Home > Articles > Mobile Application Development & Programming

This chapter is from the book

This chapter is from the book

Auto Layout and Frames

With Auto Layout, view frames play a new, less important role. In an Auto Layout world, frames are now the guys in an opera who stands around holding a spear while the constraints and intrinsic content sizes sing their arias. The focus moves from specific sizes and placement to suggestions and relations.

When you worked with Autosizing, frames said where to place views on the screen and how big those views would be. In Auto Layout, constraints determine view size and placement using a geometric element called an alignment rectangle.

As developers create complex views, they may introduce visual ornamentation such as shadows, exterior highlights, reflections, and engraving lines. As they do, these features usually become attached as subviews or sublayers or integrated into a view’s image. As a consequence, a view’s full extent may grow as items are added.

Unlike frames, a view’s alignment rectangle is limited to a core visual element. Its size remains unaffected as new items join the primary view. Consider Figure 1-13 (left). It depicts a view with an attached shadow and a badge. When laying out this view, you want Auto Layout to focus on aligning just the core element.

Figure 1.13

Figure 1-13. A view’s alignment rectangle (center) refers strictly to the core visual element to be aligned, without embellishments.

The center image shows the view’s alignment rectangle. This rectangle excludes all ornamentation, including the drop shadow and badge. It’s the part of the view you want considered when Auto Layout does its work. Contrast this with the rectangle shown in the right image of Figure 1-13. This version includes all the visual ornamentation, extending the view’s frame beyond the area that should be considered for alignment.

This rectangle encompasses all the view’s visual elements. It includes the shadow and badge. These ornaments could potentially throw off a view’s alignment features (for example, its center, bottom, and right) if they were considered during layout.

By working with alignment rectangles instead of frames, Auto Layout ensures that key information, like a view’s edges and center, are properly considered during layout. In Figure 1-14, the adorned view is perfectly aligned on the background grid. Its badge and shadow are not considered during placement.

Figure 1.14

Figure 1-14. Auto Layout only considers this view’s alignment rectangle when laying it out as centered in its parent. The shadow and badge don’t affect its placement.

Visualizing Alignment Rectangles

Both iOS and OS X enable you to overlay views with their alignment rectangles in your running application. You set a simple launch argument from your app’s scheme. This is UIViewShowAlignmentRects for iOS and NSViewShowAlignmentRects for OS X. Set the argument value to YES and make sure to prefix with a dash, as shown in Figure 1-15.

Figure 1.15

Figure 1-15. Set launch arguments in the scheme editor.

When the app runs, rectangles show over each view. The resulting rectangles are light and can be difficult to see.

Image Alignment Insets

Alignment issues affect the way you handle images. Image art often contains hard-coded embellishments, like highlights, shadows, and so forth. These items take up little memory and run more efficiently than those created by adding layer effects. Because of that, many developers use images enhancements in preference to Quartz 2D effects because of their low overhead.

Figure 1-16 demonstrates the typical problem encountered when using image-based ornamentation with Auto Layout. The left image shows a basic image view, whose art I created in Photoshop. I used a standard drop shadow effect. When added to the image view, the 20-point by 20-point area I left for the shadow throws off the view’s alignment rectangle, causing it to appear slightly too high and left.

Figure 1.16

Figure 1-16. Adjust your images to account for alignment when using Auto Layout. At the left, the image view was created with a raw, unadjusted image. It displays slightly too far left and up, which you can inspect by looking at the points where the circle crosses the background grid. I added lines over the screenshot to emphasize where the centering should have occurred. The right screenshot shows the adjusted image view. It centers exactly onto its parent view.

In its default implementation, the image view has no idea that the image contains ornamental elements. You have to tell it how to adjust its intrinsic content so that the alignment rectangle considers just that core material.

To accommodate the shadow, you load and then rebuild the image. This is a two-step process. First, you load the image as you normally would (for example, with imageNamed:). Then, you call imageWithAlignmentRectInsets: on that image to produce a new version supporting the specified insets:

UIImage *image = [[UIImage imageNamed:@"Shadowed.png"]
    imageWithAlignmentRectInsets:UIEdgeInsetsMake(0, 0, 20, 20)];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];

After specifying the alignment rect insets, the updated version now properly aligns, as you see in Figure 1-16, right. I logged out the pertinent details so that you can compare the view details. Here’s what the view frame looks like (it shows the full 200×200 image size), the intrinsic content size built from the image’s alignment insets (180×180), and the resulting alignment rectangle used to center the image view’s frame:

HelloWorld[53122:c07] Frame: {{70, 162}, {200, 200}}
HelloWorld[53122:c07] Intrinsic Content Size: {180, 180}
HelloWorld[53122:c07] Alignment Rect: {{70, 162}, {180, 180}}

Declaring Alignment Rectangles

Cocoa and Cocoa Touch offer a several additional ways to report alignment geometry. You may implement alignmentRectForFrame:, frameForAlignmentRect:, baselineOffsetFromBottom, and alignmentRectInsets. These methods allow your views to declare and translate alignment rectangles from code.

