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Mouse providers an interface that represents the mouse itself as an object with state. window.Mouse points to the constructor. Only one instance of Mouse should exist per window. window.mouse points to a context's single mouse instance.

Event Handling

window.mouse (just mouse from now on) provides existing mouse methods as well as normalizes some and adds new ones.

  • down: mousedown
  • up: mouseup
  • move: mousemove
  • click: click and contextmenu
  • dblclick: dbleclick
  • leave: Uses mouseout but only fires when the mouse leaves the window entirely
  • enter: Uses mouseover but only fires when the mouse enters the window from outside
  • wheel: mousewheel and wheel events


The following functions are provided to allow management of listeners. Types is a string of type names separated by spaces for multiple events.

  • mouse.on(types, callback): add callback as listener for each type in types
  •, callback): remove callback from listeners for each type in types
  • mouse.once(types, callback): add callback as listener for the first time each type in types fires, then removes it
  • mouse.emit(evt): takes MouseEvent object and runs the event through the callbacks the same as when a native event is received. Type is determined from the event object
  • new Mouse(view): initializes mouse instance for given view. This is done automatically for main window, but this could be run on, for example, an iframe's window to provide a mouse object scope to the iframe.

Button handling

Mouse button state is tracked and MouseEvent.prototype is augmented in two ways:

  • buttons: a getter that returns the buttons as per the W3C spec (only first 3 buttons currently). That is logical combination of the button states. left is 1, middle is 2, right is 4. All through would be 7, etc.
  • states: function that interprets the number from buttons into an object like { left: true/false, middle: true/false, right: true/false }