1 files changed, 37 insertions, 0 deletions
diff --git a/lib/handler_stack.coffee b/lib/handler_stack.coffee
new file mode 100644
index 00000000..858f2ec9
--- /dev/null
+++ b/lib/handler_stack.coffee
@@ -0,0 +1,37 @@
+root = exports ? window
+
+class root.HandlerStack
+
+  constructor: ->
+    @stack = []
+    @counter = 0
+
+  genId: -> @counter = ++@counter & 0xffff
+
+  # Adds a handler to the stack. Returns a unique ID for that handler that can be used to remove it later.
+  push: (handler) ->
+    handler.id = @genId()
+    @stack.push handler
+    handler.id
+
+  # Called whenever we receive a key event. Each individual handler has the option to stop the event's
+  # propagation by returning a falsy value.
+  bubbleEvent: (type, event) ->
+    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 && handler[type]
+        @currentId = handler.id
+        passThrough = handler[type].call(@, event)
+        if not passThrough
+          DomUtils.suppressEvent(event)
+          return false
+    true
+
+  remove: (id = @currentId) ->
+    for i in [(@stack.length - 1)..0] by -1
+      handler = @stack[i]
+      if handler.id == id
+        @stack.splice(i, 1)
+        break