Magic Cap Developer Resources

Magic Cap Frequently Asked Questions

Last Revised: 5/15/96

What's here

The members of GMDTS have been answering Magic Cap programming questions for years. They've pulled the most commonly asked questions and the answers to those questions together into this FAQ.

The topics:

1. Announcements and Public Addresses
2. Cards, Forms and Stationery
3. Creating Packages
4. Dates
5. Debugging
6. Development Environment
7. Exceptions
8. Global Data in Magic Cap
9. Indexicals
10. Install(), Load() and InstallInto()
11. Keyboards
12. ListViews
13. Magic Cap Simulator
14. Mail and Communication
15. Memory Runtime
16. Name Cards
17. ObjectLists
18. ObjectMaker
19. Object Runtime
20. Observe/Notify
21. Packages
22. PC Cards
23. Printing
24. RunSoon() and Timers
25. Security
26. Text
27. Touching
28. Viewables

Announcements and Public Addresses

• Calling operations from confirmation dialogs
• Re-using system windows
• Names of announcement stamps
• Difference between info and infoFields in PublicAddress

Cards, Forms and Stationery

• Creating piles of stationery
• Getting card data into a form

Creating Packages

• Creating new scenes in the simulator
• Subclassing another package's class
• Creating an authority
• Using Magic Xchange to download packages
• Downloading packages to a communicator
• Communicator double restarts after a download
• Extra furnishings in hallway after many downloads
• Patching software packages
• Getting your PersonaLink address into a package
• Floating buildings downtown

Dates

• First day in Magic Cap
• Getting the local time zone

Debugging

• Debugging method not found errors
• Debugging exceptions
• Cleaning up
• Using GetObj to display a package object
• Location of parsed Telebug symbols
• Saving image of PC card from Telebug
• Debugging packages in main memory
• Dumping indexical objects in Telebug

Development Environment

• Hardware requirements
• Using C library functions

Exceptions

• Commit underflow errors
• Limit to memory allocation
• Using Catch() vs. Try()
• Destroying objects after an exception is thrown
• Throwing exceptions to another package

Global Data in Magic Cap

• Static arrays in Magic Cap
• Global data in Magic Cap
• Calling private routines across segments
• Using MPW libraries from packages

Indexicals

• Using unnamed system indexicals
• Use of iPackageTextStyles
• Dumping indexical objects in Telebug

Install(), Load(), and InstallInto()

• Cleaning up before powering down
• When Load() and Install() are called
• Notification of a package going away

Keyboards

• Meaning of Mode() and ModeAlteration()
• Keyboard complexity levels

ListViews

• Selecting an entire row

Magic Cap Simulator

• Importing fonts
• Creating borders image
• Dumping script objects
• Changing simulated PC card size
• Supported modems
• Saving changes to simulated PC cards

Mail and Communication

• Adding messages to the in and out boxes
• Message IDs
• Creating messages with preset recipients
• Implementing mailbox clear and summary features
• Making the in box mail button collect from new mail services
• Keeping images on address cards
• When to destroy a TransferTicket
• Auto-formatting phone numbers
• XModem support in Magic Cap

Memory Runtime

• Initializing objects created at runtime
• Using NewTransient() vs. NewNear()
• Allocating objects in the preferred container
• Determining how much free memory is in a container
• Committing changes
• Differences between packages in ROM and in RAM
• Garbage collection and orphaned objects
• Reference objects and "new items go here"
• Where persistent objects live
• Using InstallInto() vs. SetIndexical()
• Call NewNear() from a package in ROM
• Proper use of ...Preferred() calls
• Where new items should go

Name Cards

• Destroying name cards

ObjectLists

• Destroying an object list
• Appending the contents of an object list to another object list

ObjectMaker

• Object reference limit in ObjectMaker
• Declaring operation numbers
• Splitting instances into multiple files
• Use of the global keyword
• Created and Last Modified dates
• Gaps in instance definition numbers
• Meaning of the noCopy keyword

Object Runtime

• Definition of bits in an ObjectID
• Physical object size vs. logical object size
• Specifying private data
• Usable ObjectID vs. storable ObjectID
• Statically instantiating another package's class
• Overriding from mixin classes
• Meaning of the noCopy keyword
• Unpacking large packages

Observe/Notify

• When Notice() gets called
• Using observe/notice to watch for the option key

Packages

• Finding all installed packages
• Using FindSoftwarePackageByCitation() with different package versions
• Unpacking large packages

PC Cards

• Format of kCISMagicTuple
• Changing the default name of a PC card image
• Using standard PC cards in a Magic Cap communicator

Printing

• Reformatting viewables when printing
• Counting the number of PixelMaps in a print job

RunSoon() and Timers

• Setting up parameter blocks for calls to RunSoon()
• Executing code after a period of time has elapsed
• Updating viewables from other actors
• Setting up a timeout routine
• Using package indexicals from a RunSoon() function
• Using Idle()
• When RunSoon() functions are called
• How class SharedBuffer works

Security

• Using RSA encryption from packages
• Binding a package to a device
• Preventing changes from being beamd or mailed with a package
• Preventing a package from being beamed or mailed

Text

• Format of Magic Cap 16 bit characters
• Empty text objects for TextField data store

Touching

• Constraining touches to specific viewables
• Spinning the hat at the center of the screen

Viewables

• Aligning viewables to a grid in container windows
• Creating a global drawer bank
• Images vs. stamps
• Making an animal
• Deleting copied viewables
• Help in windows
• Use of altColor and color in Magic Cap 1.5