wxruby users - Sep 2007 - Troubles with ListBox and CheckListBox events

Hi all,

Here is an excerpt of code (with the new syntax from upcoming wxRuby 1.9.2) :

    evt_checklistbox(my_checklist, :on_checklistbox)
    evt_listbox(my_checklist, :on_listbox)
    evt_listbox(my_list, :on_listbox)

  def on_checklistbox(event)
    checklist = event.event_object
#    puts "listbox - event : item[#{event.int}] checked :
#{event.checked?}"
    puts "listbox - event : item[#{event.selection}] checked :
#{checklist.checked?(event.selection)}"
  end

  def on_listbox(event)
    puts "listbox - event : item[#{event.selection}]
''#{event.string}''
- selected : #{event.selection?}"
  end

my_checklist is a CheckListBox and my_list is a ListBox.

- Trouble 1 :
When I select AND when I unselect an item in my_checklist or my_list,
the on_listbox is called and displays :
   - the index (through event.selection) and the text (through
event.string) of the item both when the item is selected AND when the
item is unselected.
  - one can know if an item is actually selected through the
event.selection? (or is_selection) call.

This is fine and this is what I expect but the wxRuby documentation
states that :
"CommandEvent#get_selection
Integer get_selection()
Returns item index for a listbox or choice selection event (not valid
for a deselection).

CommandEvent#get_string
String get_string()
Returns item string for a listbox or choice selection event (not valid
for a deselection)."

=> Question :
The documentation contradicts the actual behaviour which I find correct.
Is the documentation incorrect ?

- Troubles 2 & 3 :
When I check and when I uncheck an item in my_checklist, the
on_checklistbox is called and displays :
   - the index (through event.int or event.selection) of the item that
is checked or unchecked.
  - event.checked? doesn''t tell whether the item is checked or not
(see the ommented line). I had to go through the CheckListBox object
and calls checked? with the index (see the uncommented line).

=> Question :
The wxRuby documentation states that :
"CommandEvent#get_int
Integer get_int()
Returns the integer identifier corresponding to a listbox, choice or
radiobox selection (only if the event was a selection, not a
deselection), or a boolean value representing the value of a
checkbox."

Are int and selection synonyms or is one of them is the normal way for
accessing the index of a checked/unchecked item from a CheckListBox ?
Again the doc is not clear as int is expected to work only for a
selection and not the deselection.

=> Other question :
Is there a bug that makes checked? not working for an event of CheckListBox ?

Sorry for this long post.

Cheers.

Chauk-Mean.

Chauk-Mean P wrote:

...
> the wxRuby documentation states that :
> "CommandEvent#get_selection
> Integer get_selection()
> Returns item index for a listbox or choice selection event (not valid
> for a deselection).
>   
...
> The documentation contradicts the actual behaviour which I find correct.
> Is the documentation incorrect ?
>   
On Win32 I see the same as you, ie the desirable behaviour that these 
work whether it''s a selection or a deselection, and also whether 
multiple selections are permitted (see the doc for get_extra_long).

But the current wxWidgets documentation [1] still has the statement 
about GetSelection and GetString being invalid for deselections. I
don''t
know whether this is a wxWidgets doc error, or a warning that this is 
not guaranteed across platforms. Which have you tested
on?
>   - event.checked? doesn''t tell whether the item is checked or not
> (see the ommented line). I had to go through the CheckListBox object
> and calls checked? with the index (see the uncommented line).
>   
I took a look at the way wxWidgets implements this, and 
CommandEvent#is_checked is only meant to work with (a single) CheckBox - 
it will not work with a CheckListBox. To be fair, the docs do state 
this, but rather subtly. So for a CheckListBox it must be done by 
calling the Window''s checked? method, as you have
done.
> Are int and selection synonyms or is one of them is the normal way for
> accessing the index of a checked/unchecked item from a CheckListBox ?
> Again the doc is not clear as int is expected to work only for a
> selection and not the deselection.
>   
Yes, they are synonyms and the C++ methods do the same thing internally. 
I would be inclined to deprecate one but I find both names a bit 
inadequate, since get_selection may be returning the id of an item being 
checked or unchecked, not selected. The is_selection method does 
disambiguate these correctly though.

As with much of the docs we inherited from Wx it''s doubtless 
comprehensive and mostly accurate but also a bit short on the overall 
picture for each class. Happily it''s easy to patch the wxRuby docs...

alex

[1]
http://www.wxwidgets.org/manuals/stable/wx_wxcommandevent.html#wxcommandeventgetselection

