GUI toolkit selection for a text editor widget

Srinath Avadhanula

Hello,

Sorry to be bringing up what seems to be a somewhat beaten up topic...

This is what I wanted to do:

Create a _simple_ text editor widget which supports VI(M) style
keybindings but works with arbitrary fonts/unicode characters. Vi(m)
unfortunately, does not support Devanagari (or proportional fonts) and
it looks like it will take quite some time for these things to work. As
and when Vim supports Devanagari on Windows, I will give up this effort.

My current aims are:
1. Simple Vi(m) style keybindings.
2. Syntax highlighting for arbitrary files based on Vim-style syntax
highlighting definitions. Vim defines syntax highlighting for files
based on a very flexible regexp style approach. Thus you can define
syntax hightlighting for new file types just by writing some regexps.
3. Should be able to load/edit files written in unicode.
4. Macro capability.
5. I want to implement this purely in python.
6. Should work on windows.
7. I do not really care much about speed/looks etc as long as the thing is
functional.

The choice of the GUI toolkit is therefore almost exclusively depends on
how these conditions can be met. This is my take so far:

1. PyQT: Unfortunately, the qtext module which extends the scintilla module
to QT is available only under a commercial license for windows. The
QMultiLineEdit widget does not support any text styling at all. Hence
PyQT seems to be ruled out straight away.

2. wxPython: The wxStyledTextCtrl widget showed great promise. It has
almost everything one would wish for. Except for a _major_ bug while
editing unicode. The text caret which shows where the text insertion
will happen is offset from the actual insertion point in complex
scripts like devangari or arabic. This looks like its a problem with
calculating text extents. Robin Dunn has acknowledged this bug, but
unfortunately, unless there is a workaround, I cannot do anything with
wxStyledTextCtrl at all.

wxPython also has wxTextCtrl which has far lesser features than
wxStyledTextCtrl, but at least does not have the bug with the text
caret. Unfortunately, it looks like it does not provide some necessary
functions. For one, if I desire to do syntax highlighting based on it, I
would need to find out the current range of text displayed in the
window. But I couldn't find any way of finding out which lines are
actually displayed. The various wxScrollBar functions (which wxTextCtrl
inherits) do not give useful information.

3. Tkinter: I looked briefly at Tkinter and the Text widget looked very
impressive indeed! It looks like the way it highlights text is even
more powerful than Vim in that each character (or range) has multiple
"tags" associated with it and the most recent tag takes precedence.
This looks like something which might be very handy. It even supports
inserting bitmaps etc. All in all, very neat looking.

But there seems to be some limitations:
1. How do I recognize control key inputs? I tried
self.bind('<Key>', function)
but how to find out if CTRL-a has been pressed in the function. When
I ran a simple app, event.char reports 'a' when I press CTRL-A. So
does event.keysym and event.keycode... wxPython has something called
event.ControlDown() for keyEvents...

2. There seems to be a problem with displaying unicode which Text
suffers from too :( The problem is not as severe as the one
wxStyledTextCtrl suffers from and it looks like it can be "lived
with". When moving over certain "composing character" strings in
unicode, the caret seems to move _between_ the characters. Ideally,
each sequence of composing characters would be considered a single
"glyph"... I will elaborate if someone needs clarification.

3. Although the Text widget itself is powerful, from what I gather in
this newsgroup and on the web, Tkinter does not provide things like
a tree control widget which might be essential later on. This looks
like something which can be worked around, because idle, the editor
provided with Python 2.3 seems to have all these things constructed
using the basic primitives...

Infact, I am wondering whether I should just modify Idle to accept Vi
style key-bindinds...

I would greatly appreciate any comments.

Thank you,
Regards,
Srinath

Jul 18 '05 #1

Cameron Laird

In article <Pi*************************************@albinoni. EECS.Berkeley.EDU>,
Srinath Avadhanula <sr*************@yahoo.com> wrote:

Jul 18 '05 #2

J. Random Hacker

On Fri, 07 Nov 2003 19:43:44 -0800, Srinath Avadhanula wrote:

Hello,

Sorry to be bringing up what seems to be a somewhat beaten up topic...

This is what I wanted to do:

Create a _simple_ text editor widget which supports VI(M) style
keybindings but works with arbitrary fonts/unicode characters. Vi(m)
unfortunately, does not support Devanagari (or proportional fonts) and
it looks like it will take quite some time for these things to work. As
and when Vim supports Devanagari on Windows, I will give up this effort.

My current aims are:
1. Simple Vi(m) style keybindings.
2. Syntax highlighting for arbitrary files based on Vim-style syntax
highlighting definitions. Vim defines syntax highlighting for files
based on a very flexible regexp style approach. Thus you can define
syntax hightlighting for new file types just by writing some regexps.
3. Should be able to load/edit files written in unicode.
4. Macro capability.
5. I want to implement this purely in python.
6. Should work on windows.
7. I do not really care much about speed/looks etc as long as the thing is
functional.

Don't forget pygtk, bindings for GTK+. GTK+ has a very powerful
GtkTextView widget. There is also a GtkSourceView widget that has recently
been wrapped for python use. GTK+ supports custom keybindings throughout.
GTK+ works well on Windows. GTK+ on Windows XP uses the XP themeing
system, so GTK+ apps look native on Windows XP. The Windows classic
theme, although not perfect, works very similarly to native Windows
widgets.

If you use pygtk but would rather use the Scintilla widget you may be
interested in this: http://sra.itc.it/people/cavada/PyScintilla2.html

Jul 18 '05 #3