Q I want to write an application that can open incoming PowerTalk letters
automatically. How can my PowerTalk-savvy application access the letters stored in
the in-tray?
A Currently, there are only two ways of accessing in-tray letters from your
application. The most common method is to receive an open document ('odoc') Apple
event when a letter is opened from the Finder. In addition, calling SMPGetNextLetter
allows you to open letters from your application. It isn't possible, however, for your
application to access the in-tray from Standard File or to automatically open
arbitrary letters without user intervention.
Q When I open a letter in my PowerTalk-savvy application, I can obtain FSSpec
records referencing folders or files enclosed in the letter, but the files don't appear to
be copied to my hard drive. Where do these files reside on my system?
A PowerTalk maintains an external file system for enclosures of letters. If you
closely examine the FSSpec records returned to you, you'll see that the enclosed files
and folders reside on this external file system, named "Mail Enclosures." This is a
read-only file system, and the enclosures are available only while the letter is open.
Therefore, these FSSpecs should be used only to copy the enclosed items to your local
disk, and all references to them should be discarded by the time you call
SMPDisposeMailer.
Q When I call FrontWindow from within a VBL task, my system occasionally freezes at
this call. Is there any chance that it moves memory?
A No, but FrontWindow is not reentrant. It's been patched out since MultiFinder, and
ought to be on the list of routines that shouldn't be called at interrupt time. You'll have
to come up with another method of getting the front window from your VBL task. You
may want to keep a shadow copy of your application's window list in your application
global area where your VBL task can get to it.
Q We want a general extension for all PAP-capable printer drivers, to allow for user
authentication at print time. It would conduct a user authentication dialog with a
spooler on the order of the one described in Chapter 14, "Print Spooling
Architecture," of Inside AppleTalk, Second Edition. Is it possible to do this in the
QuickDraw GX printing architecture? Would we do anything different for
PostScript-savvy print spoolers to insert the right document-structuring comments?
A For spoolers that are PostScript-savvy, you can override the message
GXPostScriptDoDocumentHeader from a printing extension and insert your password
information in the PostScript header at that point, including password, user name, and
so on. When your spooler receives the job, it can check this data and see if it denotes a
valid user. By overriding this message you'll work with any PostScript driver, as long
as your spooler supports it. (You're actually talking only to your spooler, not to the
different drivers.)
For the authentication, you'll need to override GXOpenConnection to get the user's
name and password, since that's when you actually try to connect to the device or
spooler. You could use cool alerts (status dialogs) to get the information from the user
at that time. Be sure not to put up a "Type in your password, please" dialog except at
device communication time. At other times, the user won't be trying to connect to the
device and shouldn't need to provide authentication.
Q We plan to convert all our QuickDraw objects to QuickDraw GX objects when we
print, then use a QuickDraw GX printing loop to print our objects. We print bitmaps at
the printer's maximum resolution, through PrGeneral. How do we print bitmaps at the
printer's maximum resolution in QuickDraw GX? How do we find the printer's
maximum resolution?
A To print bitmaps at the printer's maximum resolution in QuickDraw GX, create the
bitmaps at the desired resolution (like 300 dpi) and then put a transform on the shape
to scale it by 72 divided by the bitmap's resolution. This method makes the bitmap
show up with the correct dimensions, whether it's drawn on a 72-dpi screen or a
300-dpi printer. And, on the 300-dpi printer, the bitmap will not be scaled at all --
it will render at 300 dpi. This works because, before drawing, the shape's scaling is
multiplied by the device's resolution divided by 72, to convert the shape to device
resolution.
To find a printer's maximum resolution, use the calls to get the information from the
printer's view device list (get the printer from the job via GXGetJobPrinter), pick
the highest-resolution printing device, and voilà!
Q My application won't print to a StyleWriter II although it works fine on all other
printers, including the original StyleWriter. Can you give me any suggestions? What's
different about the StyleWriter II?
