love.graphics.setFont(love.graphics.newFont(Font_height))
  Em = App.newText(love.graphics.getFont(), 'm')
  Display_settings.column_width = 40*App.width(Em)

  Font_height = settings.font_height
  Line_height = math.floor(Font_height*1.3)
  love.graphics.setFont(love.graphics.newFont(Font_height))
  Em = App.newText(love.graphics.getFont(), 'm')
  Display_settings.column_width = settings.column_width

  love.graphics.setFont(love.graphics.newFont(Font_height))
  Em = App.newText(love.graphics.getFont(), 'm')
  Display_settings.column_width = 40*App.width(Em)

    font_height=Font_height,
    column_width=Display_settings.column_width,

  -- global hotkeys
  if chord == 'C-=' then
    update_font_settings(Font_height+2)
    return
  elseif chord == 'C--' then
    update_font_settings(Font_height-2)
    return
  elseif chord == 'C-0' then
    update_font_settings(20)
    return
  end
  -- mode-specific hotkeys

function update_font_settings(font_height)
  local column_width_in_ems = Display_settings.column_width / App.width(Em)
  Font_height = font_height
  love.graphics.setFont(love.graphics.newFont(Font_height))
  Line_height = math.floor(font_height*1.3)
  Em = App.newText(love.graphics.getFont(), 'm')
  Display_settings.column_width = column_width_in_ems*App.width(Em)
  for _,column in ipairs(Surface) do
    for _,pane in ipairs(column) do
      pane.font_height = Font_height
      pane.line_height = Line_height
      pane.em = Em
      Text.redraw_all(pane)
    end
  end
end