bpo-33839: refactor IDLE's tooltips & calltips, add docstrings and tests (GH-7683)

* make CallTip and ToolTip sub-classes of a common abstract base class
* remove ListboxToolTip (unused and ugly)
* greatly increase test coverage
* tested on Windows, Linux and macOS

6 files changed, 415 insertions, 144 deletions

diff --git a/Lib/idlelib/calltip.py b/Lib/idlelib/calltip.py
index 596d2bc..758569a 100644
--- a/Lib/idlelib/calltip.py
+++ b/Lib/idlelib/calltip.py
@@ -51,7 +51,7 @@ class Calltip:
         self.open_calltip(False)
 
     def refresh_calltip_event(self, event):
-        if self.active_calltip and self.active_calltip.is_active():
+        if self.active_calltip and self.active_calltip.tipwindow:
             self.open_calltip(False)
 
     def open_calltip(self, evalfuncs):
diff --git a/Lib/idlelib/calltip_w.py b/Lib/idlelib/calltip_w.py
index 1b1ffc5..7553dfe 100644
--- a/Lib/idlelib/calltip_w.py
+++ b/Lib/idlelib/calltip_w.py
@@ -1,111 +1,118 @@
-"""A calltip window class for Tkinter/IDLE.
+"""A call-tip window class for Tkinter/IDLE.
 
-After tooltip.py, which uses ideas gleaned from PySol
-Used by calltip.
+After tooltip.py, which uses ideas gleaned from PySol.
+Used by calltip.py.
 """
-from tkinter import Toplevel, Label, LEFT, SOLID, TclError
+from tkinter import Label, LEFT, SOLID, TclError
 
-HIDE_VIRTUAL_EVENT_NAME = "<<calltipwindow-hide>>"
+from idlelib.tooltip import TooltipBase
+
+HIDE_EVENT = "<<calltipwindow-hide>>"
 HIDE_SEQUENCES = ("<Key-Escape>", "<FocusOut>")
-CHECKHIDE_VIRTUAL_EVENT_NAME = "<<calltipwindow-checkhide>>"
+CHECKHIDE_EVENT = "<<calltipwindow-checkhide>>"
 CHECKHIDE_SEQUENCES = ("<KeyRelease>", "<ButtonRelease>")
-CHECKHIDE_TIME = 100 # milliseconds
+CHECKHIDE_TIME = 100  # milliseconds
 
 MARK_RIGHT = "calltipwindowregion_right"
 
-class CalltipWindow:
 
-    def __init__(self, widget):
-        self.widget = widget
-        self.tipwindow = self.label = None
-        self.parenline = self.parencol = None
-        self.lastline = None
+class CalltipWindow(TooltipBase):
+    """A call-tip widget for tkinter text widgets."""
+
+    def __init__(self, text_widget):
+        """Create a call-tip; shown by showtip().
+
+        text_widget: a Text widget with code for which call-tips are desired
+        """
+        # Note: The Text widget will be accessible as self.anchor_widget
+        super(CalltipWindow, self).__init__(text_widget)
+
+        self.label = self.text = None
+        self.parenline = self.parencol = self.lastline = None
         self.hideid = self.checkhideid = None
         self.checkhide_after_id = None
 
-    def position_window(self):
-        """Check if needs to reposition the window, and if so - do it."""
-        curline = int(self.widget.index("insert").split('.')[0])
-        if curline == self.lastline:
-            return
-        self.lastline = curline
-        self.widget.see("insert")
+    def get_position(self):
+        """Choose the position of the call-tip."""
+        curline = int(self.anchor_widget.index("insert").split('.')[0])
         if curline == self.parenline:
-            box = self.widget.bbox("%d.%d" % (self.parenline,
-                                              self.parencol))
+            anchor_index = (self.parenline, self.parencol)
         else:
-            box = self.widget.bbox("%d.0" % curline)
+            anchor_index = (curline, 0)
+        box = self.anchor_widget.bbox("%d.%d" % anchor_index)
         if not box:
-            box = list(self.widget.bbox("insert"))
+            box = list(self.anchor_widget.bbox("insert"))
             # align to left of window
             box[0] = 0
             box[2] = 0
-        x = box[0] + self.widget.winfo_rootx() + 2
-        y = box[1] + box[3] + self.widget.winfo_rooty()
-        self.tipwindow.wm_geometry("+%d+%d" % (x, y))
+        return box[0] + 2, box[1] + box[3]
+
+    def position_window(self):
+        "Reposition the window if needed."
+        curline = int(self.anchor_widget.index("insert").split('.')[0])
+        if curline == self.lastline:
+            return
+        self.lastline = curline
+        self.anchor_widget.see("insert")
+        super(CalltipWindow, self).position_window()
 
