TweetFollow Us on Twitter

January 92 - Dinker: the Dynamic Linker

Dinker: the Dynamic Linker

Kurt Schmucker

Many application domains naturally possess an unbounded set of desired features. A signals processing application, for example, needs an unlimited number of filters. A symbolic math package, an unlimited number of mathematical operators. A graphics package, an unlimited number of sketching tools.

Of course, no real application can present an unlimited number of anything to any given user. However, the market as a whole does appear to want an unlimited number of features. What's a developer to do?

Some developers have met this challenge by building in a capability to extend their applications. Using this feature, end users can configure a graphics package, for example, with a set of sketching tools tailored to their needs, or even modify the set of available sketching tools while the application is running.

This enables users to get the maximum use of limited RAM and disk space. Instead of running in a six megabyte MultiFinder partition, for example, an extensible application, with only the needed tools loaded, could run in, say, four megabytes. In fact, one of the best selling MacApp applications, Adobe PhotoShop, uses an extensibility approach with their plug-ins to add new image manipulation algorithms and data access procedures to the application.

Up until now, MacApp has provided no support to those wanting to add extensibility to an application. To make matters worse, the most natural way to add functionality to a MacApp application-by adding new classes to the running application- was something no one had ever done. Some people even thought this was impossible to do on the Mac.

Dinker, the results of recent work by Apple's Advanced Technology Group, adds exactly this capability to MacApp. This article describes what Dinker does and how you can use it in your application. Other articles planned for later issues of FrameWorks will cover Dinker internals and case studies of adding Dinker-based extensibility to commercial MacApp applications.

Dinker is included on the next Essentials, Tools, and Objects CD (ETO 6) as a currently unsupported MacApp experiment. It will be demonstrated at the Orlando '92 MADA Conference in February.

What is Dinker?

Dinker is a dynamic linking mechanism for the Macintosh OS. It lets you write applications whose functionality can be extended at run-time by the addition of new Object Pascal or C++ classes. In particular, Dinker lets the MacApp programmer add new 'view' or 'VIEW' resources, new view classes, new command classes or any other classes at run-time, and to use instances of these classes just like any other object in the application.

The basic run-time architecture of a Dinker application is shown in Figure 1, and then in greater detail in Figure 2 (next page). Dinker will set up entry and exit points in the base and all extensions, and will ensure that the proper global environment (A5 worlds, resource chains, etc.) is established upon crossing the boundaries between the base and the extensions, or between extensions.

Building an application that can be extended at run time via the Dinker is easy. Tell the Dinker version of MABuild to build the application to make use of Dinker. Such an application is called a "base." Then, use MABuild to build each dynamically linkable extension for the application (called an "extension" or a "component"). The total Dinker package used by a MacApp programmer-Dinker itself, the Dinker-aware modified version of MacApp (either a modified version of MacApp 2.0.1, or a modified version of MacApp 3.0ß3), the Dinker-aware version of MABuild, etc.-will cause the entry and exit points to be constructed for the base and for all extensions, and will resolve, at run-time, the invocations of these references. (See future FrameWorks articles for an explanation of the Dinker's inner details.)

A note on terminology-Dinker is a dynamic linker. It lets you "dink in" a new class into a running application. Among dynamic linkers, Dinker is unique in that it enables the dynamic linking of new classes into an object oriented application, like a MacApp application. For a time, the term "oinking" was used to describe this dynamic linking, but this term has fallen into disfavor with the Dinker implementors. A later, supported version of Dinker may have a slick, marketing-approved, copyright-obtained legal name. We hope that all savvy MacApp developers will continue to call it "Dinker" in perpetuity.

What Does dynamic linking do for users?

MacApp developers are subject to the same pressures as every other developer-users want more and more functionality in applications without the resource requirements increasing.

Extensibility lets you achieve these opposing goals. Users can pick which tools to load in the default case (by, for example, placing these in a distinguished folder), yet still have easy access to the tool needed on special occasions. In this way, Dinker lets users manage the resources needed to run your application much like Fifth Generation System's Suitcase™ II lets the user manage fonts, desk accessories, FKEYs, and sounds.

In addition, for those developers who wish to encourage a third-party market surrounding their applications, Dinker provides a way for other MacApp developers to leverage off of your application by developing extensions for it. These third parties will need the entry and exit vector files the Dinker-modified version of MABuild prepares for the application. These could be part of a developer's kit for your application. Developers of extensions do not need access to the source code of the base.

