TweetFollow Us on Twitter

Newton Q&A final rev

Newton Q & A: Ask the Llama

Q I'm trying to remove indexes that I've added to the names soup. But the code to do it is kind of ugly. First I have to go through all the indexes to see if my index is in the soup. Then if I find the index, I can remove it. Is there an easier way?

A Yes, there's an easier way. Remember that a call to RemoveIndex will throw an exception if it's passed an invalid index. You can wrap your code in an exception handler and prevent the invalid index exception from leaving your code:

ExceptionBasedRemoveIndex := func(theSlotsym, theSoupName) begin local theSoup; foreach store in GetStores() do begin theSoup := store:GetSoup(theSoupName); if theSoup then try theSoup:removeIndex(theSlotsym); onexception |evt.ex.fr.store| do if CurrentException().error <> -48013 then ReThrow(); end; end

This function will remove a particular index (specified by theSlotsym) from a particular soup (specified by theSoupName) on all currently mounted stores. If the index exists, it will be removed; otherwise, the exception thrown for trying to remove an invalid index will be caught and ignored. If a different exception occurs, it will be rethrown so that other exception handlers or the system can deal with the exception.

Q I'm writing a utility that is an auto part. My utility needs preferences, but there's no application to add preferences to. Where should I put my preferences?

A The guidelines for preferences are simple: * For any addition that has an icon in the extras drawer, the preferences should be part of that application. Use the info button to access them. * For something that has no icon in the extras drawer, add your preferences to the system preferences roll.

See the sample "Preefer Madness" on this issue's CD for more information.

Q When text gets pasted into my paragraph view, that text is highlighted. I want to be able to detect when this happens and then be able to unselect the text. How do I do that? 

A When the text gets added, the viewChangedScript will get called with the slot parameter set to 'text. You can use the SetHilite message to unhighlight the text. However, the viewChangedScript will get called before the underlying implementation of the paragraph view has been changed. This means you need to call SetHilite in a deferred action.

Q I'm writing a specialized application for a corporate customer. One of the requirements is that the application launch when the Newton is turned on (a "turnkey" application). Is there a way to do this with the Newton? 

A You can use the installScript of your application to add a deferred action that opens your application:

constant kAppSymbol := '|autoLaunch:PIEDTS|; installScript := func(partFrame) begin AddDeferredAction(func() GetRoot().(kAppSymbol):Open(), []); end;

This will launch your application whenever the Newton is restarted or a card containing your application is inserted. Note that if the application is closed before the Newton is restarted again, the application will not relaunch. Nor will the user be prevented from accessing other features of the Newton such as Names, Dates, or Extras Drawer; that's a much harder problem.

Q I've been trying to use the protoRoll and protoRollItem to create a roll browser of my own. Everything works fine until I scroll. For a couple of these items I need to tap the down arrow twice for it to go to the next roll item. I see the scrolling view effect, but it just scrolls to itself.

The height slot in each of the roll items has the same value as the height in their viewBounds slot. If I move the roll items around when they're added to the protoRoll (dynamically from my own protos), they work fine. How can I fix this? 

A The problem is that one of the protoRollItems in the items array is larger than the protoRoll. If you make the roll browser larger than the largest roll item, all will work fine; otherwise, you have to scroll the roll item twice to move to the next roll item.

Also, since you imply that the entire large roll item is visible, I assume that the protoRoll has vClipping turned off. If you'd had clipping on, you would probably have noticed that the individual roll item was too large.

Q I'm having some problems with margins when I'm faxing. A fax without a cover page has different margins than a printed page. The actual viewBounds is the same, but the margins of the fax are different from the viewBounds.

Also, a fax with a cover page has even different margins. The viewBounds is different, too (20 pixels shorter in height), but that's OK. The problem is that the actual margins when faxed are different from those specified by the viewBounds slot. Is this a known problem? 

A Faxes with a cover page have a header line at the top of the fax which takes up those mysterious 20 pixels. In fact, it might be a bug that faxes without a cover page omit this header, but perhaps the only bug is not documenting that protoPrintFormat (which provides the cover page) also adds that header.

