Keyboard Operations

The graphics library contains functions that report key presses from the keyboard. The functions get-key-press and ready-key-press return a ``key-press descriptor,'' and then key-value takes the descriptor and returns an integer for the key that was pressed (usually the ASCII value)..

• (get-key-press viewport)
  get-key-press takes a viewport descriptor and returns a mouse click descriptor. It returns the next mouse click in the viewport, waiting for a click if necessary.
• (ready-key-press viewport)
  ready-key-press takes a viewport descriptor and returns either a mouse click descriptor, or else #f if none is available. Unlike the previous function, ready-key-press returns immediately.
• (key-value key-press)
  key-value takes a key press descriptor and returns an integer for the key that was pressed. Usually this is the ASCII value of a character. Special keys return other values as defined by wxWindows, the primitive GUI toolbox. For example, the up arrow key is represented by the constant wx:k-const-up.
• (viewport-flush-input viewport)
  As noted above, key presses are buffered. viewport-flush-input takes a viewport descriptor and empties the input buffer of mouse and keyboard events. This action is useful in some real-time applications. It returns unspecified.