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

1 files changed, 147 insertions, 57 deletions

diff --git a/Lib/idlelib/tooltip.py b/Lib/idlelib/tooltip.py
index 843fb4a7d0..f54ea36f05 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)