A The StyleWriter II driver is a member of the "GrayShare" driver family, with new
features such as support for grayscale printing (if Color QuickDraw is available) and
printer sharing over the network. Its internal architecture is very different from
previous printer drivers. In spite of thorough compatibility testing, some problems
have shown up since the first release. In many cases, the driver revealed weaknesses
in the applications themselves; for some other problems, a solution will be
incorporated in the next release of the driver. Here are some identified problem areas
with GrayShare drivers (note that these don't necessarily represent bugs in the
drivers, but are differences in the system's configuration at print time):
Q We've been manually writing 'PAPA', 'STR ', and 'alis' resources in the System file
and in the LaserWriter driver to change printers without using the Chooser. This
method sometimes causes errors with LaserWriter 8. What do we need to do?
A LaserWriter 8 needs to know more about the printer than its AppleTalk name -- it
also has to have a PostScript printer description (PPD) file for that printer, parsed
and ready to be used. Since there's so little memory available in applications like the
Finder during printing, the parsing is done at Chooser time, not at print time.
Apple has always said "We can't guarantee that you can change printers behind the
Chooser's back," and with LaserWriter 8 this is true. If the driver has parsed a PPD
file and has it ready, things should work OK, but everything must have been manually
set up by choosing that printer ahead of time. If you set up a LaserWriter IINTX
printer with the correct PPD file, choose a LaserWriter IIf, and then choose another
printer driver, you could probably programmatically switch back to the LaserWriter
IINTX, but the driver will use the LaserWriter IIf PPD file with it, which might or
might not produce the right behavior. Designing the driver to be switchable by other
applications simply wasn't a priority of the Adobe/Apple development team.
As long as you try to switch to a printer that uses the same PPD file that the driver
last parsed (meaning the PPD associated with the last printer selected in the Chooser),
there shouldn't be any more problems than there were before.
Q I want to create a QuickDraw GX font that will calculate check digits as the user
types the numbers in. For example, if you type "123458723" the check digit would be
5; if you type "098732734" the check digit would be 7; and so on. The formula is
check digit = sum of nine numbers MOD 10; the check digit is appended as the
number's tenth digit. Is there a way to do this using the glyph modification properties
in QuickDraw GX? I know it can be done by creating an entry in the 'mort' table for all
unique possibilities, but there are 9 ^9 possibilities, which comes to 387,420,489.
Can I enter a formula instead of creating tables? If so, how?
A It's a fascinating idea, but it's not something the 'mort' tables can handle. These
tables are basically state machines; when they detect a particular state, they take some
action based on entries in the table. There's no way to add a formula or code in any
language to these tables.
All the tables can do is take a series of glyphs and replace them with a different glyph
if a given feature is enabled by line layout. For example, you can change the two letters
"f"and "i" into the corresponding ligature"fi" (one glyph). If you wanted to do this for
check digits, you'd have to have an entry in the 'mort' table for each glyph combination
you wanted substituted. For 300000000, you'd have to have one entry that substituted
3000000003, and the substitution has to be one glyph. Since order is significant, that
means you'd have to have one billion entries in the 'mort' table and one billion glyphs
representing all the entries with their check digits added. That's where we have to
stop, because a font can't contain more than 65,536 separate glyphs. It's a really neat
idea, but it won't work.
Q I've selected AppleShare volumes to mount at system startup by checking the
volumes in the Chooser list. If I'm on a nonextended network and I call an extended
network via AppleTalk Remote Access and log into a remote server via the Chooser and
AppleShare, an error alert will say "The AppleShare Prep file needed some minor
repairs. Some AppleShare startup information may be lost." All the information about
my local nonextended network will be cleared out of the AppleShare Prep file. So I lose
all my log- in IDs and passwords for my local servers. The same thing happens going
back the other way (extended to nonextended). Why is this happening?
A There are several problems you can run into when you connect two networks
(which is what you're doing when you use AppleTalk Remote Access when you're
already connected to a network). The problems are usually the result of duplicate
names or duplicate node numbers.
The "boot mount list" (BML) kept in the AppleShare Prep file stores the location of
volumes that you want mounted at boot time. Part of that location is the zone name. If
you create BML entries when you aren't on an extended network -- that is, when you
have no zones -- the zone name stored in the BML is "*" (AppleTalk's shorthand for
"this zone"); otherwise, the zone name of the server is stored in the BML.
