Tkinter 8.5 reference: a GUI for Python |  |
Tkinter 8.5 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 26, “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 54, “Events” for the details.