TweetFollow Us on Twitter

December 96 - Newton Q & A: Ask the Llama

Newton Q & A: Ask the Llama

Q I was wondering why my autopart is taking up so much heap space after it's installed. The InstallScript and RemoveScript are quite small:

constant kGlobalDataSym := '|Globals:MYSIG|;

InstallScript := func(partFrame, removeFrame) begin
   if NOT GetGlobals().(kGlobalDataSym) exists then
      GetGlobals().(EnsureInternal(kGlobalDataSym)) := {};
   GetGlobals().(kGlobalDataSym).(EnsureInternal(kAppSymbol))
      := GetLayout("MyTool.t");
end;

RemoveScript := func(removeFrame) begin
   local NGP := GetGlobals().(kGlobalDataSym);
   if hasSlot(NGP, kAppSymbol) then
      RemoveSlot(NGP, kAppSymbol);
end;
The template in MyTool.t is only a simple proto with a few slots in the base view: a symbol, viewBounds, viewFlags, viewJustify, viewFormat, viewClickScript, and three methods. When installed, the autopart takes up about 640 bytes of heap space. Is this because of the physical representation in the extras drawer?

A A minimal autopart with no RemoveScript will take up about 240 bytes. One with a RemoveScript will take 350 bytes or more, depending on the size of the RemoveScript. The 240 bytes are used by the system to keep track of the package. This includes the name, the extras drawer entry, and any symbols that you passed to EnsureInternal.

Trying your code showed that it used 444 bytes. Of course, we don't have the MyTool.t layout in the package, but that doesn't matter since you don't call EnsureInternal on the layout. Using 444 bytes isn't out of line considering the minimum size of an autopart.

Of course, you could make your code a little smaller. For example, in your RemoveScript you check that kGlobalDataSym is a known global variable. This isn't required, since RemoveSlot will do the right thing if kAppSymbol isn't in your global data frame. Note that you may want to make sure your global data frame exists:

RemoveScript := func(removeFrame)
   RemoveSlot(GetGlobalVar(kGlobalDataSym), kAppSymbol);
Also, you use GetGlobals, which is a deprecated function for Newton OS 2.0. You should be using GetGlobalVar, DefGlobalVar, and UnDefGlobalVar.

Q I'm using a protoPeoplePicker in Newton OS 2.0 and it keeps showing an "Untitled Person." Is this an opportunity to create someone or is there really a gremlin inside the machine?

A There are only two reasons for the appearance of the "Untitled Person" entry. One is that you mistakenly entered that person in your card file, which can happen if you edit an entry and accidentally erase the name. The more likely reason is that this is your hacking Newton device. If so, you probably didn't go through the Setup application and set an owner. "Untitled Person" is the default owner of the machine. We recommend that you set up a default hacking MessagePad, back it up using NBU (Newton Backup Utility), and then use that backup to create development units.

Q I've read the article in Newton Technology Journal on package freezing and I'm still a bit confused. Can you confirm that the following questions and answers are right?

  • Does my form part still have a slot in the root after being frozen? No.

  • Is the RemoveScript called when it's frozen? Yes.

  • Is the InstallScript called when it's unfrozen? Yes.

  • Can I prevent freezing/unfreezing? No.

  • Can I get a message indicating freezing vs. pulling the card? No.

  • What happens when the user tries to put away an item routed to a frozen application? A "can't find application" error.
A Congratulations, you understand package freezing correctly. And you win an all-expenses paid visit to your nearest Green Giant food processing plant.

Q There are times in my application when I want to perform the same operation on a whole bunch of soup entries. Right now the Xmit form of the calls takes quite a while and results in a lot of messages flying around. Is there a better way to do this?

A Yes. You can use nil for the argument that tells the system which application is performing the change. This tells the system not to transmit the change notification. Then you can use XmitSoupChange to send a whatThe notification. This will inform other applications that something changed, but not give specifics of the change. As an example, here's a code snippet to remove all entries in a given cursor:

// create a function we can map over
local myRemoveFunction := func(entry) EntryRemoveFromSoupXmit(entry, nil);

// remove the entries
MapCursor(removeCursor, myRemoveFunction);

// now inform registered soups that something has changed
XmitSoupChange(kSoupName, kAppSymbol, 'whatThe, nil);
Q We're having a problem with compiled NewtonScript code. We have a function that takes an int as a parameter. We use the int type indicator in the function definition. However, it's possible for the parameter to be nil. For compiled code this results in a type mismatch error. Is there a workaround for this?

A There is a way to work around this problem; however, you'll pay a performance penalty. It's much better to redesign your API to accept only integers. If you do want a workaround, you can use the type-checking functions to make sure the parameter is an integer before you use it like one. Here's some code that will work:

func native(x) begin
   local int intx;

   if IsInteger(x) then begin
      // now you can use intx and it'll be faster than using x
      intx := x;
   end else begin
      // do whatever else is appropriate; it isn't an integer
      ...
   end;
end;
Q In our application we sometimes have to show the user a big error message, which unfortunately is too large for the Notify mechanism. Is there a way we can add a button to the Notify slip? If not, is there some other mechanism we can use?

