TweetFollow Us on Twitter

December 95 - Newton Q & A: Ask the Llama

Newton Q & A: Ask the Llama

Q The on-line discussion groups for Newton developers have a lot of references to compatibility these days. My application works fine on the 120, 110, and 100 models. Does that mean I'm compatible?

A Good question. Compatibility doesn't mean your application works now, but that it's written in such a way that it will work on future Newton devices and operating systems. There are several APIs and methods for doing things on the 120, 110, and 100 models that will work with them but are not necessarily compatible with future releases of the operating system.

There are two main points to observe for the sake of compatibility:

  • If it's not documented, don't use it.
  • Catch exceptions; they can occur (especially if you ignore the first point).
Since compatibility is such an important question, it will be the focus of this column. The rest of the column will cover the most common breaches of compatibility. Where applicable, there will be an example of the incompatible and compatible ways of doing things. After reading this and making copious notes (especially where you find yourself saying "Oh dear" and "Oh no!"), you'll be in a position to make your code compatible. We also recommend that you try out your application with the Compatibility App Package (which is on this issue's CD and is available from various on-line services).

Note that we refer often to the Newton Toolkit platform file functions. The Toolkit documentation and platform file release notes describe these functions, which are provided in lieu of future APIs. You should use these platform file functions where applicable. Call the code directly and don't modify it. That is, use the call/with syntax; don't place the code in a slot in your application and use message sending.

UNDOCUMENTED GLOBAL FUNCTIONS

There are four common offenders here: CreateAppSoup, SetupCardSoups, MakeSymbol, and GetAllFolders. The function kRegisterCardSoupFunc in the platform file replaces CreateAppSoup and SetupCardSoups. It's much simpler to use than the undocumented functions:
// RIGHT way
constant kSoupName := "MySoup:MYSIG";
constant kSoupIndices := '[]; 
constant kAppObject := '["Item", "Items"];
call kRegisterCardSoupFunc with
   (kSoupName, kSoupIndices, kAppSymbol, kAppObject);

// *** WRONG way ***
CreateAppSoup(kSoupName, kSoupIndices, EnsureInternal([appSymbol]),
   EnsureInternal(kAppObject));
AddArraySlot(cardSoups, kSoupName);
AddArraySlot(cardSoups, kSoupIndices);
SetupCardSoups();
The fix for MakeSymbol is to call the Intern function: it does the same thing as MakeSymbol and it's documented.

There's no replacement function for GetAllFolders; just don't call it.

UNDOCUMENTED GLOBAL VARIABLES

The three most common misused global variables are cardSoups, extras, and userConfiguration.

There are two uses of cardSoups: one is to register a card soup; the other to unregister it. Registering is taken care of with kRegisterCardSoupFunc (see above). Unregistering is done with another platform file function, kUnRegisterCardSoupFunc:

// RIGHT way
call kUnRegisterCardSoupFunc with (kSoupName);

// *** WRONG way ***
SetRemove(cardSoups, kSoupName);
SetRemove(cardSoups, kSoupIndices);
You should never access the extras global variable. Not only is this variable undocumented, but so is its format. Both are subject to major revisions. The platform file function kSetExtrasInfoFunc is provided for setting information about items in the extras drawer. The most common use of this function is to give your application a different icon (see the ExtraChange DTS sample code on the CD).

There are also platform file functions to manipulate userConfiguration:

  • kGetUserConfigFunc gets a slot from the userConfiguration soup entry.
  • kSetUserConfigFunc lets you set user configuration information.
  • kFlushUserConfigFunc should be called when you've changed user configuration information.
// RIGHT way
local userName := call kGetUserConfigFunc with ('name);
if userName then
begin
   if StrEqual(userName, "Doctor") then
      call kSetUserConfigFunc with ('name, "The Doctor");
   call kFlushUserConfigFunc with ();
end;

// *** WRONG way ***
if userConfiguration.name AND
      StrEqual(userConfiguration.name, "Doctor") then
   userConfiguration.name := "The Doctor";

