如何设置Coreplot axisLabels宽度？

我正在使用axisLabels，并且需要使标签并排且两者之间没有空格。但是，似乎标签会自动调整为文本大小。有没有办法设置标签的宽度？

CPTXYAxisSet *axisSet         = (CPTXYAxisSet *)self.weightHistoryChart.axisSet;
CPTXYAxis *x                  = axisSet.xAxis;
x.labelingPolicy = CPTAxisLabelingPolicyNone;
NSArray *customTickLocations = [NSArray arrayWithObjects:@1.0, @3.0, @5.0, nil];
NSMutableSet *customLabels   = [NSMutableSet setWithCapacity:3];

for ( NSNumber *tickLocation in customTickLocations ) {

    CPTTextLayer *layer = [[CPTTextLayer alloc] initWithText:@"label"];
    CPTAxisLabel *newLabel = [[CPTAxisLabel alloc] initWithContentLayer:layer];
    newLabel.tickLocation = tickLocation;
    newLabel.offset       = 0;
    [newLabel.contentLayer setBackgroundColor:[UIColor lightGrayColor].CGColor];
    [customLabels addObject:newLabel];
}

x.axisLabels = customLabels;

有空间：

删除空间：