CIS2750 Seminar 6 Created by: Anthony Koso

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CIS2750 Seminar 6 Created by Anthony Koso

• Exporting X Displays
• Python/Tk

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Exporting Your X Display

• Run a graphical program on one machine and have
  it display on another
• Can run applications from different platforms
• Will become more important for A3/A4
• Can be done with SSH tunneling
• ssh -X user_at_host
• putty - connections-gtSSH-gttunnels-gtenable X11
• ltlocal addressgt0
• X server software for windows
• Cygwin http//x.cygwin.com
• X-Win 32 http//www.starnet.com

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How To Export Your X Display

• On local machine
• Start X server
• Run xhost ltremote_computergt
• On remote machine (via telnet/ssh/etc)
• Set DISPLAY to ltlocal_computergt0
• Run X apps normally
• Alternative to setting DISPLAY (in bash)
• DISPLAYltlocal_computergt0 xapp
• Must be done each time
• If SSH tunneling used, skip xhost and setting
  DISPLAY
• It's already done for you!

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What is Tkinter

• Standard Python interface to the Tk GUI toolkit
  (from Scriptics, formerly of Sun Labs)
• Graphical toolkit for Python
• Exists on Windows, Mac, Unix, Linux
• Tk interface is located in _tkinter (a binary
  module)
• Contains low-level interface to Tk

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Tkinter

• Every element is a "widget
• Three layout styles
• Pack, Grid, Place
• Packages for Redhat Linux
• tkinter, tix, tk,

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Hello World

• File hello1.py
• from Tkinter import
• root Tk()
• w Label(root, textHello world)
• w.pack()
• root.mainloop()

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Analyze Hello World

• root Tk()
• Create a Tk root widget
• Only create one root widget for each program
• Must be created before any other widget
• w Label(root, textHello world)
• Create a Label widget
• w.pack()
• Call pack method on this widget
• Tells it to size itself to fit the given text,
  and make itself visible
• root.mainloop()
• Starts event loop
• Handles events from user, windowing system and
  operations queued by Tkinter

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Using Classes Hello World2

• class App
• def __init__ (self, master)
• frame Frame(master)
• frame.pack()
• self.button Button(frame, textQUIT,
• fgred, commandframe.quit)
• self.button.pack(sideLEFT)
• self.hi Button(frame, textHello,
• commandself.say_hi)
• def say_hi(self)
• print Hello world!
• root Tk()
• app App(root)
• root.mainloop()

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Analyze Class Example

• def __init__ (self, master)
• Constructor is called with a parent widget, to
  which it adds children widgets
• frame Frame(master)
• frame.pack()
• Create a Frame widget (simple container)
• Stored in a local variable called frame
• Call pack to make frame visible
• self.button Button(frame, textQUIT,
• fgred, commandframe.quit)
• self.button.pack(sideLEFT)
• Create two Button widgets as children to frame
• Widgets are packed relative to their parent (ex.
  master)

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Widget Reference

• In second example, frame widget is stored in
  frame (local variable)
• Tkinter automatically maintains a widget tree
• Must use destroy() to remove a widget
• However, if you have no reference to widget, you
  cannot edit it
• Beware of other examples that create widgets
  without reference to them

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Widget Classes
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Tkinter Example

• See simplegui.py

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Final Notes

• Questions?
• Comments?
• Reminder A2 due on Feb 15