#!/usr/bin/python

'''Pop up a window that tails a file.

   This is somewhat like "tail -f" in an xterm, but should be portable
   to Windows.  Unlike tail, it displays only whole lines.

   Things to add: a line count display;
                  decent fonts
                  wrap control
                  command-line options
'''
# EF 2004/09/29, derived from tktail.py

import sys, time
from Tkinter import *
import Pmw

usage = '''
Usage: tktail <filename>
   where <filename> must refer to a file that already
   exists and is readable.
'''

def no_action(event):
   return "break"


class tail(Pmw.LabeledWidget):
   def __init__(self, master=None, filename='', max_lines = 1000, **kw):
      if master == None:
         master = Tk()
         Pmw.initialise(master)
         master.title('tail')
      kw['labelpos'] = 'n'
      kw['label_text'] = filename
      Pmw.LabeledWidget.__init__(self, master, **kw)
      self.pack(fill=BOTH, expand=TRUE)
      self.file = open(filename)
      self.max_lines = max_lines
      self.text = Pmw.ScrolledText(self.interior())
      self.text.pack(side=TOP, fill=BOTH, expand=TRUE)
      self.text.bind("<KeyPress>", no_action)
      self.BVend = BooleanVar()
      self.BVend.set(True)
      self.CBend = Checkbutton(self.interior(), text="view end",
                                 variable=self.BVend,
                                 onvalue=True,
                                 offvalue=False)

      self.CBend.pack(side=TOP, fill=NONE, expand=FALSE, anchor=E)
      self.run()

   def run(self):
      lines = self.file.readlines()
      if len(lines) > 0:
         self.text.insert(END, ''.join(lines[-self.max_lines:]))
         if self.BVend.get():
            self.text.see(END)
         #self.text.appendtext(''.join(lines[-self.max_lines:]))
         self.text.delete('1.0', 'end - %d lines' % (self.max_lines,))
      self.text.after(100, self.run)

   def mainloop(self):
      self.text.mainloop()

if __name__ == "__main__":
   if len(sys.argv) != 2:
      print usage
      sys.exit()
   T = tail(filename=sys.argv[1])
   T.mainloop()