Macintosh One Liners

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This article was originally posted to newsgroups comp.sys.mac.programmer and comp.sys.mac by Eric Pepke in March 1990.
OK

Here is the latest version of the Macintosh One-Liners. It's now two pages long.

The Macintosh One-Liners are intended to condense onto a couple of sheets of paper information about some of the most common Macintosh problems and programming pitfalls. Each one-liner is a single line of text, shorter than 80 characters, which informs about one aspect of Macintosh use or programming.

The one-liners are brief and do not give complete information about their topics. This is intentional. Detailed documentation exists elsewhere, mostly in Inside Macintosh and in the Technical Notes. If you need more information than is provided in a one-liner, you should be able to determine it by a little experimentation or by looking it up using the words in the one-liner as hints.

One-liners give either facts or advice. The facts may be obvious to some people and obscure to others but are important for all. The advice is intended to help keep people from running into the most common nontrivial problems. Like proverbs, the advice may not be absolute and may sometimes be more conservative than is strictly neccessary. However, I have found that a little constructive paranoia can go a long way toward avoiding problems, and more than once I have taken a precaution which seemed extreme at the time but which saved my skin later on.

The one-liners started as a list I made for myself of things to remember while writing programs. I have augmented them with my condensed records of several years of Info-Mac, Usenet, and Delphi digests and one year of Usenet reading. People who have contributed to the list since its first release are mentioned at the end. The result is very much a gestalt of the Macintosh lore I have seen and depends on the wisdom and efforts of many people. If I have forgotten to include your name, I apologize.

Send suggestions for additional one-liners to pepke@gw.scri.fsu.edu on the Internet or PEPKE@FSU on BITNET. Have fun.

Users' One-Liners

  • A beep on trying to open a desk accessory may mean the DA Handler is missing.
  • A beep on trying to open a desk accessory may mean there is not enough memory.
  • If opening a document from Finder doesn't work, open it within the application.
  • A flashing Apple menu means the alarm clock is ringing. Pull down Alarm Clock.
  • A U-shaped icon at the right of the menu bar means Easy Access is activated.
  • HyperCard visual effects won't work on monitors set to more than 2 colors.
  • Hold down the F key and click OK in the print dialog to make a PostScript file.
  • Hold down command-K instead to make a PostScript file which contains LaserPrep.
  • Turn background printing off before trying to make a PostScript file.
  • Remove the paper tray during LaserWriter power-up to avoid the startup page.
  • Hold down the mouse button while powering on to eject any disk in the computer.
  • Don't put disks on the left side of a small Macintosh or near loudspeakers.
  • Never rotate a hard disk drive while it's running, not even gently.
  • If the cursor is surrounded by a big black rectangle, Close View is activated.
  • It is safer to rebuild the desktop under Finder than under Multifinder.
  • Finder's default memory size is a bare minimum. Increase it with Get Info.
  • Putting more than one System file on a disk can cause big trouble.
  • The maximum number of windows in Finder is stored in LAYO resource 128.
  • To make a TeachText file read-only, change its file type from 'TEXT' to 'ttro'
  • The first option-space in a TeachText file shows PICT 1000, the 2nd 1001, etc.
  • You can increase the maximum number of open files using a boot block editor.

Programmers' One-Liners

The Main Loop and Events

  • Call MaxApplZone and MoreMasters when the application starts up.
  • If you call SetApplLimit, do it before calling MaxApplZone.
  • Use HT in MacsBug while running to estimate how many times to call MoreMasters.
  • Don't use SetEventMask to disable mouseUp events. Better not to use it at all.
  • SetPort to a known good grafPort once every time through the event loop.
  • Calling WaitNextEvent with more than 50 ticks will fail on some systems.
  • Set the cursor on suspend and resume events.
  • Call GetDblTime to get the maximum time for a double click.
  • Measure double click time from mouse up to mouse down.
  • Call either WaitNextEvent or both GetNextEvent and SystemTask.
  • Call IsDialogEvents and DialogSelect even if GetNextEvent returns false.

Menus

  • Use SetItem to include meta characters literally in menus.
  • Never make MENU resources purgeable.

Resources

  • GetResource never produces resNotFound. Check for a NIL handle instead.
  • To create a resource file, call Create, then CreateResFile.
  • To open a resource file read-only for shared access, use OpenRFPerm.
  • Don't leave ResLoad set to false.
  • GetResource on a dctb may return a non-resource copy of the dctb.

