Have libtransmission keep track of idle seconds. Use this value for determining the stalled minutes in the Mac code.

libtransmission/torrent.c

@@ -1001,6 +1001,11 @@ tr_torrentStat( tr_torrent * tor )
     s->doneDate     = tor->doneDate;
     s->startDate    = tor->startDate;
 
+    if (s->activity == TR_STATUS_DOWNLOAD || s->activity == TR_STATUS_SEED)
+        s->idleSecs = difftime(tr_time(), tor->anyDate);
+    else
+        s->idleSecs = -1;
+
     s->corruptEver     = tor->corruptCur    + tor->corruptPrev;
     s->downloadedEver  = tor->downloadedCur + tor->downloadedPrev;
     s->uploadedEver    = tor->uploadedCur   + tor->uploadedPrev;

libtransmission/transmission.h

@@ -1843,6 +1843,10 @@ typedef struct tr_stat
     /** The last time we uploaded or downloaded piece data on this torrent. */
     time_t    activityDate;
     
+    /** Number of seconds since the last activity (or since started).
+        -1 if activity is not seeding or downloading. */
+    int    idleSecs;
+    
     /** A torrent is considered finished if it has met its seed ratio.
         As a result, only paused torrents can be finished. */
     tr_bool   finished;

macosx/Torrent.m

@@ -1479,16 +1479,7 @@ int trashDataFile(const char * filename)
 
 - (NSInteger) stalledMinutes
 {
-    const time_t start = fStat->startDate;
+    return fStat->idleSecs / 60;
-    if (start == 0)
-        return -1;
-    
-    NSDate * started = [NSDate dateWithTimeIntervalSince1970: start],
-            * activity = [self dateActivity];
-    
-    NSDate * laterDate = activity ? [started laterDate: activity] : started;
-    
-    return ABS([laterDate timeIntervalSinceNow]) / 60;
 }
 
 - (BOOL) isStalled