The Text Widget

[Eric Brunel]

Edward K. Ream wrote:
> Are you sure?

Yep. Definitely. In fact, we were doing the same thing than you: a syntax 
highlighting text editor. And we never did any after_idle in it, so you can 
do it just via regular bindings.

> Note that my main testing was done on Windows, if that
> makes any difference.

It should not: our editor works the same on Windows and Unices.

> If you have an example of fancy bindings for Text widgets I'd love to
> see it.  Thanks.

We had indeed to do some bizarre things to be sure that we were informed of 
anything that happened to the text. This included for example a custom 
management of the X selection (which has a pre-defined binding under X 
Windows, but is really hard to catch), and a few other things. We decided 
that we would work at the line level: changes are identified on lines (not 
at the character level or for the whole text...). Here is a very simplified 
example of what we did, just showing how you can catch almost everything 
that happens on a Text (a few things may have slipped by in the 
simplification, but hopefully not much):

---------------
from Tkinter import *

root = Tk()

t = Text(root)
t.pack()

oldSel = 0

## Prints the current line number and contents
def printCurrentLine(prefix=''):
  l, c = t.index(INSERT).split('.', 1)
  print '%sCurrent line is %s: "%s"' % \
    (prefix, l, t.get("%s.0" % l, "%s.end" % l))

## Called when a key is pressed
def keyPress(event):
  global oldSel
  printCurrentLine("Before: ")
  ## Put a custom tag on the selection at the key press
  oldSel = 0
  t.tag_delete('oldSel')
  sel = t.tag_ranges(SEL)
  if not sel: return
  start, stop = sel[0], sel[1]
  t.tag_add('oldSel', start, stop)
  oldSel = 1

## Called when a key is released
def keyRelease(event):
  printCurrentLine("After: ")
  ## If the custom tag was set and doesn't exist anymore,
  ## the selection disappeared
  if oldSel and len(t.tag_ranges('oldSel')) == 0:
    print "Selection was deleted"

t.bind('<KeyPress>', keyPress)
t.bind('<KeyRelease>', keyRelease)

root.mainloop()
---------------

As I said, there's certainly a few things missing, but starting from that, 
you should be able to actually identify every single change that happened 
to your text.

HTH
 - eric -