     def showtip(self, text, parenleft, parenright):
-        """Show the calltip, bind events which will close it and reposition it.
+        """Show the call-tip, bind events which will close it and reposition it.
+
+        text: the text to display in the call-tip
+        parenleft: index of the opening parenthesis in the text widget
+        parenright: index of the closing parenthesis in the text widget,
+                    or the end of the line if there is no closing parenthesis
         """
         # Only called in calltip.Calltip, where lines are truncated
         self.text = text
         if self.tipwindow or not self.text:
             return
 
-        self.widget.mark_set(MARK_RIGHT, parenright)
+        self.anchor_widget.mark_set(MARK_RIGHT, parenright)
         self.parenline, self.parencol = map(
-            int, self.widget.index(parenleft).split("."))
+            int, self.anchor_widget.index(parenleft).split("."))
 
-        self.tipwindow = tw = Toplevel(self.widget)
-        self.position_window()
-        # remove border on calltip window
-        tw.wm_overrideredirect(1)
-        try:
-            # This command is only needed and available on Tk >= 8.4.0 for OSX
-            # Without it, call tips intrude on the typing process by grabbing
-            # the focus.
-            tw.tk.call("::tk::unsupported::MacWindowStyle", "style", tw._w,
-                       "help", "noActivates")
-        except TclError:
-            pass
-        self.label = Label(tw, text=self.text, justify=LEFT,
+        super(CalltipWindow, self).showtip()
+
+        self._bind_events()
+
+    def showcontents(self):
+        """Create the call-tip widget."""
+        self.label = Label(self.tipwindow, text=self.text, justify=LEFT,
                            background="#ffffe0", relief=SOLID, borderwidth=1,
-                           font = self.widget['font'])
+                           font=self.anchor_widget['font'])
         self.label.pack()
-        tw.update_idletasks()
-        tw.lift()  # work around bug in Tk 8.5.18+ (issue #24570)
-
-        self.checkhideid = self.widget.bind(CHECKHIDE_VIRTUAL_EVENT_NAME,
-                                            self.checkhide_event)
-        for seq in CHECKHIDE_SEQUENCES:
-            self.widget.event_add(CHECKHIDE_VIRTUAL_EVENT_NAME, seq)
-        self.widget.after(CHECKHIDE_TIME, self.checkhide_event)
-        self.hideid = self.widget.bind(HIDE_VIRTUAL_EVENT_NAME,
-                                       self.hide_event)
-        for seq in HIDE_SEQUENCES:
-            self.widget.event_add(HIDE_VIRTUAL_EVENT_NAME, seq)
 
     def checkhide_event(self, event=None):
+        """Handle CHECK_HIDE_EVENT: call hidetip or reschedule."""
         if not self.tipwindow:
-            # If the event was triggered by the same event that unbinded
+            # If the event was triggered by the same event that unbound
             # this function, the function will be called nevertheless,
             # so do nothing in this case.
             return None
-        curline, curcol = map(int, self.widget.index("insert").split('.'))
+
+        # Hide the call-tip if the insertion cursor moves outside of the
+        # parenthesis.
+        curline, curcol = map(int, self.anchor_widget.index("insert").split('.'))
         if curline < self.parenline or \
            (curline == self.parenline and curcol <= self.parencol) or \
-           self.widget.compare("insert", ">", MARK_RIGHT):
+           self.anchor_widget.compare("insert", ">", MARK_RIGHT):
             self.hidetip()
             return "break"
-        else:
-            self.position_window()
-            if self.checkhide_after_id is not None:
-                self.widget.after_cancel(self.checkhide_after_id)
-            self.checkhide_after_id = \
-                self.widget.after(CHECKHIDE_TIME, self.checkhide_event)
-            return None
+
+        # Not hiding the call-tip.
+
+        self.position_window()
+        # Re-schedule this function to be called again in a short while.
+        if self.checkhide_after_id is not None:
+            self.anchor_widget.after_cancel(self.checkhide_after_id)
+        self.checkhide_after_id = \
+            self.anchor_widget.after(CHECKHIDE_TIME, self.checkhide_event)
+        return None
 
