UseResFile
UseResFile Make specified resource file the "current file". short rfRefNum ; resource file reference number
UseResFile selects a different file (already open) as the current resource file. On subsequent resource requests, the specified file will be searched first
and none of the more recently opened resource files will be searched.
r fRefNum is a resource file reference number; typically a value obtained from
the system resource file.
Notes: Open resource files are arranged as a linked list; the most recently opened
searches when looking for a resource. UseResFile lets you start the search with a file opened earlier; the file(s) following it in the list are then left out
of the search process. When a new resource file is opened, it's added to the
end of the list; this overrides any previous calls to UseResFile, ca using the entire list of open resource files to be searched. For example, assume
that there are four open resource files (R0 through R3) and the search
order is R3, R2, R1, R0. If you call UseResFile(R2), the search order becomes R2, R1, R0. Note that R3 is no longer searched. If you then open a
fifth resource file (R4), it is added to the end of the list and the search
order becomes R4, R3, R2, R1, R0.
UseResFile does not re-order the resource file list; it causes resource searching to start at a specified file and work backwards (chronologically)
down the list if it fails to find a resource in the current file.
GetPicture will search only the system resource file. The application's resource file is implicitly set as the current file when an
application is started. The OpenResFile function also sets the current resource file, thereby overriding any previous call to UseResFile. The resource search order is affected by the setting of the low- memory
globals RomMapInsert and TmpResLoad. These affect whether ROM-based
resources are considered to be in the normal lookup list.