redirector.py (6875B)
- from tkinter import TclError
- class WidgetRedirector:
- """Support for redirecting arbitrary widget subcommands.
- Some Tk operations don't normally pass through tkinter. For example, if a
- character is inserted into a Text widget by pressing a key, a default Tk
- binding to the widget's 'insert' operation is activated, and the Tk library
- processes the insert without calling back into tkinter.
- Although a binding to <Key> could be made via tkinter, what we really want
- to do is to hook the Tk 'insert' operation itself. For one thing, we want
- a text.insert call in idle code to have the same effect as a key press.
- When a widget is instantiated, a Tcl command is created whose name is the
- same as the pathname widget._w. This command is used to invoke the various
- widget operations, e.g. insert (for a Text widget). We are going to hook
- this command and provide a facility ('register') to intercept the widget
- operation. We will also intercept method calls on the tkinter class
- instance that represents the tk widget.
- In IDLE, WidgetRedirector is used in Percolator to intercept Text
- commands. The function being registered provides access to the top
- of a Percolator chain. At the bottom of the chain is a call to the
- original Tk widget operation.
- """
- def __init__(self, widget):
- '''Initialize attributes and setup redirection.
- _operations: dict mapping operation name to new function.
- widget: the widget whose tcl command is to be intercepted.
- tk: widget.tk, a convenience attribute, probably not needed.
- orig: new name of the original tcl command.
- Since renaming to orig fails with TclError when orig already
- exists, only one WidgetDirector can exist for a given widget.
- '''
- self._operations = {}
- self.widget = widget # widget instance
- self.tk = tk = widget.tk # widget's root
- w = widget._w # widget's (full) Tk pathname
- self.orig = w + "_orig"
- # Rename the Tcl command within Tcl:
- tk.call("rename", w, self.orig)
- # Create a new Tcl command whose name is the widget's pathname, and
- # whose action is to dispatch on the operation passed to the widget:
- tk.createcommand(w, self.dispatch)
- def __repr__(self):
- return "%s(%s<%s>)" % (self.__class__.__name__,
- self.widget.__class__.__name__,
- self.widget._w)
- def close(self):
- "Unregister operations and revert redirection created by .__init__."
- for operation in list(self._operations):
- self.unregister(operation)
- widget = self.widget
- tk = widget.tk
- w = widget._w
- # Restore the original widget Tcl command.
- tk.deletecommand(w)
- tk.call("rename", self.orig, w)
- del self.widget, self.tk # Should not be needed
- # if instance is deleted after close, as in Percolator.
- def register(self, operation, function):
- '''Return OriginalCommand(operation) after registering function.
- Registration adds an operation: function pair to ._operations.
- It also adds a widget function attribute that masks the tkinter
- class instance method. Method masking operates independently
- from command dispatch.
- If a second function is registered for the same operation, the
- first function is replaced in both places.
- '''
- self._operations[operation] = function
- setattr(self.widget, operation, function)
- return OriginalCommand(self, operation)
- def unregister(self, operation):
- '''Return the function for the operation, or None.
- Deleting the instance attribute unmasks the class attribute.
- '''
- if operation in self._operations:
- function = self._operations[operation]
- del self._operations[operation]
- try:
- delattr(self.widget, operation)
- except AttributeError:
- pass
- return function
- else:
- return None
- def dispatch(self, operation, *args):
- '''Callback from Tcl which runs when the widget is referenced.
- If an operation has been registered in self._operations, apply the
- associated function to the args passed into Tcl. Otherwise, pass the
- operation through to Tk via the original Tcl function.
- Note that if a registered function is called, the operation is not
- passed through to Tk. Apply the function returned by self.register()
- to *args to accomplish that. For an example, see colorizer.py.
- '''
- m = self._operations.get(operation)
- try:
- if m:
- return m(*args)
- else:
- return self.tk.call((self.orig, operation) + args)
- except TclError:
- return ""
- class OriginalCommand:
- '''Callable for original tk command that has been redirected.
- Returned by .register; can be used in the function registered.
- redir = WidgetRedirector(text)
- def my_insert(*args):
- print("insert", args)
- original_insert(*args)
- original_insert = redir.register("insert", my_insert)
- '''
- def __init__(self, redir, operation):
- '''Create .tk_call and .orig_and_operation for .__call__ method.
- .redir and .operation store the input args for __repr__.
- .tk and .orig copy attributes of .redir (probably not needed).
- '''
- self.redir = redir
- self.operation = operation
- self.tk = redir.tk # redundant with self.redir
- self.orig = redir.orig # redundant with self.redir
- # These two could be deleted after checking recipient code.
- self.tk_call = redir.tk.call
- self.orig_and_operation = (redir.orig, operation)
- def __repr__(self):
- return "%s(%r, %r)" % (self.__class__.__name__,
- self.redir, self.operation)
- def __call__(self, *args):
- return self.tk_call(self.orig_and_operation + args)
- def _widget_redirector(parent): # htest #
- from tkinter import Toplevel, Text
- top = Toplevel(parent)
- top.title("Test WidgetRedirector")
- x, y = map(int, parent.geometry().split('+')[1:])
- top.geometry("+%d+%d" % (x, y + 175))
- text = Text(top)
- text.pack()
- text.focus_set()
- redir = WidgetRedirector(text)
- def my_insert(*args):
- print("insert", args)
- original_insert(*args)
- original_insert = redir.register("insert", my_insert)
- if __name__ == "__main__":
- from unittest import main
- main('idlelib.idle_test.test_redirector', verbosity=2, exit=False)
- from idlelib.idle_test.htest import run
- run(_widget_redirector)