Issue #22115: Added methods trace_add, trace_remove and trace_info in the

tkinter.Variable class.  They replace old methods trace_variable, trace,
trace_vdelete and trace_vinfo that use obsolete Tcl commands and might
not work in future versions of Tcl.

2 files changed, 182 insertions, 16 deletions

diff --git a/Lib/tkinter/__init__.py b/Lib/tkinter/__init__.py
index c1d5addcd4..35643e646b 100644
--- a/Lib/tkinter/__init__.py
+++ b/Lib/tkinter/__init__.py
@@ -343,16 +343,9 @@ class Variable:
     def get(self):
         """Return value of variable."""
         return self._tk.globalgetvar(self._name)
-    def trace_variable(self, mode, callback):
-        """Define a trace callback for the variable.
 
-        MODE is one of "r", "w", "u" for read, write, undefine.
-        CALLBACK must be a function which is called when
-        the variable is read, written or undefined.
-
-        Return the name of the callback.
-        """
-        f = CallWrapper(callback, None, self).__call__
+    def _register(self, callback):
+        f = CallWrapper(callback, None, self._root).__call__
         cbname = repr(id(f))
         try:
             callback = callback.__func__
@@ -366,25 +359,99 @@ class Variable:
         if self._tclCommands is None:
             self._tclCommands = []
         self._tclCommands.append(cbname)
+        return cbname
+
+    def trace_add(self, mode, callback):
+        """Define a trace callback for the variable.
+
+        Mode is one of "read", "write", "unset", or a list or tuple of
+        such strings.
+        Callback must be a function which is called when the variable is
+        read, written or unset.
+
+        Return the name of the callback.
+        """
+        cbname = self._register(callback)
+        self._tk.call('trace', 'add', 'variable',
+                      self._name, mode, (cbname,))
+        return cbname
+
+    def trace_remove(self, mode, cbname):
+        """Delete the trace callback for a variable.
+
+        Mode is one of "read", "write", "unset" or a list or tuple of
+        such strings.  Must be same as were specified in trace_add().
+        cbname is the name of the callback returned from trace_add().
+        """
+        self._tk.call('trace', 'remove', 'variable',
+                      self._name, mode, cbname)
+        for m, ca in self.trace_info():
+            if self._tk.splitlist(ca)[0] == cbname:
+                break
+        else:
+            self._tk.deletecommand(cbname)
+            try:
+                self._tclCommands.remove(cbname)
+            except ValueError:
+                pass
+
+    def trace_info(self):
+        """Return all trace callback information."""
+        splitlist = self._tk.splitlist
+        return [(splitlist(k), v) for k, v in map(splitlist,
+            splitlist(self._tk.call('trace', 'info', 'variable', self._name)))]
+
+    def trace_variable(self, mode, callback):
+        """Define a trace callback for the variable.
+
+        MODE is one of "r", "w", "u" for read, write, undefine.
+        CALLBACK must be a function which is called when
+        the variable is read, written or undefined.
+
+        Return the name of the callback.
+
+        This deprecated method wraps a deprecated Tcl method that will
+        likely be removed in the future.  Use trace_add() instead.
+        """
+        # TODO: Add deprecation warning
+        cbname = self._register(callback)
         self._tk.call("trace", "variable", self._name, mode, cbname)
         return cbname
+
     trace = trace_variable
+
     def trace_vdelete(self, mode, cbname):
         """Delete the trace callback for a variable.
 
         MODE is one of "r", "w", "u" for read, write, undefine.
         CBNAME is the name of the callback returned from trace_variable or trace.
+
+        This deprecated method wraps a deprecated Tcl method that will
+        likely be removed in the future.  Use trace_remove() instead.
         """
+        # TODO: Add deprecation warning
         self._tk.call("trace", "vdelete", self._name, mode, cbname)
-        self._tk.deletecommand(cbname)
-        try:
-            self._tclCommands.remove(cbname)
-        except ValueError:
-            pass
+        cbname = self._tk.splitlist(cbname)[0]
+        for m, ca in self.trace_info():
+            if self._tk.splitlist(ca)[0] == cbname:
+                break
+        else:
+            self._tk.deletecommand(cbname)
+            try:
+                self._tclCommands.remove(cbname)
+            except ValueError:
+                pass
+
     def trace_vinfo(self):
-        """Return all trace callback information."""
+        """Return all trace callback information.
+
+        This deprecated method wraps a deprecated Tcl method that will
+        likely be removed in the future.  Use trace_info() instead.
+        """
+        # TODO: Add deprecation warning
         return [self._tk.splitlist(x) for x in self._tk.splitlist(
             self._tk.call("trace", "vinfo", self._name))]
+
     def __eq__(self, other):
         """Comparison for equality (==).
 
