The Gestalt Manager has been included with the Mac OS since System 6.0.4. It allows every application to know about the exact environment which it has been launched in. Dozens of topics are included for applications that use the Gestalt function defined in the Macintosh Toolbox API. The applications provide a “selector” as a parameter coded with exactly four characters and Gestalt returns information also coded as four bytes or an error code.
The aim of Gestalt.Appl application is to show any user (not only developers) this information. Gestalt.Appl is a database of information published (or sometimes not published) by Apple and an interactive tool that allows you to ask the system and its extensions about features they implement.
Versions 2.6 and later are optimized for Power Macintosh and should run on every Mac OS machine (including M.A.E. and A/UX). Some balloon help is provided with menus and the main windows, and the text associated with ‘vers’ selector gives additional information.
Main window is divided in four zones:
• The selector list. By default, it lists only active system selectors. But you can choose an exhaustive list and display all selectors defined in Gestalt.Appl. Inactive selectors appear in italics but information about them is available. In this list the user chooses a selector with a click, by typing the first characters on the keyboard, or with the navigation keys, etc.
• Just under the selector list, the hexadecimal result returned by the chosen selector and the error code are shown (all non active selectors return an error code, sometimes active selectors too).
• On the right, a global interpretation of the result is shown. This area displays different forms depending on the nature of the information: attributes are a fixed list with 32 items (some are valid, others are invalid); variable list in which only one item is valid; a version number; an icon; etc. If the cursor shape becomes a question mark in this area, additional information is available. Press and hold down the mouse button to read it in the lower right corner of the window.
• Under the result area, general information about the chosen selector or additional information about one item from a list of items (given by the question mark cursor) is displayed.
Note: if Gestalt.Appl was launched on a machine with a System before version 6.0.4, a SysEnvirons window is displayed instead of a Gestalt window.
Among all selectors, ‘tabl’ has a distinctive meaning: it provides a list of all active Gestalt selectors in the present system configuration. Selectors can be posted by the System, Finder file or any other software (extension, control panel, application…). Gestalt.Appl has a specific way to deal with the ‘tabl’ selector: it displays in the interpretation zone a list of active selectors, and a new menu is added in the menu bar. By default only selectors not present in the main list, those Gestalt.Appl does not know explicitly, are displayed. But it is possible to choose an exhaustive list, or mark some selectors and display only the unmarked ones. If a selector is the same as a software signature in the desktop database, Gestalt.Appl displays also this additional information. It is a good tip to know who posted this selector.
Note: if the ‘tabl’ selector does not exist, Gestalt.Appl cannot be launched. Until now, all Gestalt Manager versions used ‘tabl’ mechanism, but this is likely to change with Copland.
Note: if Gestalt.Appl has a system error when the ‘tabl’ selector is displayed, there is likely a wrong and buggy selector posted by a poorly tested or not yet completed software. Gestalt.Appl provides no mechanism to prevent these errors. You have to trash the offending extension or to not display the ‘tabl’ selector.
Gestalt.Appl and remote machines
Currently there is no way to provide system information about any machine connected by an AppleTalk network. A mechanism based on ADSP messages was provided in older versions but it has been removed now. A future version will use the Apple Event the scriptable Finder provides (see AppleScript “computer” command).
Virtual configurations
Beginning with version 2.1.6 of Gestalt.Appl, the feature to save as a file the state of the local configuration has been available. The file is under 3 KB and keeps a list of all the active Gestalt selectors with the returned result and the associated error code. This configuration file can be reopened later or on another machine, but no automatic comparative feature between two configurations is provided for now.
Note: the menu Machines displays the opened virtual configuration list (16 windows maximum).
Export as text
Beginning with version 2.7 of Gestalt.Appl, the feature to export any configuration as a SimpleText file has been available. You have to use the command Export as text… of the menu File. The result is the same as what is displayed when the ‘tabl’ selector is selected: Exhaustive list with all the selectors (and pseudo-selectors), with code and result both in hexadecimal and ASCII, and error code in decimal. With SimpleText, this list is displayed using Monaco 9 font.
Note: if the Option key was pressed when this command was called, the export is made in a special format: Selector code in ASCII, error code in decimal, result in hexadecimal, decimal and binary. Cells are tab-separated and records are return-separated, so the file can be imported within a database where it can be analyzed. If the code contains a non-printing character, the selector is not recorded.
Alternate displays
By default only active selectors are displayed in the main list. You can choose to display all selectors defined in Gestalt.Appl application. Then non active selectors are in italics and an error message is displayed in the global interpretation zone unless the command Interpretation always displayed of the menu File is marked. In this case Gestalt.Appl works as if the selector had returned zero value and displays the interpretation of this value.
Preferences
Gestalt.Appl allows you to set some preferences like exhaustivity of the main list or the ‘tabl’ selector list. Window colors (local machine and virtual configurations) can also be set.
Note: it is possible to have some trouble with using the Color Picker. Try to give more room in the Gestalt.Appl memory partition if this happens.
If you have problems with color (for instance texts are not readable), choose the default colors. To revert to a clean version of Gestalt.Appl, you can trash the Gestalt.Prefs file created in the Preferences folder of the System Folder.
Advanced users
With ResEdit or Resorcerer, you can modify information displayed by Gestalt.Appl: you can override its resources by putting resources with the same type and id in the Gestalt.Prefs file. By the way, resources ‘Sel+’ id=1201 and ‘STR#’ id=1201 are for your use only: when an unknown selector is appearing in your ‘tabl’ list, you can associate a comment by putting selector name in the ‘Sel+’ resource (a template is provided) and the comment at the same index in the ‘STR#’ resource. Never modify the Gestalt.Appl application itself, since it is upgraded often (read: replaced), but your settings are preserved in the Gestalt.Prefs file.
Freeware
The Gestalt.Appl 2.6.x application can be freely copied for non-commercial goals, but it is not public domain and its author holds and reserves all rights of the intellectual property in it.
It is often upgraded by two distinct ways:
• The data in it can be modified but not the code (for instance when Apple publishes new information or when a new extension is available). In these examples, date and version number are not modified, only the modification date of the data;
• Gestalt.Appl code is itself modified (bug correction, new features). Then date and version numbers are modified.
Application version and data version appear in two places: in the Get Info window displayed by the Finder and when invoking the About Gestalt.Appl command in the Apple menu.
All suggestions, positive criticism, correction of English mistakes and new information are welcome. I evidently cannot test this application in every system configuration on every Macintosh or compatible model. Tell me if you find interpretation mistakes or incomplete items, they will be incorporated in the next upgrade. Even better, send me your compressed and binhexed configuration file (Save config as… command): this allows me to create an even more exhaustive database!
To contact me, use my preferred Internet address (for now): JPC83@calvacom.fr
Other Gestalt fanatics
If you are a fan of the Gestalt world, don’t miss the superb work made by Rene G.A. Ros (Internet address: rgaros@bio.vu.nl). He has been maintaining a Gestalt Selectors List (GSL) for many years.
Have a look on his Web page at http://www.bio.vu.nl/home/rgaros/.
If you send to him your configuration file, he will filter out the new info and include that with the GSL updates.
Expect some evolution of Gestalt.Appl in the future due to the attention Rene Ros gave to my application, my own willingness to its evolution and your suggestions.