2007/9/20, Alex Fenton <alex at pressure.to>:
> Chauk-Mean P wrote:
>
> ...
> > the wxRuby documentation states that :
> > "CommandEvent#get_selection
> > Integer get_selection()
> > Returns item index for a listbox or choice selection event (not valid
> > for a deselection).
> >
> ...
> > The documentation contradicts the actual behaviour which I find
correct.
> > Is the documentation incorrect ?
> >
> On Win32 I see the same as you, ie the desirable behaviour that these
> work whether it''s a selection or a deselection, and also whether
> multiple selections are permitted (see the doc for get_extra_long).
I don''t understand the added value of get_extra_long as is_selection
gives the same information.
>
> But the current wxWidgets documentation [1] still has the statement
> about GetSelection and GetString being invalid for deselections. I
don''t
> know whether this is a wxWidgets doc error, or a warning that this is
> not guaranteed across platforms. Which have you tested on?
I understand. I''m running on Win32.
> >   - event.checked? doesn''t tell whether the item is checked
or not
> > (see the ommented line). I had to go through the CheckListBox object
> > and calls checked? with the index (see the uncommented line).
> >
> I took a look at the way wxWidgets implements this, and
> CommandEvent#is_checked is only meant to work with (a single) CheckBox -
> it will not work with a CheckListBox. To be fair, the docs do state
> this, but rather subtly. So for a CheckListBox it must be done by
> calling the Window''s checked? method, as you have done.
OK even if it''s a pity :-).
> > Are int and selection synonyms or is one of them is the normal way for
> > accessing the index of a checked/unchecked item from a CheckListBox ?
> > Again the doc is not clear as int is expected to work only for a
> > selection and not the deselection.
> >
> Yes, they are synonyms and the C++ methods do the same thing internally.
OK.
> I would be inclined to deprecate one but I find both names a bit
> inadequate, since get_selection may be returning the id of an item being
> checked or unchecked, not selected. The is_selection method does
> disambiguate these correctly though.
If agree. For a "selection event", selection is meaningful.
For a "check event", both int and selection are not appropriate.

I would propose to add the more general name index (get_index) which
is both meaningful for a selection and a check.
Thus, the same method may be used for the two kinds of event.
selection and int methods may be kept for "compatibility reasons" with
wxWidgets.
>
> As with much of the docs we inherited from Wx it''s doubtless
> comprehensive and mostly accurate but also a bit short on the overall
> picture for each class. Happily it''s easy to patch the wxRuby
docs...
It would be great if wxRuby doc clarifies these subtle things.


Chauk-Mean.

Chauk-Mean P wrote:
> 2007/9/20, Alex Fenton <alex at pressure.to>:
>   
>> But the current wxWidgets documentation [1] still has the statement
>> about GetSelection and GetString being invalid for deselections. I
don''t
>> know whether this is a wxWidgets doc error, or a warning that this is
>> not guaranteed across platforms. Which have you tested on?
>>     
>
> I understand. I''m running on Win32.
>   
I''ll try on Linux later, but don''t have a OS X machine at the
moment.
>> I would be inclined to deprecate one but I find both names a bit
>> inadequate, since get_selection may be returning the id of an item
being
>> checked or unchecked, not selected. The is_selection method does
>> disambiguate these correctly though.
>>     
>
> If agree. For a "selection event", selection is meaningful.
> For a "check event", both int and selection are not appropriate.
>
> I would propose to add the more general name index (get_index) which
> is both meaningful for a selection and a check.
Yes, that was my first thought for a name for such a
method.
> It would be great if wxRuby doc clarifies these subtle things.
>   
It would. We do try and write overviews, eg the recently updated event 
handling one*. The focus of the small dev team is naturally enough on 
the core library right now; small contributions to the docs are thus 
really welcome.

cheers
alex

* 
http://wxruby.rubyforge.org/svn/trunk/wxruby2/doc/textile/eventhandlingoverview.txtl

2007/9/20, Alex Fenton <alex at pressure.to>:
> > It would be great if wxRuby doc clarifies these subtle things.
> >
> It would. We do try and write overviews, eg the recently updated event
> handling one*. The focus of the small dev team is naturally enough on
> the core library right now; small contributions to the docs are thus
> really welcome.
>
I will be glad to contribute to the documentation.
Can you give me a link to a HOW TO for contributing to the doc.

Cheers.

Chauk-Mean.

Chauk-Mean P wrote:
> I will be glad to contribute to the documentation.
> Can you give me a link to a HOW TO for contributing to the doc.
>   
Thank you. I quickly put together this page:

http://wxruby.rubyforge.org/wiki/wiki.pl?DocumentingWxRuby

Alex

Chauk-Mean P wrote:
> 2007/9/20, Alex Fenton <alex at pressure.to>:
>   
>> But the current wxWidgets documentation [1] still has the statement
>> about GetSelection and GetString being invalid for deselections. I
don''t
>> know whether this is a wxWidgets doc error, or a warning that this is
>> not guaranteed across platforms. Which have you tested on?
>>     
>
> I understand. I''m running on Win32.
>   
I just tried this out on Linux/GTK and indeed get_selection and 
get_string are empty when it''s a deselection event. So
wxWidget''s docs
are correct and you shouldn''t rely on this working if you want to use 
this cross-platform.

Also committed the get_index alias to core

alex

2007/9/20, Alex Fenton <alex at pressure.to>:
>
> I just tried this out on Linux/GTK and indeed get_selection and
> get_string are empty when it''s a deselection event. So
wxWidget''s docs
> are correct and you shouldn''t rely on this working if you want to
use
> this cross-platform.
>
Thanks for the information.
> Also committed the get_index alias to core
That''s great.

Chauk-Mean.