UNDOCUMENTED SLOTS AND METHODS

This is a broad category of problems. The most common is keyboardChicken in the root view. But there are others, like cursor.current, paperRoll.dataSoup, dockerChooser in the root view, UnionSoup:Add, and anything in a built-in application. Unfortunately, there is no right way to access most of these. The exceptions are cursor.current and Add.
// RIGHT way
local currentEntry := cursor:Entry();
myUnionSoup:AddToDefaultStore(anEntry);

// *** WRONG way ***
local currentEntry := cursor.current;
myUnionSoup:Add(anEntry);
Also, don't rely on the routing slips, such as mailSlip and printSlip, being in the root view. You can, however, still use those symbols in your routing frame.

UNDOCUMENTED MAGIC POINTERS

If you use one of these, you know it. Just think what would happen if the magic pointer changed from a view to a string: you would get some pretty bad behavior. Note that most of this could be dealt with by catching exceptions.

STORE AND SOUP ASSUMPTIONS

All you can assume is that store 0 is the internal store. You can't rely on there being only one other store, nor can you rely on the position of a store in the array returned by GetStores. Also, don't assume that another store is a card or even that there is just one store per card.

If you support moving or copying items between stores, you shouldn't find the title of the store. Use the constant ROM_cardAction as provided in the platform file:

// RIGHT way
routingFrame := {
   print: ...
   ...
   card: ROM_cardAction
}
In addition, don't assume that your soup will exist on every store. Currently, if you register your union soup, it's automatically created on every store that enters the Newton; however, this may change in the future:
// RIGHT way
GetUnionSoup(kSoupName):AddToDefaultStore(anEntry);

// *** WRONG way ***
aStore:GetSoup(kSoupName):Add(anEntry);
Remember that AddToDefaultStore or Add could throw exceptions. Wrap your calls to these functions in exception handlers.

Finally, if you support the soup change mechanism, don't assume that the change is adding or deleting an entry. It could be something else, such as a soup being created or removed from a store.

SCREEN SIZE

Don't assume the screen is any particular size. It could be larger or smaller than current devices. It could also be wider than it is tall. Your application size setup routine (usually in the viewSetupFormScript) should take this into account. Have maximum and minimum sizes. Close your application if it can't handle the current screen size.
// Code to close your application
constant kUnsupportedScreenSize :=
   "WiggyWorld does not support this screen size";

DefConst('closeMeFunc, func(x) x:Close());

:Notify(kNotifyQAlert, EnsureInternal(kAppName),
   EnsureInternal(kUnsupportedScreenSize));
AddDeferredAction(closeMeFunc, [self]);

UNDOCUMENTED FEATURES OF DATA TYPES

Rely only on the features and details of built-in data types that are documented. There are three common problem areas: order of slots in a frame, precision of integers, and implementation of strings.

The order of slots in a frame is undefined. It just so happens that in the current implementation the first 20 slots are returned in the order added. This is not a documented feature, so don't rely on it.

Integers are documented as having at least 30 bits of precision. This doesn't mean they'll always be 30 bits; they could be wider (as anyone who has used compiled NewtonScript can tell you). Note that compiled NewtonScript integers may not be 32 bits; they also follow the "at least 30 bits" rule.

The biggest offender is assumptions about how strings are implemented. Don't rely on strings being null terminated or being composed of two-byte Unicode characters. The practical upshot is that you should use StrLen to find the length, and StrMunger (or &) for length changes. Don't use Length, SetLength, or BinaryMunger with strings. Don't use the array accessor to set a string; you can check a character, but don't set a character.

MISCELLANEOUS BITS

Don't send messages directly to the IOBox; use the kSendFunc platform file function. Nor should you read the items in the IOBox soups.

Also note that there are platform file functions to register and unregister for Find that you should use.

Always use SetValue when you're changing the view or other system values.

Use only the body slot in items that you route. Don't assume that slots other than body will survive the routing process. On a related note, don't rely on the category slot of fields in your SetupRoutingSlip method either.

