Expand an expandable item (directory)
int PtFSFolderExpand( PtWidget_t *fs, PtFileSelItem_t *item, PhEvent_t *event );
This function expands the given item. The fs argument must point to the file selector that contains the item or be NULL if the item doesn't belong to any file selector.
If fs isn't NULL, its Pt_CB_FS_STATE callback is invoked. The event argument is to the callback. If the item isn't expanded, the return value reflects that.
PhEvent_t in the Photon Library Reference