jerky scrolling in NSTableView

Question

Hello All,

I have a NSTableView with around 70 - 80 rows, each row contain a checkbox, title text and a drop down menu to select data. The problem i am facing is that when i scroll the table it does not scroll smooth. When i remove the NSComboBoxCell it works ok.

Here is the code i used to add NSComboBoxCell -

        NSTableColumn* checkColumn = [tblEditData  tableColumnWithIdentifier:@"Timer"];
        NSCell *aCell = [aTableColumn dataCellForRow:rowIndex];

        [aCell setState:3];

        NSComboBoxCell *comboBoxCell = [NSComboBoxCell new];
        [comboBoxCell addItemWithObjectValue:@"Timer"];
        [comboBoxCell addItemWithObjectValue:@"1"];
        [comboBoxCell addItemWithObjectValue:@"3"];
        [comboBoxCell addItemWithObjectValue:@"6"];
        [comboBoxCell addItemWithObjectValue:@"9"];
        [comboBoxCell addItemWithObjectValue:@"12"];
        [comboBoxCell setStringValue:aDataRow1.timer_val];

        [checkColumn setDataCell:comboBoxCell];

        return comboBoxCell;

Please advice what should i do to remove the jerky scrolling.

Update here is the full code -

-(id) tableView:(NSTableView *)aTableView
objectValueForTableColumn:(NSTableColumn *)aTableColumn
            row:(int)rowIndex
{
    NSString *identifier = [aTableColumn identifier];
    if (aTableView == tblAddData)
    {
        AdvancedProtocolDataRow * aDataRow1 = [arrayAddData objectAtIndex:rowIndex];

        //NSTableColumn* checkColumn = [tblAddData  tableColumnWithIdentifier:@"Title"];

        if ([identifier isEqualToString:@"Title"])
        {
            NSTableColumn* checkColumn = [tblAddData  tableColumnWithIdentifier:@"Title"];

            //NSCell *aCell = [aTableColumn dataCellForRow:rowIndex];
            NSButtonCell* checkBoxCell = [NSButtonCell new];
            [checkBoxCell setButtonType:NSSwitchButton];


            [checkBoxCell setTitle:aDataRow1.name];

            NSString *myString = [checkBoxCell title];

            NSMutableParagraphStyle *pStyle = [[NSMutableParagraphStyle alloc] init];


            NSDictionary *dict = [NSDictionary  dictionaryWithObjectsAndKeys:[NSColor whiteColor],
                                  NSForegroundColorAttributeName,
                                  [checkBoxCell font],  NSFontAttributeName,
                                  pStyle, NSParagraphStyleAttributeName, nil];

            NSAttributedString *atted = [[NSAttributedString alloc] initWithString:myString attributes:dict];
            [checkBoxCell setAttributedTitle: atted];







            if ([aDataRow1.checkbox_val isEqualToString:@"selected"])
                [checkBoxCell setState:NSOnState];
            else
                [checkBoxCell setState:NSOffState]; 


            [checkColumn setDataCell:checkBoxCell];
            return checkBoxCell;

        }  
        else if ([identifier isEqualToString:@"Timer"])
        {
            /*
            NSTableColumn* checkColumn = [tblAddData  tableColumnWithIdentifier:@"Timer"];
            NSCell *aCell = [aTableColumn dataCellForRow:rowIndex];
            [aCell setState:3];
            NSComboBoxCell *comboBoxCell = [NSComboBoxCell new];
            [comboBoxCell addItemWithObjectValue:@"Timer"];
            [comboBoxCell addItemWithObjectValue:@"1"];
            [comboBoxCell addItemWithObjectValue:@"3"];
            [comboBoxCell addItemWithObjectValue:@"6"];
            [comboBoxCell addItemWithObjectValue:@"9"];
            [comboBoxCell addItemWithObjectValue:@"12"];
            //[comboBoxCell setStringValue:@"Timer"];
            [comboBoxCell setStringValue:aDataRow1.timer_val];
            [checkColumn setDataCell:comboBoxCell];
            return comboBoxCell;
            */

            NSTableColumn* checkColumn = [tblAddData  tableColumnWithIdentifier:@"Timer"];
            NSCell *aCell = [aTableColumn dataCellForRow:rowIndex];
            [aCell setState:3];

            [comboBoxCell setStringValue:aDataRow1.timer_val];
            [checkColumn setDataCell:comboBoxCell];

            return comboBoxCell;
        }    
    }
}

Thanks