TweetFollow Us on Twitter

November 93 - TDialogBehaviors

TDialogBehaviors

Bob Hablutzel

This article is the first article in what I hope will be a regular series of technical questions and answers on object oriented programming. The intent of this column is to go beyond simple answers. I intend to take a question, answer it, and then use that question as a springboard to a more general discussion on programming. I hope you find the results interesting.

The first articles will be culled from frequently asked questions on MacApp3Tech$, but I need your questions! I can be reached electronically at AppleLink: B.HABLUTZEL; by telephone at 708.328.0130; or by post at Bob Hablutzel, Hablutzel Consulting, 606 Asbury, Evanston, IL, USA 60202.

Q: I need to create a modal dialog using MacApp 3.0. I create the dialog using ViewEdit, but when I attempt to pose the dialog it opens briefly and immediately closes. How can I create a modal dialog?

A: Modal dialogs in MacApp 3.0 are handled with a TDialogBehavior, which is attached to the dialog window. This behavior is responsible for receiving and handling keystrokes, looking for keystrokes that dismiss the dialog, and sending events off to the appropriate control.

The problem with ViewEdit (in this case) is that it does not attach a TDialogBehavior to the dialog when it is created. When TWindow::PoseModally() is called, the first thing it does is attempt to locate the dialog behavior; if this lookup fails it closes the window and returns immediately (returning kNoIdentifier as the dismisser).

There are a few work-arounds for this. In ViewEdit, you can add a TDialogView to the window. TDialogView is really not required in MacApp 3.0; it is a holdover from the old mechanisms in MacApp 2.0. However, if there is one in the window, it will cause the TDialogBehavior to be added when the window is opened.

Alternatively, you can create the TDialogBehavior yourself, and attach it to the window before the TWindow::PoseModally() method is called. When you create the dialog behavior, you have to supply the identifiers for the default and cancel items (in the call to IDialogBehavior()). Once this behavior is added to the window, TWindow::PoseModally() can be called.

You can also call TWindow::SetModality() before calling TWindow::PoseModally(). This method will create the dialog behavior if none exists. However, this routine may not properly set up the default and cancel identifiers; you would then have to call TWindow::GetDialogBehavior() to retrieve the dialog, and stuff the identifiers into its fCancelItem and fDefaultItem fields.

Even if you do all of this, the dialog will still not dismiss properly unless you change the default event for the dismissing control to mDismiss (==34). So if you use ViewEdit to create the dialog, you need to change the event number for the control by hand. If you leave the control at its default event number (mButton for TButtons), the control will activate, but the dialog will not dismiss.

Finally, the best solution is to avoid using ViewEdit. Either AdLib or IcePick (3.0) will add the dialog behavior to the window when you use them to create the dialog. Using either of these products will ensure that the dialog has the appropriate behavior. These programs will also take care of changing the event number for the dismissing controls to mDismiss for you. (Both these applications are available from MADA).

More About TDialogBehavior

It is somewhat interesting to notice the actual mechanism used to handle the dismissing of the modal dialogs. The TDialogBehavior does not in itself dismiss the dialog, which as we will see in a second has some interesting implications. The TDialogBehavior simply activates the control that is designated as the default (or cancel) item. It does this by sending the control its default event number. The control then accepts the event, reacts appropriately (in the case of a TButton, it flashes), and sends the event up the event chain.

The event eventually reaches the TDialogBehavior attached to the window, which checks the see if the event is mDismiss. Notice that this is the first time that the behavior checks the event type. If the event is mDismiss, the behavior records the identifier of the source of the event in the fDismisser field, and ends the modal posing. TWindow::PoseModally(), which started the modal posing in the first place, retrieves the value of the TDialogBehavior::fDismisser field, and returns that as the result of the modal posing.

What is interesting about all this is that TDialogBehavior does not necessarily have to be used with modal dialogs; it can be used with modeless dialogs just as easily. When the return key is struck, for example, the default item will be invoked. If you attach a behavior to the default control that intercepts that control's default event number, you can quickly and easily create modeless dialogs that contain default (and closing) items.

Take, for example, a drawing application that supports 1° rotations. A modeless dialog could be created that presents the user with the number of degrees of rotation, and a default Rotate button. Every time the user strikes the return key, the Rotate button would be activated. You could attach a behavior to the Rotate button that checks for events where (a) the source of the event is the owner of the behavior, and (b) the event number matches the default event number (fEventNumber) of the owner. When it receives an event that matches this criteria, it would create whatever command was responsible for the rotation of the object, and post it to the application.

The question of where to attach the behavior is an interesting one. The behavior can be attached anywhere in the event chain and still function properly. It is mostly a question of style to decide where the behavior best fits.

For example, if the behavior is attached to the button itself, it will clearly get the event that the button generates. However, if the button does not handle the event, it will pass the event up the event chain; for views this means that the superview will receive the event. This passing along continues through each respective superview until someone handles the event, the TWindow used to draw the dialog will get the event eventually, provided no-one else has handled it.

In the example above, there are two ways of designing the interface. If the TNumberText used to hold the rotation amount is just a generic TNumberText, then it would make sense to have the behavior attached to the dialog. This would allow the dialog access to a child view to retrieve the rotation amount. (If the behavior were attached to the button, it would have to access a sibling view to retrieve the rotation amount; there is nothing actually wrong with this but it forces the dialog to have additional information about its environment, which will limit its overall reusability).

However, if the TNumberText holding the rotation amount where overridden to set a value in the application (fRotationAmount, e.g.) when stopping editing, then the behavior could be attached to the button. In this case, the button would be set to want to become the target of the view. When the user clicks this button, the TNumberText would resign its target, which would cause it to stop editing, which in turn would cause it to update the application value. The button would then be free to post a command using this value.

