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Tkinter focus problem

John Grayson johngrayson at home.com
Fri Jun 30 13:25:47 EDT 2000 
In article <395CC8DE.AA663D4 at ieee.org>,
  Didier WILLAME <didier.willame at ieee.org> wrote:
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> Hello all,
>
> I've slight problems with focus in Tkinter, running under win NT.
>
> With the following script I'm able to create 'nodes' (left button) in
a
> canvas. The color of a 'node' toggles if the mouse is putting on.
> Moreover, I would like display "Hello World!" when I press on the key
> '1' and, when the mouse is putting on this 'node'.
>
> But I'm unable to bind a key event (line 25), although I can run the
> script with a button event (line 26 instead of line 25).
> I should probably give the focus to the 'node' object inside the
> entryNode function (line 57).
>
> Thank you for your time,
> Didier
>

Well, you need to give the canvas focus. However, I don't think that
your original code is adequate, since I'm sure you will want to know
*which* node is active.

I've restructured your code a bit, storing the current item that
has been entered, giving it a new highlight when '1' is pressed.

Should get you going again...

   John Grayson    (Python and Tkinter Programming)


# ----------
from Tkinter import *

class Graph( Frame ):

 # ----------
  def __init__( self, master=None ):
    Frame.__init__( self, master )
    self.pack()
    self.createCanvas()
    self.activeNode = None

  # ----------
  def createCanvas( self ):
     self.editingArea = Canvas( self )

     # --- To create a node with the left button.
     self.editingArea.bind( '<Button-1>',   self.mkNode )
     self.editingArea.bind( '<KeyPress-1>', self.activateNode )
     self.editingArea.bind( '<Button-2>',   self.activateNode )

     # --- To toggle the node color when passing with the mouse.
     self.editingArea.tag_bind( 'node', '<Any-Enter>', self.entryNode )
     self.editingArea.tag_bind( 'node', '<Any-Leave>', self.leaveNode )

     self.editingArea.pack(side=TOP)
     self.editingArea.focus_set()

  # ----------
  def mkNode( self, event ):
    """Create a new node at (x,y)"""

    x = event.x
    y = event.y

    new = self.editingArea.create_oval( x-5, y-5, x+5, y+5 )
    self.editingArea.itemconfigure( new, tag='node', outline='black',
                                         fill='red' )

  # ----------
  def entryNode( self, event ):
    self.editingArea.itemconfigure( CURRENT, fill='blue' )
    self.activeNode = self.editingArea.find_withtag( CURRENT )

  # ----------
  def leaveNode( self, event ):
    self.editingArea.itemconfigure( CURRENT, fill= 'red' )
    self.activeNode = None

  # ----------
  def srcNode( self, event=None ):
    print 'Hello World!'

  def activateNode( self, event ):
      if self.activeNode:
	self.srcNode()
	self.editingArea.itemconfigure( self.activeNode, fill='green')

# -----------------------------------------------

graph = Graph()
try:
  graph.mainloop()
except KeyboardInterrupt:
  graph.quit()


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