Tkinter reference: a GUI for Python |  |
Tkinter reference: a GUI for Python | |
To say a widget has focus means that keyboard input is currently directed to that widget.
By focus traversal, we mean the sequence of widgets that will be visited as the user moves from widget to widget with the tab key. See below for the rules for this sequence.
You can traverse backwards using shift-tab.
The Entry and
Text widgets are intended to
accept keyboard input, and if an entry or text widget
currently has the focus, any characters you type into
it will be added to its text. The usual editing
characters such as ← and → will have
their usual effects.
Because Text widgets can
contain tab characters, you must use the special key
sequence control-tab to move the focus
past a text widget.
Most of the other types of widgets will normally be visited by focus traversal, and when they have focus:
Button widgets can be
“pressed” by pressing the
spacebar.
Checkbutton widgets can
be toggled between set and cleared states using the
spacebar.
In Listbox widgets, the
↑ and ↓ keys scroll up or down one line;
the PageUp and
PageDown keys scroll by pages; and
the spacebar selects the current line, or
de-selects it if it was already
selected.
You can set a
Radiobutton widget by
pressing the spacebar.
Horizontal Scale widgets
respond to the ← and → keys, and vertical
ones respond to ↑ and ↓.
In a Scrollbar widget,
the PageUp and
PageDown keys move the scrollbar
by pageloads. The ↑ and ↓ keys will move
vertical scrollbars by units, and the ← and
→ keys will move horizontal scrollbars by
units.
Many widgets are provided with an outline called
the focus highlight that shows
the user which widget has the highlight. This is
normally a thin black frame located just outside the
widget's border (if any). For widgets that don't
normally have a focus highlight (specifically, frames,
labels, and menus), you can set the
highlightthickness option to a
nonzero value to make the focus highlight
visible.
You can also change the color of the focus
highlight using the
highlightcolor
option.
Widgets of class Frame,
Label, and
Menu are not normally visited by
the focus. However, you can set their
takefocus options to
1 to get them included in focus
traversal. You can also take any widget out of focus
traversal by setting its
takefocus option to
0.
The order in which the tab key traverses the widgets is:
For widgets that are children of the same parent, focus goes in the same order the widgets were created.
For parent widgets that contain other widgets (such
as frames), focus visits the parent widget first
(unless its takefocus option is
0), then it visits the child
widgets, recursively, in the order they were
created.
To sum up: to set up the focus traversal order of your
widgets, create them in that order. Remove widgets from
the traversal order by setting their
takefocus options to 0, and for
those whose default takefocus option
is 0, set it to
1 if you want to add them to the
order.
The above describes the default functioning of input
focus in Tkinter. There is another, completely different
way to handle it—let the focus go wherever the mouse
goes. Under Section 19, “Universal widget methods”, refer to the
.tk_focusFollowsMouse() method.
You can also add, change or delete the way any key on the keyboard functions inside any widget by using event bindings. See Section 24, “Events” for the details.