Finally, we can take this one step further, and change the default event number of the button from mButtonHit to some application defined event (mRotate, e.g. ). We could then attach a behavior to the application that looks for the mRotate event and creates the appropriate command. This would allow us the flexibility of generating the mRotate command in multiple places in our interface, and handling them all identically. (Remember that the dialog we are discussing is modeless; this would not work in a modal dialog as it requires the event number of the default button to be mDismiss).

Once you understand how they function, TDialogBehaviors provide a simple, generic means of handling a common user interface problem. By carefully using them in cooperation with other built-in mechanisms, powerful interfaces can be designed with a minimum of coding. They can be used with modeless as well as modal dialogs, giving you complete freedom in designing your interface.

 
AAPL
$97.03
Apple Inc.
-0.16
MSFT
$44.40
Microsoft Corpora
-0.47
GOOG
$593.35
Google Inc.
-2.63

MacTech Search:
Community Search:

Software Updates via MacUpdate

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
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
Together 3.2 - Store and organize all of...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Smart storage. With simple drag-and-drop functionality,... Read more
Cyberduck 4.5 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more

Latest Forum Discussions

See All

LEX Goes Free For One Day In Honor of Ne...
LEX Goes Free For One Day In Honor of New Update Posted by Jennifer Allen on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Thomas Was Alone Goes Universal, Slashes...
Thomas Was Alone Goes Universal, Slashes Price to $3.99 Posted by Ellis Spice on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Meerkatz Challenge Review
Meerkatz Challenge Review By Jennifer Allen on July 24th, 2014 Our Rating: :: FONDLY PUZZLINGUniversal App - Designed for iPhone and iPad Cute and challenging, Meerkatz Challenge is a fun puzzle game, particularly for fans of... | Read more »
Book Your Appointment with F.E.A.R. this...
Book Your Appointment with F.E.A.R. | Read more »
It Came From Canada: Epic Skater
For all the hate that it gets for being a pastime for slackers, skateboarding really does require a lot of skill. All those flips and spins take real athleticism, and there’s all the jargon to memorize. Fortunately for us less extreme individuals,... | Read more »
Cultures Review
Cultures Review By Jennifer Allen on July 24th, 2014 Our Rating: :: SLOW-PACED EMPIRE BUILDINGiPad Only App - Designed for the iPad Cute it might seem, but Cultures is a bit too slow paced when it comes to those pesky timers to... | Read more »
More Paintings Have Been Added to Paint...
More Paintings Have Been Added to Paint it Back! Posted by Jessica Fisher on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
The Order of Souls Review
The Order of Souls Review By Campbell Bird on July 24th, 2014 Our Rating: :: STORY GRINDUniversal App - Designed for iPhone and iPad The Order of Souls is a free-to-play, turn-based RPG with a genre-mixing art style, interesting... | Read more »
Revolution 60 Review
Revolution 60 Review By Jordan Minor on July 24th, 2014 Our Rating: :: LASS EFFECTUniversal App - Designed for iPhone and iPad Revolution 60 is a bold, cinematic action game with ambition to spare.   | Read more »
Matter (Photography)
Matter 1.0.1 Device: iOS Universal Category: Photography Price: $1.99, Version: 1.0.1 (iTunes) Description: Add stunning 3D effects to your photos with real-time shadows and reflections. Export your creations as photos or video loops... | Read more »

Price Scanner via MacPrices.net

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
Apple 27″ Thunderbolt Display (refurbished) a...
The Apple Store has Apple Certified Refurbished 27″ Thunderbolt Displays available for $799 including free shipping. That’s $200 off the cost of new models. Read more
WaterField Designs Unveils Cycling Ride Pouch...
High end computer case and bag maker WaterField Designs of San Francisco now enters the cycling market with the introduction of the Cycling Ride Pouch – an upscale toolkit with a scratch-free iPhone... Read more
Kingston Digital Ships Large Capacity Near 1T...
Kingston Digital, Inc., the Flash memory affiliate of Kingston Technology Company, Inc.,has announced its latest addition to the SSDNow V300 series, the V310. The Kingston SSDNow V310 solid-state... Read more
Apple’s Fiscal Third Quarter Results; Record...
Apple has announced financial results for its fiscal 2014 third quarter ended June 28, 2014, racking up quarterly revenue of $37.4 billion and quarterly net profit of $7.7 billion, or $1.28 per... Read more
15-inch 2.0GHz MacBook Pro Retina on sale for...
B&H Photo has the 15″ 2.0GHz Retina MacBook Pro on sale for $1829 including free shipping plus NY sales tax only. Their price is $170 off MSRP. B&H will also include free copies of Parallels... Read more

Jobs Board

Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full Read more
Senior Interaction Designer, *Apple* Online...
**Job Summary** Apple is looking for a hands on Senior…will be a key player in designing for the Apple Online Store. The ideal designer will have a Read more
*Apple* Sales Chat Rep - Apple (United State...
…is looking for motivated, outgoing, and tech savvy individuals who want to offer Apple Customers an unparalleled customer experience over chat. At Apple , we believe Read more
Mac Expert - *Apple* Online Store Mexico -...
…MUST be fluent in English and Spanish to be considered for this position At Apple , we believe that hard work, a fun environment, creativity and innovation fuel the Read more
*Apple* Industrial Design CAD Sculptor - App...
**Job Summary** The Apple Industrial Design team is looking for a CAD sculptor/Digital 3D modeler to create high quality CAD models used in the industrial design process Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.