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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Kodi 15.1.rc1 - Powerful media center to...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
Bookends 12.5.8 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Access the power of Bookends directly from Mellel, Nisus Writer Pro, or MS Word (... Read more
Chromium 44.0.2403.125 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 44.0.2403.125: This release contains a number... Read more
iMazing 1.2.2 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Audio Hijack 3.2.0 - Record and enhance...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
FontExplorer X Pro 5.0.1 - Font manageme...
FontExplorer X Pro is optimized for professional use; it's the solution that gives you the power you need to manage all your fonts. Now you can more easily manage, activate and organize your... Read more
Calcbot 1.0.2 - Intelligent calculator a...
Calcbot is an intelligent calculator and unit converter for the rest of us. Featuring an easy-to-read history tape, expression view, intuitive conversion, and much more! Features History Tape -... Read more
MTR 5.0.0.1 - The Mac's oldest and...
MTR (was MacTheRipper)--the Mac's oldest and smartest DVD-backup app--is now updated to version 5.001 MTR -- the complete toolbox, not a one-trick, point-and-click extractor. MTR is intended for... Read more
LibreOffice 4.4.5.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
Adobe Lightroom 6.1.1 - Import, develop,...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more

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

Price Scanner via MacPrices.net

11-inch MacBook Airs on sale for $100 off MSR...
Best Buy has 11-inch MacBook Airs on sale for $100 off MSRP. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary: - 11″ 1.6GHz... Read more
iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
Sale! 13-inch MacBook Pros on sale for $100 o...
B&H Photo has 13″ MacBook Pros on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.5GHz/500GB MacBook Pro: $999.99 save $100 - 13″ 2.7GHz/128GB Retina... Read more
Sale! Save $100 on 13-inch MacBook Airs this...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model.... Read more
Worldwide Tablet Market Decline Continues, Ap...
The worldwide tablet market declined -7.0% year-over-year in the second quarter of 2015 (2Q15) with shipments totaling 44.7 million units according to preliminary data from the International Data... Read more
TP-LINK TL-PA8030P KIT Powerline Featuring Ho...
Consumer and business networking products provider TP-LINK is now shipping its TL-PA8030P KIT AV1200 3-Port Gigabit Passthrough Powerline Starter Kit that expands your home’s network over its... Read more
Apple refurbished iPad Air 2s available for u...
The Apple Store has Apple Certified Refurbished iPad Air 2s available for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: - 128GB... Read more
Updated Apple iPad Price Trackers
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers. Read more
Apple refurbished 2014 13-inch 128GB MacBook...
The Apple Store has Apple Certified Refurbished 2014 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 13″ 1.4GHz/128GB... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more

Jobs Board

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