KON and BAL still lay claim to the Puzzle Page, and they assure us they'll be back, but
meanwhile they'd like to have some guest puzzlers take over for a while. (They say
they're busy with work at Catapult Entertainment and Rocket Science, but we all know
about those vacations they take!) This puzzle is from Cary Clark, presented in the
form of a dialog between his astute pug dogs, Shelley and Byron (who, Cary says, will
eat anything, including codecs and Texas Hold'ems). The dialog gives clues to help you.
Keep guessing until you're done; your score is the number to the left of the clue that
gave you the correct answer. And please, help out KON and BAL by submitting puzzles
of your own to AppleLink DEVELOP.
Shelley KON and BAL have gone the way of the dodo bird (or at least the way of the
hedgehog), so it's time to replace all of their arcane QuickDraw knowledge with arcane
QuickDraw GX knowledge.
Byron I tried to use QuickDraw GX, but since installing it off the 1994 WWDC CD, I
can't launch any of my applications.
Shelley Are you sure?
100 Byron Well, the applications launch, but double-clicking a document doesn't do
anything, even though the icons look all right.
Shelley The problem is in the desktop database, which the Finder uses to tell which
document file types correspond to which applications. Did you try rebuilding your
desktop?
90 Byron Sure, but it didn't help.
Shelley How about booting off a different disk?
85 Byron That works, but only for some files. So I removed QuickDraw GX altogether
and rebuilt the original desktop by holding down Option-Command at system startup.
Then everything worked fine.
Shelley That must mean that one of the files you removed got rid of the problem.
80 Byron Nope, grr. I tried explicitly taking the QuickDraw GX extension out of my
Extensions folder and rebooting, and nothing happened, except that my desktop
printers went away.
Shelley So how do you like the LQ, anyway?
Byron It's a lot faster than the Qume. But I miss watching it hammer the period to
make my LisaDraw pictures.
Shelley So, what else is a part of QuickDraw GX? Let's take a peek in the System
Folder. There's the printer drivers, ATM . . .
Byron That's never caused any trouble.
Shelley . . . ColorSync, the new Color Picker, PrinterShare GX. Hmmm, that's odd --
PrinterShare GX's icon is dimmed as if it were an open application, but it doesn't show
up in the process menu as PrintMonitor used to.
75 Byron Oh, you dog. That's because PrinterShare's file type is 'appe'. It's a faceless
application that's always running in the background.
Shelley I don't remember reading about that in the Processes volume of Inside
Macintosh .
Byron That's because dogs can't read. But I've heard it's briefly mentioned in Volume VI
on page 9-41. Anyway, that's beside the point. If you type procinfo in MacsBug,
you'll get a list that looks like this:
Displaying Process Information PSN Process Name Size Free HeapAt Type Crtr Status 2000 PowerTalk Manager 00044800 00003AE4 05892960 appe kl02 BgOnly 2002 Finder 00026C00 000012DC 05846E80 FNDR MACS Bkgnd 2003 File Sharing Ext... 00029C00 00005A2A 057A2C60 INIT hhgg BgOnly 2005 Eudora 1.4.2 0005CC60 000154F8 057242E0 APPL CSOm Front 2006 NCSA Telnet 2.6 00088000 0003E0B2 056982D0 APPL NCSA Bkgnd 2007 THINK Project Ma... 003E8000 001E1A68 052AC2C0 APPL KAHL Bkgnd 2008 Find File 00046000 00014F4A 052622B0 APPL fndf Bkgnd 200B Microsoft Word 00200000 000C1D5C 0505E2A0 APPL MSWD Bkgnd 200C PrinterShare GX 0001C000 00011488 0503E290 appe PtSr BgOnly
Shelley OK, try removing PrinterShare GX and rebuilding the desktop.
70 Byron Hey, that fixed it!
Shelley But the question remains, what's wrong with PrinterShare GX? And how did
you get into this sorry situation anyway?
65 Byron Well, I ran Norton Utilities on my disk, and it said it was fixing some
applications with bad bundle bits.
Shelley So Norton must force the desktop to rebuild in order to register the
applications it thought needed to be reregistered with the Finder's desktop database.
Bad dog. And the Finder fails when rebuilding the desktop.
Byron Wait a minute. PowerTalk Manager is also an 'appe'. What's different about it?
60 Shelley AOCE requires that PowerTalk Manager always run as a background
application, while QuickDraw GX needs PrinterShare GX to run only when a document
is printing.
Byron So, how does the system know to run PowerTalk Manager, but not to run
PrinterShare GX?
55 Shelley PowerTalk Manager contains a resource of type 'appe', ID = 0. This
resource returns true when called as a Pascal function, which tells the Startup
Manager to launch it. PrinterShare GX has no such resource.
Byron I bet we could figure this out from the Process Manager source, but barring
that, let's use MacsBug to figure out why the Finder fails.
Shelley We can stop on file opens using atb openrf to figure out when the Finder is
accessing PrinterShare GX.
Byron But how do you get it to stop only for PrinterShare GX?
Shelley Well, I need to find the filename. I put a break on _Open; then I display the
parameter block using dm a0 iopb.
Byron iopb?
