def _set_plot_x_axis_leader(ax):
    """The first plot to add some data is the leader. All other's X-axis will follow this one."""
    if ax.vb.linkedView(0):
        return
    for _ax in ax.vb.win.ci.items:
        if not _ax.vb.linkedView(0) and _ax.vb.name != ax.vb.name:
            ax.setXLink(_ax.vb.name)
            break