Don't rely on the closing order of views in the viewQuitScript. If you need to do some ordered cleanup, you can initiate your own message (for example, myViewQuitScript) from the view that first receives the viewQuitScript.

Replace system functions and messages at your peril. It's possible they will support other data types in the future (for example, to take NIL now where before they only took a string).

Don't assume anything about the built-in applications. Don't assume that they exist, or that their soups are there, or that the view structure will stay the same. If you do need to use a system feature (for example, a particular prototype, global function, or root method), test your assumptions.

local cardFileExists := GetRoot().cardfile;

if cardFileExists then
begin
   local cardFileSoup := GetUnionSoup(ROM_cardfilesoupname);
   if cardFileSoup then
      ...
end;
// :-0
if GetRoot().keyboardChicken then
begin
   ...
end;
Current Newtons have two levels of Undo; this may change. There could be more or fewer levels and it could change to Undo/Redo. It's safest to call AddUndoAction from inside your undo action; this will support Undo/Redo if we implement it, but will do nothing if we do not.

The llama is the unofficial mascot of the Developer Technical Support group in Apple's Newton Systems Group. Send your Newton-related questions to NewtonMail or eWorld DRLLAMA or to AppleLink DR.LLAMA. The first time we use a question from you, we'll send you a T-shirt.

Thanks to our Newton Partners for the questions used in this column, and to jXopher Bell, Henry Cate, Bob Ebert, David Fedor, Stephen Harris, Jim Schram, Maurice Sharp, James Speir, and Bruce Thompson for the answers.

Have more questions? Take a look at Newton Developer Info on AppleLink.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

calibre 3.1.1 - Complete e-book library...
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 librarian... Read more
Sparkle Pro 2.2 - $79.99
Sparkle Pro will change your mind if you thought building websites wasn't for you. Sparkle is the intuitive site builder that lets you create sites for your online portfolio, team or band pages, or... Read more
Spotify 1.0.57.474. - Stream music, crea...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
beaTunes 5.0.1 - Organize your music col...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more
LibreOffice 5.3.4.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
VOX 2.8.26 - Music player that supports...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
iFFmpeg 6.4.0 - Convert multimedia files...
iFFmpeg is a comprehensive media tool to convert movie, audio and media files between formats. The FFmpeg command line instructions can be very hard to master/understand, so iFFmpeg does all the hard... Read more
Beamer 3.3 - Stream any movie file from...
Beamer streams to your Apple TV.... Plays any movie file - Just like the popular desktop movie players, Beamer accepts all common formats, codecs and resolutions. AVI, MKV, MOV, MP4, WMV, FLV. To... Read more
jAlbum Pro 14.0 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. You can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly... Read more
Apple Remote Desktop Client 3.9.3 - Clie...
Apple Remote Desktop Client is the best way to manage the Mac computers on your network. Distribute software, provide real-time online help to end users, create detailed software and hardware reports... Read more

Latest Forum Discussions

See All

This War of Mine gets a new ending and m...
This War of Mine just got a big new update, featuring free DLC that adds a new ending to the game, among other exciting changes. The update is celebrating the game's two-year release anniversary. Apart from the new ending, which will be quite... | Read more »
Summon eight new heroes in Fire Emblem H...
Nintendo keeps coming at us with Fire Emblem Heroes updates, and it doesn't look like that trend is stopping anytime soon. The folks behind the game have just announced the new War of the Clerics Voting Gauntlet, expected to start next Tuesday. [... | Read more »
The best deals on the App Store this wee...
iOS publishers are pulling out all the stops this week -- there's a huge number of seriously great games at discounted prices this week. Let's not waste any time and get right down to business. [Read more] | Read more »
The House of da Vinci (Games)
The House of da Vinci 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Enter The House of Da Vinci, a new must-try 3D puzzle adventure game. Solve mechanical puzzles, discover hidden... | Read more »
Solve the disappearance of history’s gre...
Blue Brain Games invites you to indulge in an immersive hands-on 3D puzzle adventure in similar vein to The Room series, with its debut release The House of Da Vinci. Set during the historic period of the Italian Renaissance (when Leonardo himself... | Read more »
Age of Rivals (Games)
Age of Rivals 3.3 Device: iOS Universal Category: Games Price: $.99, Version: 3.3 (iTunes) Description: Deep civilization-building strategy in a fast-paced card game! | Read more »
Panthera Frontier (Games)
Panthera Frontier 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
Angry Birds Evolution beginner's gu...
Angry Birds changes things up a fair bit in its latest iteration, Angry Birds Evolution. The familiar sling-shot physics mechanics are still there, but the game now features team-based gameplay, RPG elements, and a new top-down view. With all of... | Read more »
Sega Forever is for the retro game fans
Sega is launching a new retro games service titled Sega Forever, in a move that's sure to delight games enthusiasts with a bit of nostalgia. Sega's releasing five classic games for free. The titles include Sonic the Hedgehog, Phantasy Star II,... | Read more »
The Little Acre (Games)
The Little Acre 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