     def hide_event(self, event):
+        """Handle HIDE_EVENT by calling hidetip."""
         if not self.tipwindow:
             # See the explanation in checkhide_event.
             return None
@@ -113,51 +120,76 @@ class CalltipWindow:
         return "break"
 
     def hidetip(self):
+        """Hide the call-tip."""
         if not self.tipwindow:
             return
 
-        for seq in CHECKHIDE_SEQUENCES:
-            self.widget.event_delete(CHECKHIDE_VIRTUAL_EVENT_NAME, seq)
-        self.widget.unbind(CHECKHIDE_VIRTUAL_EVENT_NAME, self.checkhideid)
-        self.checkhideid = None
-        for seq in HIDE_SEQUENCES:
-            self.widget.event_delete(HIDE_VIRTUAL_EVENT_NAME, seq)
-        self.widget.unbind(HIDE_VIRTUAL_EVENT_NAME, self.hideid)
-        self.hideid = None
-
-        self.label.destroy()
+        try:
+            self.label.destroy()
+        except TclError:
+            pass
         self.label = None
-        self.tipwindow.destroy()
-        self.tipwindow = None
 
-        self.widget.mark_unset(MARK_RIGHT)
         self.parenline = self.parencol = self.lastline = None
+        try:
+            self.anchor_widget.mark_unset(MARK_RIGHT)
+        except TclError:
+            pass
 
-    def is_active(self):
-        return bool(self.tipwindow)
+        try:
+            self._unbind_events()
+        except (TclError, ValueError):
+            # ValueError may be raised by MultiCall
+            pass
+
+        super(CalltipWindow, self).hidetip()
+
+    def _bind_events(self):
+        """Bind event handlers."""
+        self.checkhideid = self.anchor_widget.bind(CHECKHIDE_EVENT,
+                                                   self.checkhide_event)
+        for seq in CHECKHIDE_SEQUENCES:
+            self.anchor_widget.event_add(CHECKHIDE_EVENT, seq)
+        self.anchor_widget.after(CHECKHIDE_TIME, self.checkhide_event)
+        self.hideid = self.anchor_widget.bind(HIDE_EVENT,
+                                              self.hide_event)
+        for seq in HIDE_SEQUENCES:
+            self.anchor_widget.event_add(HIDE_EVENT, seq)
+
+    def _unbind_events(self):
+        """Unbind event handlers."""
+        for seq in CHECKHIDE_SEQUENCES:
+            self.anchor_widget.event_delete(CHECKHIDE_EVENT, seq)
+        self.anchor_widget.unbind(CHECKHIDE_EVENT, self.checkhideid)
+        self.checkhideid = None
+        for seq in HIDE_SEQUENCES:
+            self.anchor_widget.event_delete(HIDE_EVENT, seq)
+        self.anchor_widget.unbind(HIDE_EVENT, self.hideid)
+        self.hideid = None
 
 
 def _calltip_window(parent):  # htest #
     from tkinter import Toplevel, Text, LEFT, BOTH
 
     top = Toplevel(parent)
-    top.title("Test calltips")
+    top.title("Test call-tips")
     x, y = map(int, parent.geometry().split('+')[1:])
-    top.geometry("200x100+%d+%d" % (x + 250, y + 175))
+    top.geometry("250x100+%d+%d" % (x + 175, y + 150))
     text = Text(top)
     text.pack(side=LEFT, fill=BOTH, expand=1)
     text.insert("insert", "string.split")
     top.update()
-    calltip = CalltipWindow(text)
 
