Based on Java's AWT and Swing frameworks

Component
  position within container(x, y), size(w, h)
  horizontal and vertical padding, ints
  text: string
  font_size: int
  colours: foreground, background, and border
  parent: a container
  
Container: a kind of component
  content: a vector of components
  orientation: horizontal or vertical
  spacing: number of pixels to leave between components
  
Frame: a kind of container which represents a whole window
  focus: component * // which component has the input focus

Component methods:
  get_absolute_position(int & x, int & y)
      // gets position withing frame
      // gets parents absolute position and adds own x, y
      // frame has absolute position of (0, 0)
  get_ideal_size(int & w, int & h)
      // works out what size should be, based on contents
  set_position(x, y)
  set_size(w, h)
  bool do_you_contain(x, y)
  pack()
      // work out what your own size should be
  draw()
      // makes the component appear on the screen

Panel: a kind of contaniner
  usually has no text or border, just used to position its components
  
Label: a kind of component
  usually has invisible background and border,
  just used to make fixed text appear

Spacer: a kind of component
  invisible, just used to help position other components
  constructor takes width and height
  
Container methods:
  add(component *)
  pack()
      // tell all contents to work out their own sizes
      // position contents based on orientation and their ideal sizes
  draw()
      // draws itself, then tells all contents to draw themselves
      // on top of it in their calculated positions

Frame methods:
  draw()
      this is usually the last thing in a program.
      As well as doing all that container::draw() does, it also
      contains the unending loop that waits for mouse clicks and
      key presses, and passes those events on to the correct
      component

ActionListener: an object which can react to mouse clicks or key presses
  every component has an ActionListener which may be NULL
  methods:
    mouse_clicked(x, y) // receives coordinates of the click
    key_pressed(char c)

Useful library.h functions:
  measure_string(string s, int & w, int & h)
  measure_char(int c, int & w, int & h)
  
  wait_for_mouse_click_or_key_typed(double timeout - default infinite)
  int what_happened()
      // returns event::mouse_left_click or event::key_typed or event::none, etc
  int get_click_x()
  int get_click_y()
  char get_key_typed()
  
More component methods:
  act_on_mouse_click(x, y);
      // container delivers it to appropriate component (remember x, y are relative)
      // component may fire ActionListener's mouse_clicked()
  act_on_keypress(char c);
      // always delivered to the component that has focus, often ignored
  
Button: a kind of component that reacts when clicked on

TextField: a kind of component
  if a key is pressed when it has focus, that char is added to the text displayed,
  backspace etc treated specially
  
Checkbox: a kind of component
  can be set to checked or unchecked
  changes when mouse clicked on it