1 from __future__ import print_function 2 from Tkinter import TclError 3 4 class WidgetRedirector: 5 """Support for redirecting arbitrary widget subcommands. 6 7 Some Tk operations don't normally pass through tkinter. For example, if a 8 character is inserted into a Text widget by pressing a key, a default Tk 9 binding to the widget's 'insert' operation is activated, and the Tk library 10 processes the insert without calling back into tkinter. 11 12 Although a binding to <Key> could be made via tkinter, what we really want 13 to do is to hook the Tk 'insert' operation itself. For one thing, we want 14 a text.insert call in idle code to have the same effect as a key press. 15 16 When a widget is instantiated, a Tcl command is created whose name is the 17 same as the pathname widget._w. This command is used to invoke the various 18 widget operations, e.g. insert (for a Text widget). We are going to hook 19 this command and provide a facility ('register') to intercept the widget 20 operation. We will also intercept method calls on the Tkinter class 21 instance that represents the tk widget. 22 23 In IDLE, WidgetRedirector is used in Percolator to intercept Text 24 commands. The function being registered provides access to the top 25 of a Percolator chain. At the bottom of the chain is a call to the 26 original Tk widget operation. 27 """ 28 def __init__(self, widget): 29 '''Initialize attributes and setup redirection. 30 31 _operations: dict mapping operation name to new function. 32 widget: the widget whose tcl command is to be intercepted. 33 tk: widget.tk, a convenience attribute, probably not needed. 34 orig: new name of the original tcl command. 35 36 Since renaming to orig fails with TclError when orig already 37 exists, only one WidgetDirector can exist for a given widget. 38 ''' 39 self._operations = {} 40 self.widget = widget # widget instance 41 self.tk = tk = widget.tk # widget's root 42 w = widget._w # widget's (full) Tk pathname 43 self.orig = w + "_orig" 44 # Rename the Tcl command within Tcl: 45 tk.call("rename", w, self.orig) 46 # Create a new Tcl command whose name is the widget's pathname, and 47 # whose action is to dispatch on the operation passed to the widget: 48 tk.createcommand(w, self.dispatch) 49 50 def __repr__(self): 51 return "WidgetRedirector(%s<%s>)" % (self.widget.__class__.__name__, 52 self.widget._w) 53 54 def close(self): 55 "Unregister operations and revert redirection created by .__init__." 56 for operation in list(self._operations): 57 self.unregister(operation) 58 widget = self.widget 59 tk = widget.tk 60 w = widget._w 61 # Restore the original widget Tcl command. 62 tk.deletecommand(w) 63 tk.call("rename", self.orig, w) 64 del self.widget, self.tk # Should not be needed 65 # if instance is deleted after close, as in Percolator. 66 67 def register(self, operation, function): 68 '''Return OriginalCommand(operation) after registering function. 69 70 Registration adds an operation: function pair to ._operations. 71 It also adds a widget function attribute that masks the Tkinter 72 class instance method. Method masking operates independently 73 from command dispatch. 74 75 If a second function is registered for the same operation, the 76 first function is replaced in both places. 77 ''' 78 self._operations[operation] = function 79 setattr(self.widget, operation, function) 80 return OriginalCommand(self, operation) 81 82 def unregister(self, operation): 83 '''Return the function for the operation, or None. 84 85 Deleting the instance attribute unmasks the class attribute. 86 ''' 87 if operation in self._operations: 88 function = self._operations[operation] 89 del self._operations[operation] 90 try: 91 delattr(self.widget, operation) 92 except AttributeError: 93 pass 94 return function 95 else: 96 return None 97 98 def dispatch(self, operation, *args): 99 '''Callback from Tcl which runs when the widget is referenced. 100 101 If an operation has been registered in self._operations, apply the 102 associated function to the args passed into Tcl. Otherwise, pass the 103 operation through to Tk via the original Tcl function. 104 105 Note that if a registered function is called, the operation is not 106 passed through to Tk. Apply the function returned by self.register() 107 to *args to accomplish that. For an example, see ColorDelegator.py. 108 109 ''' 110 m = self._operations.get(operation) 111 try: 112 if m: 113 return m(*args) 114 else: 115 return self.tk.call((self.orig, operation) + args) 116 except TclError: 117 return "" 118 119 120 class OriginalCommand: 121 '''Callable for original tk command that has been redirected. 122 123 Returned by .register; can be used in the function registered. 124 redir = WidgetRedirector(text) 125 def my_insert(*args): 126 print("insert", args) 127 original_insert(*args) 128 original_insert = redir.register("insert", my_insert) 129 ''' 130 131 def __init__(self, redir, operation): 132 '''Create .tk_call and .orig_and_operation for .__call__ method. 133 134 .redir and .operation store the input args for __repr__. 135 .tk and .orig copy attributes of .redir (probably not needed). 136 ''' 137 self.redir = redir 138 self.operation = operation 139 self.tk = redir.tk # redundant with self.redir 140 self.orig = redir.orig # redundant with self.redir 141 # These two could be deleted after checking recipient code. 142 self.tk_call = redir.tk.call 143 self.orig_and_operation = (redir.orig, operation) 144 145 def __repr__(self): 146 return "OriginalCommand(%r, %r)" % (self.redir, self.operation) 147 148 def __call__(self, *args): 149 return self.tk_call(self.orig_and_operation + args) 150 151 152 def _widget_redirector(parent): # htest # 153 from Tkinter import Tk, Text 154 import re 155 156 root = Tk() 157 root.title("Test WidgetRedirector") 158 width, height, x, y = list(map(int, re.split('[x+]', parent.geometry()))) 159 root.geometry("+%d+%d"%(x, y + 150)) 160 text = Text(root) 161 text.pack() 162 text.focus_set() 163 redir = WidgetRedirector(text) 164 def my_insert(*args): 165 print("insert", args) 166 original_insert(*args) 167 original_insert = redir.register("insert", my_insert) 168 root.mainloop() 169 170 if __name__ == "__main__": 171 import unittest 172 unittest.main('idlelib.idle_test.test_widgetredir', 173 verbosity=2, exit=False) 174 from idlelib.idle_test.htest import run 175 run(_widget_redirector) 176
