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
$103.30
Apple Inc.
+0.80
MSFT
$45.09
Microsoft Corpora
-0.34
GOOG
$577.33
Google Inc.
+5.73

MacTech Search:
Community Search:

Software Updates via MacUpdate

TextSoap 7.4.0 - Flexible text editing u...
TextSoap is for people who work with text. TextSoap effortlessly cleans up text from endlessly different formats. Wash away unwanted characters, spaces, tabs. Fix paragraphs with hard returns at the... Read more
NetShade 6.0.2 - Browse privately using...
NetShade is an Internet security tool that conceals your IP address on the web. NetShade routes your Web connection through either a public anonymous proxy server, or one of NetShade's own dedicated... Read more
Mac DVDRipper Pro 5.0 - Copy, backup, an...
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
pwSafe 3.1 - Secure password management...
pwSafe provides simple and secure password management across devices and computers. pwSafe uses iCloud to keep your password databases backed-up and synced between Macs and iOS devices. It is... Read more
StatsBar 1.8 - Monitor system processes...
StatsBar gives you a comprehensive and detailed analysis of the following areas of your Mac: CPU usage Memory usage Disk usage Network and bandwidth usage Battery power and health (MacBooks only)... Read more
Path Finder 6.5.5 - Powerful, award-winn...
Path Finder is a file browser that combines the familiar Finder interface with the powerful utilities and innovative features. Just a small selection of the Path Finder 6 feature set: Dual pane... Read more
QuarkXPress 10.2.1 - Desktop publishing...
With QuarkXPress, you can communicate in all the ways you need to -- and always look professional -- in print and digital media, all in a single tool. Features include: Easy to Use -- QuarkXPress is... Read more
Skype 6.19.0.450 - Voice-over-internet p...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
VueScan 9.4.41 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Cloud 3.0.0 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more

Latest Forum Discussions

See All

Modern Combat 5 Gets a Major Multiplayer...
Modern Combat 5 Gets a Major Multiplayer Update Posted by Jessica Fisher on September 2nd, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Alien Creeps TD Review
Alien Creeps TD Review By Jennifer Allen on September 2nd, 2014 Our Rating: :: EXPENSIVE DEFENSESUniversal App - Designed for iPhone and iPad Alien Creeps TD would be a fun if unremarkable Tower Defense game, but its heavy focus on... | Read more »
The Journey Down: Chapter Two Review
The Journey Down: Chapter Two Review By Jennifer Allen on September 2nd, 2014 Our Rating: :: DARK YET ENTICINGUniversal App - Designed for iPhone and iPad It’s a little dark, in every sense of the word, but The Journey Down:... | Read more »
Function Space, a Social Network App for...
Function Space, a Social Network App for Science, Launches on iOS Posted by Ellis Spice on September 2nd, 2014 [ permalink ] | Read more »
Stupidfast – How Taylor Martinez Switche...
How do you make an Endless Running game more than just another Endless Running game? By adding real life prizes to it, of course! That’s the thinking behind StupidFast: a game designed for football enthusiasts, and the brainchild of former college... | Read more »
Little Raiders: Robin’s Revenge Review
Little Raiders: Robin’s Revenge Review By Jennifer Allen on September 2nd, 2014 Our Rating: :: CASUAL RAIDINGUniversal App - Designed for iPhone and iPad Combining simple combat with village building is a potent combination for... | Read more »
Treasure Tombs: Ra Deal Coming from Bulk...
Treasure Tombs: Ra Deal Coming from Bulkypix and Dark Tonic This Fall Posted by Jessica Fisher on September 2nd, 2014 [ permalink ] Dark Tonic and | Read more »
Pirate Bash Review
Pirate Bash Review By Nadia Oxford on September 2nd, 2014 Our Rating: :: BAD PIRATES, GOOD TIMESUniversal App - Designed for iPhone and iPad Pirate Bash’s turn-based battles add an intriguing twist to a typical physics game.   | Read more »
Tiny Tower Vegas Review
Tiny Tower Vegas Review By Jennifer Allen on September 2nd, 2014 Our Rating: :: STEADY DEVELOPMENTUniversal App - Designed for iPhone and iPad Build a huge tower again but Vegas-style in Tiny Tower Vegas.   | Read more »
The Manhattan Project Review
The Manhattan Project Review By Andrew Fisher on September 2nd, 2014 Our Rating: :: ROCKET SCIENCEUniversal App - Designed for iPhone and iPad The Manhattan Project offers a great Euro-style gameplay experience, but it is totally... | Read more »

Price Scanner via MacPrices.net

Apple refurbished iPads available for up to $...
Apple is offering Certified Refurbished iPad Airs for up to $140 off MSRP. Apple’s one-year warranty is included with each model, and shipping is free. Stock tends to come and go with some of these... Read more
Are We Now In The Post-Post-PC Era?
A longtime and thoroughgoing laptop aficionado, I was more than a little dismayed by Steve Jobs’s declaration back in 2010 when he sprang the iPad on an unsuspecting world. that we’d entered a “post-... Read more
PC Outlook Improves, But 2014 Shipments Still...
According to the International Data Corporation (IDC) Worldwide Quarterly PC Tracker, worldwide PC shipments are expected to fall by -3.7 percent in 2014. To hat’s actually an improvement from the... Read more
IDC Lowers Tablet Sales Projections for 2014...
Following a second consecutive quarter of softer than expected demand, International Data Corporation (IDC) has lowered its worldwide tablet plus 2-in-1 forecast for 2014 to 233.1 million units. The... Read more
Apple now offering refurbished 21-inch 1.4GHz...
The Apple Store is now offering Apple Certified Refurbished 21″ 1.4GHz iMacs for $929 including free shipping plus Apple’s standard one-year warranty. Their price is $170 off the cost of new models,... Read more
Save $50 on the 2.5GHz Mac mini, on sale for...
B&H Photo has the 2.5GHz Mac mini on sale for $549.99 including free shipping. That’s $50 off MSRP, and B&H will also include a free copy of Parallels Desktop software. NY sales tax only. Read more
Save up to $300 on an iMac with Apple refurbi...
The Apple Store has Apple Certified Refurbished iMacs available for up to $300 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. These are the best prices on... Read more
The Rise of Phablets
Carlisle & Gallagher Consulting Group, a businesses and technology consulting firm focused solely on the financial services industry, has released an infographic depicting the convergence of... Read more
Bad Driver Database App Allows Good Drivers t...
Bad Driver Database 1.4 by Facile Group is a new iOS and Android app that lets users instantly input and see how many times a careless, reckless or just plain stupid driver has been added to the... Read more
Eddy – Cloud Music Player for iPhone/iPad Fre...
Ukraine based CapableBits announces the release of Eddy, its tiny, but smart and powerful cloud music player for iPhone and iPad that allows users to stream or download music directly from cloud... 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
*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
*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
*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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.