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
$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

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
TurboTax 2013.r17.002 - Manage your 2013...
TurboTax guides you through your tax return step by step, does all the calculations, and checks your return for errors and overlooked deductions. It lets you file your return electronically to get... Read more

Latest Forum Discussions

See All

Livescribe 3 Smartpen Review
Made by: Livescribe Price: $149.99 for Livescribe 3 Hardware/iOS Integration Rating: 4.5 out of 5 stars Usability Rating: 4 out of 5 stars Reuse Value Rating: 4.75 out of 5 stars Build Quality Rating: 4.5 out of 5 stars Overall Rating: 4.44 out of... | Read more »
Unpossible Review
Unpossible Review By Carter Dotson on April 17th, 2014 Our Rating: :: RALPH WIGGUM APPROVESUniversal App - Designed for iPhone and iPad Unpossible is much better than its English!   | Read more »
Hitman GO Review
Hitman GO Review By Carter Dotson on April 17th, 2014 Our Rating: :: GO HITMAN, GO!Universal App - Designed for iPhone and iPad Hitman GO is not the obvious way to do a mobile version of the Hitman series, but it’s an incredibly... | Read more »
Monster High Ghouls and Jewels is a Frea...
Monster High Ghouls and Jewels is a Freaky Fashion-Forward Match-3 Puzzler Posted by Rob Rich on April 17th, 2014 [ permalink ] | Read more »
Dinosaur Train A to Z Review
Dinosaur Train A to Z Review By Amy Solomon on April 17th, 2014 Our Rating: :: DINO DETAILSUniversal App - Designed for iPhone and iPad Dinosaur Train A to Z is an educational app about dinosaurs that includes In-App Purchases... | Read more »
Easter Comes to Junk Jack X – Bringing N...
Easter Comes to Junk Jack X – Bringing New Crafts, Chemistry, and More Posted by Rob Rich on April 17th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Call of Cookie Review
Call of Cookie Review By Jordan Minor on April 17th, 2014 Our Rating: :: COOKIE CRUMBLESUniversal App - Designed for iPhone and iPad Call of Cookie proves that plants aren’t the only fighting foods out there.   | Read more »
Corel Launches Video Editing App Pinnacl...
Corel Launches Video Editing App Pinnacle Studio for iPhone, Updates iPad Version for iOS 7 Posted by Tre Lawrence on April 17th, 2014 [ | Read more »
Bad Vamp Review
Bad Vamp Review By Jennifer Allen on April 17th, 2014 Our Rating: :: BASIC VAMPIRIC ADVENTURESUniversal App - Designed for iPhone and iPad Run or destroy the vampires in this simple, single-screen game that lacks real bite.   | Read more »
The Shadow Sun gets a New Update, Goes o...
The Shadow Sun gets a New Update, Goes on Sale for the First Time Since its Release Posted by Tre Lawrence on April 17th, 2014 [ permalink ] | Read more »

Price Scanner via MacPrices.net

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
Free Local Carrot iPhone App Helps Find Fresh...
I love fresh vegetables. I’m not a vegan, although I was for several years in the 1980s, but fresh vegetables and other whole foods are still my dietary mainstays as a matter of taste rather than... Read more
CarSO Pro – Car Service and Finance Manager/O...
Lviv, Ukraine-based BM-Studios’ CarSO Pro is a tool to manage operations concerning your car. Never forget to change the oil or prolong the insurance for your car. Remember when you’ve done the car... 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* 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
*Apple* Retail - Market Leader - Cincinnati...
…challenges of developing individuals, building teams, and affecting growth across Apple Stores. You demonstrate successful leadership ability - focusing on excellence Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.