| Technote FL 15 | January 1986 |
Changes since January 1986: The information about how to find the "Blessed
Folder" has been deleted from this technical note. The FindFolder function can
now be used to find the "Blessed Folder" and is documented in Inside Macintosh
Volume VI, pages 9-42 to 9-44. This note now includes information about how
to bless a folder to the new system folder.
Note: The following information may be effected by future changes to
system software. If you choose to use this information, you must do so at
your own risk.
The way to bless a folder is by taking the longword which is the directory ID of the blessed folder and putting it into the Master Directory Block (MDB). This can be accomplished by using the HFS call PBSetVInfo. You should not attempt to change this block directly. First call PBHGetVInfo and set ioVFnderInfo[1] to the directory ID of the the new folder to be blessed. Then call PBSetVInfo to save this information. Once you have done this, you will find that the Finder takes a little while to realize that you have blessed the folder. Therefore, the icon will take a little while to change. Exactly how long you will have to wait to see the new icon is unknown.
Forcing the icon to change sooner is not a difficult task. The best way for you
to see the icon change more quickly is to change the modification date of the
directory into which you are copying the new System Folder. Doing this will
cause the Finder to reexamine the window and its contents. When the Finder
notices that the volume's modification date has changed, it begins scanning for
changes in all the open folders. This scanning process takes place about once
every 10 seconds. You can change the last modification date for that volume and
the System Folder's directory ID for that volume using PBSetVInfo.
Changing the file's FndrInfo or renaming the file does not change the
modification date. When you call PBSetVInfo you will need to put the
System Folder's directory ID in the longword at ioVfndrInfo. This
longword will be the first four bytes of this directory ID. (As usual, whenever
you make a change to a field of a structure you need to first do a
PBGetCatInfo, change what you are going to change, and then do
PBSetCatInfo. This ensures that you change only the portion of the
volume that you intended, in this case a longword, and not the whole
structure.)
Further Reference: