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

Printopia 2.1.14 - Share Mac printers wi...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
Google Drive 1.24 - File backup and shar...
Google Drive is a place where you can create, share, collaborate, and keep all of your stuff. Whether you're working with a friend on a joint research project, planning a wedding with your fiancé, or... Read more
Chromium 45.0.2454.85 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 45.0.2454.85: Note: Does not contain the "... Read more
OmniFocus 2.2.5 - GTD task manager with...
OmniFocus helps you manage your tasks the way that you want, freeing you to focus your attention on the things that matter to you most. Capturing tasks and ideas is always a keyboard shortcut away in... Read more
iFFmpeg 5.7.1 - Convert multimedia files...
iFFmpeg is a graphical front-end for FFmpeg, a command-line tool used to convert multimedia files between formats. The command line instructions can be very hard to master/understand, so iFFmpeg does... Read more
VOX 2.6 - Music player that supports man...
VOX is a beautiful music player that supports many filetypes. 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... Read more
Box Sync 4.0.6567 - Online synchronizati...
Box Sync gives you a hard-drive in the Cloud for online storage. Note: You must first sign up to use Box. What if the files you need are on your laptop -- but you're on the road with your iPhone? No... Read more
Carbon Copy Cloner 4.1.4 - 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
OmniGraffle Pro 6.3.1 - Create diagrams,...
OmniGraffle Pro helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use... Read more
Monosnap 3.1.2 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Capture: Capture full screen, just part of the screen, or a selected window Make your crop area pixel perfect with... Read more

Goat Simulator MMO Simulator (Games)
Goat Simulator MMO Simulator 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: ** IMPORTANT - SUPPORTED DEVICESiPhone 4S, iPad 2, iPod Touch 5 or better.** Coffee Stain Studios brings next-gen... | Read more »
Worms™ 4 (Games)
Worms™ 4 1.02 Device: iOS Universal Category: Games Price: $4.99, Version: 1.02 (iTunes) Description: The latest instalment in the worldwide mega hit franchise! Coming soon to iPhone, iPad and iPod touch. When the guys and girls at... | Read more »
The Deer God (Games)
The Deer God 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: 30% off launch sale!!! “It can be a struggle, but it's all worth it when you're shooting fire out your antlers.” Kotaku “The... | Read more »
AppSpy's Patreon campaign kicks off
Occasionally you'll see us use AppSpy's videos here on 148Apps to support an article we've written. That's because we're part of Steel Media, and AppSpy is Steel's video arm, so we're all part of one happy family. [Read more] | Read more »
We're Sorry to Report that Moonrise...
Moonrise is a very promising-looking, Pokemon-esque monster collecting and battling game that we were really looking forward to reviewing, but unfortunately it looks like that's never going to happen. [Read more] | Read more »
The Latest Update for The Sims FreePlay...
Commerce has gotten a little more active with the newest update for The Sims FreePlay, making Sunset Mall more of a hangout than ever before. [Read more] | Read more »
This Week at 148Apps: August 24-28, 2015
The Apps of August With 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out... | Read more »
NASCAR in Real Racing 3? Sure, Why Not?
I have to give Firemonkeys credit - it's very cool of them to add NASCAR to Real Racing 3 via an update rather than making a separate game for it. But that's a different discussion for another time; for now let's sit back and enjoy driving in... | Read more »
The nuyu is an Inexpensive Activity Moni...
Today, Health o Meter nuyu has announced a series of health and fitness-related products, including the aforementioned activity monitor along with a wireless scale. All at a decent pricepoint, no less. [Read more] | Read more »
The Makers of Overkill are Trying Someth...
Craneballs, the studio responsible for the Overkill series, is taking a little break from all that violence (a little break) to bring us Cube Worm - a 3D take on one of the most classic PC/calculator games in existence. [Read more] | Read more »

Price Scanner via MacPrices.net

Will You Buy An iPad Pro? – The ‘Book Mystiqu...
It looks like we may not have to wait much longer to see what finally materializes as a new, larger-panel iPad (Pro/Plus?) Usually reliable Apple product prognosticator KGI Securities analyst Ming-... Read more
eFileCabinet Announces SMB Document Managemen...
Electronic document management (EDM) eFileCabinet, Inc., a hosted solutions provider for small to medium businesses, has announced that its SecureDrawer and eFileCabinet Online services will be... Read more
WaterField Designs Unveils American-Made, All...
San Francisco’s WaterField Designs today unveiled their all-leather Cozmo 2.0 — an elegant attach laptop bag with carefully-designed features to suit any business environment. The Cozmo 2.0 is... Read more
Apple’s 2015 Back to School promotion: Free B...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
128GB MacBook Airs on sale for $100 off MSRP,...
B&H Photo has 11″ & 13″ MacBook Airs with 128GB SSDs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air: $799.99, $100 off MSRP... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
27-inch 3.2GHz iMac on sale for $1679, save $...
B&H Photo has the 27″ 3.2GHz iMac on sale for $1679.99 including free shipping plus NY sales tax only. Their price is $120 off MSRP. Read more
Apple and Cisco Partner to Deliver Fast-Lane...
Apple and Cisco have announced a partnership to create a “fast lane” for iOS business users by optimizing Cisco networks for iOS devices and apps. The alliance integrates iPhone with Cisco enterprise... Read more
Apple offering refurbished 2015 13-inch Retin...
The Apple Store is offering Apple Certified Refurbished 2015 13″ Retina MacBook Pros for up to $270 (15%) off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Apple refurbished 2015 MacBook Airs available...
The Apple Store has Apple Certified Refurbished 2015 11″ and 13″ MacBook Airs (the latest models), available for up to $180 off the cost of new models. An Apple one-year warranty is included with... Read more

Jobs Board

Simply Mac *Apple* Specialist- Repair Techn...
Simply Mac is the greatest premier retailer of Apple products expertise in North America. We're looking for dedicated individuals to provide personalized service and Read more
Simply Mac *Apple* Specialist- Service Repa...
Simply Mac is the greatest premier retailer of Apple products expertise in North America. We're looking for dedicated individuals to provide personalized service and Read more
*Apple* Desktop Analyst - KDS Staffing (Unit...
…field and consistent professional recruiting achievement. Job Description: Title: Apple Desktop AnalystPosition Type: Full-time PermanentLocation: White Plains, NYHot Read more
Simply Mac- *Apple* Specialist- Store Manag...
Simply Mac is the largest premier retailer for Apple products and solutions. We're looking for dedicated individuals with a passion to simplify and enhance the Read more
*Apple* Evangelist - JAMF Software (United S...
The Apple Evangelist is responsible for building and cultivating strategic relationships with Apple 's small and mid-market business development field teams. This Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.