A The answer is simple: just don't let your user generate such a large error. But seriously, there is no way to modify the slip that comes up from Notify. Here are two ways to solve your problem:

  • Have the Notify message tell the user to click on some user interface element in your application for more information. This is the recommended solution.

  • Instead of Notify, use a dialog to inform the user of the error. Since you control the dialog, you control which buttons are in it. You could set up such a dialog with AsyncConfirm.
Q We need a way to find out whether a particular view inherits from a particular proto. For example:
aView := {_proto: anotherView,
          // more slots...}

anotherView := {_proto: protoFloater,
                // more slots...}
Is there a function I could call that would take aView and return true if it's an instance of protoFloater?

A There is no built-in function that will do this, but it's relatively simple to write:

func(frame, prot) begin
   while (frame AND (frame <> prot))
      frame := frame._proto;
   return (frame <> nil)
end;
Q How do I define a pickerDef column to be "lastname, firstname" in a single column?

A You can specify a Get method in your pickerDef and modify your columns appropriately. As an example, take a look at the protoListPicker sample on the Newton Developer CD. One of the subsamples is called ListPickerSoup. The default is to display the first item in the first column and the second item in the second column. The original pickerDef is defined as follows (from pickerDef.f):

DefConst('kMyBasicSoupDataDef, {
   _proto: protoNameRefDataDef,  // required
   validationFrame: nil,         // used if editing is supported
   name: "Random Data ",         // name at top left of picker if 
                                 // foldersTabs are present
   HitItem: func(tapInfo, context) begin
      context:ThingChosen(tapInfo);
   end,
   });
Then in myListPicker in the listPickerSoup.t layout file, the pickerDef slot is:
{_proto: kMyBasicSoupDataDef,   // defined in the pickerDef.f file
   class: 'nameRef,              // always include 
   columns: [   
      // Column 1
      {
         fieldPath: 'first,      // field to display in column
         tapWidth: 100,    // width for checkbox & name combined,
                                 // offset from the right margin
         doRowHilite: true,
      },
      // Column 2
      {
         fieldPath: 'second,      // field to display in column
         tapWidth: 0,             // width from preceding column to
                                  // right bounds
         doRowHilite: true,
      },
   ],
}
To modify this sample to show one column in the format "second, first", you would add the following Get method to kMyBasicSoupDataDef:
Get: func(object, fieldPath, format) begin
   if fieldPath = 'second AND
      (format = 'text OR format = 'sortText) then
   begin
      local realData := EntryFromObj(object);
      if realData then      // format is "second, first"
         return (realData.second & ", " & realData.first);
      else
         return "- -";
   end else
      inherited:?Get(object, fieldPath, format);
end
This Get method will return the correct string for a column that displays the slot 'second. It will also sort on a string that's in the format "second, first".

The other thing you need to do is modify the columns definition. Simply remove the first column, so that the pickerDef in myListPicker looks like this:

{_proto: kMyBasicSoupDataDef,     // defined in the pickerDef.f file
   class: 'nameRef,               // always include 
   columns:
   [   
      // Column 2
      {
         fieldPath: 'second,      // slot to display in column
         tapWidth: 0,             // width from preceding column to
                                  // right bounds
         doRowHilite: true,
      },
   ],
}
Q I have a pick list that takes quite a while to create. I'd like to use a weak array so that I don't have to keep creating the list. That way I get garbage collection for free. But I don't want to make the array "weak" until after the pick list has been opened by the picker so that items don't accidentally get garbage collected. How do I turn a regular array into a weak array? Or will this work at all?

A You can't turn a regular array into a weak array; an array is one or the other. But using a weak array should work, with these minor modifications to your code: Create a slot in your picker (say myWeakArray) and initialize it to a weak array. Create your regular array of pick items as usual. Let the user pop up the picker; then in either the pickCancelledScript or the pickActionScript, set the first element of myWeakArray to the array of list items. Next time you want to construct the pick list, check for the first element of myWeakArray. If it exists, you have your pick list; if not, create a new one.

Q I'm using one of the newt name views to select a name. Whenever the people picker comes up, it's viewing "All Names." How can I programmatically change the default folder used by the picker?

A You need to change the Picker method of the newt name flavor as follows:

Picker: func()
   protoPeoplePopup:New('|nameRef.people|, nil, self, 
      {labelsFilter: <symbol-for-desired-folder>});
The final argument to the New method is a frame of options. Each slot/value pair is used to set up a slot/value pair in the protoPeoplePicker. So grab the symbol for the default folder that you want and set the labelsFilter of the protoPeoplePopup.

Q What is the path to true enlightenment and wisdom?

A Simple: Buy and read all the books that claim to show you such a path. As you read, make a list of the major points. Take that list, cross off the contradictions, take the inverse of what's left, and then get a life. Alternatively, go and code another thousand lines of NewtonScript.


