[Tkinter] Drag & drop

[Tom Vrankar]

Enjoy.

							twv@


#!/usr/local/bin/python

import sys, os, string, time
import Tkinter
tk =Tkinter

# A Python example of drag and drop functionality within a single Tk widget.
# The trick is in the bindings and event handler functions.
# Tom Vrankar twv at ici.net

# empirical events between dropee and target, as determined from Tk 8.0
# down.
# leave.
# up, leave, enter.

class CanvasDnD (tk.Frame):
  def __init__ (self, master):
    self.master =master
    self.loc =self.dragged =0
    tk.Frame.__init__ (self, master)
    canvas =tk.Canvas (self, width =256, height =256,
      relief =tk.RIDGE, background ="white", borderwidth =1)
    self.defaultcolor =canvas.itemcget (canvas.create_text (30, 25,
      font =("Helvetica", 14), text ="Item 1", tags ="DnD"), "fill")
    canvas.create_text (75, 75,
      font =("Helvetica", 14), text ="Item 2", tags ="DnD")
    canvas.create_text (125, 125,
      font =("Helvetica", 14), text ="Item 3", tags ="DnD")
    canvas.create_text (175, 175,
      font =("Helvetica", 14), text ="Item 4", tags ="DnD")
    canvas.create_text (225, 225,
      font =("Helvetica", 14), text ="Item 5", tags ="DnD")
    canvas.pack (expand =1, fill =tk.BOTH)
    canvas.tag_bind ("DnD", "<ButtonPress-1>", self.down)
    canvas.tag_bind ("DnD", "<ButtonRelease-1>", self.chkup)
    canvas.tag_bind ("DnD", "<Enter>", self.enter)
    canvas.tag_bind ("DnD", "<Leave>", self.leave)

  def down (self, event):
    print "Click on %s" %event.widget.itemcget (tk.CURRENT, "text")
    self.loc =1
    self.dragged =0
    event.widget.bind ("<Motion>", self.motion)

  def motion (self, event):
    root.config (cursor ="exchange")
    event.widget.itemconfigure (tk.CURRENT, fill ="blue")
    event.widget.unbind ("<Motion>")
  
  def leave (self, event):
    self.loc =0

  def enter (self, event):
    self.loc =1
    if self.dragged ==event.time:
      self.up (event)

  def chkup (self, event):
    root.config (cursor ="")
    self.target =event.widget.find_withtag (tk.CURRENT)
    event.widget.itemconfigure (tk.CURRENT, fill =self.defaultcolor)
    if self.loc: # is button released in same widget as pressed?
      self.up (event)
    else:
      self.dragged =event.time

  def up (self, event):
    event.widget.unbind ("<Motion>")
    if (self.target ==event.widget.find_withtag (tk.CURRENT)):
      print "Select %s" %event.widget.itemcget (tk.CURRENT, "text")
    else:
      event.widget.itemconfigure (tk.CURRENT, fill ="blue")
      self.master.update()
      time.sleep (.1)
      print "%s Drag-N-Dropped onto %s" \
        %(event.widget.itemcget (self.target, "text"),
	  event.widget.itemcget (tk.CURRENT, "text"))
      event.widget.itemconfigure (tk.CURRENT, fill =self.defaultcolor)

root =tk.Tk()
root.title ("Drag-N-Drop Demo")
CanvasDnD (root).pack()
root.mainloop()





In article <199910201305.OAA19676 at axil.hvision.nl>, apocalyptica at hvision.nl 
says...
>
>
>Hello,
>
>Does anyone have a drag & drop example for my snippets page? I am 
>aware of the Tkinter demos in the Python distribution, but that's not 
>really what I'm looking for. What I would like to see is something 
>with, say, two labels, and the possibility to drag one label to the 
>other, after which the text of the 'target' label changes. In other 
>words, I need a way to determine where an object was dropped on. 
>Haven't seen such an example so far, but maybe I just didn't search 
>hard enough...
>
>TIA,
>
>--Hans Nowak (ivnowa at hvision.nl)
>Homepage: http://fly.to/zephyrfalcon
>Snippets: http://tor.dhs.org/~zephyrfalcon/snippets/
>
>

-- 
                         ---------------------------------
                                               Tom Vrankar
                                            twv at ici.net
                                 http://home.ici.net/~twv/
                                         Rhode Island, USA