Sample code usable Tkinter listbox

[Alf P. Steinbach]

In case Someone Else(TM) may need this.

This code is just how it currently looks, what I needed for my code, so it's not
a full-fledged or even tested class.

But it works.

<code language="Py3">
import tkinter as t
import tkinter.simpledialog
import tkinter.messagebox
t.askstring = tkinter.simpledialog.askstring
t.warningbox = tkinter.messagebox.showwarning

class UsableListbox( t.Frame ):
def __init__( self, parent_widget ):
t.Frame.__init__( self, parent_widget )
scrollbar = t.Scrollbar( self, orient = "vertical" )
self.lb = t.Listbox( self, yscrollcommand = scrollbar.set )
scrollbar.config( command = self.lb.yview )
scrollbar.pack( side = "right", fill = "y" )
self.lb.pack( side = "left", fill = "both", expand = 1 )

def current_index( self ):
indices = self.lb.curselection()
assert( len( indices ) <= 1 ) # TODO: about multi-selection.
return None if len( indices ) == 0 else int( indices[0] )

def current( self ):
#return self.lb.get( "active" ) # Incorrect with mousing
i = self.current_index()
return "" if i is None else self.lb.get( i )

def append( self, item ):
return self.lb.insert( "end", item )

def add_selection_event_handler( self, handler ):
"An event handler takes one argument, a Tkinter Event"
return self.lb.bind( "<<ListboxSelect>>", handler )
</code>

Cheers,

- Alf

[Alf P. Steinbach]

* rantingrick:

> On Feb 28, 6:30 pm, "Alf P. Steinbach" <al...@start.no> wrote:
>> In case Someone Else(TM) may need this.
>>
>> This code is just how it currently looks, what I needed for my code, so it's not
>> a full-fledged or even tested class.
>

> Thanks for sharing Alf,
> Thats works fine "as-is" but what about inheriting from "tk.Listbox"
> directly and having the "container frame" as an attribute? I prefer
> this API because I hate to write the laborious
> "megawidget.mainwidget.methodX()" when i could instead write
> "megawidget.methodX()". What is your opinion on this?

Well the frame contains a listbox and scrollbar. And with the frame as attribute
the object that you have a direct reference to would then not be the complete
thing on screen, with respect to sizing and placement and such. I generally
don't like widgets that present stuff outside their bounding box. I guess that
could be fixed up somehow by overriding this and that, but I find it simpler to
just make the enclosing widget the widget that one has a reference to. And in a
way it's also good that it's more laborious to directly access the tkinter
listbox stuff, because what I discovered so far is that much of it requires work
arounds and fixups, i.e. that it should be wrapped in higher level methods.

I had to add some more such functionality after I posted that code.

So, current (this is untested except that it works for what I'm using it for!):

<code language="Py3">

class UsableListbox( t.Frame ):
def __init__( self, parent_widget ):
t.Frame.__init__( self, parent_widget )
scrollbar = t.Scrollbar( self, orient = "vertical" )

self.lb = t.Listbox( self, exportselection = 0, yscrollcommand =

scrollbar.set )
scrollbar.config( command = self.lb.yview )
scrollbar.pack( side = "right", fill = "y" )
self.lb.pack( side = "left", fill = "both", expand = 1 )

def current_index( self ):
indices = self.lb.curselection()
assert( len( indices ) <= 1 ) # TODO: about multi-selection.
return None if len( indices ) == 0 else int( indices[0] )

def current( self ):
#return self.lb.get( "active" ) # Incorrect with mousing
i = self.current_index()
return "" if i is None else self.lb.get( i )

def item_count( self ):
return self.lb.size()

def clear( self ):
self.lb.delete( 0, "end" )

def append( self, item ):
return self.lb.insert( "end", item )

def select_item( self, i ):
assert( 0 <= i < self.item_count() )
self.lb.selection_set( i )

[Alf P. Steinbach]

* rantingrick:
>
> kw.setdefault('activestyle', 'none')

Hm, let me steal this line... Thanks!

Cheers,

- Alf

[Alf P. Steinbach]

* Alf P. Steinbach:

> In case Someone Else(TM) may need this.
>
> This code is just how it currently looks, what I needed for my code, so
> it's not a full-fledged or even tested class.
>
> But it works.

That code evolved a little to cover more Tk listbox quirks (thanks to Ratingrick
for the "activestyle"):

<code>

class UsableListbox( t.Frame ):
def __init__( self, parent_widget ):
t.Frame.__init__( self, parent_widget )
scrollbar = t.Scrollbar( self, orient = "vertical" )
self.lb = t.Listbox(
self,

exportselection = 0, activestyle = "none", selectmode = "browse",

yscrollcommand = scrollbar.set
)
scrollbar.config( command = self.lb.yview )
scrollbar.pack( side = "right", fill = "y" )
self.lb.pack( side = "left", fill = "both", expand = 1 )

def current_index( self ):
indices = self.lb.curselection()
assert( len( indices ) <= 1 ) # TODO: about multi-selection.
return None if len( indices ) == 0 else int( indices[0] )

def item_at( self, i ):

assert( 0 <= i < self.item_count() )

return "" if i is None else self.lb.get( i )

def current( self ):

#return self.lb.get( "active" ) # Incorrect with mousing

return self.item_at( self.current_index() )

def item_count( self ):
return self.lb.size()

def clear( self ):
self.lb.delete( 0, "end" )

def append( self, item ):

self.lb.insert( "end", item )

return self.item_count() - 1

def scroll_into_view( self, i ):
self.lb.see( i )

def select_item( self, i ):
assert( 0 <= i < self.item_count() )

old_i = self.current_index();
self.scroll_into_view( i )
if old_i is not None and old_i == i:
return
self.lb.selection_set( i )
if old_i is not None:
self.lb.selection_clear( old_i )