How to delete entries within HLIST and have it update itself?

I always have this issue with HLIST where when you delete an entry - it
remembers all of the original entry positions. This presents a problem
when you have developed a logic for mapping the position in the list
when it was created with some array or other data structure - or to be
able to add new items to the list -

Here is a simple example - you can add items by clicking the add button
- then delete one by selecting the delete button - however the original
positions are all still associated to the remaining items - even though
they are now incorrect. Is there a way to re-fresh the entry paths?
------------- simple example ---------------
use Tk;
use Tk::HList;

@more_colors = (qw/green magenta orange purple blue
yellow red white black fuscia brown pink viloet grey indigo/);

my $mw = MainWindow->new;
$mw->geometry('300x600');

my $list = $mw->HList()
->pack(qw/-fill both -expand yes/);

$list->configure(-command=>sub{&show_me});

my $text = $mw->Text(-width=>60,-height=>10)
->pack(qw/-fill both -expand yes/);

foreach (@more_colors[2..5]) {
$list_pos = () = $list->info("children");
$list->add($list_pos, -text => "[$list_pos]".$_);
} # end foreach

$button{del_path}= $mw->Button(
-text => 'Delete selected color ',
-command => sub{&del_path},
)->pack(-side=>left);

$button{add_path}= $mw->Button(
-text => 'Add new color ',
-command => sub{&add_path},
)->pack(-side=>left);

MainLoop;

sub show_me {
my $path = $_[0];
$text->insert('end',"You selected path $path \n");
} # end sub

sub add_path {
my $list_pos = () = $list->info("children");
$list->add($list_pos, -text => "[$list_pos]".(&get_color));
} # end sub

sub get_color {
if ($colors >= $#more_colors) {$colors = -1};
unless ($colors++ >= $#more_colors) {
return @more_colors[$#more_colors-$colors];
} # end
return @more_colors[$colors];
} # end sub

sub del_path {
my @path = $list->selectionGet;
$list->delete('entry',$path[0]);
$text->insert('end',"You deleted path $path[0]\n");
} # end sub

-------------------------------------

thanks, john

In article <1106664657.886790.152550@c13g2000cwb.googlegroups.com>, bayxarea-
usenet@yahoo.com says...
> I always have this issue with HLIST where when you delete an entry - it
> remembers all of the original entry positions. This presents a problem
> when you have developed a logic for mapping the position in the list
> when it was created with some array or other data structure - or to be
> able to add new items to the list -
>
> Here is a simple example - you can add items by clicking the add button
> - then delete one by selecting the delete button - however the original
> positions are all still associated to the remaining items - even though
> they are now incorrect. Is there a way to re-fresh the entry paths?

Thanks for including a small working example. Tk::HList does not have
a sense of indexes for items as does Tk::Listbox. The paths are named
and have no implicit order. Perhaps you should use Tk::Listbox?

--
Go to http://MarcDashevsky.com to send me e-mail.

Marc Dashevsky <usenet@MarcDashevsky.com> wrote in message-id:
<MPG.1c6067c244bf8cfb9896a7@news.comcast.giganews.com>
>
>In article <1106664657.886790.152550@c13g2000cwb.googlegroups.com>, bayxarea-
>usenet@yahoo.com says...
>> I always have this issue with HLIST where when you delete an entry - it
>> remembers all of the original entry positions. This presents a problem
>> when you have developed a logic for mapping the position in the list
>> when it was created with some array or other data structure - or to be
>> able to add new items to the list -
>>
>> Here is a simple example - you can add items by clicking the add button
>> - then delete one by selecting the delete button - however the original
>> positions are all still associated to the remaining items - even though
>> they are now incorrect. Is there a way to re-fresh the entry paths?
>
>Thanks for including a small working example. Tk::HList does not have
>a sense of indexes for items as does Tk::Listbox. The paths are named
>and have no implicit order. Perhaps you should use Tk::Listbox?
>
>--
> Go to http://MarcDashevsky.com to send me e-mail.

Perhaps _hiding_ the entry rather than _deleting_ it would provide a solution
of sorts.

gl

On 25 Jan 2005 06:50:57 -0800, bayxarea-usenet@yahoo.com wrote:

>I always have this issue with HLIST where when you delete an entry - it
>remembers all of the original entry positions. This presents a problem
>when you have developed a logic for mapping the position in the list
>when it was created with some array or other data structure - or to be
>able to add new items to the list -
>
>Here is a simple example - you can add items by clicking the add button
>- then delete one by selecting the delete button - however the original
>positions are all still associated to the remaining items - even though
>they are now incorrect. Is there a way to re-fresh the entry paths?

Yeah, that is the biggest hassle with HList, it keeps an internal
numbering of entries, which just keeps rising for each entry. I was
often tempted to wonder if this affects performance in long running
apps, where the internal counter is up into the millions. :-) But I
guess computers don't really care, a number is a number; 9 is as
good as 16,000,0009.

It really becomes a hassle when you want to insert at some position.

A couple of ways I have dealt with it.....(from memory so I may be off a
bit) :-)

1. Only create a set number of entries and reuse them, by reconfiguring
them. This is what I do when I want to have a "pager mechanism", say
10 pages of 10 entries each. When you want to change entry2 for
instance, you don't delete it, you reconfigure it.

2. The other option is to keep a separate hash of which entries have
which entry paths.

So it seems that you are forced to track them yourselves in a separate
hash.

A couple of my HList apps have some really wacky insertion subs, where I
loop thru all entries, testing if the next or previous entry exists,
(since they may have been deleted earlier)
then do something accordingly. Like this, where I delete the selected
entry, and want to find the next available entry to set as selected:

my $listnum =$h->info('selection');
$h->delete('entry',$h->info('selection'));
if($h->info('exists', $listnum + 1)){
$h->selectionSet($listnum + 1)
}else{
while($listnum--){

if($h->info('exists',$listnum)){

$h->selectionSet($listnum);last}
}

It should be easier than that. I should be able just to select the next
number, but you risk getting "entry dosn't exist" errors.
Like you say, if there was an internal
command to HList, to "refresh" it's internal counter, it would be nice.
But there probably is some obscure reason why the counter is done
this way, maybe the author knows? I'm guessing it has something to do
with making an entry "hidden", then returning it to "normal"...that has
to be tracked somehow.

(Just blowing off HList "steam" :-) ).

--
I'm not really a human, but I play one on earth.
http://zentara.net/japh.html

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