TweetFollow Us on Twitter

Jun 97 - Newton Q and A

Volume Number: 13 (1997)
Issue Number: 6
Column Tag: develop

Newton Q&A: Ask the Llama

by Apple Developer Technical Support Group

Q: I'm probably missing something obvious, but when I try to use an asynchronous output call in some situations, I get an exception, while synchronous calls seem to work fine. For instance, this code fails consistently with bus errors:

endpoint:output(headerCache,
   nil,
   {async: true,
   form: 'string,
   completionScript: func(ep, options, result)
      self:SendData(endpoint, qfCursor)});

On the other hand, this code works fine:

endpoint:output(headerCache, nil, nil);
self:SendData(endpoint, qfCursor);

I'd really prefer to use asynchronous calls, but I keep running into problems. Do you have any suggestions?

A: The key thing you're missing is that self (that is, the receiver) is not what you expect in your asynchronous callback. In your first example, you pass a completion frame as the third argument of the Output message. It's this frame that will be self (that is, that will be the context of the completionScript). This means that you send the sendData message to that completion frame.

What you probably want is to send the message to the ep argument passed to the completionScript. This will be the endpoint to which you sent the Output message. In general, you will have set this endpoint to have a _parent slot that points to your application. Assuming that the sendData method is in either the endpoint or your application, you would modify the body of the completionScript to be

ep:sendData(endpoint, qfCursor);

The same restrictions apply for Input and Option calls as well.


Q: I have a pop-up view that has an icon with some text, and I'd like the user to be able to edit the icon. I call MakeShape on the icon and draw it into a bitmap. I then have an interface for the user to modify the icon. The problem occurs when I try to display the modified icon in the pop-up. It either doesn't show up, has incorrect bounds, or throws an exception. Before I modify the icon, it looks like something that would be returned by GetPictAsBits:

{data: <bits, Length 42>, bounds: {0,0,15,15}, }

Once I call MakeShape on the icon, it looks like this:

{class: bitmap, bounds: <boundsRect, Length 8>,
   data: <pixels, Length 54>, }

The pop-up chokes on this when I try to display it. First it threw an exception because it was expecting a frame instead of a binary object in the bounds frame. So I called SetBounds to set the bounds frame to {0,0,15,15}. This enabled the pop-up to open, but the icon wasn't in the right place. Fiddling with the bounds frame didn't seem to help. So I'm guessing that the next problem is that I have pixels instead of bits in the data slot. I tried calling SetClass on the slot to change it from pixels to bits. That actually didn't throw an exception, but the length is still different and it didn't look right. How can I get my shape or bitmap back into a form that the pop-up will be happy with?

A: The basic problem is that the binary object used by MakeShape to represent the picture (that is, <pixels, Length 54>) is not the same as that used in the bitmap structure (<bits, Length 42>). You have a couple of choices. Since the formats are documented, you can write some code to convert the object returned by MakeShape into a NewtonScript bitmap object. The other option, which seems more complex but is probably easier to implement, is to use the MakeShape representation only for your icon editor. Let the user modify the MakeShape representation, but keep track of the changes and use them to modify the bitmap. So, while the user is editing the icon, there will be two data objects: the original icon representation using the bitmap data structure and the MakeShape representation that the user sees and modifies. As the user changes the MakeShape object, your code is also modifying the bitmap object.

As a related side note, you can use DrawIntoBitmap to get the bits that represent the shape.


Q: In an application I'm building, I want to keep a serial communication session open with a GPS unit 24 hours a day, unattended by the user. Both the MessagePad and the GPS unit are powered by the car. The GPS unit sends out data approximately every two seconds. I'm using the "Basic Serial" Newton DTS sample code as the starting point. The communications code in the application works fine except that occasionally I get a -18003 exception, which results in a kMessage_BufferOverrun message. I've tried turning on useSoftFlowControl and useHardFlowControl in the kCMOInputFlowControlParms parameter frame inside the MBuildConfigOptions method, but that doesn't seem to help.

Can you explain when/why this exception is raised? Can I safely ignore the exception by revising the MNotifyError method? What can I do to prevent the occurrence of the exception in the first place?

A: A -18003 error can indicate several things, including bad parity or a framing error. Usually it indicates that the Newton's UART (SCC chip) buffer has overrun. You can just ignore this error, repost the input specification, and go on your merry way.

