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