176 lines
6.8 KiB
Python
176 lines
6.8 KiB
Python
from tkinter import TclError
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class WidgetRedirector:
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"""Support for redirecting arbitrary widget subcommands.
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Some Tk operations don't normally pass through tkinter. For example, if a
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character is inserted into a Text widget by pressing a key, a default Tk
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binding to the widget's 'insert' operation is activated, and the Tk library
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processes the insert without calling back into tkinter.
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Although a binding to <Key> could be made via tkinter, what we really want
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to do is to hook the Tk 'insert' operation itself. For one thing, we want
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a text.insert call in idle code to have the same effect as a key press.
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When a widget is instantiated, a Tcl command is created whose name is the
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same as the pathname widget._w. This command is used to invoke the various
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widget operations, e.g. insert (for a Text widget). We are going to hook
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this command and provide a facility ('register') to intercept the widget
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operation. We will also intercept method calls on the tkinter class
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instance that represents the tk widget.
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In IDLE, WidgetRedirector is used in Percolator to intercept Text
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commands. The function being registered provides access to the top
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of a Percolator chain. At the bottom of the chain is a call to the
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original Tk widget operation.
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"""
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def __init__(self, widget):
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'''Initialize attributes and setup redirection.
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_operations: dict mapping operation name to new function.
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widget: the widget whose tcl command is to be intercepted.
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tk: widget.tk, a convenience attribute, probably not needed.
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orig: new name of the original tcl command.
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Since renaming to orig fails with TclError when orig already
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exists, only one WidgetDirector can exist for a given widget.
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'''
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self._operations = {}
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self.widget = widget # widget instance
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self.tk = tk = widget.tk # widget's root
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w = widget._w # widget's (full) Tk pathname
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self.orig = w + "_orig"
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# Rename the Tcl command within Tcl:
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tk.call("rename", w, self.orig)
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# Create a new Tcl command whose name is the widget's pathname, and
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# whose action is to dispatch on the operation passed to the widget:
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tk.createcommand(w, self.dispatch)
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def __repr__(self):
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return "%s(%s<%s>)" % (self.__class__.__name__,
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self.widget.__class__.__name__,
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self.widget._w)
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def close(self):
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"Unregister operations and revert redirection created by .__init__."
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for operation in list(self._operations):
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self.unregister(operation)
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widget = self.widget
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tk = widget.tk
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w = widget._w
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# Restore the original widget Tcl command.
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tk.deletecommand(w)
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tk.call("rename", self.orig, w)
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del self.widget, self.tk # Should not be needed
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# if instance is deleted after close, as in Percolator.
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def register(self, operation, function):
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'''Return OriginalCommand(operation) after registering function.
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Registration adds an operation: function pair to ._operations.
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It also adds a widget function attribute that masks the tkinter
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class instance method. Method masking operates independently
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from command dispatch.
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If a second function is registered for the same operation, the
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first function is replaced in both places.
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'''
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self._operations[operation] = function
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setattr(self.widget, operation, function)
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return OriginalCommand(self, operation)
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def unregister(self, operation):
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'''Return the function for the operation, or None.
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Deleting the instance attribute unmasks the class attribute.
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'''
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if operation in self._operations:
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function = self._operations[operation]
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del self._operations[operation]
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try:
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delattr(self.widget, operation)
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except AttributeError:
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pass
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return function
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else:
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return None
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def dispatch(self, operation, *args):
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'''Callback from Tcl which runs when the widget is referenced.
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If an operation has been registered in self._operations, apply the
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associated function to the args passed into Tcl. Otherwise, pass the
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operation through to Tk via the original Tcl function.
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Note that if a registered function is called, the operation is not
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passed through to Tk. Apply the function returned by self.register()
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to *args to accomplish that. For an example, see colorizer.py.
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'''
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m = self._operations.get(operation)
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try:
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if m:
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return m(*args)
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else:
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return self.tk.call((self.orig, operation) + args)
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except TclError:
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return ""
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class OriginalCommand:
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'''Callable for original tk command that has been redirected.
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Returned by .register; can be used in the function registered.
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redir = WidgetRedirector(text)
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def my_insert(*args):
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print("insert", args)
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original_insert(*args)
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original_insert = redir.register("insert", my_insert)
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'''
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def __init__(self, redir, operation):
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'''Create .tk_call and .orig_and_operation for .__call__ method.
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.redir and .operation store the input args for __repr__.
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.tk and .orig copy attributes of .redir (probably not needed).
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'''
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self.redir = redir
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self.operation = operation
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self.tk = redir.tk # redundant with self.redir
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self.orig = redir.orig # redundant with self.redir
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# These two could be deleted after checking recipient code.
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self.tk_call = redir.tk.call
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self.orig_and_operation = (redir.orig, operation)
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def __repr__(self):
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return "%s(%r, %r)" % (self.__class__.__name__,
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self.redir, self.operation)
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def __call__(self, *args):
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return self.tk_call(self.orig_and_operation + args)
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def _widget_redirector(parent): # htest #
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from tkinter import Toplevel, Text
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import re
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top = Toplevel(parent)
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top.title("Test WidgetRedirector")
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width, height, x, y = list(map(int, re.split('[x+]', parent.geometry())))
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top.geometry("+%d+%d"%(x, y + 150))
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text = Text(top)
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text.pack()
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text.focus_set()
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redir = WidgetRedirector(text)
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def my_insert(*args):
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print("insert", args)
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original_insert(*args)
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original_insert = redir.register("insert", my_insert)
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if __name__ == "__main__":
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import unittest
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unittest.main('idlelib.idle_test.test_redirector',
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verbosity=2, exit=False)
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from idlelib.idle_test.htest import run
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run(_widget_redirector)
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