Make elements fill column / row

[bc-arl]

Hi, I am developing an application where I have several buttons that I want all in a column like so:

  cvui::init(WINDOW);
  cv::Mat frame = cv::Mat(height, width, CV_8UC3);
  while (cv::waitKey(20) != 27) { // wait for esc
    frame = cv::Scalar(49, 52, 49); // color
    // I want this column to fill 1/3rd of the width, and the elements to stretch to fill the column
    cvui::beginColumn(frame, padding, padding, width/3, height - padding * 2);
      cvui::text("Bowlzone Calibration");`
      if (cvui::button("NE")) {
        megaMgr->adjustBowlZone("NE");
      }
      if (cvui::button("NW")) {
        megaMgr->adjustBowlZone("NW");
      }
      if (cvui::button("SE")) {
        megaMgr->adjustBowlZone("SE");
      }
      if (cvui::button("SW")) {
        megaMgr->adjustBowlZone("SW");
      }
    cvui::endColumn();
    // Will be adding some stuff here to fill the middle and right parts of the frame, not just left column
    cvui::update(WINDOW);
    cvui::imshow(WINDOW, frame);
  }

My goal is to have these elements in a column that takes up 1/3rd of the width of the column, and I want the elements to fill the column, evenly. I would assume this is the default behavior. However they are actually all bunched up at the top left of the column.

How do I make it so that elements stretch to fill the container (row/column) they are placed in? Here's a sketch of what I mean (excuse the bad paint sketch)

So here the column is 1/3rd width of frame, and elements evenly stretch to fill it.

Thanks for the help.