+    calltip = CalltipWindow(text)
     def calltip_show(event):
-        calltip.showtip("(s=Hello world)", "insert", "end")
+        calltip.showtip("(s='Hello world')", "insert", "end")
     def calltip_hide(event):
         calltip.hidetip()
     text.event_add("<<calltip-show>>", "(")
     text.event_add("<<calltip-hide>>", ")")
     text.bind("<<calltip-show>>", calltip_show)
     text.bind("<<calltip-hide>>", calltip_hide)
+
     text.focus_set()
 
 if __name__ == '__main__':
diff --git a/Lib/idlelib/idle_test/htest.py b/Lib/idlelib/idle_test/htest.py
index 95f6274..03bee51 100644
--- a/Lib/idlelib/idle_test/htest.py
+++ b/Lib/idlelib/idle_test/htest.py
@@ -80,11 +80,14 @@ AboutDialog_spec = {
            "are correctly displayed.\n [Close] to exit.",
     }
 
+# TODO implement ^\; adding '<Control-Key-\\>' to function does not work.
 _calltip_window_spec = {
     'file': 'calltip_w',
     'kwds': {},
     'msg': "Typing '(' should display a calltip.\n"
            "Typing ') should hide the calltip.\n"
+           "So should moving cursor out of argument area.\n"
+           "Force-open-calltip does not work here.\n"
     }
 
 _module_browser_spec = {
diff --git a/Lib/idlelib/idle_test/test_calltip_w.py b/Lib/idlelib/idle_test/test_calltip_w.py
index 59e6967..a5ec76e 100644
--- a/Lib/idlelib/idle_test/test_calltip_w.py
+++ b/Lib/idlelib/idle_test/test_calltip_w.py
@@ -23,7 +23,7 @@ class CallTipWindowTest(unittest.TestCase):
         del cls.text, cls.root
 
     def test_init(self):
-        self.assertEqual(self.calltip.widget, self.text)
+        self.assertEqual(self.calltip.anchor_widget, self.text)
 
