On 2/7/08, Julien Moutinho <julien.moutinho@gmail.com> wrote:

On Wed, Feb 06, 2008 at 08:34:04PM +0000, David Powers wrote:
> I am attempting to use the GnoCanvas to build what is essentially a custom
> container.  Placing widgets on the canvas works like a charm, but I can't
> seem to find where the normal containers are reading their sizing hints
> from.  I can read the height/width_request properties, but they seem to be
> minimal sizes (e.g. for a text entry box I get a height and width of 1).
> Does anyone have any hints on where I could go hunting - or maybe I should
> be taking a different approach?

According to the following links, gtk_widget_size_request() is the way
containers read their sizing hints:

http://library.gnome.org/devel/gtk/stable/GtkContainer.html#size-requisition

  "The size requisition phase of the widget layout process operates top-down.
  It starts at a top-level widget, typically a GtkWindow.
  The top-level widget asks its child for its size requisition by calling
  gtk_widget_size_request(). To determine its requisition, the child asks
  its own children for their requisitions and so on.
  Finally, the top-level widget will get a requisition back from its child."

http://library.gnome.org/devel/gtk/stable/GtkWidget.html#gtk-widget-size-request

  "This function is typically used when implementing a GtkContainer subclass.
  Obtains the preferred size of a widget. The container uses this information
  to arrange its child widgets and decide what size allocations to give them
  with gtk_widget_size_allocate()."

Unfortunately, gtk_widget_size_request() has not been wrapped inside LablGTK yet.
However, I'm joining a little patch which wraps it plus an example that may help you.
I've also applied the patch to:
  svn://julien_moutinho@svn.gna.org/svn/lablgtk/branches/moutinho

NOTE: my lablgtk2 top-loop fails to run the example:
% lablgtk2 lablgtk_example__size_request.ml
Fatal error: exception Failure("float_of_string")
2%
(This bug may be related to ~x ~y ~width ~height parameters,
because without them it does not fail)

So you may have to run the example with this command:

% ocamlc -g -I +lablgtk2 lablgtk.cma lablgnomecanvas.cma gtkInit.cmo \
    lablgtk_example__size_request.ml && ./a.out
root_group#get_bounds: 0. 0. 0. 0.
widget#get_bounds: 0. 0. 23. 12.
widget#get_bounds: 25. 14. 52. 26.
List.length root_group#get_items = 2
root_group#get_bounds: 0. 0. 52. 26.
found a widget item:
  requested_width  = 23
  requested_height = 12
found a widget item:
  requested_width  = 27
  requested_height = 12

HTH.

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