TweetFollow Us on Twitter

OD Contain Yourself
Volume Number:12
Issue Number:1
Column Tag:New Apple Technology

OpenDoc: Contain Yourself ...

Updating applications to work with OpenDoc

By Eric Soldan, Apple Developer Technical Support

It’s time to be an OpenDoc™ container application. It’s not too soon, and it’s not too late. So how do you decide if your application should be an OpenDoc container application or not? Here’s an easy test:

• Will your application benefit from Internet access?

If the answer is yes, then being an OpenDoc container application is probably the right thing to do. By becoming an OpenDoc container application, you automatically get the benefits of everything that is OpenDoc, including CyberDog, which will provide component oriented Internet clients and other Internet services. Now is not the time to ignore the Internet bandwagon. It’s worth jumping on. The only question remaining is how to jump. Do you learn Open Transport and MacTCP and recode your entire application to support the Internet? Or do you look for alternatives, like OpenDoc?

A logical question therefore would be: “Is OpenDoc really the fastest way to add Internet to your application?” Adding Internet support with OpenDoc boils down to adding basic OpenDoc support; in this article we will evaluate the difficulty of adding OpenDoc to an existing application. Then you can decide.

The Container Application Library: Your Friend.

CALib, the Container Application Library, has been evolving for a while. It’s looking really good right now. Joshua Susser, of OpenDoc engineering, and I have been adding CALib support to an application I originally developed in Developer Tech Support called DTS.Draw. I wrote DTS.Draw years ago, without ever considering the possibility of adding something like OpenDoc later. DTS.Draw’s document model, while flexible, is a closed model, so adding OpenDoc support is therefore a very interesting test case for CALib.

It turns out that the amount of additional coding necessary is minimal. However, due to CALib’s flexibility, there were many development issues that had to be discussed for quite a while. If these discussions were not held, the implementation would not have been as robust. I will present what we’ve learned from these discussions.

First, let’s talk about DTS.Draw for a while. When adding OpenDoc, it’s important to understand how the existing application works. Since you are probably not familiar with DTS.Draw, I’ll give you a quick overview.

DTS.Draw is an AppsToGo framework based application. AppsToGo is an object-oriented C framework written by DTS. DTS.Draw is also all C code. DTS.Draw is a “standard” drawing application. It has a tool palette of a variety of drawing objects. It has a hierarchical document architecture which allows for grouping and ungrouping of draw objects. It supports infinite undo. It supports drag and drop.

When a document is saved, the object hierarchy is flattened and streamed to the file. When a drag-out occurs, the selected objects are streamed into a handle; this stream represents a sub-hierarchy of the document. This sub-hierarchy is then just a flavor for the clippings file. When a file is opened (or a drag-in occurs), the hierarchy is reconstructed. Very standard stuff.

Here’s a diagram of a representative DTS.Draw document:

For a save, the objects in the hierarchy are streamed in simple tree-walk order, as indicated by the numbering. The drag objects 2, 4, 5, and 6 can be any supported object. The current implementation of DTS.Draw allows for line, rect, round rect, oval, and pie objects. More can be added of course, and this exactly is how we added OpenDoc support to DTS.Draw; we just added a new OpenDoc Part object into the application. The difference with this object is that the content isn’t anything specifically manipulated by DTS.Draw. It is simply a part the user adds to the document. The DTS.Draw object just serves as a “container” for the OpenDoc part. If a user were to add two OpenDoc parts to the above DTS.Draw document, the document hierarchy might end up looking something like:

The implementation in DTS.Draw is relatively simple. The Part object inherits from DTS.Draw’s native rect object. The difference is that it has a much more complex content that the rect object in the standard DTS.Draw application. The content of the Part object can be any OpenDoc part, of course. The content of the Part object is managed using CALib. Given this information, look at this diagram and see exactly what the relationship between the Part objects and CALib :

As shown above, there’s a lot more to the DTS.Draw document now. Fortunately, most of the new stuff is managed by CALib and OpenDoc. CALib uses a “proxy part” to contain the parts that are placed into the document content. Normally, OpenDoc expects there to be a root part that is an OpenDoc container, but since other parts are “embedded” into your application’s non-OpenDoc document, a proxy container part is created and the “embedded” parts are stored in there. The proxy part, as far as OpenDoc is concerned, is what actually contains the other parts that are referenced from the DTS.Draw native content.