The boot mounting code checks the validity of the BML when the system starts up, and
the AppleShare Chooser package checks the validity of the BML when it's opened. If
there are no zones, entries with zone names other than "*" are cleared and the alert
"The AppleShare Prep file needed some minor repairs. Some AppleShare startup
information may be lost" is displayed because those entries aren't valid. If there are
zones, entries with zone names of "*" are cleared and the alert is displayed because the
"*" zone name isn't a reliable way to save the zone location of a server on an extended
network. The "*" zone isn't reliable for storing the zone name because a workstation
can easily be moved from zone to zone, keeping the same NBP object and NBP type
names. This is especially true with AppleTalk Phase 2, which supports multiple zones
on a single network (for example, multiple zones on the same piece of Ethernet cable).
The workaround for boot-mounting volumes is to create alias files to the file servers
you want to mount at boot time and then drop those alias files into the Startup Items
folder inside your System Folder. The only drawback to this is that aliases don't save
the user's password. If you need boot-mounted volumes without the password dialog,
you'll have to use guest access.
Q What is a Macintosh IIvm? One of the System Enabler files defines the computer in
gestaltMachineType 45. Is this just another name for the Performa 600? The
Macintosh IIvx Developer Note says that the Performa 600 returns type 45.
A Apple had planned to release a model called the Macintosh IIvm but consumer testing
showed that users thought "vm" was an abbreviation for "virtual memory." This was
about the same time Apple was about to introduce the Performa line. So, to avoid
confusion, the model became the Performa 600. There are, therefore, three models in
the "v" series: the Macintosh IIvi, Performa 600 (Macintosh IIvm), and Macintosh
IIvx. As you can see, using the nonreleased "Macintosh IIvm" designation confuses
people, so try to avoid it.
Q What do those numbers at the end of System Enabler file names mean?
A If you hold down a certain modifier key combination while opening your System
Folder, the System 7.1 Finder will reward you with a special message from Apple's
Advanced Technology Group -- if and only if the current tick count (as returned by
TickCount) divided by the number at the end of the machine's enabler file name (in
decimal) is exactly equal to the model number of the Macintosh for which the enabler
is intended.
Legal restrictions prevent us from revealing the message itself, but enterprising
techno-nerds may attempt to find it with these instructions.
Q Which variables does the stack sniffer VBL task look at to determine that the stack
has crossed over into the heap? I create stacks for my own subtasks in the heap. Will
modifying those variables affect anything else besides the stack sniffer? What's the
correct process to defeat the stack sniffer task (leaving it installed) or remove the
task?
A Disabling the stack sniffer is reasonably simple -- storing four bytes of $00 in the
low-memory global StkLowPt ($110) will turn the sniffer off. However, when using
your own internal stack, be sure not to call any Toolbox routines, because many of
them rely on the stack for temporary storage, which will screw things up if you've
played with the value of register A7.
When you're using your own stack within your heap, you should definitely save the
values in StkLowPt and A7 before changing them, so that you can reset their values
before and after any Toolbox calls.
Q How can I tell whether a picture is QuickTime-compressed?
A The key to your question is "sit in the bottlenecks." If the picture contains any
QuickTime- compressed images, the images will need to pass through the StdPix
bottleneck. This is a new graphics routine introduced with QuickTime. Unlike standard
QuickDraw images, which only call StdBits, QuickTime-compressed images need to be
decompressed first in the StdPix routine. Then QuickDraw uses StdBits to render the
decompressed image. So swap out the QuickDraw bottlenecks and put some code in the
StdPix routine. If it's called when you call DrawPicture, you know you have a
compressed picture. To determine the type of compression, you can access the image
description using GetCompressedPixMapInfo. The cType field of the ImageDescription
record will give you the codec type.
See the CollectPictColors snippet on this issue's CD and "Inside QuickTime and
Component- Based Managers" in develop Issue 13, specifically pages 46 and 47, for
more information on swapping out the bottlenecks.
Q Is there a way to embed a QuickTime movie into a Macintosh file containing
non-QuickTime stuff and get the Movie Toolbox to play the movie back correctly? If so,
can we pass the same movie handle to QuickTime for Windows and get it to play back
the same data from the same file?
