Re: A suggestion for Tcl 9

Am 05.11.2024 um 23:34 schrieb Rich:

Helmut Giese <hgiese@ratiosoft.com> wrote:

Hello out there,
currently Tk accepts only  _gobal_ variables for widgets which set a
value. I always wondered why it doesn't also accept a fully namespaced
variable, too.

 Unless something has changed in 9, Tk has always accepted fully
qualified namespaced variables for Tk widget variables.
 I.e.:
      $ rlwrap wish
     % namespace eval ns {
     variable someVar ""
     }
     % puts $::ns::someVar
      % ttk::radiobutton .r1 -text R1 -value R1 -variable ::ns::someVar
     .r1
     % ttk::radiobutton .r2 -text R2 -value R2 -variable ::ns::someVar
     .r2
     % pack .r1 .r2 -side top
     % puts $::ns::someVar
      % # clicks upon r1
     % puts $::ns::someVar
     R1
     % # clicks upon r2
     % puts $::ns::someVar
     R2
     %
 The thing is, they do have to be 'fully qualified' (which is something
that is easy to forget).
 

In Tcl 8 a syntax like
         -var ::ns::someVar
is not illegal: it just doesn't have any effect

 As I show above, it does.  But, for a radio button, you do need to give
each widget a -value or the widget never sets anything into the
variable.
 

I think, the idea by Helmut is a bit different.
The idea is, that the command does a lookup in the caller namespace and resolves the namespace within this scope.
E.g. the request is to have the following "namespace which" automatically included into the command:
namespace eval ns {
variable someVar ""
ttk::radiobutton .r1 -text R1 -value R1 -variable [namespace which -variable someVar]
}
This is a sensible request.
Unfortunately, currently, it does not work like that.
Currently, it is possible to revert the order, of widget and varible creation:
ttk::radiobutton .r1 -text R1 -value R1 -variable someVar]
variable someVar ""
Or it is even possible to use a non-existing variable.
For example, ttk::checkbutton  is set to the alternate state, if the variable does not exist.
Helmut, I can understand the request. It would be handy.
It specially gets handy for oo widgets.
Sorry, Helmut, without a big redesign, this would not work due to many incompatibilites.
In the mean time, it is good practice to always use [namepscpace which -variable someVar] in the function call.
If you like, you may do a function for your own, which does this (untested):
proc myradiobutton {path args} {
if {[dict exist $args -command]} {
dict set args -commmand [uplevel 1 [namepsace which -variable [dict get $args -command]]]
}
tailcall ttk::radiobutton $path {*}$args
}
Thank you for all,
Harald