The difficulty here is that the proxy part isn’t “real.” It has no geometry information, and OpenDoc doesn’t automatically bind the proxy part to any code, as is the normal case with OpenDoc parts. Thus, OpenDoc is unable to offer the full range of services for the embedded parts. But this is okay. The proxy part isn’t all that smart, nor should it be. It is simply a part that is used by CALib to have somewhere to put the other parts.

So it’s up to DTS.Draw to control the layout and presentation for the OpenDoc parts. Only the application knows the geometry information for the embedded parts, which is stored in DTS.Draw Part objects. The DTS.Draw Part object also has a persistent reference to the corresponding object embedded in the proxy part. Fortunately, CALib offers API calls to help manage these and other OpenDoc interactions, so the above and other OpenDoc related tasks are relatively simple to implement.

For example, to perform screen updates and such, DTS.Draw simply tells CALib to tell the part to draw itself. All that is needed is the Part Ref value, which indicates to CALib which embedded part to draw. The application doesn’t have to care what it references. It references something, and that thing knows how to draw itself.

Streaming Your Objects

Given that the proxy part can’t really deal with containing parts by itself, (i.e., without your application doing the geometry), the proxy part and its embedded parts do not constitute a valid OpenDoc document. This is important when we decide what type of document you want to create when you save it to disk.

The choices are:

1. A Bento stream placed inside your document.

2. Your document stream placed inside a Bento document.

The right choice will of course depend on your application. For DTS.Draw, we chose 1. Choice 1 is closer to existing Macintosh applications. Choice 2 is closer to regular OpenDoc parts. If you were to consider the development choices, from application to OpenDoc part, with CALib applications somewhere in between, your choices look something like this:

Application:

Standard document architecture.

CALib-friendly application:

Standard document architecture with embedded Bento stream.

CALib-savvy application:

Bento document with application data streamed into an OpenDoc storage unit
value.

OpenDoc part editor:

Bento document with part editor data residing in an OpenDoc storage unit.

When considering drag and drop, the above categories are very important. When applications drag something to the desktop, a clippings file is created. When OpenDoc parts are dragged to the desktop, an OpenDoc document is created, instead of a clippings file. This is an important distinction between applications and OpenDoc. Applications create clippings files because they are a standard and flexible intermediate format. OpenDoc parts create OpenDoc documents on a drag-out because an OpenDoc document is already a universal format. There’s no reason to resort to creating a clippings file.

If you are a CALib application, the choice is no longer so clear. Our suggestion is to base your drag-out decision on whether your document format is still “native,” or if you use a Bento file with your native content embedded.

So, if you are a CALib application, what is one to do on a drag-out? The answer lies in the document type. If the document type is an OpenDoc document (CALib-savvy), then the drag-out type is OpenDoc document. If the document type is a standard document (CALib-friendly), then the drag-out type is a clippings file.

DTS.Draw’s native content is simply streamed out. After adding CALib support, this is still the case. The Bento document is streamed out, as well. Here’s the new document format:

Byte offset Description

0 to 3: length of Bento stream

4 to nativeContent - 1: Bento stream

nativeContent to EOF: native content stream, i.e.,
DTS.Draw old format

There was much discussion as to whether or not the Bento stream should be at the front of the file or the end. It turns out that you can do some interesting things if it is at the front of the file. Try out this situation:

1. Your machine has CALib. You add some OpenDoc parts to your DTS.Draw document.

2. You then send the document to some poor individual who doesn’t have CALib or OpenDoc.

Guess what? If the Bento stream is in the front of the file, the unfortunate individual can still use the file with your CALib-friendly application. The user without CALib can actually edit the native content and save it out. The native content changes size, but hey, it’s on the end of the file.

On machines that don’t have CALib but need to display Part objects in their content, the standard look for “NoPart” should be used. This is what OpenDoc displays when an editor for a particular part isn’t available. In the case of CALib applications, it works for when CALib isn’t available, as well.