A To add QuickTime movie data to non-QuickTime files, just store the movie data in
the file using FlattenMovieData with the flattenAddMovieToDataFork flag. Since
FlattenMovieData will simply append to a data fork of a file, you can pass it any data
file and it will append the movie data to that file. QuickTime doesn't care what's stored
before or after the movie data, as long as you don't reposition the movie data within the
data file. If you do, the movie references will be incorrect since they aren't updated
when you edit the file. The returned movie (from FlattenMovieData) will properly
resolve to that data file. You can then save this movie in the data fork with
PutMovieIntoDataFork or in the resource fork with AddMovieResource. If the movie is
saved in the data fork, it can be retrieved by both QuickTime and QuickTime for
Windows with NewMovieFromDataFork.
You can, in fact, store multiple movies simply by calling FlattenMovieData and
PutMovieIntoDataFork several times on the same file. Each FlattenMovieData call
appends new data, assuming the createMovieFileDataCurFile flag isn't set.
Q Is there a way that the action filter procedure of a QuickTime movie controller
component can have a user reference field so that I can know which movie "object" the
movie controller refers to? There are local variables associated with a particular
movie that I would like to access from the action filter procedure; currently there's no
way to reference back to the variables in my program except through globals.
A This was a difficult task under QuickTime 1.0, requiring you to stuff some sort of
pointer in the movie user data fields. The good news is that in response to developer
requests, starting with version 1.5, QuickTime includes a new call in the Movie
Controller suite allowing you to pass and receive a long value when you set up your
filter procedure, as follows:
pascal ComponentResult MCSetActionFilterWithRefCon(MovieController
mc, MCActionFilterWithRefCon
myUserPlayerFilter, long refCon) =
{0x2F3C,0x8,0x2D,0x7000,0xA82A};
The procedure is of the form
pascal Boolean userPlayerFilter(MovieController mc, short action,
void *params, long refCon);
The procedure returns true if it handles the action, false if not. The action parameter
identifies the action to be executed; params is the set of potential parameters that go
with the action; and refCon is any long value passed to MCSetActionFilterWithRefCon.Q
We want to add temporal compression for our long movies with similar sequential
frames. How do I use the Compression Manager routines (CompressionSequenceBegin
and CompressSequenceFrame, for instance) in conjunction with the normal
movie-making routines (such as CompressImage)?
A Sequence compression is useful for temporal compression, with processes like
animation. Sequence compression works by providing one description handle for a
series of frames, whereas CompressImage may use a description handle for each image.
Thus, functions such as CompressImage are normally used separately from the
sequence calls. It's a bit confusing; the Movie Construction FD sample on the QuickTime
CD should help clarify how to use the calls.
Sequence compression performs similarly to creating a movie with CompressImage,
but the major difference is the specification of key frames. (Key frames are frames
against which all the following frames are differenced.) CompressSequenceFrame
returns a similarity value, which tells you whether the frame is a key frame (0
means key frame). Based on this value, you can tell AddMediaSample the type of frame
it is. Here's some pseudo code:
err = CompressSequenceFrame(seqID, ..., similarity, nil);
err = AddMediaSample(gMedia, ..., similarity ? mediaSampleNotSync :
0, &sampTime);
Q When we try to digitize frames (grabbed with QuickTime) into an off-screen pixel
map, our VDGrabOneFrame call crashes. How would you suggest we do this?
A You need to check whether the 'vdig' resource supports digitizing off-screen by
calling the PreflightDestination routine. If the PreflightDestination call with an
off-screen destination fails, you need to digitize to a window on the digitizing device
and then copy the image (using CopyBits or your own algorithm for speed) from the
window to your off-screen pixel map. Some 'vdig' resources don't support digitizing
directly to off-screen pixel maps because their hardware does the digitizing
asynchronously. You should always preflight your destination before setting it with
SetPlayThruDestination.
Q Why doesn't the QuickDraw GX LaserWriter driver have a 'pdip' resource? Isn't it
required?