For the most part, thankfully, you can ignore alignment rectangles and insets. Things just, for the most part, work. The edge cases you encounter usually happen when Auto Layout comes into conflict with transforms (and other circumstances when the actual frame doesn’t match the visual frame as with buttons).

A few notes on these items:

  • alignmentRectForFrame: and frameForAlignmentRect: must always be mathematical inverses of each other.
  • Most custom views only need to override alignmentRectInsets to report content location within their frame.
  • baselineOffsetFromBottom is available only for NSView and refers to the distance between the bottom of a view’s alignment rectangle and the view’s content baseline, such as that used for laying out text. This is important when you want to align views to text baselines and not to the lowest point reached by typography descenders, like j and q.

Here’s some information about alignmentRectForFrame:and frameForAlignmentRect: from the UIView.h documentation:

  • These two methods should be inverses of each other. UIKit will call both as part of layout computation. They may be overridden to provide arbitrary transforms between frame and alignment rect, though the two methods must be inverses of each other. However, the default implementation uses alignmentRectInsets, so just override that if it’s applicable. It’s easier to get right.
  • A view that displayed an image with some ornament would typically override these, because the ornamental part of an image would scale up with the size of the frame. Set the NSUserDefault UIViewShowAlignmentRects to YES to see alignment rects drawn.

NSLayoutConstraint.h on OS X adds the following comment:

  • If you do override these be sure to account for the top of your frame being either minY or maxY depending on the superview’s flippedness.

You’ll see this flippedness adjustment made in Listing 1-1, which is introduced in the next section.

Implementing Alignment Rectangles

Listing 1-1 offers a trivial example of code-based alignment geometry. This OS X app builds a fixed-size view and draws a shadowed rounded rectangle into it. When USE_ALIGNMENT_RECTS is set to 1, its alignmentRectForFrame: and frameForAlignmentRect: methods convert to and from frames and alignment rects. As Figure 1-17 shows, these reporting methods allow the view to display with proper alignment.

Figure 1.17

Figure 1-17. Implementing intrinsic content size and frame/alignment rect conversion methods ensures that your view will align and display correctly (left) rather than be misaligned and clipped (right).

Listing 1-1. Using Code-Based Alignment Frames

@interface CustomView : NSView

@implementation CustomView
- (void) drawRect:(NSRect)dirtyRect
    NSBezierPath *path;

    // Calculate offset from frame for 170x170 art
    CGFloat dx = (self.frame.size.width - 170) / 2.0f;
    CGFloat dy = (self.frame.size.height - 170);

    // Draw a shadow
    NSRect rect = NSMakeRect(8 + dx, -8 + dy, 160, 160);
    path = [NSBezierPath
        bezierPathWithRoundedRect:rect xRadius:32 yRadius:32];
    [[[NSColor blackColor] colorWithAlphaComponent:0.3f] set];
    [path fill];

    // Draw fixed-size shape with outline
    rect.origin = CGPointMake(dx, dy);
    path = [NSBezierPath
        bezierPathWithRoundedRect:rect xRadius:32 yRadius:32];
    [[NSColor blackColor] set];
    path.lineWidth = 6;
    [path stroke];
    [ORANGE_COLOR set];
    [path fill];

- (NSSize)intrinsicContentSize
    // Fixed content size - base + frame
    return NSMakeSize(170, 170);

- (NSRect)frameForAlignmentRect:(NSRect)alignmentRect
    // 1 + 10 / 160 = 1.0625
    NSRect rect = (NSRect){.origin = alignmentRect.origin};
    rect.size.width = alignmentRect.size.width * 1.06250;
    rect.size.height = alignmentRect.size.height * 1.06250;
    return rect;

- (NSRect)alignmentRectForFrame:(NSRect)frame
    // 160 / 170 = 0.94117
    // Account for vertical flippage
    CGFloat dy = (frame.size.height - 170) / 2.0;
    rect.origin = CGPointMake(frame.origin.x, frame.origin.y + dy);

    rect.size.width = frame.size.width * 0.94117;
    rect.size.height = frame.size.height * 0.94117;
    return rect;

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020