Shelley I/O parameter block. It looks like this:
Displaying IOParamBlockRec at 0008D720 0008D720 qLink NIL 0008D724 qType 0000 0008D726 ioTrap A000 0008D728 ioCmdAddr NIL 0008D72C ioCompletion NIL 0008D730 ioResult 0000 0008D732 ioNamePtr 0008A8D6 -> "PrinterShare GX" 0008D736 ioVRefNum FFFF 0008D738 ioRefNum 0000 0008D73A ioVersNum #0 0008D73B ioPermssn #4 0008D73C ioMisc NIL 0008D740 ioBuffer NIL 0008D744 ioReqCount 00000000 0008D748 ioActCount 00000000 0008D74C ioPosMode 0000 0008D74E ioPosOffset 00000000
Byron So the 18th byte into the block can be a pointer to a string; we can dereference
that and look for strings that start with 'Prin'.
Shelley You C mutt. You have to think Pascal; the first byte will be the string length,
15, so you want to break when @@(a0+12)=0F507269.
50 Byron By George, this won't work. The file is already open!
Shelley How do you know?
Byron I used the MacsBug file dcmd, and there it is, near the bottom of the list.
Displaying File Control Blocks
fRef File Vol Type Fl Fork LEof Mark FlNum Parent FCB at0002 System fat zsys dW rsrc #2303194 #920 008359 007bfe 2fb3520060 fat **** dw data #1032192 #0 000003 000000 2fb3b000be fat **** dw data #3096576 #0 000004 000000 2fb40e011c Apple Chanc… fat FFIL dW rsrc #269497 #219985 008220 007c02 2fb46c017a Chicago fat FFIL dW rsrc #48064 #38423 008351 007c02 2fb4ca. . .0874 PowerTalk M… fat appe dW rsrc #507556 #413184 007ca8 007bff 2fbbc408d2 PrinterShar… fat appe dW rsrc #32978 #708 008236 007bff 2fbb220930 Finder fat FNDR dW rsrc #456553 #362328 00835c 007bfe 2fbc80098e Finder Pref… fat pref dW rsrc #19983 #328 007cde 007c95 2fbcde09ec Desktop DB fat BTFL dW data #196608 #150528 000011 000002 2fbd3c0a4a Desktop DF fat DTFL dW data #351810 #101184 000010 000002 2fbd9a0bc2 QMgrCatalog fat BTFL dW data #65536 #1024 007ce5 007ce4 2fbf120c20 WSBTree fat BTFL dW data #65536 #1024 007ce7 007ce2 2fbf70131a Mail En… **** dw data #0 #0 000003 000000 2fc66a#74 FCBs, #35 in use, #39 free
45 Shelley That could be OK. It depends on whether the Finder is opening a read-only
path on the file. We can tell by looking at the parameter block as we did before and
seeing what's in the ioPermssn field.
40 Byron As I suspected, it's a 3, meaning the Finder is opening it for reading and
writing, when it only needs to read the bundle resource.
35 Shelley Well, not exactly, since it wants to mark the file as initialized, so that
next time it won't add the file to the database again.
Byron But isn't that data in the Finder info, which is in neither the data fork nor the
resource fork, but just part of the file identifier, like the filename?
30 Shelley Oh, yeah. I know! The standard call OpenResFile always tries for
read/write permission. The Finder desktop-building code is old and tired, but I'm sure
when they rewrite it they'll correctly use OpenRF instead. In any case, the Finder is
getting an error it doesn't expect when opening the file, so it gives up building the
desktop database before it has retrieved the bundle information from all of the
applications.
25 Byron So one possible fix is to prevent the Startup Manager from opening the file
in the first place, since QuickDraw GX doesn't need it to be open all the time.
20 Shelley Or we could cause the file to be opened as read-only by setting its shared
bundle bit. There's a more obscure way to solve the problem: if we put the right stuff
in the 'appe' resource, the Startup Manager will be instructed to close the file after
executing some code.
15 Byron I happen to have a copy of ResEdit right here. It's a little difficult to work
with my paws, so give me a minute. Hey -- look at that little man going in and out of
the jack- in-the-box. I could watch this all day!
Shelley Cool. It even changes all the colors in the system palette, causing all of the
screens to redraw, and then redraw again when you quit. State of the art, man -- I
mean, dog.
10 Byron Well, the problem is now obvious. PrinterShare GX is a background
application that doesn't need to run all the time, but it doesn't have the shared bit set,
and it doesn't have an 'appe' resource. The 'appe' resource is code, and I don't have that
nifty ResEdit code editor.
5 Shelley We can use MacsBug to write it for us. All we need are enough instructions
to create a Pascal function that returns false. We can cheat by disassembling PtInRect
and steal a little code from there. We can verify our code by using the MacsBug
command dh to disassemble our hex. I think 422e 0004 4e74 0004 ought to do
the trick.
Byron What does that do?
Shelley It causes an illegal instruction error on a 68000 machine. Good thing Apple
doesn't sell those anymore.
Byron But I just bought a luggable for a steal at the flea market! What can I do?
Shelley Hit your smushed-faced little head against it. QuickDraw GX runs only on
68020 and better, so this code is just fine.
Byron Arf.
Shelley Grr.
SCORING
CARY CLARK, once on the QuickDraw GX engineering team at Apple, has joined BAL at
Rocket Science. He's co-owner of Shelley and Byron, who often know more than he
does. Cary was working on QuickDraw when BAL made Microsoft Word skanky and KON
made GM (not General Magic) what it is today. Next time you see KON, ask him if he
wants to cut for a hundred and watch him wince. *
Thanks to Dave Hersey, KON (Konstantin Othmer), and BAL (Bruce Leak) for
reviewing this column, and to Ron Voss for tracking the problem down and fixing it in
the shipping version of QuickDraw GX. *