Re: Queries on tree items and signals

[muppet <scott asofyet org>]

On Mar 8, 2005, at 2:09 AM, rashwin wrote:

> Hi, I am new to the list and I have a couple of queries on the  
> following:

welcome.


> 1. Signals and callback functions.
> I have a requirement in which I have to a function like below:
>
> sub display_type {
>
> my ($tree, $ext_name, $help) = @_;
>
> $::button_ok->signal_handlers_destroy();
> $::button_cancel->signal_handlers_destroy();

these aren't bound, as you probably already found.  since it destroys  
*all* signal handlers, it's not what you really want to do, anyway.

> $::button_ok->signal_connect( 'clicked',  
> \&type_direct_apply,$tree,$::external_text,$help_text);

also, you can only pass one user-data argument to callbacks via  
signal_connect().  the workaround is to create an anonymous hash or the  
like, put your extra values in that, and pass that instead.

> $::button_cancel->signal_connect( 'clicked',  
> \&type_sample_cancel,$tree, $::external_text,$help_text );
...
> I stopped the infinite loop by calling the signal connect functions  
> for the buttons only once but the problem is the apply and cancel  
> functions are called with the first values of the arguements when they  
> were created.

the right thing to do is indeed to connect only once.  you don't *have*  
to store the arguments in the signal_connect data; you can place them  
in the instance and therefore use the same handler with all such  
events.


> Can someone throw light on why it keeps calling the signal connect  
> functions
> endlessly when $button_ok is clicked on once?

signal_connect() sets up a callback function to be invoked at a later  
time.  it doesn't get invoked at signal_connect() time.  you use this  
to set up behavior, not to pass data around.

the fragment you posted is too small to give you any advice on how to  
fix it -- sorry.


> 2. THis is on dynamically changing labels of tree items.
> When you create a tree item the first time and when selecting that  
> tree item,
> I want the user to change the label of the tree item on the fly.
> Is that possible? What commands to be used for the same?

"label" of a tree item?  a GtkTreeView does not contain GtkLabels, it  
contains GtkTreeViewColumns which are drawn by GtkCellRenderers.

do you mean you want to allow the user to edit cells in-place?  in that  
case, you need to make the cell renderer editable and hook into its  
"edited" signal to apply the changes to the model.

see the editable-cells example program in the gtk-demo directory of the  
Gtk2 source tarball, or at  
http://cvs.sourceforge.net/viewcvs.py/gtk2-perl/gtk2-perl-xs/Gtk2/gtk- 
demo/editable_cells.pl?rev=1.7&view=auto

--
Package contains eight 13-inch aliens in assorted colors.
 -- Catalog copy for space invaders wall decals.