Windows, Alerts, and Dialogs

  • Move and size windows to the bounding box of GetGrayRgn.
  • Hide scroll bars when deactivating a window.
  • Call DrawGrowIcon when activating or deactivating a window with a grow region.
  • DrawGrowIcon does not check to see if the window has a grow region.
  • Call PenNormal before calling DrawGrowIcon.
  • itemHit will not be set when a dialog filter is called.
  • Use a disabled UserItem to draw the roundrect outline around the OK button.
  • ModalDialog assumes the dialog is already visible and in the front.
  • Use screenBits . bounds to center dialogs, alerts, etc. below the menu bar.
  • If you save window locations in files, they may not be valid for all monitors.
  • DragWindow expects startPt in boundsRect; if not it may not call SelectWindow.
  • SelectWindow does not automatically call SetPort. You must do that yourself.
  • DialogSelect responds to activate events but ignores suspend/resume events.

Drawing

  • Always set the VisRgn and ClipRgn of offscreen ports.
  • Set the ClipRgn first when making a picture.
  • Don't make rowBytes in bitMaps greater than 8191.
  • To dim text, draw a rectangle with penPat=gray and penMode=patBic over it.
  • To draw rotated text, draw to an offscreen bitmap, rotate it, and CopyBits it.
  • Don't use picSize to determine the size of a picture. Check the handle size.
  • Never draw outside a window except in XOR mode for temporary effects like drag.
  • To avoid animation flicker, synchronize drawing to the vertical retrace.
  • Lock handles to pictures before calling DrawPicture.
  • CopyBits on more than 3Kb data will work, but it might have to allocate memory.
  • The small Mac screen is 512 pixels wide by 342 pixels high including menu bar.

Files

  • Don't write in the application file. This will fail with read-only devices.
  • Use PBGetVInfo to convert a VRefNum to a volume name.
  • Delete uses the Poor Man's Search Path, so don't delete blindly.
  • File Manager routines with dirID=0 use the Poor Man's Search Path.
  • Truncate and reallocate files before overwriting to reduce fragmentation.
  • Check/change the creator and type of Save As... files before overwriting.
  • If you rewrite files by deleting and creating, copy all Finder information.
  • Directory ID's are longs, not shorts. Shorts work ALMOST all the time.
  • Always set the version number that appears in some file manager calls to 0.
  • To convert a pathRefNum to a name or file number, use PBGetFCBInfo.
  • Prevent the creation of files with names that begin with a period.

Interrupts and VBL Tasks

  • Don't call any Memory Manager routines during an interrupt.
  • Unlocked handles may not be valid during an interrupt.
  • To synchronize to the vertical retrace on Macs with slots, use SlotVInstall.

Handles and Pointers

  • Lock handles before passing their dereferenced pointers to any routine.
  • Lock handles before setting referenced data to expressions containing functions
  • Put an odd long at location zero on a 68000 to help find NIL handle references.
  • Call MoveHHi before locking a handle to avoid memory fragmentation.
  • Use HGetState/HLock/HSetState to lock a handle then put it back as it was.

General

  • Always use unsigned characters within text and Pascal-format strings.
  • Save application preferences in a folder named Preferences in the System Folder
  • Use SysEnvirons to find the System (Blessed) Folder.
  • Use GetAppParms to get the name of the application.
  • The high bit of SysParam . volClik enables the alarm clock.
  • Check the application name at $910 before exiting with ES within MacsBug.
  • To exit to shell in the mini-debugger, enter SM 0 A9 F4 and then G 0.
  • In Pascal, don't nest procedures to be passed by procedure pointer.
  • In Pascal, "with theHandle^^" is unsafe if memory compaction can occur.

Controversy Corner (Don't shoot me; I'm just the messenger.)

  • Avoid writing tail patches for traps.
  • There is no official way to tell if MultiFinder is running or not.

Credits

Compiled by Eric Pepke. Additional material by Steve Maker, Keith Rollin, Gregory Dudek, Brian Bechtel, Henry Minsky, Carl C. Hewitt, Jim Lyons, Alex Lau, Kent Borg, Peter W. Poorman, Ross Yahnke, Mark Fleming, Mark Anderson.