review By Carter Dotson on April 18th, 2014 Our Rating: :: A ROUGH LANDINGUniversal App - Designed for iPhone and iPad Trials Frontier finally brings the famed stunt racing franchise to mobile, but how much does its... | Read more »
Evernote Business Notebook by Moleskin I...
Evernote Business Notebook by Moleskin Introduced – Support Available in Evernote for iOS Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
Sparkle Unleashed Review
Sparkle Unleashed Review By Jennifer Allen on April 18th, 2014 Our Rating: :: CLASSY MARBLE FLINGINGUniversal App - Designed for iPhone and iPad It’s a concept we’ve seen before, but Sparkle Unleashed is a solidly enjoyable orb... | Read more »

Price Scanner via MacPrices.net

iMacs on sale for up to $160 off MSRP this we...
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
iPad Airs on sale this weekend for up to $100...
Best Buy has WiFi iPad Airs on sale for $50 off MSRP and WiFi + Cellular iPad Airs on sale for $100 off MSRP on their online store for a limited time, with prices now starting at $449. Choose free... Read more
Apple restocks refurbished Mac minis starting...
The Apple Store has restocked Apple Certified Refurbished Mac minis for up to $150 off the cost of new models. Apple’s one-year warranty is included with each mini, and shipping is free: - 2.5GHz Mac... Read more
Hyundai Brings Apple CarPlay To The 2015 Sona...
Hyundai Motor America has announced it will bring Apple CarPlay functionality to the 2015 Sonata. CarPlay is pitched as a smarter, safer and easier way to use iPhone in the car and gives iPhone users... Read more
Updated iPads Coming Sooner Than We Had Thoug...
MacRumors, cites KGI securities analyst Ming Chi Kuo, well-respected as an Apple product prognisticator, saying that Apple will introduce an upgraded iPad Air and iPad mini in 2014/Q3, meaning the... Read more
Toshiba Unveils New High And Low End Laptop M...
Toshiba has announced new laptop models covering both the high-end and low-end of the notebook computer spectrum. Toshiba 4K Ultra HD Laptop Toshiba’s new Satellite P55t features one of the world’s... Read more
Save up to $270 with Apple refurbished 13-inc...
The Apple Store has Apple Certified Refurbished October 2013 13″ Retina MacBook Pros available starting at $1099, with models up to $270 off MSRP. Apple’s one-year warranty is standard, and shipping... Read more
Apple now offering refurbished iPad mini with...
The Apple Store has Certified Refurbished 2nd generation iPad minis with Retina Displays now available starting at $339. Apple’s one-year warranty is included with each model, and shipping is free.... Read more
Microsoft Blinks – Drops Microsoft Office 365...
Microsoft has dropped the annual subscription fee for Microsoft Office 365 Personal – which is needed in order to create and edit documents in Microsoft Office for iPad. However, Apple’s iOS and OS X... Read more
New AVG Vault Apps for iOS and Android Help K...
AVG Technologies N.V. an online security company for 177 million active users, has announced the launch of its latest mobile application, AVG Vault. The free app introduces an innovative user... Read more

Jobs Board

*Apple* Automotive Parts Department position...
Apple Automotive is one of the fastest growing dealer…and it shows. Consider making the switch to the Apple Automotive Group today! At Apple Automotive, we 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
*Apple* Retail - Manager - Holyoke - Apple I...
Job Summary Keeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you’re a master of them all. In the store’s fast-paced, Read more
*Apple* Retail - Manager - Apple (United Sta...
Job SummaryKeeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you're a master of them all. In the store's fast-paced, dynamic 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.