To repost the input specification, call the endpoint's SetInputSpec with the relevant input specification. Before reposting the input specification, you may also want to flush the communication tools buffers using the serial discard data option (kCMOSerialDiscard) and flush the NewtonScript buffer with FlushInput. Regardless of whether you flush, you will have lost some data in the process, although for most GPS applications that should be fine. You may also want to try increasing the size of the serial input buffer; this might give you just enough time to process all the data.

A better solution would be to have the GPS receiver support some type of flow control, though this will depend on the manufacturer of the unit.


Q: I have a view with a protoKeyboard button. The input lines within the view all take numeric input, and when the user double-taps, the numeric keypad pops up. But the keyboard button brings up the full QWERTY keyboard instead. How can I make the button open the numeric keypad?

A: The keyboard button is behaving correctly. If you don't specify which keyboard to open, it will always open the global alphanumeric keyboard. There are two ways you can get the behavior you want:

  • Override the 'defaultKeyboard slot in your protoKeyboardButton. This slot contains the keyboard that you want to use. In this case you want the symbol 'numericKeyboard, which specifies the default numeric keyboard.
  • Override the buttonClickScript in the protoKeyboardButton. You can use the OpenKeypadFor function and specify your input line as the view. This will usually do the right thing since calling OpenKeypadFor has just about the same effect as the user's double-tapping in an input line.

Q: I noticed that the NTK project preferences dialog lets you compress your application. How much slower will the application run if I do this?

A: Unfortunately, there's no simple answer to this question. The speed of execution depends on a number of factors, including how many times the system has to uncompress pages from your application into a cache and how full the system heap is.

The best way to find out is to try your application with the three different compression options: none, compressed, or faster compression. Make sure that you perform your tests a number of times and under different memory-loading conditions. If your application will be doing communications, that's a good thing to test. You can also use HeapShow (which comes with NTK) to fill the system and NewtonScript heaps to simulate low-memory conditions.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

BetterTouchTool 2.305 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
calibre 3.8.0 - 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
Carbon Copy Cloner 5.0.2 - Easy-to-use b...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
Evernote 6.12.3 - Create searchable note...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
Default Folder X 5.1.6 - 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 on... Read more
Geekbench 4.1.2 - Measure processor and...
Geekbench provides a comprehensive set of benchmarks engineered to quickly and accurately measure processor and memory performance. Designed to make benchmarks easy to run and easy to understand,... Read more
GraphicConverter 10.5 - $39.95
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
Dropbox 35.4.20 - Cloud backup and synch...
Dropbox is an application that creates a special Finder folder that automatically syncs online and between your computers. It allows you to both backup files and keep them up-to-date between systems... Read more
XMind 8 Update 4 - Popular mind mapping...
XMind is the most popular mind mapping tool. Millions of people use XMind to clarify thinking, manage complex information, run brainstorming and get work organized. It couldn't be easier to get... Read more
Safari Technology Preview 11.1 - The new...
Safari Technology Preview contains the most recent additions and improvements to WebKit and the latest advances in Safari web technologies. And once installed, you will receive notifications of... Read more

Stormbound: Kingdom Wars guide - how to...
Stormbound: Kingdom Wars is an excellent new RTS turned card battler out now on iOS and Android. Lovers of strategy will get a lot of enjoyment out of Stormbound's chess-like mechanics, and it's cardbased units are perfect for anyone who loves the... | Read more »
The best AR apps and games on iOS right...
iOS 11 has officially launched, and with it comes Apple's ARKit, a helpful framework that makes it easier than ever for developers to create mobile AR experiences. To celebrate the occassion, we're featuring some of the best AR apps and games on... | Read more »
Phoenix Wright: Ace Attorney - Spirit of...
Phoenix Wright: Ace Attorney - Spirit of Justice 1.00.00 Device: iOS Universal Category: Games Price: $.99, Version: 1.00.00 (iTunes) Description: ************************************************※IMPORTANT※・Please read the “When... | Read more »
Kpressor (Utilities)
Kpressor 1.0.0 Device: iOS Universal Category: Utilities Price: $4.99, Version: 1.0.0 (iTunes) Description: The ultimate ZIP compression application for iPhone and iPad. - Full integration of iOS 11 with support for multitasking.-... | Read more »
Find out how you can save £35 and win a...
Nothing raises excitement like a good competition, and we’re thrilled to announce our latest contest. We’ll be sending one lucky reader and a friend to the Summoners War World Arena Championship at Le Comedia in Paris on October 7th. It’s the... | Read more »
Another Lost Phone: Laura's Story...
Another Lost Phone: Laura's Story 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Another Lost Phone is a game about exploring the social life of a young woman whose phone you have just... | Read more »
The Witness (Games)
The Witness 1.0 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0 (iTunes) Description: You wake up, alone, on a strange island full of puzzles that will challenge and surprise you. You don't remember who you are, and... | Read more »
Egg, Inc. guide - how to build your gold...
Egg, Inc.'s been around for some time now, but don't you believe for one second that this quirky clicker game has gone out of style. The game keeps popping up on Reddit and other community forums thanks to the outlandish gameplay (plus, the... | Read more »
The best deals on the App Store this wee...
Good news, everyone! Your favorite day of the week has arrived at last -- it's discount roundup day! This fine Wednesday evening we're gathering up the hottest deals on the App Store. We've got action platformers, we've got puzzle games, we've got... | Read more »
Morphite (Games)
Morphite 1.08 Device: iOS Universal Category: Games Price: $7.99, Version: 1.08 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