A A 'pdip' resource isn't required; if it isn't present in the driver, the default
(LaserWriter Plus) preferences are used. Those preferences are currently as listed
below. They're subject to change, so don't depend on them. If you need a specific value
for any of these preferences, just include your own 'pdip' resource.
| language level | 1 |
| device color space | graySpace |
| device color profile | nil |
| render options | noOptions |
| path limit | 1496 |
| gsave limit | 1 |
| operand stack limit | 500 |
| font type | type1Stream + |
| type3Stream | |
| printer VM | 200K |
Q Inside Macintosh: Macintosh Toolbox Essentials recommends calling CloseDialog
instead of DisposeDialog when allocating memory for a dialog record manually instead
of letting the Toolbox do it. But doing so causes a memory leak, because GetNewDialog
copies the DITL resource in memory. The DITL copy isn't released by CloseDialog and
isn't purgeable, even if the original DITL was purgeable. What's the official method of
completely getting rid of a dialog whose storage you've allocated by hand?
A CloseDialog was intended to mirror NewDialog; it allows you to close a dialog that
you provided the storage for, including the item list. Page 6-119 of Inside Macintosh:
Macintosh Toolbox Essentials states that the item list is specifically not disposed of by
CloseDialog, so it's acting as documented. It does this so that it won't dispose of a dialog
item list you might be planning to use again. If you do want to dispose of the item list,
just do so after calling CloseDialog.
Q As a MacApp developer, am I supposed to be using the .h files in the MPW:Interfaces
folder, or the ones in the {MacApp}CPlusIncludes folder?
A As a default, MacApp 3.0 first searches through the {MacApp}CPlusIncludes folder
for header files specified in your source, so we suggest using the CPlusIncludes
headers. The path to these include files is defined in the {MacApp}Startup
Items:Startup folder. MacApp 3.1 uses the universal interfaces for both 680x0 and
PowerPC development. It no longer uses its own custom headers in the
{MacApp}CPlusIncludes folder. MacApp 3.1 searches MPW's {CIncludes} folder for its
headers.
Q When starting a new MacApp program, I get the message "Couldn't create new
document because an internal component is missing. Please contact the developer." How
do I find out which component is missing?
A When building an application, the linker strips out any unused code from the final
application. The problem is that it determines which code is to be stripped out by
finding all objects that are constructed with the new operator. Because objects derived
from TView might instead be instantiated through calls to TViewServer methods, the
linker thinks that calls to your derived TView objects aren't used, so those objects are
stripped from the build. To circumvent this, you have to fool the linker into not
stripping out this code. MacApp defines a macro that makes it easy for you to trick the
linker. Place this line of code in your implementation of
TSomeApplication::ISomeApplication:
macroDontDeadStrip(TSomeView);
Do this for any subclass of TView defined in your program. Good examples of the use of
this routine can be found throughout the MacApp C++ code.
MacApp takes care of this for you for any TView subclasses defined by MacApp,
provided you call InitUDialogs, InitUTEView, and so on in your main routine. The exact
set of routines you have to call depends on the TView classes you use in your
application. All of these routine names begin with "InitU."
MacApp uses two alerts to indicate that you're missing components. The first one ends
with "because an internal component is missing. Please contact the developer." The
second one is identical except that it's preceded by the class name of the missing
component. In the former case it's very likely you forgot one of the "InitU" calls; in
the latter case you're very likely missing a macroDontDeadStrip on one of your TView
subclasses. If you need to find out more precisely which components are missing, you
can break on the Failure routine with a debugger.
Q How many new Inside Macintosh books will there be by the time all the new
technologies are documented?
A How much shelf space do you have?
These answers are supplied by the technical gurus in Apple's Developer Support
Center. Special thanks to Sonya Andreae, Mark Baumwell, Brian Bechtel, Chris
Berarducci, Matt Deatherage, Tim Dierks, Steve Falkenburg, Nitin Ganatra, Bill
Guschwan, Dave Hersey, Jim Luther, Joseph Maurer, Kevin Mellander, Martin
Minow, Eric Mueller, Ed Navarrete, Mike Neil, Guillermo Ortiz, Jeroen Schalk,
Brigham Stevens, Dan Strnad, and John Wang for the material in this Q & A column.
Extra special thanks and a fond farewell to Rilla Reynolds, who took a thankless job and
made it work for all of us. *
For more information on LaserWriter 8, see this issue's "Print Hints" column. *
For more information on universal interfaces, see the article "Making the Leap to
PowerPC" in this issue. *
Have more questions? Need more answers? Take a look at the Macintosh Q&A Technical
Notes on this issue's CD and in the Dev Tech Answers library on AppleLink. *