make the pieces view a bit more efficient in terms of not storing values when it's not shown

macosx/InfoWindowController.m

@@ -690,9 +690,14 @@ typedef enum
         
         switch (oldTabTag)
         {
+            case TAB_ACTIVITY_TAG:
+                [fPiecesView clearView];
+                break;
+            
             case TAB_TRACKER_TAG:
                 oldResizeSaveKey = @"InspectorContentHeightTracker";
                 break;
+            
             case TAB_PEERS_TAG:
                 //if in the middle of animating, just stop and resize immediately
                 if (fWebSeedTableAnimation)
@@ -705,6 +710,7 @@ typedef enum
                 
                 oldResizeSaveKey = @"InspectorContentHeightPeers";
                 break;
+            
             case TAB_FILES_TAG:
                 [[QuickLookController quickLook] updateQuickLook];
                 
@@ -736,8 +742,6 @@ typedef enum
         case TAB_ACTIVITY_TAG:
             identifier = TAB_ACTIVITY_IDENT;
             title = NSLocalizedString(@"Activity", "Inspector -> title");
-            
-            [fPiecesView resetView];
             break;
         case TAB_TRACKER_TAG:
             identifier = TAB_TRACKER_IDENT;
@@ -1142,7 +1146,8 @@ typedef enum
     [fPiecesControl setSelected: !available forSegment: PIECES_CONTROL_PROGRESS];
     
     [[NSUserDefaults standardUserDefaults] setBool: available forKey: @"PiecesViewShowAvailability"];
-    [fPiecesView resetView];
+    [fPiecesView clearView];
+    [fPiecesView updateView];
 }
 
 - (void) revealTorrentFile: (id) sender

macosx/PiecesView.h

@@ -40,7 +40,7 @@
 
 - (void) setTorrent: (Torrent *) torrent;
 
-- (void) resetView;
+- (void) clearView;
 - (void) updateView;
 
 @end

macosx/PiecesView.m

@@ -80,13 +80,7 @@
 
 - (void) setTorrent: (Torrent *) torrent
 {
-    //reset the view to blank
-    NSImage * newBack = [fBack copy];
-    [self setImage: newBack];
-    [newBack release];
-    
-    tr_free(fPieces);
-    fPieces = NULL;
+    [self clearView];
     
     fTorrent = torrent;
     if (fTorrent)
@@ -98,19 +92,20 @@
         float width = [self bounds].size.width;
         fWidth = (width - (fAcross + 1) * BETWEEN) / fAcross;
         fExtraBorder = (width - ((fWidth + BETWEEN) * fAcross + BETWEEN)) / 2;
-        
-        [self updateView];
     }
-    else
-        [self setNeedsDisplay];
+    
+    //reset the view to blank
+    NSImage * newBack = [fBack copy];
+    [self setImage: newBack];
+    [newBack release];
+    
+    [self setNeedsDisplay];
 }
 
-- (void) resetView
+- (void) clearView
 {
     tr_free(fPieces);
     fPieces = NULL;
-    
-    [self updateView];
 }
 
 - (void) updateView