The llama is the unofficial mascot of the Developer Technical Support group in Apple's Newton Systems Group. Send your Newton-related questions to dr.llama@newton.apple.com. The first time we use a question from you, we'll send you a T-shirt.*

Thanks to jXopher Bell, Henry Cate, Bob Ebert, David Fedor, Ryan Robertson, Jim Schram, Maurice Sharp, Bruce Thompson, and Scott Wright for these answers.*

If you need more answers, take a look at the Newton developer Web page, at http://www.devworld.apple.com/dev/newtondev.shtml.*

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

How to evolve Eevee in Pokemon GO
By now, almost everyone should be hip to how to evolve Pokemon in Pokemon GO (and if not, there's a guide for that). Just gather enough candy of the appropriate type, feed them all to the Pokemon, and evolution happens. It's a miracle that would... | Read more »
CSR Racing 2: Guide to all game modes
It might not seem like there are all that many ways to go fast in a straight line, but CSR Racing 2 begs to differ. [Read more] | Read more »
Bulb Boy (Games)
Bulb Boy 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Multi-award winning 2D point & click horror adventure about a boy with a glowing head. | Read more »
5 top free emoji keyboard apps
If we're not at peak emoji yet as a society, it feels like we definitely should be. The emoji concept has gone far beyond what anyone in Japan could have envisioned when the people there unleashed it on an unsuspecting world, but the West has... | Read more »
How to unlock more characters in Disney...
One of the big charms of Disney Emoji Blitz is seeing a wide variety of beloved Disney and Pixar characters transformed into smiling emojis. Even someone like the sneaky Randall from Monsters Inc., who probably never cracked a smile on film, is... | Read more »
Cubway (Games)
Cubway 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Cubway is a journey with an abstract story of lifecycle of rebirth, called Samsara. Guide the cube through the long way full of dangers... | Read more »
Colorcube (Games)
Colorcube 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Turn pieces and blend colours in this minimal yet visually stunning puzzler.Over 200 handcrafted and challenging levels. Features... | Read more »
Doodle God Griddlers (Games)
Doodle God Griddlers 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
Crusader Kings: Chronicles (Games)
Crusader Kings: Chronicles 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Crusader Kings: Chronicles is an interactive text based game that puts you in the shoes of Guy de Rose as you make... | Read more »
Roads of Rome: New Generation (Games)
Roads of Rome: New Generation 1.0 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0 (iTunes) Description: | Read more »

Price Scanner via MacPrices.net

Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
13-inch 2.5GHz MacBook Pro (Apple refurbished...
Apple has 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″ 2.5GHz MacBook Pros... Read more
21-inch iMacs on sale for up to $120 off MSRP
B&H Photo has 21″ iMacs on sale for up to $120 off MSRP including free shipping plus NY sales tax only: - 21″ 3.1GHz iMac 4K: $1379 $120 off MSRP - 21″ 2.8GHz iMac: $1199.99 $100 off MSRP - 21″ 1... Read more
Charitybuzz Set to Auction Unique Apple-1 Com...
Offering an opportunity to own the computer that sparked a revolution, on Monday, July 25, leading online charity auction platform Charitybuzz will auction what is claimed to be the world’s most... Read more
MacBook Airs on sale for up to $150 off MSRP
Amazon has 11″ and 13″ MacBook Airs on sale for up to $150 off MSRP for a limited time. Shipping is free: - 13″ 1.6GHz/128GB MacBook Air (sku MMGF2LL/A): $899.99 $100 off MSRP - 13″ 1.6GHz/256GB... Read more
Apple refurbished 13-inch Retina MacBook Pros...
Apple has Certified Refurbished 13″ Retina MacBook Pros available for up to $270 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: - 13″ 2.7GHz... Read more
Apple refurbished 11-inch MacBook Airs availa...
Apple has Certified Refurbished 11″ MacBook Airs (the latest models), available for up to $170 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Apple iPad Pro Sales Far Outpacing Microsoft...
A report on Appleinsider notes that despite Microsoft Surface tablet PC sales growing by 9 percent year over year, revenues remained below $1 billion, and are down sequentially from the $1.1 billion... Read more
DEVONthink 2.9 Features Ultra-fast, Robust, A...
DEVONthink 2.9 allows users to keep databases synchronized using many means of transport. It transmits them between Macs on the local network or stores them in a syncable form on removable hard... Read more
12-inch WiFi Apple iPad Pros on sale for up t...
B&H Photo has 12″ WiFi iPad Pros on sale for up to $100 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $749 $50 off MSRP - 12″... Read more

Jobs Board

*Apple* Retail - Multiple Positions, Willow...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, 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
*Apple* Solutions Consultant - APPLE (United...
Job Summary As an Apple Solutions Consultant, you'll be the link between our future customers and our products. You'll showcase your entrepreneurial spirit as you Read more
*Apple* Professional Learning Specialist - A...
Job Summary The Apple Professional Learning Specialist is a full-time position for one year with Apple in the Phoenix, AZ area. This position requires a high Read more
*Apple* Picker - Apple Hill Orchard (United...
Apple Hill Orchard, Co. Rte. 21,Whitehall, NY 9/7/16-10/228/16. Pick fresh market or processing apples Productivity of 60 boxes and 80 boxes processing fruit per Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.