Mouse Operations

The graphics library contains functions that determine where the mouse is, if there are any clicks, etc. The functions get-mouse-click and ready-mouse-click first return a ``mouse-click descriptor,'' and then other functions take the descriptor and return the mouse's position, which button was pushed, etc.

• (get-mouse-click viewport)
  get-mouse-click 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-mouse-click viewport)
  ready-mouse-click takes a viewport descriptor and returns either a mouse click descriptor, or else #f if none is available. Unlike the previous function, ready-mouse-click returns immediately.
• (ready-mouse-release viewport)
  ready-mouse-release takes a viewport descriptor and returns either a click descriptor from a mouse-release (button-up) event, or else #f if none is available.
• (query-mouse-posn viewport)
  query-mouse-posn takes a viewport descriptor and returns either the position of the mouse cursor within the viewport, or else #f if the cursor is currently outside the viewport.
• (mouse-click-posn mouse-click)
  mouse-click-posn takes a mouse click descriptor and returns the position of the pixel where the click occurred.
• (left-mouse-click? mouse-click)
  left-mouse-click? takes a mouse click descriptor and returns #t if the click occurred with the left mouse button, or else #f.
• (middle-mouse-click? mouse-click)
  Similar to left-mouse-click?.
• (right-mouse-click? mouse-click)
  Similar to left-mouse-click?.
• (viewport-flush-input viewport)
  As noted above, mouse clicks 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.