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126 lines
4.4 KiB
Python
126 lines
4.4 KiB
Python
from Tkinter import *
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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.
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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.
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In IDLE, the function being registered provides access to the top of a
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Percolator chain. At the bottom of the chain is a call to the original
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Tk widget operation.
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"""
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def __init__(self, widget):
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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 "WidgetRedirector(%s<%s>)" % (self.widget.__class__.__name__,
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self.widget._w)
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def close(self):
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for operation in list(self._operations):
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self.unregister(operation)
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widget = self.widget; del self.widget
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orig = self.orig; del self.orig
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tk = widget.tk
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w = widget._w
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tk.deletecommand(w)
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# restore the original widget Tcl command:
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tk.call("rename", orig, w)
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def register(self, operation, function):
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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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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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if hasattr(self.widget, operation):
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delattr(self.widget, operation)
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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 ColorDelegator.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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def __init__(self, redir, operation):
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self.redir = redir
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self.operation = operation
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self.tk = redir.tk
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self.orig = redir.orig
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self.tk_call = self.tk.call
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self.orig_and_operation = (self.orig, self.operation)
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def __repr__(self):
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return "OriginalCommand(%r, %r)" % (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 main():
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root = Tk()
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root.wm_protocol("WM_DELETE_WINDOW", root.quit)
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text = Text()
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text.pack()
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text.focus_set()
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redir = WidgetRedirector(text)
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global previous_tcl_fcn
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def my_insert(*args):
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print "insert", args
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previous_tcl_fcn(*args)
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previous_tcl_fcn = redir.register("insert", my_insert)
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root.mainloop()
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redir.unregister("insert") # runs after first 'close window'
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redir.close()
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root.mainloop()
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root.destroy()
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if __name__ == "__main__":
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main()
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