How to get buffer data?

[davidlampach]

I am attempting to get one of the basic chart examples to work with the BitmapBackend::with_buffer function. The exact same code works well when I am exporting a file (an unaltered example from this repo). But if I change it to output to a buffer, I can't seem to find the data. The buffer is just an empty array of zero values. How can I access and manipulate the buffer? I have also tried the following with root_area and it also doesn't have any data.

fn main() {

let mut buffer_ = vec![0; 300 * 200 * 3]; 
    

let a = || {
        
        root_area = BitMapBackend::with_buffer(&mut buffer_, (600, 400))
        .into_drawing_area();
        root_area.fill(&WHITE).unwrap();
        
        let mut ctx = ChartBuilder::on(&root_area)
            .set_label_area_size(LabelAreaPosition::Left, 40)
            .set_label_area_size(LabelAreaPosition::Bottom, 40)
            .caption("Bar Demo", ("sans-serif", 40))
            .build_cartesian_2d(0..50, (0..10).into_segmented())
            .unwrap();
        
        ctx.configure_mesh().draw().unwrap();
        
        let data = [25, 37, 15, 32, 45, 33, 32, 10, 0, 21, 5];
        
        ctx.draw_series((0..).zip(data.iter()).map(|(y, x)| {
            let mut bar = Rectangle::new([
                (0, SegmentValue::Exact(y)), 
                (*x, SegmentValue::Exact(y + 1))
            ], BLUE.filled());
            bar.set_margin(5, 5, 0, 0);
            bar
        })).unwrap();
};  
        println!("{:?}", &buffer_);