#


# editing canvas items


#


# fredrik lundh, december 1998


#


# fredrik@pythonware.com


# http://www.pythonware.com


#




from Tkinter import *



class MyCanvas(Frame):



  def __init__(self, root):

          Frame.__init__(self, root)

          self.canvas = Canvas(self)

          self.canvas.pack(fill=BOTH, expand=1)



          # standard bindings


          self.canvas.bind("<1>", self.set_focus)

          self.canvas.bind("<Double-Button-1>", self.set_cursor)

          self.canvas.bind("<Key>", self.handle_key)



          # add a few items to the canvas


          self.canvas.create_text(50, 50, text="hello")

          self.canvas.create_text(50, 100, text="world")



  def highlight(self, item):

          # mark focused item.  note that this code recreates the


          # rectangle for each update, but that's fast enough for


          # this case.


          bbox = self.canvas.bbox(item)

          self.canvas.delete("highlight")

          if bbox:

              i = self.canvas.create_rectangle(

                  bbox, fill="white",

                  tag="highlight"

                  )

              self.canvas.lower(i, item)



  def has_focus(self):

          return self.canvas.focus()



  def has_selection(self):

          # FIXME: hack to work around bug in Tkinter 1.101 (Python 1.5.1)


          return self.canvas.tk.call(self.canvas._w, 'select', 'item')



  def set_focus(self, event):

          if self.canvas.type(CURRENT) != "text":

              return



          self.highlight(CURRENT)



          # move focus to item


          self.canvas.focus_set() # move focus to canvas


          self.canvas.focus(CURRENT) # set focus to text item


          self.canvas.select_from(CURRENT, 0)

          self.canvas.select_to(CURRENT, END)



  def set_cursor(self, event):

          # move insertion cursor


          item = self.has_focus()

          if not item:

              return # or do something else




          # translate to the canvas coordinate system


          x = self.canvas.canvasx(event.x)

          y = self.canvas.canvasy(event.y)



          self.canvas.icursor(item, "@%d,%d" % (x, y))

          self.canvas.select_clear()



  def handle_key(self, event):

          # widget-wide key dispatcher


          item = self.has_focus()

          if not item:

              return



          insert = self.canvas.index(item, INSERT)



          if event.char >= " ":

              # printable character


              if self.has_selection():

                  self.canvas.dchars(item, SEL_FIRST, SEL_LAST)

                  self.canvas.select_clear()

              self.canvas.insert(item, "insert", event.char)

              self.highlight(item)



          elif event.keysym == "BackSpace":

              if self.has_selection():

                  self.canvas.dchars(item, SEL_FIRST, SEL_LAST)

                  self.canvas.select_clear()

              else:

                  if insert > 0:

                      self.canvas.dchars(item, insert-1, insert)

              self.highlight(item)



          # navigation


          elif event.keysym == "Home":

              self.canvas.icursor(item, 0)

              self.canvas.select_clear()

          elif event.keysym == "End":

              self.canvas.icursor(item, END)

              self.canvas.select_clear()

          elif event.keysym == "Right":

              self.canvas.icursor(item, insert+1)

              self.canvas.select_clear()

          elif event.keysym == "Left":

              self.canvas.icursor(item, insert-1)

              self.canvas.select_clear()



          else:

              pass # print event.keysym




if __name__ == "__main__":

    root = Tk()

    ui=MyCanvas(root)

    ui.pack()

    root.mainloop()