Am 01.02.17 um 00:02 schrieb MRAB:
On 2017-01-31 22:34, Christian Gollwitzer wrote:
.!frame.!checkbutton
.!frame.!checkbutton2
.!frame2.!checkbutton
.!frame2.!checkbutton2
Perhaps someone who knows Tcl and tk can tell me, but I notice that in
the first example, the second part of the widget names are unique,
whereas in the second example, the second part of the widget names are
the reused (both "!checkbutton" and "!checkbutton2" occur twice).
It is indeed the reason, but it has some strange legacy cause: the
default name for the checkbutton-linked variable is the name of the
button inside the parent. Therefore creating a checkbutton has the side
effect of creating a variable with the button's name.
In this case, the first buttons in the frames are linked to a variable
called "!checkbutton" and the other two are linked to "!checkbutton2".
(a variable name in Tcl can be anything apart from the empty string).
This can also be demonstrated by this Tcl script:
package require Tk
pack [frame .f1]
pack [frame .f2]
pack [checkbutton .f1.c1 -text "A" ]
pack [checkbutton .f1.c2 -text "B" ]
pack [checkbutton .f2.c1 -text "C" ]
pack [checkbutton .f2.c2 -text "D" ]
which is equivalent to the Python code above.
Note that this surprising behaviour was corrected for the (modern) ttk
widgets, so if "checkbutton" is replaced by "ttk::checkbutton", they are
not any longer linked. In Python, that would be
from tkinter import ttk
...
w = ttk.Checkbutton()
(Personally, I'm not using the legacy widgets any longer)
Do the names need to be:
.!frame.!checkbutton
.!frame.!checkbutton2
.!frame2.!checkbutton3
.!frame2.!checkbutton4
Good question. Maybe there should be unique variable names? I.e., if the
script is changed into package require Tk
pack [frame .f1]
pack [frame .f2]
pack [checkbutton .f1.c1 -text "A" -variable v1]
pack [checkbutton .f1.c2 -text "B" -variable v2]
pack [checkbutton .f2.c1 -text "C" -variable v3]
pack [checkbutton .f2.c2 -text "D" -variable v4]
then they are also not linked.
Christian
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