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This Technical Note discusses the format of the System 7.1 Scrapbook file
format. The format may change in the future so be warned.
[May 01 1993]
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Introduction
This Technical Note discusses the format of the Scrapbook file. Previously the
format was undocumented. Developers, however, have consistently asked for
documentation of the format, so we are providing it with a strong word of
warning. The format may change in the future, and your application risks
compatibility if you rely on it.
If you have decided to rely on the Scrapbook format, you should always code for
a specific version of the Scrapbook file. The Scrapbook file will always have a
'vers' resource, which you can check.
Scrapbook Brief Overview
The Scrapbook consists of a Scrapbook application and a Scrapbook file. The
Scrapbook file is stored at the root of the System Folder. The Scrapbook
application is usually stored in the Apple Menu Items folder.
Scrapbook File Format Overview
The resource fork of the Scrapbook file contains two permanent resources
('SMAP' and 'vers'), and up to 255 scrap items. The data fork is empty. Thus,
any empty Scrapbook file will contain both a 'vers' resource and an 'SMAP'
resource. Each scrap item will have a variable number of associated resources.
It may also have a dependent alias, as discussed below.
Check the 'vers' Resource
The Scrapbook file is part of the Scrapbook application. Because the Scrapbook
application is part of system software, the Scrapbook file format is highly
subject to change. If you choose to open the file, you will need to identify
the Scrapbook file format version by checking the 'vers' resource in the
Scrapbook file. Your access of the Scrapbook file should be subject to the
version of the file that your application understands. If you do not understand
the version, then your application should not access the file. Your application
should never have Scrapbook File format access as a requirement.
Format of the 'SMAP' Resource
The 'SMAP' resource is the key to the Scrapbook file format. The 'SMAP'
resource is a resource of 255 bytes. It is a three-dimensional table of
information. The 'SMAP' keeps track of the resource IDs for Scrapbook items on
one axis, and it keeps track of the order of the Scrapbook items on the
other.
Scrapbook Items
The Scrapbook application works with Scrapbook items, which are groupings of
related resources. Many objects associated with the Macintosh desktop contain
more than one resource. An icon, for example, has about six resources
associated with it. The Scrapbook, however, needs to treat these groupings as
one item. To the end user, he or she is merely pasting in an icon and removing
it.
A Scrapbook item is uniquely identified to the Scrapbook by a resource ID. All
resources with the same resource ID belong to the same Scrapbook item. Thus, an
icon's resources would be considered a Scrapbook item.
Generating Unique Resource IDs
When you paste a Scrapbook item in to the Scrapbook, the Scrapbook needs to
generate a unique resource ID for that item. And because Scrapbook items can be
cut and pasted at will, this method needs some way of recovering resource IDs
that are no longer being used.
The location of each of the 255 bytes in the 'SMAP' resource represents a
unique ID. For example, the first byte in the 'SMAP' is associated with a
resource ID of -32768. The second byte is associated with a resource ID of
-32767. This continues sequentially until the Scrapbook limit of 255 items (a
resource ID of -32512) is reached.
A used resource ID is represented by a nonzero value at that byte's position. A
zero indicates an unused resource ID. When the Scrapbook needs a unique ID, it
sequentially scans the Scrapbook file for a zero byte, calculates the resource
ID, and uses it for the new Scrapbook item.
On the other hand, when a Scrapbook item is cut, the application first cuts all
the resources of the corresponding resource ID. It then finds the Scrapbook
item's resource ID in the 'SMAP' resource, and sets its value to zero.
Maintaining the Ordering of Scrapbook Items
The 'SMAP' file also maintains the order of Scrapbook items in the Scrapbook.
The nonzero value at each location in an 'SMAP' is the location in the
Scrapbook of the Scrapbook item. The value of the byte corresponds to the entry
number in the Scrapbook.
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Example
For example, in the 'SMAP' resource of your Scrapbook data file you may find
the following (looking with ResEdit at the 'SMAP' resource):
Thus, if we take the first byte, the tenth Scrapbook item is identified by the
resource ID-32768.
The information further translated:
Res ID Byte offset Entry in Scrapbook Entry in Scrapbook (Hex$) Type
-32768 00 10 A moov
-32767 01 7 7 PICT
-32766 02 5 5 PICT
-32765 03 9 9 PICT
-32764 04 8 8 PICT
-32763 05 1 1 PICT
-32762 06 6 6 snd
-32761 07 2 2 PICT (QT)
-32760 08 4 4 PICT (QT)
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Thus, the snd resource is the sixth Scrapbook item in the Scrapbook. Its
resource ID is -32768 + 5 = -32762. The fourth item in the Scrapbook is a
QuickTime picture with resource ID -32760.
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Scrapbook and QuickTime
When you paste a QuickTime movie into the Scrapbook, you will copy only the
movie resource. Remember, even if you cut a movie from a self-contained movie,
only the movie resource will be cut. When you paste the movie into the
Scrapbook, the movie gets pasted into the Scrapbook's file and the file is now
a dependent file. The FinderInfo of the Scrapbook file will now have
its shared bit set, and a dependent alias will be put in the resource fork of
the Scrapbook file. When the movie is cut from the Scrapbook, its shared bit
should be reset and the dependent alias needs to be removed. Unfortunately,
this does not occur with all versions of the Scrapbook because they do not
support QuickTime.
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