 if __name__ == '__main__':
     unittest.main(verbosity=2)
diff --git a/Lib/idlelib/idle_test/test_tooltip.py b/Lib/idlelib/idle_test/test_tooltip.py
new file mode 100644
index 0000000..44ea111
--- /dev/null
+++ b/Lib/idlelib/idle_test/test_tooltip.py
@@ -0,0 +1,146 @@
+from idlelib.tooltip import TooltipBase, Hovertip
+from test.support import requires
+requires('gui')
+
+from functools import wraps
+import time
+from tkinter import Button, Tk, Toplevel
+import unittest
+
+
+def setUpModule():
+    global root
+    root = Tk()
+
+def root_update():
+    global root
+    root.update()
+
+def tearDownModule():
+    global root
+    root.update_idletasks()
+    root.destroy()
+    del root
+
+def add_call_counting(func):
+    @wraps(func)
+    def wrapped_func(*args, **kwargs):
+        wrapped_func.call_args_list.append((args, kwargs))
+        return func(*args, **kwargs)
+    wrapped_func.call_args_list = []
+    return wrapped_func
+
+
+def _make_top_and_button(testobj):
+    global root
+    top = Toplevel(root)
+    testobj.addCleanup(top.destroy)
+    top.title("Test tooltip")
+    button = Button(top, text='ToolTip test button')
+    button.pack()
+    testobj.addCleanup(button.destroy)
+    top.lift()
+    return top, button
+
+
+class ToolTipBaseTest(unittest.TestCase):
+    def setUp(self):
+        self.top, self.button = _make_top_and_button(self)
+
+    def test_base_class_is_unusable(self):
+        global root
+        top = Toplevel(root)
+        self.addCleanup(top.destroy)
+
+        button = Button(top, text='ToolTip test button')
+        button.pack()
+        self.addCleanup(button.destroy)
+
+        with self.assertRaises(NotImplementedError):
+            tooltip = TooltipBase(button)
+            tooltip.showtip()
+
+
+class HovertipTest(unittest.TestCase):
+    def setUp(self):
+        self.top, self.button = _make_top_and_button(self)
+
+    def test_showtip(self):
+        tooltip = Hovertip(self.button, 'ToolTip text')
+        self.addCleanup(tooltip.hidetip)
+        self.assertFalse(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        tooltip.showtip()
+        self.assertTrue(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+
+    def test_showtip_twice(self):
+        tooltip = Hovertip(self.button, 'ToolTip text')
+        self.addCleanup(tooltip.hidetip)
+        self.assertFalse(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        tooltip.showtip()
+        self.assertTrue(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        orig_tipwindow = tooltip.tipwindow
+        tooltip.showtip()
+        self.assertTrue(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        self.assertIs(tooltip.tipwindow, orig_tipwindow)
+
+    def test_hidetip(self):
+        tooltip = Hovertip(self.button, 'ToolTip text')
+        self.addCleanup(tooltip.hidetip)
+        tooltip.showtip()
+        tooltip.hidetip()
+        self.assertFalse(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+
+    def test_showtip_on_mouse_enter_no_delay(self):
+        tooltip = Hovertip(self.button, 'ToolTip text', hover_delay=None)
+        self.addCleanup(tooltip.hidetip)
+        tooltip.showtip = add_call_counting(tooltip.showtip)
+        root_update()
+        self.assertFalse(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        self.button.event_generate('<Enter>', x=0, y=0)
+        root_update()
+        self.assertTrue(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        self.assertGreater(len(tooltip.showtip.call_args_list), 0)
+
+    def test_showtip_on_mouse_enter_hover_delay(self):
+        tooltip = Hovertip(self.button, 'ToolTip text', hover_delay=50)
+        self.addCleanup(tooltip.hidetip)
+        tooltip.showtip = add_call_counting(tooltip.showtip)
+        root_update()
+        self.assertFalse(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        self.button.event_generate('<Enter>', x=0, y=0)
+        root_update()
+        self.assertFalse(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        time.sleep(0.1)
+        root_update()
+        self.assertTrue(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        self.assertGreater(len(tooltip.showtip.call_args_list), 0)
+
+    def test_hidetip_on_mouse_leave(self):
+        tooltip = Hovertip(self.button, 'ToolTip text', hover_delay=None)
+        self.addCleanup(tooltip.hidetip)
+        tooltip.showtip = add_call_counting(tooltip.showtip)
+        root_update()
+        self.button.event_generate('<Enter>', x=0, y=0)
+        root_update()
+        self.button.event_generate('<Leave>', x=0, y=0)
+        root_update()
+        self.assertFalse(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        self.assertGreater(len(tooltip.showtip.call_args_list), 0)
+
+    def test_dont_show_on_mouse_leave_before_delay(self):
+        tooltip = Hovertip(self.button, 'ToolTip text', hover_delay=50)
+        self.addCleanup(tooltip.hidetip)
+        tooltip.showtip = add_call_counting(tooltip.showtip)
+        root_update()
+        self.button.event_generate('<Enter>', x=0, y=0)
+        root_update()
+        self.button.event_generate('<Leave>', x=0, y=0)
+        root_update()
+        time.sleep(0.1)
+        root_update()
+        self.assertFalse(tooltip.tipwindow and tooltip.tipwindow.winfo_viewable())
+        self.assertEqual(tooltip.showtip.call_args_list, [])
+
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)
diff --git a/Lib/idlelib/tooltip.py b/Lib/idlelib/tooltip.py
index 843fb4a..f54ea36 100644
--- a/Lib/idlelib/tooltip.py
+++ b/Lib/idlelib/tooltip.py
@@ -1,80 +1,167 @@
-# general purpose 'tooltip' routines - currently unused in idlelib
-# (although the 'calltips' extension is partly based on this code)
-# may be useful for some purposes in (or almost in ;) the current project scope
-# Ideas gleaned from PySol
+"""Tools for displaying tool-tips.
 