How is dinker used in an application?

To use Dinker, you willl probably need to change your application's source; most applications aren't currently designed for extensibility. Do you have a fixed number of items in a palette-items that the end user may want to add to, or replace? Do you check, upon resuming after a MultiFinder switch, if the user has added functionality to the application "behind your back?" Probably not. There will be as many ways of designing extensibility into MacApp applications as there are clever MacApp programmers.

Automatic loading of components

One way of adding new functionality to an application is to have the user configure a folder with the desired extensions in it. Dinker supports this approach. (If this sounds vaguely like the System 7 Extensions folder, it is. The Finder Extensions mechanism used in System 7 is a special case of the full Dinker design.) The Dinker version of MacApp provides a number of ways to find out which extensions have been loaded. TApplication (in this modified version of MacApp) maintains a list of the currently loaded extensions, and several utility methods and procedures let you easily query this list.

One interesting technique uses a MacApp method that you probably haven't used before: ForAllSubClassesDo in TObject. I used this technique to add an indeterminate number of dinked-in views to a window. It just happened to be the case that while each of these new subviews was a instance of a different class, all the classes were subclasses of a class unique to my application (TBannerView). The code looks like this:

PROCEDURE TBannerDocument.DoMakeViews(…);  
                                                OVERRIDE;
    VAR theWindow:  TWindow;
        theFirstView:   TBannerView;
        currentLoc:     VPoint;
        aView:          TBannerView;
        
        PROCEDURE AddAView(theClass: ObjClassID);
        BEGIN
            currentLoc.v := currentLoc.v + 135;
            aView := TBannerView(NewObjectByClassID(theClass));
            FailNIL(aView );
            aView.IBannerView(…); { this will add it as subView }
        END;
        
    BEGIN
        SetVPt(currentLoc, 0, 0);
        
        { Prime the pump by setting up the window
            with the first view }
        theWindow := NewTemplateWindow(2222, SELF);
        FailNIL(theWindow);
        theFirstView := TBannerView(theWindow.FindSubView('MNBN'));
        
        { Now add the rest of the views }
        theFirstView.ForAllSubClassesDo(AddAView)
    END;

You could use the same technique to build a palette (when all the new tools to be configured into the palette are subclasses of something like TAbstractTool), or a hierarchical menu.

Manual loading of components

Another way to add functionality is to let the user load new components at any time the application is running. Dinker also supports this. One way you can use this support is to add the appropriate menu items to your application and to process these in a DoMenuCommand something like this code from the Dinker version of DrawShapes:
PROCEDURE TShapeApplication.DoMenuCommand(
            aCommandNumber: CommandNumber); OVERRIDE;
    VAR
        anExtensionFile:    TList;
        aDomain:            TDomain;
        r:                  Rect;
        shape:              TShape;
        toolsView:          TToolsPalette;
        toolsMenu:          TToolsMenu;

        PROCEDURE DoToItemInExtensionList(item: TObject);
    BEGIN
        aDomain := GetExtension ( TFile (item) );
        IF longint(aDomain) <> 0 THEN BEGIN
            { Define the prototype shape this component }   
            SetRect(r, 9, 49, 31, 71 );                     
            OffSetRect(r, 0, 40 * ( gShapesInPalette ) );
            shape := TShape ( Instantiate( aDomain ) );
            FailNil(shape);
            gShapesInPalette := gShapesInPalette + 1;
            shape.IShapeExtension(r, gShapesInPalette );
            gShapesArray[gShapesInPalette] := shape;
        END;
    END;
    
    PROCEDURE ForceWindowRedraw ( aWindow: TWindow );
    BEGIN
        aWindow.ForceRedraw;
    END;

    BEGIN
    CASE aCommandNumber OF
        ...
        cGetComponent:                      
            BEGIN
                IF ChooseDocument( cGetComponent, anExtensionFile )
                THEN BEGIN
                    anExtensionFile.Each( DoToItemInExtensionList );
                    anExtensionFile.Free;
                    { Now add the new shape to the palette }
                    toolsMenu := TToolsMenu(gToolsMenu);
                    IF longint(toolsMenu) <> 0 THEN
                        toolsMenu.AddTool;
                    ... { Add to Tear offs, etc. here }
                    ForAllWindowsDo( ForceWindowRedraw );
                END;
    
            OTHERWISE
            INHERITED DoMenuCommand(aCommandNumber);
    END; {Case}
END;

