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root = exports ? window
class HandlerStack
constructor: ->
@stack = []
@counter = 0
# A handler should return this value to immediately discontinue bubbling and pass the event on to the
# underlying page.
@stopBubblingAndTrue = new Object()
# A handler should return this value to indicate that the event has been consumed, and no further
# processing should take place.
@stopBubblingAndFalse = new Object()
# Adds a handler to the stack. Returns a unique ID for that handler that can be used to remove it later.
push: (handler) ->
@stack.push handler
handler.id = ++@counter
# Called whenever we receive a key or other event. Each individual handler has the option to stop the
# event's propagation by returning a falsy value, or stop bubbling by returning @stopBubblingAndFalse or
# @stopBubblingAndTrue.
bubbleEvent: (type, event) ->
# extra is passed to each handler. This allows handlers to pass information down the stack.
extra = {}
for i in [(@stack.length - 1)..0] by -1
handler = @stack[i]
# We need to check for existence of handler because the last function call may have caused the release
# of more than one handler.
if handler and handler.id and handler[type]
@currentId = handler.id
passThrough = handler[type].call @, event, extra
if not passThrough
DomUtils.suppressEvent(event) if @isChromeEvent event
return false
return true if passThrough == @stopBubblingAndTrue
return false if passThrough == @stopBubblingAndFalse
true
remove: (id = @currentId) ->
# This is more expense than splicing @stack, but better because splicing can interfere with concurrent
# bubbleEvents.
@stack = @stack.filter (handler) ->
# Mark this handler as removed (to notify any concurrent bubbleEvent call).
if handler.id == id then handler.id = null
handler?.id?
# The handler stack handles chrome events (which may need to be suppressed) and internal (fake) events.
# This checks whether that the event at hand is a chrome event.
isChromeEvent: (event) ->
event?.preventDefault? and event?.stopImmediatePropagation?
# Convenience wrappers.
alwaysContinueBubbling: (handler) ->
handler()
true
neverContinueBubbling: (handler) ->
handler()
false
root.HandlerStack = HandlerStack
root.handlerStack = new HandlerStack
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