The way to find the correct page bounds is to set the viewBounds of your base print view to that of the parent. The base print view is usually a clView that is a child of a print layout. You can use the following code in the viewSetupFormScript of your base print view to set your bounds to those of your parent: viewBounds := :Parent():LocalBox();

Q I've got an auto part that installs a template for the formulas roll. On the roll item I've got a protoLabelInputLine for data entry, and a button that I want to use to clear the input line. My buttonClickScript is very simple:

buttonClickScript := func() begin SetValue(myInputLine.entryLine, 'text, ""); end;

The first time the button is tapped, the input line gets cleared OK; after that it never seems to work, no matter how I code it. Can you help? 

A This is a very subtle problem. The answer will be revealed in stages, so that you too can experience the "Aha!"

Observation 1: When you edit the text in any clParagraphView, no new strings are generated. The existing string is destructively modified (excluding the usual _proto copying, of course).

Observation 2: During the compile cycle, the Newton Toolkit will turn all your strings into constants. Contrast this to using braces to construct a frame. As an illustration, assume you have these three methods:

Method1 := func() begin return {slot1: "also string"}; end;

Method2 := func() begin return '{slot2: "also also string"}; end;

Method3 := func() begin return "a string"; end;

The braces specify a frame constructor. Each time you call Method1 it will return a reference to a newly allocated frame, though not different contents. For example, when the following is executed

myVar := call Method1() with ();

here's what you get in memory:

[IMAGE Newton_Q&A_final_html1.GIF]

On the other hand, Method2 quotes the frame, which makes it a quoted constant. In other words, each time you call Method2 it will return a reference to the same frame. And Method3 does something else altogether: In the Newton Toolkit, a string is treated like a quoted frame (or array). It's a constant object, so each time you call Method3 it will return a reference to the same string. Note that this means that in both Method1 and Method2 the slot in each frame will reference the same string. Diagrams that show what happens in memory when each of these three methods is executed are provided on this issue's CD along with this Q & A column.

Observation 3: When you call SetValue, you're actually copying the reference to the empty string from your buttonClickScript into the text slot of the entry line. You might think this would cause an error, because the string constant can't be modified. But clParagraphViews are smart: if the string can't be modified (that is, if it's read-only), a copy is made.

Observation 4: I checked in the inspector, and your buttonClickScript is not read- only. This means that the string constant "" in that script is also not read-only.

Observation 5: To prevent the grip of death on a card, you would need to call EnsureInternal on your formula roll entry. This effectively makes a copy of the entire template, including constants, in the NewtonScript heap. The following illustration contrasts a Clone with a DeepClone (which is what EnsureInternal uses). Note that the DeepClone creates a new read/write copy of the string.
















Conclusion: You press the Clear Data button once. This sets the reference of the input line string to point to the string constant in your buttonClickScript. Since the string constant is no longer read-only, changing the input line string destructively modifies the string constant. You may think that this would lead to a bus error or worse, but thanks to NewtonScript, it works as it should. The next time you press the Clear Data button, the input line string reference gets replaced with a reference to the now modified string constant.

[IMAGE Newton_Q_A_final_html2.GIF]

The solution is to change the SetValue call to

SetValue(dataItem.entryLine, 'text, Clone(""));

This will make a copy of the string constant and return a reference to the copy.

Q Just recently I came into possession of a sword. It was handed to me by a lady in a lake whose arm was clad in the finest shimmering samite. I figure with this sign of divine providence I should be able to wield supreme executive power. What do you think? 

A Fortunately, strange women in ponds have not been used as the basis for a system of government since the Dark Ages. These days supreme executive power derives from a mandate from the masses, not from a farcical aquatic ceremony. If I claimed to be President just because some aquatic gymnast threw a sword at me, I'd be locked up for sure.

