gh-70273: Document default class bindings in tkinter (GH-152389)

Note in the Bindings and events section that every widget inherits Tk
class bindings for its standard behavior, where they are documented, and
how to suppress an unwanted one by returning "break" from a callback.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

diff --git a/Doc/library/tkinter.rst b/Doc/library/tkinter.rst
index 5c7227a21fc30ee1fa71b9b04194fb428c562db0..c368141126403ac854082f2a9cf6348be374019e 100644 (file)
--- a/Doc/library/tkinter.rst
+++ b/Doc/library/tkinter.rst
@@ -885,6 +885,20 @@ they are denoted in Tk, which can be useful when referring to the Tk man pages.
 | %d | detail              | %D | delta               |
 +----+---------------------+----+---------------------+
 
+The ``add`` parameter above only affects the bindings you make yourself.
+Every widget also inherits *class bindings*
+that implement its standard behavior --
+for example a :class:`Text` widget binds :kbd:`Control-t`
+to transpose two characters.
+These are described in the bindings section of the widget's Tk man page
+(such as :manpage:`text(3tk)` or :manpage:`entry(3tk)`).
+
+Class bindings are processed separately from your own,
+so binding an event yourself does not replace the default; both run.
+To suppress an unwanted default binding,
+bind the event on the widget
+and return the string ``"break"`` from your callback.
+
 
 The index parameter
 ^^^^^^^^^^^^^^^^^^^