Python Tk Tix GUI documentation & builder overview and tips

[baloand at googlemail.com]

I have recently started development for a small video conversion
project using a GUI. After some research I decided to use Tkinter/Tix
(Tk/Tix). The reasons are mainly:

1. the GUI is rather simple, and

2. the end-user is not necessarily technically inclined so I want to
keep
  a) required libraries as few as possible, and
  b) installation as painless as possible.

3. Tk/Tix is included with Python. Thus only a Python installation is
needed. Nothing else.

4. Tk itsself misses some rudimentary widgets like meters, multi/colum
lists, grid and scrolled widgets. Tix provides those. Good enough for
my little application (more advanced and more modern widgets are
available in frameworks like Qt, Gtk, or wxWindows).


Before starting I spent some effort to find
a) relevant documentation,
b) GUI Builders which might help me,
c) answers to non-obvious questions.

The process took some time and effort so I want to share my findings:

a) Documentation resources

Python Docs
        http://docs.python.org/library/tkinter.html
Tk Commands
        http://www.tcl.tk/man/tcl8.5/TkCmd/contents.htm
Tix Reference
        http://tix.sourceforge.net/man/html/contents.htm
Tix demo application
	You want to extract the Tix demo application coming with the Tix
8.4.3 source distribution. It contains 	examples for many widgets -
unfortunately none for multi-column HList or the Grid (see below).
	https://sourceforge.net/project/showfiles.php?group_id=5649&package_id=5704
	Tix8.4.3-src.tar.gz, then look in /Tix8.4.3/Python/Demo/tix
Thinking in Tkinter
	I recommend the "Individual programs online"
	http://www.ferg.org/thinking_in_tkinter/index.html


b) GUI development tools

ActiveState GUI Builder (using grid layout)
	SpecTcl is the predecessor of GUI Builder (by ActivaState).
        http://spectcl.sourceforge.net/
        FAQ (where to get source)
        http://aspn.activestate.com/ASPN/Mail/Message/komodo-announce/3355346

PAGE v3.0 by Stewart Allen (using placer layout)
        http://page.sourceforge.net/

There are many more for other GUI toolkits mentioned in this post:
	http://mail.python.org/pipermail/python-list/2004-February/250727.html

Finally I decided to use the packer layout and create the widgets
manually. Just the simplest and quickest way for me.


c) How do I ...?

How do I use all methods available in the Tix Grid?

Tix Grid with full implementation of all methods
        http://klappnase.bubble.org/TixGrid/index.html


How do I create a multi-column Tix.HList?

	import Tkinter as Tk
	import Tix

	root = Tix.Tk()
	# setup HList
        hl = Tix.HList(root, columns = 5, header = True)
        hl.header_create(0, text = "File")
        hl.header_create(1, text = "Date")
        hl.header_create(1, text = "Size")
	# create a multi-column row
	hl.add("row1", text = "filename.txt")
	hl.item_create(entry_path, 1, text = "2009-03-26 21:07:03")
	hl.item_create(entry_path, 2, text = "200MiB")

I haven't found out how to right-justify individual columns? Anyone?


How to implement Tk GUI with multiple threads?

Usually there are two options to make threads wait for an event:

  * gui thread polling (lame)
    see here how to use Tk.after() (actually a Tcl command) to poll
    	http://uucode.com/texts/pylongopgui/pyguiapp.html

    see here how to imitate the Tk event loop to poll for non-Tk
events (a socket, for example)
	https://sourceforge.net/project/showfiles.php?group_id=5649&package_id=5704
	Tix8.4.3-src.tar.gz, then look in /Tix8.4.3/Python/Demo/tix/
tixwidgets.py, find loop()


  * multithreaded with events (the option to choose)
    Basically this uses bind and event_generate to send "Notify"
messages to the Tk instance.
    I suspect the following example failed due to not synchronising
the event_generate call
        http://coding.derkeiler.com/Archive/Python/comp.lang.python/2006-07/msg01479.html

For multithreading Python Tk GUI applications the following rules
apply:
1. same thread calling Tk must do all subsequent GUI calls,
2. other threads may send events with send_event to the root Tk
instance,
3. with threading problems you might try to synchonise access to
event_generate(). Using event_generate() with one non-GUI thread seems
to be safe.