The llama is the unofficial mascot of the Developer Technical Support group in Apple's Personal Interactive Electronics (PIE) division. Send your Newton-related questions to NewtonMail DRLLAMA or AppleLink DR.LLAMA. The first time we use a question from you, we'll send you a T-shirt. *

Thanks to Don Gummow and our Newton Partners for the questions used in this column, and to jXopher Bell, Bob Ebert, Mike Engber, Kent Sandvik, Jim Schram, and Maurice Sharp for the answers.

*Have more questions? Need more answers? Take a look at PIE Developer Info on AppleLink. *

 
AAPL
$98.38
Apple Inc.
-0.64
MSFT
$43.89
Microsoft Corpora
-0.09
GOOG
$585.61
Google Inc.
-4.99

MacTech Search:
Community Search:

Software Updates via MacUpdate

Drive Genius 3.2.4 - Powerful system uti...
Drive Genius is an OS X utility designed to provide unsurpassed storage management. Featuring an easy-to-use interface, Drive Genius is packed with powerful tools such as a drive optimizer, a... Read more
Vitamin-R 2.15 - Personal productivity t...
Vitamin-R creates the optimal conditions for your brain to work at its best by structuring your work into short bursts of distraction-free, highly focused activity alternating with opportunities for... Read more
Toast Titanium 12.0 - The ultimate media...
Toast Titanium goes way beyond the very basic burning in the Mac OS and iLife software, and sets the standard for burning CDs, DVDs, and now Blu-ray discs on the Mac. Create superior sounding audio... Read more
OS X Yosemite Wallpaper 1.0 - Desktop im...
OS X Yosemite Wallpaper is the gorgeous new background image for Apple's upcoming OS X 10.10 Yosemite. This wallpaper is available for all screen resolutions with a source file that measures 5,418... Read more
Acorn 4.4 - Bitmap image editor. (Demo)
Acorn is a new image editor built with one goal in mind - simplicity. Fast, easy, and fluid, Acorn provides the options you'll need without any overhead. Acorn feels right, and won't drain your bank... Read more
Bartender 1.2.20 - Organize your menu ba...
Bartender lets you organize your menu bar apps. Features: Lets you tidy your menu bar apps how you want. See your menu bar apps when you want. Hide the apps you need to run, but do not need to... Read more
TotalFinder 1.6.2 - Adds tabs, hotkeys,...
TotalFinder is a universally acclaimed navigational companion for your Mac. Enhance your Mac's Finder with features so smart and convenient, you won't believe you ever lived without them. Tab-based... Read more
Vienna 3.0.0 RC 2 :be5265e: - RSS and At...
Vienna is a freeware and Open-Source RSS/Atom newsreader with article storage and management via a SQLite database, written in Objective-C and Cocoa, for the OS X operating system. It provides... Read more
VLC Media Player 2.1.5 - Popular multime...
VLC Media Player is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, MP3, OGG, ...) as well as DVDs, VCDs, and various streaming protocols. It... Read more
Default Folder X 4.6.7 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click... Read more

