Each Tracker window defines a "Poses" property representing the contents of the window. Each poses, in turn, defines the two properties "Entry" and "Selection". An "Entry" is an item in the window, e.g. either a file or a directory, while a "Selection" represents a selected "Entry".
When a Tracker window receives a scripting message with a "Poses" property, it pops the current specifier off the specifier stack and then forwards the scripting message to the view handling the "Poses" property. From there, the "Entry" and "Selection" properties are processed. For example, the following function returns the number of entries present in a given Tracker window:
int32 CountEntries(const char *name)
{
int32 count;
BMessage message, reply;
// form scripting request
message.what = B_COUNT_PROPERTIES;
message.AddSpecifier("Entry");
message.AddSpecifier("Poses");
message.AddSpecifier("Window", name);
// deliver request and fetch response
BMessenger("application/x-vnd.Be-TRAK").SendMessage(&message, &reply);
// return result
if (reply.FindInt32("result", &count) == B_OK)
return count;
return -1;
}
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The Tracker scripting API defines a number of ways of specifying entries in a Poses. These methods are summarized below:
|
Specifier |
Description |
| B_DIRECT_SPECIFIER |
Used for specifying the entire Poses or selection as appropriate. |
| B_INDEX_SPECIFIER |
"index" contains int32 index of file in the Poses. Ranges are specified with a pair of indices. |
| 'sref' |
"refs" contains entry_refs of specified files. |
| 'sprv' |
Refers to item immediately following file whose entry_ref is found in "data." |
| 'snxt' |
Refers to item immediately preceeding file whose entry_ref is found in "data." |
Always remember that other programs (or the user) may also be adding or removing entries to the view and selection, so do not rely upon indices as a safe method of referring to a specific file. Instead, use entry_refs.