How to get a correct scrolling using TkInter's text widget?

Question

I'm trying to program a simple GUI using the Text widget of TkInter and I'm stuck with a strange behavior when I scroll within it.

When I reach the end of the text, sometime, I get a blank line at the bottom of the widget (and sometime not)...

Here you can see the blank line :

And this time, there's no...

Or course I don't want to see this blank line.

Here is a simple snippet that illustrate my issue. Play with it : scroll up and down using the up/down arrows, the home/end/pageup/pagedown keys. At one time, you should see the blank line...

import sys,Tkinter

escape,up,down,home,end,pageup,pagedown = 27,38,40,36,35,33,34

class HText ( Tkinter.Text ):
    def __init__(self,parent,lines,w,h ):
        Tkinter.Text.__init__( self,parent )
        self.config( takefocus=True,width=w,height=h )
        self._len   = len( lines )
        self._index = 0
        self.config( state=Tkinter.NORMAL )
        for i,t in enumerate( lines ):
            self.insert( Tkinter.END,'%-4d : %s\n'%(i,t),'#%d'%i )
        self.focus( 1 )
    def focus (self,on):
        self.tag_config( '#%d'%self._index,background='#daf' if on else 'white' )
    def move (self,keycode):
        delta = { up:-1,down:+1,home:-self._len,end:self._len,pageup:-20,pagedown:+20 }.get( keycode,0 )
        index = max( 0,min( self._index+delta,self._len-1 ))
        if index != self._index :
            self.focus( 0 )
            self._index = index
            self.see( '#%d.first'%self._index )
            self.focus( 1 )

def Gui ( text ):
    self = Tkinter.Tk()
    self.bind('<Escape>',lambda e : self.quit())
    self.bind('<Key>'   ,lambda e : htext.move( e.keycode ))
    htext = HText( self,text.split('\n'),120,30 )
    htext.pack()
    self.mainloop()
    self.destroy()

Gui( open( sys.argv[0] ).read()*10 )

Do you see what I'm doing wrong ? Is it a bug in TkInter ?

By the way, I'm using python 2.7 under Windows 7 x64.

Thank in advance for your time.

Hadrien

Answer 1

After the string insertion is done use this line to remove the last newline character:

htext.delete('end-1c', 'end')