Apple Offering Up To $455 Credit Toward iPhon...
iPhone 8 and 8 Plus are now available at the Apple Store, and you can receive up to $375 credit toward a new iPhone purchase when you trade in your eligible smartphone. Photo Courtesy Apple Just... Read more
AnyTrans Offers iOS Users Three Ways For Movi...
iMobie Inc. today announceed AnyTrans v6.0.1, which now can help iOS users move all data to iPhone 8/8 Plus seamlessly. The software is available both on Mac and Windows and fully able to move all... Read more
Snag a 13-inch 2.3GHz MacBook Pro for $100 of...
B&H Photo has 2017 13″ 2.3GHz MacBook Pros in stock today and on sale for $100 off MSRP, each including free shipping plus NY & NJ sales tax only: – 13-inch 2.3GHz/128GB Space Gray MacBook... Read more
Verizon offers new iPhone 8 for $100-$300 off...
Verizon is offering the new iPhone 8 for up to $300 off MSRP with an eligible trade-in: • $300 off: iPhone 6S/6S Plus/7/7 Plus, Google Pixel XL, LG G6, Moto Z2 Force, Samsung Galaxy S7/S7 edge/S8/S8... Read more
Apple Refurbished 2017 13-inch MacBook Pros a...
Apple has Certified Refurbished 2017 13″ Touch Bar MacBook Pros in stock today and available for $200-$300 off MSRP. A standard Apple one-year warranty is included with each MacBook, and shipping is... Read more
OWC USB-C Travel Dock with 5 Ports Connectivi...
OWC have announced the new OWC USB-C Travel Dock, the latest addition to their line of connectivity solutions. The USB-C Travel Dock lets you connect its integrated USB-C cable to a Mac or PC laptop... Read more
Pelican Products, Inc. Unveils Cases For All...
Pelican Products, Inc. has announced the launch of its full line of cases including Voyager, Adventurer, Protector, Ambassador, Interceptor (for the Apple iPhone 8 and 8 Plus backwards compatible... Read more
$100 off new 2017 13-inch MacBook Airs
B&H Photo has 2017 13″ MacBook Airs on sale today for $100 off MSRP including free shipping. B&H charges NY & NJ sales tax only: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $100 off... Read more
Apple restocks Certified Refurbished 13-inch...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $719 and 2016 models available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Is iPhone X Really The Future Of The Smartpho...
Should iPhone X even be called a telephone? It does of course support telephony and texting, but its main feature set is oriented to other things. It is also debatable whether it makes any rational... Read more

Jobs Board

Specialist - Retail Customer Services and Sal...
The position listed below is not with Tennessee Interviews but with Apple , Inc. Tennessee Interviews is a private organization that works in collaboration with Read more
Specialist - Retail Customer Services and Sal...
The position listed below is not with South Carolina Interviews but with Apple , Inc. South Carolina Interviews is a private organization that works in collaboration Read more
Behavior Technician with *Apple* Consulting...
The position listed below is not with Washington Interviews but with APPLE CONSULTING Washington Interviews is a private organization that works in collaboration Read more
Infection Control RN with *Apple* Rehab - A...
The position listed below is not with Georgia Interviews but with Apple Rehab Georgia Interviews is a private organization that works in collaboration with Read more
Specialist - Retail Customer Services and Sal...
The position listed below is not with South Carolina Interviews but with Apple , Inc. South Carolina Interviews is a private organization that works in collaboration Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.