+This includes:
+ * an abstract base-class for different kinds of tooltips
+ * a simple text-only Tooltip class
+"""
 from tkinter import *
 
-class ToolTipBase:
 
-    def __init__(self, button):
-        self.button = button
-        self.tipwindow = None
-        self.id = None
-        self.x = self.y = 0
-        self._id1 = self.button.bind("<Enter>", self.enter)
-        self._id2 = self.button.bind("<Leave>", self.leave)
-        self._id3 = self.button.bind("<ButtonPress>", self.leave)
+class TooltipBase(object):
+    """abstract base class for tooltips"""
 
-    def enter(self, event=None):
-        self.schedule()
+    def __init__(self, anchor_widget):
+        """Create a tooltip.
 
-    def leave(self, event=None):
-        self.unschedule()
-        self.hidetip()
+        anchor_widget: the widget next to which the tooltip will be shown
 
-    def schedule(self):
-        self.unschedule()
-        self.id = self.button.after(1500, self.showtip)
+        Note that a widget will only be shown when showtip() is called.
+        """
+        self.anchor_widget = anchor_widget
+        self.tipwindow = None
 
-    def unschedule(self):
-        id = self.id
-        self.id = None
-        if id:
-            self.button.after_cancel(id)
+    def __del__(self):
+        self.hidetip()
 
     def showtip(self):
+        """display the tooltip"""
         if self.tipwindow:
             return
-        # The tip window must be completely outside the button;
+        self.tipwindow = tw = Toplevel(self.anchor_widget)
+        # show no border on the top level window
+        tw.wm_overrideredirect(1)
+        try:
+            # This command is only needed and available on Tk >= 8.4.0 for OSX.
+            # Without it, call tips intrude on the typing process by grabbing
+            # the focus.
+            tw.tk.call("::tk::unsupported::MacWindowStyle", "style", tw._w,
+                       "help", "noActivates")
+        except TclError:
+            pass
+
+        self.position_window()
+        self.showcontents()
+        self.tipwindow.update_idletasks()  # Needed on MacOS -- see #34275.
+        self.tipwindow.lift()  # work around bug in Tk 8.5.18+ (issue #24570)
+
+    def position_window(self):
+        """(re)-set the tooltip's screen position"""
+        x, y = self.get_position()
+        root_x = self.anchor_widget.winfo_rootx() + x
+        root_y = self.anchor_widget.winfo_rooty() + y
+        self.tipwindow.wm_geometry("+%d+%d" % (root_x, root_y))
+
+    def get_position(self):
+        """choose a screen position for the tooltip"""
+        # The tip window must be completely outside the anchor widget;
         # otherwise when the mouse enters the tip window we get
         # a leave event and it disappears, and then we get an enter
         # event and it reappears, and so on forever :-(
-        x = self.button.winfo_rootx() + 20
-        y = self.button.winfo_rooty() + self.button.winfo_height() + 1
-        self.tipwindow = tw = Toplevel(self.button)
-        tw.wm_overrideredirect(1)
-        tw.wm_geometry("+%d+%d" % (x, y))
-        self.showcontents()
+        #
+        # Note: This is a simplistic implementation; sub-classes will likely
+        # want to override this.
+        return 20, self.anchor_widget.winfo_height() + 1
 
-    def showcontents(self, text="Your text here"):
-        # Override this in derived class
-        label = Label(self.tipwindow, text=text, justify=LEFT,
-                      background="#ffffe0", relief=SOLID, borderwidth=1)
-        label.pack()
+    def showcontents(self):
+        """content display hook for sub-classes"""
+        # See ToolTip for an example
+        raise NotImplementedError
 
     def hidetip(self):
+        """hide the tooltip"""
+        # Note: This is called by __del__, so careful when overriding/extending
         tw = self.tipwindow
         self.tipwindow = None
         if tw:
-            tw.destroy()
+            try:
+                tw.destroy()
+            except TclError:
+                pass
+
+
+class OnHoverTooltipBase(TooltipBase):
+    """abstract base class for tooltips, with delayed on-hover display"""
+
+    def __init__(self, anchor_widget, hover_delay=1000):
+        """Create a tooltip with a mouse hover delay.
+
+        anchor_widget: the widget next to which the tooltip will be shown
+        hover_delay: time to delay before showing the tooltip, in milliseconds
 
