macosx: fix another case where the user would see double negative time values

Time can be greater than duration, when you scroll right to much.
Furthermore, this commit moves the duplicated code into a own method.

modules/gui/macosx/MainWindow.m

@@ -864,25 +864,14 @@ static VLCMainWindow *_o_sharedInstance = nil;
     p_input = pl_CurrentInput( VLCIntf );
     if( p_input != NULL )
     {
-        vlc_value_t time;
         vlc_value_t pos;
         NSString * o_time;
-        char psz_time[MSTRTIME_MAX_SIZE];
 
         pos.f_float = f_updated / 10000.;
         var_Set( p_input, "position", pos );
         [o_time_sld setFloatValue: f_updated];
 
-        var_Get( p_input, "time", &time );
-
-        mtime_t dur = input_item_GetDuration( input_GetItem( p_input ) );
-        if( [o_time_fld timeRemaining] && dur != -1 )
-        {
-            o_time = [NSString stringWithFormat: @"-%s", secstotimestr( psz_time, ((dur - time.i_time) / 1000000) )];
-        }
-        else
-            o_time = [NSString stringWithUTF8String: secstotimestr( psz_time, (time.i_time / 1000000) )];
-
+        o_time = [self getCurrentTimeAsString: p_input];
         [o_time_fld setStringValue: o_time];
         [o_fspanel setStreamPos: f_updated andTime: o_time];
         vlc_object_release( p_input );
@@ -1205,32 +1194,44 @@ static VLCMainWindow *_o_sharedInstance = nil;
     b_splitview_removed = NO;
 }
 
+- (NSString *)getCurrentTimeAsString:(input_thread_t *)p_input
+{
+    assert( p_input != nil );
+
+    vlc_value_t time;
+    char psz_time[MSTRTIME_MAX_SIZE];
+
+    var_Get( p_input, "time", &time );
+
+    mtime_t dur = input_item_GetDuration( input_GetItem( p_input ) );
+    if( [o_time_fld timeRemaining] && dur > 0 )
+    {
+        mtime_t remaining = 0;
+        if( dur > time.i_time )
+            remaining = dur - time.i_time;
+        return [NSString stringWithFormat: @"-%s", secstotimestr( psz_time, ( remaining / 1000000 ) )];
+    }
+    else
+        return [NSString stringWithUTF8String: secstotimestr( psz_time, ( time.i_time / 1000000 ) )];
+}
+
 - (void)updateTimeSlider
 {
     input_thread_t * p_input;
     p_input = pl_CurrentInput( VLCIntf );
     if( p_input )
     {
-        vlc_value_t time;
         NSString * o_time;
         vlc_value_t pos;
-        char psz_time[MSTRTIME_MAX_SIZE];
         float f_updated;
 
         var_Get( p_input, "position", &pos );
         f_updated = 10000. * pos.f_float;
         [o_time_sld setFloatValue: f_updated];
 
-        var_Get( p_input, "time", &time );
+        o_time = [self getCurrentTimeAsString: p_input];
 
         mtime_t dur = input_item_GetDuration( input_GetItem( p_input ) );
-        if( [o_time_fld timeRemaining] && dur > 0 )
-        {
-            o_time = [NSString stringWithFormat: @"-%s", secstotimestr( psz_time, ((dur - time.i_time) / 1000000))];
-        }
-        else
-            o_time = [NSString stringWithUTF8String: secstotimestr( psz_time, (time.i_time / 1000000) )];
-
         if (dur == -1) {
             [o_time_sld setEnabled: NO];
             [o_time_sld setHidden: YES];