'lView' templates in extensions

Often, TView objects are not allocated explicitly by the programmer, but rather are instantiated indirectly via 'view' resources. Extensions also have their own resource chain (forked off of the top of the base's resource chain). You can put 'view' and 'VIEW' resources in your extension. The Dinker extensions to MacApp include Dinker analogs of the familiar utility routines NewTemplateWindow and DoCreateViews, NewComponentTemplateWindow() and DoCreateDinkedViews(), which you can then use to dink in these views from other extensions. Like the standard NewTemplateWindow , NewComponentTemplateWindow lets you access a view by its resource id. However, NewComponentTemplateWindow also lets you access the new window type by the name of the extension that contains it. We have found this to be a natural way to add new functionality to an application in the case that the "important" portion of the extension was the new views being added. In this application, we made the names of the extensions the same as the names of the view.

What are the Drawbacks of using Dinker?

There is no free lunch, and Dinker, too, has some costs. These costs are not in the area of performance. Using instances of dinked-in classes carries only a tiny performance hit on the application. The gotchas of the current Dinker implementation are as follows.

Launch time

Dinker applications take longer to launch than "normal" applications. Remember that Dinker is a dynamic linker. Thus, it is doing the work of the linker at run-time. The amount of time depends mostly on the Mac model you are executing on (no surprise here) and the version of MacApp you are using (remember that MacApp 3 has about twice the number of classes and methods of MacApp 2, and there is a lot more to link in a MacApp 3 application). The additional amounts of launch time can range from less than two seconds (FX, MacApp 2) to more than 30 seconds (Portable, MacApp 3). I hope that future versions of Dinker will be able to reduce these times, but they will never go to zero.

Extensions are application specific

The Dinker internals that make it the only dynamic linker that enables the addition of new classes at run-time also require that a built extension, ready for dinking, be application specific. In addition, any significant changes to the class structure of the application require that all the application's extensions be rebuilt.

What is "significant?" Addition or removal of classes, addition or removal of methods, addition or removal of any entities that the linker needs to know about (for example, invocation of a new Toolbox routine, or moving something from the private interface to the public interface) are prime examples. "Insignificant," from a Dinker point of view, are changes to the implementations of methods or functions that don't add or remove Toolbox calls.

Debugging support

The ease of debugging a Dinker application depends on whether MacApp is used, and what version of MacApp is used. The best case is MacApp 2.0.1. The two main debugging tools designed for MacApp 2.0.1, the Inspector and the MacApp Debugger, are fully integrated with Dinker. The dinked-in classes and any instances of these classes are viewable from these tools and, in fact, you'll have a hard time distinguishing between an instance of a dynamically linked class and a statically linked class. This was a goal of the Dinker implementation, and we believe it has been met (after a lot of hard work and many late night sessions double checking on this integration).

Unfortunately, the situation is not so rosy with respect to a MacApp 3.0ß3 application, or a non-MacApp application. Yes, you can use Dinker without using MacApp. However, it isn't as easy or as convenient, mostly because we planned the first Dinker release to concentrate on the use of Dinker by a MacApp programmer.

The new MABuild, for example, handles the complexity of building the entry and exit vector segments without any work by the MacApp programmer. There are currently no such automated build facilities for the non-MacApp developer. There isn't much debugging support in either SourceBug or SADE® for dynamically linked extensions. Basically, neither of these tools yet know how to read the multiple SYM files associated with the base and all of its currently dinked in extensions, nor do they know to reassess a class hierarchy that has been modified dynamically by Dinker. However, that doesn't mean these debugging tools are useless with a Dinker application. You can use SourceBug with Dinker applications, but with these limitations:

  • SourceBug is confused by the new Class hierarchy that Dinker creates. So SourceBug's browser displays the source code filenames of the base and of the MacApp library rather than its classes.
  • SourceBug only really knows about the code in your base. You must go into your low level debugger if you want to step into your extension.

I hope that these limitations will be removed in the future.

Finally, a goal of Dinker was to require only minimal-and preferably pro forma-changes to a class to change it from being a statically linked piece of functionality to one that could be dynamically linked into the application. We believe this goal has been met. Thus, one possible debugging strategy is to develop and debug your application as a monolithic, statically linked application, and then when it is "bug free," to peel off various pieces of functionality into dynamically linked extensions. (Okay, okay. We know that this is kind of lame, and that your testing manager just had a heart attack even considering this approach. But it's better than nothing, and this is only the early experimental release.)