diff --git a/Lib/tkinter/test/test_tkinter/test_variables.py b/Lib/tkinter/test/test_tkinter/test_variables.py
index abdce96998..c529259190 100644
--- a/Lib/tkinter/test/test_tkinter/test_variables.py
+++ b/Lib/tkinter/test/test_tkinter/test_variables.py
@@ -1,5 +1,5 @@
 import unittest
-
+import gc
 from tkinter import (Variable, StringVar, IntVar, DoubleVar, BooleanVar, Tcl,
                      TclError)
 
@@ -87,6 +87,105 @@ class TestVariable(TestBase):
         v.set("value")
         self.assertTrue(v.side_effect)
 
+    def test_trace_old(self):
+        # Old interface
+        v = Var(self.root)
+        vname = str(v)
+        trace = []
+        def read_tracer(*args):
+            trace.append(('read',) + args)
+        def write_tracer(*args):
+            trace.append(('write',) + args)
+        cb1 = v.trace_variable('r', read_tracer)
+        cb2 = v.trace_variable('wu', write_tracer)
+        self.assertEqual(sorted(v.trace_vinfo()), [('r', cb1), ('wu', cb2)])
+        self.assertEqual(trace, [])
+
+        v.set('spam')
+        self.assertEqual(trace, [('write', vname, '', 'w')])
+
+        trace = []
+        v.get()
+        self.assertEqual(trace, [('read', vname, '', 'r')])
+
+        trace = []
+        info = sorted(v.trace_vinfo())
+        v.trace_vdelete('w', cb1)  # Wrong mode
+        self.assertEqual(sorted(v.trace_vinfo()), info)
+        with self.assertRaises(TclError):
+            v.trace_vdelete('r', 'spam')  # Wrong command name
+        self.assertEqual(sorted(v.trace_vinfo()), info)
+        v.trace_vdelete('r', (cb1, 43)) # Wrong arguments
+        self.assertEqual(sorted(v.trace_vinfo()), info)
+        v.get()
+        self.assertEqual(trace, [('read', vname, '', 'r')])
+
+        trace = []
+        v.trace_vdelete('r', cb1)
+        self.assertEqual(v.trace_vinfo(), [('wu', cb2)])
+        v.get()
+        self.assertEqual(trace, [])
+
+        trace = []
+        del write_tracer
+        gc.collect()
+        v.set('eggs')
+        self.assertEqual(trace, [('write', vname, '', 'w')])
+
+        trace = []
+        del v
+        gc.collect()
+        self.assertEqual(trace, [('write', vname, '', 'u')])
+
+    def test_trace(self):
+        v = Var(self.root)
+        vname = str(v)
+        trace = []
+        def read_tracer(*args):
+            trace.append(('read',) + args)
+        def write_tracer(*args):
+            trace.append(('write',) + args)
+        tr1 = v.trace_add('read', read_tracer)
+        tr2 = v.trace_add(['write', 'unset'], write_tracer)
+        self.assertEqual(sorted(v.trace_info()), [
+                         (('read',), tr1),
+                         (('write', 'unset'), tr2)])
+        self.assertEqual(trace, [])
+
+        v.set('spam')
+        self.assertEqual(trace, [('write', vname, '', 'write')])
+
+        trace = []
+        v.get()
+        self.assertEqual(trace, [('read', vname, '', 'read')])
+
+        trace = []
+        info = sorted(v.trace_info())
+        v.trace_remove('write', tr1)  # Wrong mode
+        self.assertEqual(sorted(v.trace_info()), info)
+        with self.assertRaises(TclError):
+            v.trace_remove('read', 'spam')  # Wrong command name
+        self.assertEqual(sorted(v.trace_info()), info)
+        v.get()
+        self.assertEqual(trace, [('read', vname, '', 'read')])
+
+        trace = []
+        v.trace_remove('read', tr1)
+        self.assertEqual(v.trace_info(), [(('write', 'unset'), tr2)])
+        v.get()
+        self.assertEqual(trace, [])
+
+        trace = []
+        del write_tracer
+        gc.collect()
+        v.set('eggs')
+        self.assertEqual(trace, [('write', vname, '', 'write')])
+
+        trace = []
+        del v
+        gc.collect()
+        self.assertEqual(trace, [('write', vname, '', 'unset')])
+
 
 class TestStringVar(TestBase):