Latest Forum Discussions

See All

Note Review
Note Review By Jennifer Allen on July 29th, 2014 Our Rating: :: TOO SIMPLEiPhone App - Designed for the iPhone, compatible with the iPad Note is a note taking app that’s a little too short on features to be worth its asking price... | Read more »
Chainsaw Warrior Goes on Sale & Ther...
Chainsaw Warrior Goes on Sale & There’s a Chance to Win a Copy of the Original Board Game Posted by Jennifer Allen on July 29th, 2014 [ permalink | Read more »
It Came From Canada: Tiny Tower Vegas
If you go to a casino, you might make a lot of money. If you run a casino, you’re guaranteed to make a lot of money. The choice seems pretty obvious. So while waiting for your shady real estate deals to move forward, get prepared with Tiny Tower... | Read more »
Z Hunter Review
Z Hunter Review By Lee Hamlet on July 29th, 2014 Our Rating: :: RIGHT ON TARGETUniversal App - Designed for iPhone and iPad While it might not necessarily break new ground, Z Hunter has enough tricks up its sleeve to ensure that... | Read more »
Huge Update Comes To Duet, Adding 48 New...
Huge Update Comes To Duet, Adding 48 New Stages Posted by Jennifer Allen on July 29th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Sharknado: The Video Game Available Now....
Sharknado: The Video Game Available Now. Seriously. Posted by Rob Rich on July 29th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Frog Orbs 2 Review
Frog Orbs 2 Review By Nadia Oxford on July 29th, 2014 Our Rating: :: THIS MAGIC IS A TAD MONOTONOUS Universal App - Designed for iPhone and iPad Frog Orbs 2 is repetitive, but younger players should enjoy it nonetheless.   | Read more »
Puzzix Review
Puzzix Review By Jennifer Allen on July 29th, 2014 Our Rating: :: NICE IDEAUniversal App - Designed for iPhone and iPad A little like Tetris, Puzzix is all about piecing together blocks and watching them vanish. It could do with... | Read more »
Cannonball eMail is Now Live – Works Wit...
Cannonball eMail is Now Live – Works With Gmail, Yahoo, Outlook, Hotmail, and AOL Posted by Jessica Fisher on July 29th, 2014 [ permalink ] | Read more »
To The End Review
To The End Review By Lee Hamlet on July 29th, 2014 Our Rating: :: A VICIOUS CYCLEUniversal App - Designed for iPhone and iPad To The End will test players’ patience, timing, and dedication as they try to navigate all 13 levels in... | Read more »

Price Scanner via MacPrices.net

WaterField Unveils 15″ Outback Solo & 13″...
Hard on the heels of Apple’s refreshed MacBook Pro Retina laptops announcement, WaterField Designs has unveiled a 15-inch version of the waxed-canvas and leather Outback Solo and a 13-inch version of... Read more
New Roxio Toast 12 Delivers Digital Media Pow...
Roxio Toast 12 is a hub for sharing digital media to virtually any platform or device. has introduced two new additions to its Roxio Toast product family – Roxio Toast 12 Titanium and Roxio Toast 12... Read more
The lowest prices on leftover Retina MacBook...
Best Buy has dropped prices on leftover 13″ and 15″ Retina MacBook Pros by up to $300 off original MSRP on their online store for a limited time. Choose free local store pickup (if available) or free... Read more
Apple Updates MacBook Pro with Retina Display...
Apple today updated its MacBook Pro with Retina display with faster processors and double the amount of memory in both entry-level configurations. MacBook Pro with Retina display features a Retina... Read more
Up to $250 price drop on leftover 15-inch Mac...
B&H Photo has dropped prices on 2013 15″ Retina MacBook Pros by as much as $250 off original MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.3GHz Retina MacBook Pro: $2349... Read more
Updated MacBook Pro Price Trackers
We’ve updated our MacBook Pro Price Trackers with the latest information on prices, bundles, and availability on the new 2014 models from Apple’s authorized internet/catalog resellers as well as... Read more
Apple updates MacBook Pros with slightly fast...
Apple updated 13″ and 15″ Retina MacBook Pros today with slightly faster Haswell processors. 13″ models now ship with 8GB of RAM standard, while 15″ MacBook Pros ship with 16GB across the board. Most... Read more
Apple drops price on 13″ 2.5GHz MacBook Pro b...
The Apple Store has dropped their price for the 13″ 2.5GHz MacBook Pro by $100 to $1099 including free shipping. Read more
Apple drops prices on refurbished 2013 MacBoo...
The Apple Store has dropped prices on Apple Certified Refurbished 13″ and 15″ 2013 MacBook Pros, with model now available starting at $929. Apple’s one-year warranty is standard, and shipping is free... Read more
iOS 8 and OS X 10.10 To Support DuckDuckGo As...
Writing for Quartz, Dan Frommer reports that Apple’s forthcoming iOS 8 and OS X 10.10 operating systems version updates will allow users to select DuckDuckGo as their default search engine. He notes... Read more

Jobs Board

Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full 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
Sr. Product Leader, *Apple* Store Apps - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring 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* 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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.