Support, in general

The Dinker ETO #6 release is an unsupported, experimental release, but Dinker or other dynamic linking mechanisms may be incorporated into future releases of MacApp, MPW, or other development tools.

While it is implemented according to the same architecture as Finder Extensions, Dinker adds significant new dynamic linking functionality to Finder Extensions and thus an extended period of testing is needed. The Dinker work was done by Apple's Advanced Technology Group and is being shared with third-party developers for experimentation and evaluation. If you find dynamic linking to be a useful feature, then it may be supported and extended in future MacApp and MPW releases. Let us know by sending an AppleLink message to the Dinker Product Manager, Tom Chavez (TOM.CHAVEZ).

FUTURE FRAMEWORKS ARTICLES

How Dinker works, and what it is like to add extensibility to an existing commercial MacApp application, will be covered in detail in future FrameWorks articles.

Acknowledgements

The Dinker folder on ETO #6 is the result of many months of work by employees from several parts of Apple, as well as some Apple contractors. Jed Harris, then in ATG, now in the Developer Tools group, did the original Dinker design. He and Scott Douglass, now in the System Software group at Apple, implemented the first proof of concept that Dinker would actually work. Frank Kurzawa of Refried Software, and Andrew Donoho of Donoho Design Group did the current Dinker implementation under contract to ATG. Frank also designed and implemented the changes to MacApp 2.0.1 and MacApp 3.0ß3 that make it work with Dinker, and he did many of the Dinker sample programs. Joost Kemink and Kurt Schmucker, both of ATG, were the "typical" Dinker users whose dinking needs drove the design, and who did all the testing of Dinker with MacApp. Kurt Schmucker was the author of two of the Dinker sample programs. Tom Chavez is the Dinker Product Manager and guided the Dinker work onto ETO.

 
AAPL
$105.01
Apple Inc.
+0.18
MSFT
$45.45
Microsoft Corpora
+0.43
GOOG
$539.20
Google Inc.
-4.79

MacTech Search:
Community Search:

Software Updates via MacUpdate

BusyCal 2.6.3 - Powerful calendar app wi...
BusyCal is an award-winning desktop calendar that combines personal productivity features for individuals with powerful calendar sharing capabilities for families and workgroups. BusyCal's unique... Read more
calibre 2.7 - Complete e-library managem...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital... Read more
Skitch 2.7.3 - Take screenshots, annotat...
With Skitch, taking, annotating, and sharing screenshots or images is as fun as it is simple.Communicate and collaborate with images using Skitch and its intuitive, engaging drawing and annotating... Read more
Delicious Library 3.3.2 - Import, browse...
Delicious Library allows you to import, browse, and share all your books, movies, music, and video games with Delicious Library. Run your very own library from your home or office using our... Read more
Art Text 2.4.8 - Create high quality hea...
Art Text is an OS X application for creating high quality textual graphics, headings, logos, icons, Web site elements, and buttons. Thanks to multi-layer support, creating complex graphics is no... Read more
Live Interior 3D Pro 2.9.6 - Powerful an...
Live Interior 3D Pro is a powerful yet very intuitive interior designing application. View Video Tutorials It has every feature of Live Interior 3D Standard, plus some exclusive ones: Create multi... Read more
The Hit List 1.1.7 - Advanced reminder a...
The Hit List manages the daily chaos of your modern life. It's easy to learn - it's as easy as making lists. And it's powerful enough to let you plan, then forget, then act when the time is right.... Read more
jAlbum Pro 12.2.4 - Organize your digita...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code!... Read more
jAlbum 12.2.4 - Create custom photo gall...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results Simply drag and drop photos into groups, choose a design... Read more
ExpanDrive 4.1.7 - Access remote files o...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more

