Re: Virtual list boxes (using GtkTreeView or other)

["Nuno Lucas" <ntlucas gmail com>]

On 6/1/07, David Nečas (Yeti) <yeti physics muni cz> wrote:
> On Fri, Jun 01, 2007 at 03:47:36PM +0100, Nuno Lucas wrote:
> > >
> > > You have to derive your own GtkTreeModel, if the predefined GtkListStore
> > > or GtkTreeStore are not sufficient (They simply stores all data at once).
> >
> > I may be missing something, but I don't see a way to set the number of
> > "virtual" rows.
>
> See http://gwyddion.net/documentation/head/libgwydgets/GwyNullStore.php
> for a simple purely virtual store.  This is a cheap hack,
> but it demonstrates the point IMO.

Thanks! That is exactly the kind of sample I needed to look at!

> > From what I see in the documentation, the only way to grow is by
> > appending a single row at a time (which I guess then emits the
> > "row-changed" signal and updates the scrollbar).
>
> You are mixing two things here:
> - if the model grows is must emit the row-inserted signal,
>   because if it does not do this, the tree views showing it
>   break
> - however, if no one is watching, namely when the model is
>   created, it can be instantaneously created with a million
>   of rows

I see. Now I understand. I only need to implement my own "store"
and make sure I only call gtk_tree_set_model() after I set the
number of rows I want.

> There are more troubles with huge tree views, namely the
> tree view needs to know the sizes of the columns and rows --
> even those not currently visible as they still affect what
> is visible.  So you will probably end up using all the
> confusing fixed size modes, and avoiding work in cell data
> functions for invisible cells.

I am aware of this kind of problems and am expecting them.

> However, for a milion of rows scrolling through the tree
> manually is no longer useful anyway, i.e. the user interface
> ceases to be suitable for the task.  You may want to use
> a multilevel or search+paging base interface instead --
> essentially something that avoids the signle list with
> a million of rows by design.

I agree, but that's what the boss wants ;-)

On the other hand, as I'm using a generic tree view to show a list, I
could use that property to show a next and previous page controls (as
"owner drawn" root columns) and restrict the ouput to some row limit.

> Yeti

Thank you, you were most helpful.

Best regards,
~Nuno Lucas