-class ToolTip(ToolTipBase):
-    def __init__(self, button, text):
-        ToolTipBase.__init__(self, button)
+        Note that a widget will only be shown when showtip() is called,
+        e.g. after hovering over the anchor widget with the mouse for enough
+        time.
+        """
+        super(OnHoverTooltipBase, self).__init__(anchor_widget)
+        self.hover_delay = hover_delay
+
+        self._after_id = None
+        self._id1 = self.anchor_widget.bind("<Enter>", self._show_event)
+        self._id2 = self.anchor_widget.bind("<Leave>", self._hide_event)
+        self._id3 = self.anchor_widget.bind("<Button>", self._hide_event)
+
+    def __del__(self):
+        try:
+            self.anchor_widget.unbind("<Enter>", self._id1)
+            self.anchor_widget.unbind("<Leave>", self._id2)
+            self.anchor_widget.unbind("<Button>", self._id3)
+        except TclError:
+            pass
+        super(OnHoverTooltipBase, self).__del__()
+
+    def _show_event(self, event=None):
+        """event handler to display the tooltip"""
+        if self.hover_delay:
+            self.schedule()
+        else:
+            self.showtip()
+
+    def _hide_event(self, event=None):
+        """event handler to hide the tooltip"""
+        self.hidetip()
+
+    def schedule(self):
+        """schedule the future display of the tooltip"""
+        self.unschedule()
+        self._after_id = self.anchor_widget.after(self.hover_delay,
+                                                  self.showtip)
+
+    def unschedule(self):
+        """cancel the future display of the tooltip"""
+        after_id = self._after_id
+        self._after_id = None
+        if after_id:
+            self.anchor_widget.after_cancel(after_id)
+
+    def hidetip(self):
+        """hide the tooltip"""
+        try:
+            self.unschedule()
+        except TclError:
+            pass
+        super(OnHoverTooltipBase, self).hidetip()
+
+
+class Hovertip(OnHoverTooltipBase):
+    "A tooltip that pops up when a mouse hovers over an anchor widget."
+    def __init__(self, anchor_widget, text, hover_delay=1000):
+        """Create a text tooltip with a mouse hover delay.
+
+        anchor_widget: the widget next to which the tooltip will be shown
+        hover_delay: time to delay before showing the tooltip, in milliseconds
+
+        Note that a widget will only be shown when showtip() is called,
+        e.g. after hovering over the anchor widget with the mouse for enough
+        time.
+        """
+        super(Hovertip, self).__init__(anchor_widget, hover_delay=hover_delay)
         self.text = text
-    def showcontents(self):
-        ToolTipBase.showcontents(self, self.text)
 
-class ListboxToolTip(ToolTipBase):
-    def __init__(self, button, items):
-        ToolTipBase.__init__(self, button)
-        self.items = items
     def showcontents(self):
-        listbox = Listbox(self.tipwindow, background="#ffffe0")
-        listbox.pack()
-        for item in self.items:
-            listbox.insert(END, item)
+        label = Label(self.tipwindow, text=self.text, justify=LEFT,
+                      background="#ffffe0", relief=SOLID, borderwidth=1)
+        label.pack()
+
 
 def _tooltip(parent):  # htest #
     top = Toplevel(parent)
@@ -83,14 +170,17 @@ def _tooltip(parent):  # htest #
     top.geometry("+%d+%d" % (x, y + 150))
     label = Label(top, text="Place your mouse over buttons")
     label.pack()
-    button1 = Button(top, text="Button 1")
-    button2 = Button(top, text="Button 2")
+    button1 = Button(top, text="Button 1 -- 1/2 second hover delay")
     button1.pack()
+    Hovertip(button1, "This is tooltip text for button1.", hover_delay=500)
+    button2 = Button(top, text="Button 2 -- no hover delay")
     button2.pack()
-    ToolTip(button1, "This is tooltip text for button1.")
-    ListboxToolTip(button2, ["This is","multiple line",
-                            "tooltip text","for button2"])
+    Hovertip(button2, "This is tooltip\ntext for button2.", hover_delay=None)
+
 
 if __name__ == '__main__':
+    from unittest import main
+    main('idlelib.idle_test.test_tooltip', verbosity=2, exit=False)
+
     from idlelib.idle_test.htest import run
     run(_tooltip)