Latest Forum Discussions

See All

nPlayer looks to be the ultimate choice...
Developed by Newin Inc, nPlayer may seem like your standard video player – but is aiming to be the best in its field by providing high quality video play performance and support for a huge number of video formats and codecs. User reviews include... | Read more »
Fighting Fantasy: Caverns of the Snow Wi...
Fighting Fantasy: Caverns of the Snow Witch Review By Jennifer Allen on October 24th, 2014 Our Rating: :: CLASSY STORYTELLINGUniversal App - Designed for iPhone and iPad Fighting Fantasy: Caverns of the Snow Witch is a sterling... | Read more »
A Few Days Left (Games)
A Few Days Left 1.01 Device: iOS Universal Category: Games Price: $3.99, Version: 1.01 (iTunes) Description: Screenshots are in compliance to App Store's 4+ age rating! Please see App Preview for real game play! **Important: Make... | Read more »
Toca Boo (Education)
Toca Boo 1.0.2 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0.2 (iTunes) Description: BOO! Did I scare you!? My name is Bonnie and my family loves to spook! Do you want to scare them back? Follow me and I'll... | Read more »
Intuon (Games)
Intuon 1.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.1 (iTunes) Description: Join the battle with your intuition in a new hardcore game Intuon! How well do you trust your intuition? Can you find a needle in a... | Read more »
Ravenous Rampage (Games)
Ravenous Rampage 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: | Read more »
Partia 2 (Games)
Partia 2 1.0.1 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0.1 (iTunes) Description: Partia 2 is a SRPG (Strategy Role-playing) video game inspired by Fire Emblem and Tear Ring Saga series. In a high fantasy... | Read more »
Puzzle to the Center of the Earth Review
Puzzle to the Center of the Earth Review By Campbell Bird on October 23rd, 2014 Our Rating: :: SPELUNKING PUZZLESUniversal App - Designed for iPhone and iPad Do some puzzles to make some platforms in this smart and fun free-to-play... | Read more »
Puzzle to the Center of the Earth – Tips...
Dig this: Would you like to know what we thought of all this puzzling-around the deep recesses of the planet? Check out our Puzzle to the Center of the Earth review! Puzzle to the Center of the Earth is a surprisingly deep and challenging puzzle... | Read more »
Sleep Attack TD Review
Sleep Attack TD Review By Jennifer Allen on October 23rd, 2014 Our Rating: :: A TRUE TWISTUniversal App - Designed for iPhone and iPad Sleep Attack TD is a tower defense game with a difference – you can rotate the layout – and it’s... | Read more »

Price Scanner via MacPrices.net

13-inch 2.5GHz MacBook Pro on sale for $949,...
Best Buy has the 13″ 2.5GHz MacBook Pro available for $949.99 on their online store. Choose free shipping or free instant local store pickup (if available). Their price is $150 off MSRP. Price is... Read more
Save up to $125 on Retina MacBook Pros
B&H Photo has the new 2014 13″ and 15″ Retina MacBook Pros on sale for up to $125 off MSRP. Shipping is free, and B&H charges NY sales tax only. They’ll also include free copies of Parallels... Read more
Apple refurbished Time Capsules available sta...
The Apple Store has certified refurbished Time Capsules available for up to $60 off MSRP. Apple’s one-year warranty is included with each Time Capsule, and shipping is free: - 2TB Time Capsule: $255... Read more
Textilus New Word, Notes and PDF Processor fo...
Textilus is new word-crunching, notes, and PDF processor designed exclusively for the iPad. I haven’t had time to thoroughly check it out yet, but it looks great and early reviews are positive.... Read more
WD My Passport Pro Bus-Powered Thunderbolt RA...
WD’s My Passport Pro RAID solution is powered by an integrated Thunderbolt cable for true portability and speeds as high as 233 MB/s. HighlightsOverviewSpecifications Transfer, Back Up And Edit In... Read more
Save with Best Buy’s College Student Deals
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through November 1st. Anyone with a valid .EDU email address can take advantage... Read more
iPad Air 2 & iPad mini 3 Best Tablets Yet...
The new iPads turned out to be pretty much everything I’d been hoping for and more than I’d expected.”More” particularly in terms of a drinking-from-a-firehose choice of models and configurations,... Read more
Drafts 4 Reinvents iOS Productivity App
N Richland Hills, Texas based Agile Tortoise has announced the release of Drafts 4 for iPhone and iPad. Drafts is a quick capture note taking app with flexible output actions. Drafts 4 scales from... Read more
AT&T accepting preorders for new iPads fo...
AT&T Wireless is accepting preorders for the new iPad Air 2 and iPad mini 3, cellular models, for $100 off MSRP with a 2-year service agreement: - 16GB iPad Air 2 WiFi + Cellular: $529.99 - 64GB... Read more
Apple offering refurbished Mac Pros for up to...
The Apple Store is offering Apple Certified Refurbished 2013 Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more

Jobs Board

*Apple* Solutions Consultant - Apple Inc. (U...
…important role that the ASC serves is that of providing an excellent Apple Customer Experience. Responsibilities include: * Promoting Apple products and solutions 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
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.