Making your CALib-based documents work on machines with or without CALib takes a bit of extra coding, but from a version control standpoint, it is well worth it. Documents can go anywhere. A CALib document can be given to someone without CALib. That this person can actually edit the native content of the document, and then give the document back to you, is pretty nifty.

On machines where CALib isn’t available, users obviously won’t be able to add any new parts to the document. They will be restricted to editing the native content. However, this may include moving part objects around that someone else was nice enough to put in the document. This works. Remember that the geometry information is stored in the native objects, which all users can edit. The proxy part doesn’t handle the geometry. In addition, the user can delete the Part objects (which are displayed using the “No Part” look). This of course means that there is data orphaned in the Bento stream. (Since the user doesn’t have CALib, there is no way their machine can modify the Bento stream.) Fortunately, the stream will be compacted the next time the document is saved on a machine with CALib.

With some extra work, you can even allow the user to resize the Part objects without CALib. When this occurs, the information in the Bento stream for that part is no longer up to date. The native content object will need to be flagged as having been resized. When the document is opened on a machine with CALib, these objects will need to have their frame information renegotiated and resolved to reflect their new size.

We’ve been discussing types of editing that can still occur to a CALib document Part object when CALib isn’t available. There are, of course, edits that can’t be performed. Here are two:

1. Dragging that includes a Part object. Streaming the drag data must include streaming the Bento information into the flavor. This can’t be done without CALib. All that’s in the native object is a persistent reference to somewhere inside the Bento stream. You can’t resolve the reference without CALib.

2. Copying the object. At first, it would seem that you would just copy the native content object. It has a persistent reference. Both copies of the object would then point to the same Bento information, i.e., the part. This is a bad thing. When opened again on a CALib machine, each copy of the part should be independent of the other. (You could flag the copy as an unresolved copy, and then clone the object when the document is next opened on a CALib machine.)

As you can see from this discussion, CALib can be used to add OpenDoc capability to your existing applications without radically changing the way they work. The actual amount of code added to an application isn’t all that bad, either. Of course, this will vary, depending on architecture and document content, but most likely, it’s not a complete recode with major modifications throughout your application. Look for the latest CALib and CASample sample code on the OpenDoc DR4 release.

Have fun out there!

 
AAPL
$102.13
Apple Inc.
+1.24
MSFT
$44.87
Microsoft Corpora
-0.14
GOOG
$571.00
Google Inc.
-6.86

MacTech Search:
Community Search:

Software Updates via MacUpdate

Viber 4.2.2 - Send messages and make cal...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device,... Read more
Cocktail 7.6 - General maintenance and o...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
LaunchBar 6.1 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... 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
BBEdit 10.5.12 - Powerful text and HTML...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
Microsoft Office 2011 14.4.4 - Popular p...
Microsoft Office 2011 helps you create professional documents and presentations. And since Office for Mac 2011 is compatible with Office for Windows, you can work on documents with virtually anyone... Read more
TextWrangler 4.5.10 - Free general purpo...
TextWrangler is the powerful general purpose text editor, and Unix and server administrator's tool. Oh, and also, like the best things in life, it's free. TextWrangler is the "little brother" to... Read more
BitTorrent Sync 1.4.72 - Sync files secu...
BitTorrent Sync allows you to sync unlimited files between your own devices, or share a folder with friends and family to automatically sync anything. File transfers are encrypted. Your information... Read more
Cyberduck 4.5.2 - FTP and SFTP browser....
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
Tinderbox 6.0.3 - Store and organize you...
Tinderbox is a personal content management assistant. It stores your notes, ideas, and plans. It can help you organize and understand them. And Tinderbox helps you share ideas through Web journals... Read more

