Examples of selector instances

A Selector allows you to configure the following:

• What events should trigger the activation of the Selector.
• What feedback to present the user at the different stages of a Selector interaction, i.e., how should we highlight the button when the mouse button is pressed.
• What label to display inside the selector. The label can be any Picture value (Note See section Structured Graphics in Haskell).

Default values for the different options are provided, so creating a new Selector only requires you to override the default values you want to. The defaults provided gives you a push button like behaviour and feedback:

mkSelector :: SelectorResource -> a -> DC -> IO (Selector a, DisplayHandle)

main =
 mkDC []              >>= \dc ->
  mkSelector [] () dc >>= \ (sel, dh) ->
 realiseDH dc dh      >>
 return ()

A single selector is displayed in a window,

To dynamically add a label,

setSelectorLabel :: Selector a -> Picture -> IO ()

main =
 ..as before..
 setSelectorLabel sel (text "Hello, world!")

The mkSelector function returns an abstract Selector handle that is used to change the label. This handle is also used to receive selector `clicks' by the application

getSelectorClick :: Selector a -> IO a

which returns a value of type a each time a selector interaction has completed (more on this later). The value returned is the same as the second argument given to mkSelector.