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      1 from Tkinter import *
      2 
      3 # allows moving dots with multiple selection.
      4 
      5 SELECTED_COLOR = "red"
      6 UNSELECTED_COLOR = "blue"
      7 
      8 class Test(Frame):
      9     ###################################################################
     10     ###### Event callbacks for THE CANVAS (not the stuff drawn on it)
     11     ###################################################################
     12     def mouseDown(self, event):
     13         # see if we're inside a dot. If we are, it
     14         # gets tagged as CURRENT for free by tk.
     15 
     16         if not event.widget.find_withtag(CURRENT):
     17             # we clicked outside of all dots on the canvas. unselect all.
     18 
     19             # re-color everything back to an unselected color
     20             self.draw.itemconfig("selected", fill=UNSELECTED_COLOR)
     21             # unselect everything
     22             self.draw.dtag("selected")
     23         else:
     24             # mark as "selected" the thing the cursor is under
     25             self.draw.addtag("selected", "withtag", CURRENT)
     26             # color it as selected
     27             self.draw.itemconfig("selected", fill=SELECTED_COLOR)
     28 
     29         self.lastx = event.x
     30         self.lasty = event.y
     31 
     32 
     33     def mouseMove(self, event):
     34         self.draw.move("selected", event.x - self.lastx, event.y - self.lasty)
     35         self.lastx = event.x
     36         self.lasty = event.y
     37 
     38     def makeNewDot(self):
     39         # create a dot, and mark it as current
     40         fred = self.draw.create_oval(0, 0, 20, 20,
     41                                      fill=SELECTED_COLOR, tags=CURRENT)
     42         # and make it selected
     43         self.draw.addtag("selected", "withtag", CURRENT)
     44 
     45     def createWidgets(self):
     46         self.QUIT = Button(self, text='QUIT', foreground='red',
     47                            command=self.quit)
     48 
     49         ################
     50         # make the canvas and bind some behavior to it
     51         ################
     52         self.draw = Canvas(self, width="5i", height="5i")
     53         Widget.bind(self.draw, "<1>", self.mouseDown)
     54         Widget.bind(self.draw, "<B1-Motion>", self.mouseMove)
     55 
     56         # and other things.....
     57         self.button = Button(self, text="make a new dot", foreground="blue",
     58                              command=self.makeNewDot)
     59 
     60         message = ("%s dots are selected and can be dragged.\n"
     61                    "%s are not selected.\n"
     62                    "Click in a dot to select it.\n"
     63                    "Click on empty space to deselect all dots."
     64                    ) % (SELECTED_COLOR, UNSELECTED_COLOR)
     65         self.label = Message(self, width="5i", text=message)
     66 
     67         self.QUIT.pack(side=BOTTOM, fill=BOTH)
     68         self.label.pack(side=BOTTOM, fill=X, expand=1)
     69         self.button.pack(side=BOTTOM, fill=X)
     70         self.draw.pack(side=LEFT)
     71 
     72     def __init__(self, master=None):
     73         Frame.__init__(self, master)
     74         Pack.config(self)
     75         self.createWidgets()
     76 
     77 test = Test()
     78 test.mainloop()
     79