Latest Forum Discussions

See All

Almightree: The Last Dreamer (Games)
Almightree: The Last Dreamer 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The world is shattering and you are the only hope to restore the balance. A thrilling and challenging 3D puzzle... | Read more »
Mobile Convolution (Music)
Mobile Convolution 1.0.0 Device: iOS Universal Category: Music Price: $9.99, Version: 1.0.0 (iTunes) Description: | Read more »
Invaders! From Outer Space Review
Invaders! From Outer Space Review By Rob Thomas on August 27th, 2014 Our Rating: :: RETRO NOSTALGIAUniversal App - Designed for iPhone and iPad It’s a shame that Invaders! doesn’t offer deeper gameplay, as this retro-inspired... | Read more »
Spooklands Review
Spooklands Review By Jennifer Allen on August 27th, 2014 Our Rating: :: ONE-TOUCH SHOOTERUniversal App - Designed for iPhone and iPad One-touch simultaneously controls your direction and your weapon in this unique arena shooter.   | Read more »
Heroes of Order & Chaos Add Twitch I...
Heroes of Order & Chaos Add Twitch Integration, New Heroes, and More Posted by Ellis Spice on August 27th, 2014 [ permalink ] | Read more »
Foodie Yama Review
Foodie Yama Review By Jennifer Allen on August 27th, 2014 Our Rating: :: BRIEFLY HOOKSUniversal App - Designed for iPhone and iPad Foodie Yama will draw you in for a brief while, and you’ll never be entirely sure why.   | Read more »
Spotify Connect Turns One, Now Supports...
Spotify Connect Turns One, Now Supports New Devices Posted by Ellis Spice on August 27th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
The Rise of PicsaStock and How You Can M...
We all take plenty of photos, right? That’s the joy of having a reasonably powerful camera in your pocket, thanks to your trusty iPhone and a bevy of similarly useful apps. Wouldn’t it be great to make some money out of those snaps? While your... | Read more »
Appointment With F.E.A.R Review
Appointment With F.E.A.R Review By Jennifer Allen on August 27th, 2014 Our Rating: :: CAMP DELIGHTUniversal App - Designed for iPhone and iPad Ever wanted to be a superhero? Appointment With F.E.A.R is a fine way to live that dream... | Read more »
Indie MOBA ÆRENA’s 2.0 Summer Update Bri...
Indie MOBA ÆRENA’s 2.0 Summer Update Brings New Missions, Skins, and a Champion Posted by Jessica Fisher on August 27th, 2014 [ permalink | Read more »

Price Scanner via MacPrices.net

The iPad’s Real Competitive Challenger (Not S...
It’s been my contention for some time that the iPad is suffering from something of an identity crisis, and I suspect that may be a factor in slackening sales this year. Apple can’t seem to decide... Read more
13-inch 2.6GHz/256GB Retina MacBook Pro on sa...
B&H Photo has the 13″ 2.6GHz/256GB Retina MacBook Pro on sale for $1379 including free shipping plus NY sales tax only. Their price is $120 off MSRP. Read more
Life Inventory iOS Apps – Learn to Know Thyse...
James Hollender’s Life Inventory apps s are now on sale with 20% off thru Labor Day, 09/01/2014. This is a great opportunity to get started on that Moral Inventory you’ve been putting off doing for... Read more
Pocket Watch, LLC. Reveals Cloud Server For P...
Beaumont, Texas based Pocket Watch, LLC. has announced the availability of its new ActivePrint Cloud Server Powered by Raspberry Pi. With this small standalone box almost any USB printer or available... Read more
902it Simplifies Area Code Changes For Nova S...
The east coast Canadian provinces of Nova Scotia and Prince Edward Island are phasing in 10 digit telephone dialing, to be fully in place by November, in order to accommodate a second area code to... Read more
Boomerang iPad Stand Mounts Your iPad Anywher...
Boomerang, a Mountable Stand with Multiple Viewing Angles, is now available for iPad Air. Boomerang combines several functions that aim to expand your iPad’s potential in one, elegant product. The... Read more
Retina MacBook Pros available starting at $10...
The Apple Store has Apple Certified Refurbished 13″ and 15″ MacBook Pros available starting at $929. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.5GHz MacBook Pros (4GB RAM/... Read more
Apple 27-inch Thunderbolt Display (refurbishe...
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
Apple offers free $25 iTunes gift card with p...
The Apple Store is offering a free $25 iTunes Gift Card with the purchase of a $99 Apple TV for a limited time. Shipping is free. Read more
Apple’s 2014 Back to School promotion: $100 g...
 Apple’s 2014 Back to School promotion includes a free $100 App Store Gift Card with the purchase of any new Mac (Mac mini excluded), or a $50 Gift Card with the purchase of an iPad or iPhone,... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, 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
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
Position Opening at *Apple* - Apple (United...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.