Source Code for Module library.pyjamas.ui.DropHandler

  1  # Copyright (C) 2010 Jim Washington 
  2  # 
  3  # Licensed under the Apache License, Version 2.0 (the "License"); 
  4  # you may not use this file except in compliance with the License. 
  5  # You may obtain a copy of the License at 
  6  # 
  7  #     http://www.apache.org/licenses/LICENSE-2.0 
  8  # 
  9  # Unless required by applicable law or agreed to in writing, software 
 10  # distributed under the License is distributed on an "AS IS" BASIS, 
 11  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 12  # See the License for the specific language governing permissions and 
 13  # limitations under the License. 
 14   
 15  from pyjamas import DOM 
 16  from pyjamas.ui import Event 
 17   
 18  DROP_EVENTS = [ "dragenter", "dragover", "dragleave", "drop"] 
 19   
 20 -def fireDropEvent(listeners, event): 
 21      etype = DOM.eventGetType(event) 
 22      if etype == "dragenter": 
 23          for listener in listeners: 
 24              listener.onDragEnter(event) 
 25          return True 
 26      elif etype == "dragover": 
 27          for listener in listeners: 
 28              listener.onDragOver(event) 
 29          return True 
 30      elif etype == "dragleave": 
 31          for listener in listeners: 
 32              listener.onDragLeave(event) 
 33          return True 
 34      elif etype == "drop": 
 35          for listener in listeners: 
 36              listener.onDrop(event) 
 37          return True 
 38      return False 
 39   
 40   
 41 -class DropHandler(object): 
 42   
 43 -    def __init__(self): 
 44          self._dropListeners = [] 
 45          self.sinkEvents(Event.DROPEVENTS) 
 46   
 47 -    def onBrowserEvent(self, event): 
 48          event_type = DOM.eventGetType(event) 
 49          if event_type in DROP_EVENTS: 
 50              return fireDropEvent(self._dropListeners, event) 
 51          return False 
 52   
 53 -    def addDropListener(self, listener): 
 54          self._dropListeners.append(listener) 
 55   
 56 -    def removeDropListener(self, listener): 
 57          self._dropListeners.remove(listener) 
 58   
 59 -    def onDragEnter(self,event): 
 60          """ 
 61          Decide whether to accept the drop. 
 62   
 63          You may inspect the event's dataTransfer member. 
 64   
 65          You may get the types using pyjamas.dnd.getTypes(event). 
 66   
 67          This event is used to determine whether the drop target may 
 68          accept the drop. If the drop is to be accepted, then this event has 
 69          to be canceled using DOM.eventPreventDefault(event). 
 70          """ 
 71          pass 
 72   
 73 -    def onDragOver(self,event): 
 74          """ 
 75          This event determines what feedback is to be shown to the user. If 
 76          the event is canceled, then the feedback (typically the cursor) is 
 77          updated based on the dropEffect attribute's value, as set by the event 
 78          handler; otherwise, the default behavior (typically to do nothing) 
 79          is used instead. 
 80   
 81          Setting event.dataTransfer.dropEffect may affect dropping behavior. 
 82   
 83          Cancel this event with DOM.eventPreventDefault(event) if you want the 
 84          drop to succeed. 
 85   
 86          """ 
 87          pass 
 88   
 89 -    def onDragLeave(self,event): 
 90          """ 
 91          This event happens when the mouse leaves the target element. 
 92          """ 
 93          pass 
 94   
 95 -    def onDrop(self,event): 
 96          """allows the actual drop to be performed. This event also needs to be 
 97          canceled, so that the dropEffect attribute's value can be used by the 
 98          source (otherwise it's reset). 
 99          """ 
100          pass 
101