ABBYY TextGrabber 6 for iOS Implements Instan...
ABBYY has announced the release of TextGrabber 6.0.0, an important feature update to the company’s productivity app developed for iOS and Android devices. TextGrabber 6.0 now offers Real-Time... Read more
vPhone, First Smartphone That Can’t Be Lost,...
Austin, Texas based Hypori has introduced the vPhone, a virtual smartphone that affords every business user the benefits of separate work and personal phones, conveniently delivered on a single... Read more
Save this weekend with 2016 refurbished MacBo...
Apple has dropped prices on Certified Refurbished 2016 15″ and 13″ MacBook Pros by as much as $590 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: -... Read more
New 27-inch 3.4GHz iMac on sale for $1699, sa...
MacMall has the new 2017 27″ 3.4GHz iMac (MNE92LL/A) in stock and on sale for $1699 including free shipping. Their price is $100 off MSRP. Read more
Clearance 2016 MacBook Pros available for up...
B&H Photo has clearance 2016 13″ and 15″ MacBook Pros in stock today and on sale for up to $400 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 15″ 2.7GHz... Read more
Apple Ranks 9th In comScore Top 50 U.S. Digit...
comScore, Inc. has released its monthly ranking of U.S. online activity at the top digital media properties for May 2017 based on data from comScore Media Metrix Multi-Platform. * Entity has... Read more
10.5-inch iPad Pros available for up to $20 o...
B&H Photo has the new 2017 10.5″ iPad Pros available for up to $20 off MSRP including free shipping plus NY & NJ sales tax only: - 64GB iPad Pro WiFi: $649 - 256GB iPad Pro WiFi: $749 - 512GB... Read more
Three Off-The-Beaten-Track iOS Apps That Dese...
One of the great things about using iPads and iPhones is the vast selection of apps available for most anything you want or need to do. The three outlined in this article have been in my core app... Read more
Apple No. 1 Spot In Gartner Top 100 Vendors i...
Gartner, Inc. has unveiled the top global 100 vendors in IT in 2016 based on their revenue across IT (excluding communication services) and component market segments. In the Gartner Global Top 100:... Read more
Clearance iMacs available for up to $300 off...
B&H Photo has clearance 21″ and 27″ Apple iMacs available starting at $949, each including free shipping plus NY & NJ sales tax only: - 27″ 3.3GHz iMac 5K: $1999 $300 off original MSRP - 27″... Read more

Jobs Board

*Apple* News Product Marketing Mgr., Publish...
…organizational consensus on strategy and vision for publisher tools, authoring, and Apple News Format.Carries this strategy and vision across the organization to Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject matter Read more
Lead *Apple* Solutions Consultant - Apple I...
…integrity, and trust.Success Metrics/Key Performance Indicators:Quantitative* Year over Year growth in Apple Product and Beyond the Box sales in the assigned Point of Read more
*Apple* Solutions Consultant till v%u00E5r...
…ethics, integrity, and trust.Success Metrics/Key Performance Indicators:QuantitativeYear over Year growth in Apple Product and Beyond the Box sales in the assigned Point Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.